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|
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<head>
<title>Embedded C++/Parser Mapping Getting Started Guide</title>
<meta name="copyright" content="© 2005-2017 Code Synthesis Tools CC"/>
<meta name="keywords" content="xsd,xml,schema,c++,mapping,data,binding,parser,validation,embedded,mobile"/>
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<body>
<div id="container">
<div id="content">
<div class="noprint">
<div id="titlepage">
<div class="title" id="first-title">Embedded C++/Parser Mapping</div>
<div class="title" id="second-title">Getting Started Guide</div>
<p>Copyright © 2005-2017 CODE SYNTHESIS TOOLS CC</p>
<p>Permission is granted to copy, distribute and/or modify this
document under the terms of the
<a href="http://www.codesynthesis.com/licenses/fdl-1.2.txt">GNU Free
Documentation License, version 1.2</a>; with no Invariant Sections,
no Front-Cover Texts and no Back-Cover Texts.
</p>
<p>This document is available in the following formats:
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/index.xhtml">XHTML</a>,
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/cxx-parser-e-guide.pdf">PDF</a>, and
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/cxx-parser-e-guide.ps">PostScript</a>.</p>
</div>
<h1>Table of Contents</h1>
<table class="toc">
<tr>
<th></th><td><a href="#0">Preface</a>
<table class="toc">
<tr><th></th><td><a href="#0.1">About This Document</a></td></tr>
<tr><th></th><td><a href="#0.2">More Information</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>1</th><td><a href="#1">Introduction</a>
<table class="toc">
<tr><th>1.1</th><td><a href="#1.1">Mapping Overview</a></td></tr>
<tr><th>1.2</th><td><a href="#1.2">Benefits</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>2</th><td><a href="#2">Hello World Example</a>
<table class="toc">
<tr><th>2.1</th><td><a href="#2.1">Writing XML Document and Schema</a></td></tr>
<tr><th>2.2</th><td><a href="#2.2">Translating Schema to C++</a></td></tr>
<tr><th>2.3</th><td><a href="#2.3">Implementing Application Logic</a></td></tr>
<tr><th>2.4</th><td><a href="#2.4">Compiling and Running</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>3</th><td><a href="#3">Parser Skeletons</a>
<table class="toc">
<tr><th>3.1</th><td><a href="#3.1">Implementing the Gender Parser</a></td></tr>
<tr><th>3.2</th><td><a href="#3.2">Implementing the Person Parser</a></td></tr>
<tr><th>3.3</th><td><a href="#3.3">Implementing the People Parser</a></td></tr>
<tr><th>3.4</th><td><a href="#3.4">Connecting the Parsers Together</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>4</th><td><a href="#4">Type Maps</a>
<table class="toc">
<tr><th>4.1</th><td><a href="#4.1">Object Model</a></td></tr>
<tr><th>4.2</th><td><a href="#4.2">Type Map File Format</a></td></tr>
<tr><th>4.3</th><td><a href="#4.3">Parser Implementations</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>5</th><td><a href="#5">Mapping Configuration</a>
<table class="toc">
<tr><th>5.1</th><td><a href="#5.1">Standard Template Library</a></td></tr>
<tr><th>5.2</th><td><a href="#5.2">Input/Output Stream Library</a></td></tr>
<tr><th>5.3</th><td><a href="#5.3">C++ Exceptions</a></td></tr>
<tr><th>5.4</th><td><a href="#5.4">XML Schema Validation</a></td></tr>
<tr><th>5.5</th><td><a href="#5.5">64-bit Integer Type</a></td></tr>
<tr><th>5.6</th><td><a href="#5.6">Parser Reuse</a></td></tr>
<tr><th>5.7</th><td><a href="#5.7">Support for Polymorphism</a></td></tr>
<tr><th>5.8</th><td><a href="#5.8">Custom Allocators</a></td></tr>
<tr><th>5.9</th><td><a href="#5.9">A Minimal Example</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>6</th><td><a href="#6">Built-In XML Schema Type Parsers</a>
<table class="toc">
<tr><th>6.1</th><td><a href="#6.1"><code>QName</code> Parser</a></td></tr>
<tr><th>6.2</th><td><a href="#6.2"><code>NMTOKENS</code> and <code>IDREFS</code> Parsers</a></td></tr>
<tr><th>6.3</th><td><a href="#6.3"><code>base64Binary</code> and <code>hexBinary</code> Parsers</a></td></tr>
<tr><th>6.4</th><td><a href="#6.4">Time Zone Representation</a></td></tr>
<tr><th>6.5</th><td><a href="#6.5"><code>date</code> Parser</a></td></tr>
<tr><th>6.6</th><td><a href="#6.6"><code>dateTime</code> Parser</a></td></tr>
<tr><th>6.7</th><td><a href="#6.7"><code>duration</code> Parser</a></td></tr>
<tr><th>6.8</th><td><a href="#6.8"><code>gDay</code> Parser</a></td></tr>
<tr><th>6.9</th><td><a href="#6.9"><code>gMonth</code> Parser</a></td></tr>
<tr><th>6.10</th><td><a href="#6.10"><code>gMonthDay</code> Parser</a></td></tr>
<tr><th>6.11</th><td><a href="#6.11"><code>gYear</code> Parser</a></td></tr>
<tr><th>6.12</th><td><a href="#6.12"><code>gYearMonth</code> Parser</a></td></tr>
<tr><th>6.13</th><td><a href="#6.13"><code>time</code> Parser</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>7</th><td><a href="#7">Document Parser and Error Handling</a>
<table class="toc">
<tr><th>7.1</th><td><a href="#7.1">Document Parser</a></td></tr>
<tr><th>7.2</th><td><a href="#7.2">Exceptions</a></td></tr>
<tr><th>7.3</th><td><a href="#7.3">Error Codes</a></td></tr>
<tr><th>7.4</th><td><a href="#7.4">Reusing Parsers after an Error</a></td></tr>
</table>
</td>
</tr>
<tr>
<th></th><td><a href="#A">Appendix A — Supported XML Schema Constructs</a></td>
</tr>
</table>
</div>
<h1><a name="0">Preface</a></h1>
<h2><a name="0.1">About This Document</a></h2>
<p>The goal of this document is to provide you with an
understanding of the C++/Parser programming model and allow you
to efficiently evaluate XSD/e against your project's technical
requirements. As such, this document is intended for embedded
C++ developers and software architects who are looking for an
embedded XML processing solution. Prior experience with XML
and C++ is required to understand this document. Basic
understanding of XML Schema is advantageous but not expected
or required.
</p>
<h2><a name="0.2">More Information</a></h2>
<p>Beyond this guide, you may also find the following sources of
information useful:</p>
<ul class="list">
<li><a href="http://www.codesynthesis.com/projects/xsde/documentation/xsde.xhtml">XSD/e
Compiler Command Line Manual</a></li>
<li>The <code>INSTALL</code> file in the XSD/e distribution provides
build instructions for various platforms.</li>
<li>The <code>examples/cxx/parser/</code> directory in the XSD/e
distribution contains a collection of examples and a README
file with an overview of each example.</li>
<li>The <a href="http://www.codesynthesis.com/mailman/listinfo/xsde-users">xsde-users</a>
mailing list is the place to ask technical questions about XSD/e and the
Embedded C++/Parser mapping. Furthermore, the
<a href="http://www.codesynthesis.com/pipermail/xsde-users/">archives</a>
may already have answers to some of your questions.</li>
</ul>
<!-- Introduction -->
<h1><a name="1">1 Introduction</a></h1>
<p>Welcome to CodeSynthesis XSD/e and the Embedded C++/Parser mapping.
XSD/e is a dependency-free W3C XML Schema to C++ compiler for mobile,
embedded, and light-weight applications. Embedded C++/Parser is an
XML Schema to C++ mapping that represents an XML vocabulary as a set
of parser skeletons which you can implement to perform XML processing
as required by your application logic.
</p>
<h2><a name="1.1">1.1 Mapping Overview</a></h2>
<p>The Embedded C++/Parser mapping provides event-driven, stream-oriented
XML parsing, XML Schema validation, and C++ data binding. It was
specifically designed and optimized for mobile and embedded
systems where hardware constraints require high efficiency and
economical use of resources. As a result, the generated
parsers are 2-10 times faster than general-purpose validating
XML parsers while at the same time maintaining extremely low static
and dynamic memory footprints. For example, a validating parser
executable can be as small as 120KB in size. The size can be
further reduced by disabling support for XML Schema validation.
</p>
<p>The generated code and the runtime library are also highly-portable
and, in their minimal configuration, can be used without STL, RTTI,
iostream, C++ exceptions, and C++ templates.</p>
<p>To speed up application development, the C++/Parser mapping
can be instructed to generate sample parser implementations
and a test driver which can then be filled with the application
logic code. The mapping also provides a wide range of
mechanisms for controlling and customizing the generated code.</p>
<p>The next chapter shows how to create a simple application
that uses the Embedded C++/Parser mapping to parse, validate,
and extract data from a simple XML instance document. The
following chapters describe the Embedded C++/Parser mapping
in more detail.</p>
<h2><a name="1.2">1.2 Benefits</a></h2>
<p>Traditional XML access APIs such as Document Object Model (DOM)
or Simple API for XML (SAX) as well as general-purpose XML Schema
validators have a number of drawbacks that make them less suitable
for creating mobile and embedded XML processing applications. These
drawbacks include:
</p>
<ul class="list">
<li>Text-based representation results in inefficient use of
resources.</li>
<li>Extra validation code that is not used by the application.</li>
<li>Generic representation of XML in terms of elements, attributes,
and text forces an application developer to write a substantial
amount of bridging code that identifies and transforms pieces
of information encoded in XML to a representation more suitable
for consumption by the application logic.</li>
<li>String-based flow control defers error detection to runtime.
It also reduces code readability and maintainability.</li>
<li>Lack of type safety because all information is represented
as text.</li>
<li>Resulting applications are hard to debug, change, and
maintain.</li>
</ul>
<p>In contrast, statically-typed, vocabulary-specific parser
skeletons produced by the Embedded C++/Parser mapping use
native data representations (for example, integers are passed as
integers, not as text) and include validation code only for
XML Schema constructs that are used in the application. This
results in efficient use of resources and compact object code.</p>
<p>Furthermore, the parser skeletons allow you to operate in your
domain terms instead of the generic elements, attributes, and
text. Static typing helps catch errors at compile-time rather
than at run-time. Automatic code generation frees you for more
interesting tasks (such as doing something useful with the
information stored in the XML documents) and minimizes the
effort needed to adapt your applications to changes in the
document structure. To summarize, the C++/Parser mapping has
the following key advantages over generic XML access APIs:</p>
<ul class="list">
<li><b>Ease of use.</b> The generated code hides all the complexity
associated with recreating the document structure, maintaining the
dispatch state, and converting the data from the text representation
to data types suitable for manipulation by the application logic.
Parser skeletons also provide a convenient mechanism for building
custom in-memory representations.</li>
<li><b>Natural representation.</b> The generated parser skeletons
implement parser callbacks as virtual functions with names
corresponding to elements and attributes in XML. As a result,
you process the XML data using your domain vocabulary instead
of generic elements, attributes, and text.
</li>
<li><b>Concise code.</b> With a separate parser skeleton for each
XML Schema type, the application implementation is
simpler and thus easier to read and understand.</li>
<li><b>Safety.</b> The XML data is delivered to parser callbacks as
statically typed objects. The parser callbacks themselves are virtual
functions. This helps catch programming errors at compile-time
rather than at runtime.</li>
<li><b>Maintainability.</b> Automatic code generation minimizes the
effort needed to adapt the application to changes in the
document structure. With static typing, the C++ compiler
can pin-point the places in the application code that need to be
changed.</li>
<li><b>Efficiency.</b> The generated parser skeletons use native
data representations and combine data extraction, validation,
and even dispatching in a single step. This makes them much
more efficient than traditional architectures with separate
stages for validation and data extraction/dispatch.</li>
</ul>
<!-- Hello World Example -->
<h1><a name="2">2 Hello World Example</a></h1>
<p>In this chapter we will examine how to parse a very simple XML
document using the XSD/e-generated C++/Parser skeletons.
All the code presented in this chapter is based on the <code>hello</code>
example which can be found in the <code>examples/cxx/parser/</code>
directory of the XSD/e distribution.</p>
<h2><a name="2.1">2.1 Writing XML Document and Schema</a></h2>
<p>First, we need to get an idea about the structure
of the XML documents we are going to process. Our
<code>hello.xml</code>, for example, could look like this:</p>
<pre class="xml">
<?xml version="1.0"?>
<hello>
<greeting>Hello</greeting>
<name>sun</name>
<name>moon</name>
<name>world</name>
</hello>
</pre>
<p>Then we can write a description of the above XML in the
XML Schema language and save it into <code>hello.xsd</code>:</p>
<pre class="xml">
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:complexType name="hello">
<xs:sequence>
<xs:element name="greeting" type="xs:string"/>
<xs:element name="name" type="xs:string" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
<xs:element name="hello" type="hello"/>
</xs:schema>
</pre>
<p>Even if you are not familiar with the XML Schema language, it
should be easy to connect declarations in <code>hello.xsd</code>
to elements in <code>hello.xml</code>. The <code>hello</code> type
is defined as a sequence of the nested <code>greeting</code> and
<code>name</code> elements. Note that the term sequence in XML
Schema means that elements should appear in a particular order
as opposed to appearing multiple times. The <code>name</code>
element has its <code>maxOccurs</code> property set to
<code>unbounde</code> which means it can appear multiple times
in an XML document. Finally, the globally-defined <code>hello</code>
element prescribes the root element for our vocabulary. For an
easily-approachable introduction to XML Schema refer to
<a href="http://www.w3.org/TR/xmlschema-0/">XML Schema Part 0:
Primer</a>.</p>
<p>The above schema is a specification of our vocabulary; it tells
everybody what valid XML instances of our vocabulary should look
like. The next step is to compile this schema to generate C++ parser
skeletons.</p>
<h2><a name="2.2">2.2 Translating Schema to C++</a></h2>
<p>Now we are ready to translate our <code>hello.xsd</code> to C++ parser
skeletons. To do this we invoke the XSD/e compiler from a terminal
(UNIX) or a command prompt (Windows):
</p>
<pre class="terminal">
$ xsde cxx-parser hello.xsd
</pre>
<p>The XSD/e compiler produces two C++ files: <code>hello-pskel.hxx</code>
and <code>hello-pskel.cxx</code>. The following code fragment is taken
from <code>hello-pskel.hxx</code>; it should give you an idea about what
gets generated:
</p>
<pre class="c++">
class hello_pskel
{
public:
// Parser callbacks. Override them in your implementation.
//
virtual void
pre ();
virtual void
greeting (const std::string&);
virtual void
name (const std::string&);
virtual void
post_hello ();
// Parser construction API.
//
void
greeting_parser (xml_schema::string_pskel&);
void
name_parser (xml_schema::string_pskel&);
void
parsers (xml_schema::string_pskel& /* greeting */,
xml_schema::string_pskel& /* name */);
private:
...
};
</pre>
<p>The first four member functions shown above are called parser
callbacks. You would normally override them in your implementation
of the parser to do something useful. Let's go through all of
them one by one.</p>
<p>The <code>pre()</code> function is an initialization callback. It is
called when a new element of type <code>hello</code> is about
to be parsed. You would normally use this function to allocate a new
instance of the resulting type or clear accumulators that are used
to gather information during parsing. The default implementation
of this function does nothing.</p>
<p>The <code>post_hello()</code> function is a finalization callback. Its
name is constructed by adding the parser skeleton name to the
<code>post_</code> prefix. The finalization callback is called when
parsing of the element is complete and the result, if any, should
be returned. Note that in our case the return type of
<code>post_hello()</code> is <code>void</code> which means there
is nothing to return. More on parser return types later.
</p>
<p>You may be wondering why the finalization callback is called
<code>post_hello()</code> instead of <code>post()</code> just
like <code>pre()</code>. The reason for this is that
finalization callbacks can have different return types and
result in function signature clashes across inheritance
hierarchies. To prevent this, the signatures of finalization
callbacks are made unique by adding the type name to their names.</p>
<p>The <code>greeting()</code> and <code>name()</code> functions are
called when the <code>greeting</code> and <code>name</code> elements
have been parsed, respectively. Their arguments are of type
<code>std::string</code> and contain the data extracted from XML.</p>
<p>The last three functions are for connecting parsers to each other.
For example, there is a predefined parser for built-in XML Schema type
<code>string</code> in the XSD/e runtime. We will be using
it to parse the contents of <code>greeting</code> and
<code>name</code> elements, as shown in the next section.</p>
<h2><a name="2.3">2.3 Implementing Application Logic</a></h2>
<p>At this point we have all the parts we need to do something useful
with the information stored in XML documents. The first step is
to implement the parser:
</p>
<pre class="c++">
#include <iostream>
#include "hello-pskel.hxx"
class hello_pimpl: public hello_pskel
{
public:
virtual void
greeting (const std::string& g)
{
greeting_ = g;
}
virtual void
name (const std::string& n)
{
std::cout << greeting_ << ", " << n << "!" << std::endl;
}
private:
std::string greeting_;
};
</pre>
<p>We left both <code>pre()</code> and <code>post_hello()</code> with the
default implementations; we don't have anything to initialize or
return. The rest is pretty straightforward: we store the greeting
in a member variable and later, when parsing names, use it to
say hello.</p>
<p>An observant reader my ask what happens if the <code>name</code>
element comes before <code>greeting</code>? Don't we need to
make sure <code>greeting_</code> was initialized and report
an error otherwise? The answer is no, we don't have to do
any of this. The <code>hello_pskel</code> parser skeleton
performs validation of XML according to the schema from which
it was generated. As a result, it will check the order
of the <code>greeting</code> and <code>name</code> elements
and report an error if it is violated.</p>
<p>Now it is time to put this parser implementation to work:</p>
<pre class="c++">
using namespace std;
int
main (int argc, char* argv[])
{
try
{
// Construct the parser.
//
xml_schema::string_pimpl string_p;
hello_pimpl hello_p;
hello_p.greeting_parser (string_p);
hello_p.name_parser (string_p);
// Parse the XML instance.
//
xml_schema::document_pimpl doc_p (hello_p, "hello");
hello_p.pre ();
doc_p.parse (argv[1]);
hello_p.post_hello ();
}
catch (const xml_schema::parser_exception& e)
{
cerr << argv[1] << ":" << e.line () << ":" << e.column ()
<< ": " << e.text () << endl;
return 1;
}
}
</pre>
<p>The first part of this code snippet instantiates individual parsers
and assembles them into a complete vocabulary parser.
<code>xml_schema::string_pimpl</code> is an implementation of a parser
for built-in XML Schema type <code>string</code>. It is provided by
the XSD/e runtime along with parsers for other built-in types (for
more information on the built-in parsers see <a href="#6">Chapter 6,
"Built-In XML Schema Type Parsers"</a>). We use <code>string_pimpl</code>
to parse the <code>greeting</code> and <code>name</code> elements as
indicated by the calls to <code>greeting_parser()</code> and
<code>name_parser()</code>.
</p>
<p>Then we instantiate a document parser (<code>doc_p</code>). The
first argument to its constructor is the parser for
the root element (<code>hello_p</code> in our case). The
second argument is the root element name.
</p>
<p>The final piece is the calls to <code>pre()</code>, <code>parse()</code>,
and <code>post_hello()</code>. The call to <code>parse()</code>
perform the actual XML parsing while the calls to <code>pre()</code> and
<code>post_hello()</code> make sure that the parser for the root
element can perform proper initialization and cleanup.</p>
<p>While our parser implementation and test driver are pretty small and
easy to write by hand, for bigger XML vocabularies it can be a
substantial effort. To help with this task XSD/e can automatically
generate sample parser implementations and a test driver from your
schemas. You can request the generation of a sample implementation with
empty function bodies by specifying the <code>--generate-noop-impl</code>
option. Or you can generate a sample implementation that prints the
data store in XML by using the <code>--generate-print-impl</code>
option. To request the generation of a test driver you can use the
<code>--generate-test-driver</code> option. For more information
on these options refer to the
<a href="http://www.codesynthesis.com/projects/xsde/documentation/xsde.xhtml">XSD/e
Compiler Command Line Manual</a>. The <code>'generated'</code> example
in the XSD/e distribution shows the sample implementation generation
feature in action.</p>
<h2><a name="2.4">2.4 Compiling and Running</a></h2>
<p>After saving all the parts from the previous section in
<code>driver.cxx</code>, we are ready to compile our first
application and run it on the test XML document. On UNIX
this can be done with the following commands:
</p>
<pre class="terminal">
$ c++ -I.../libxsde -c driver.cxx hello-pskel.cxx
$ c++ -o driver driver.o hello-pskel.o .../libxsde/xsde/libxsde.a
$ ./driver hello.xml
Hello, sun!
Hello, moon!
Hello, world!
</pre>
<p>Here <code>.../libxsde</code> represents the path to the
<code>libxsde</code> directory in the XSD/e distribution.
We can also test the error handling. To test XML well-formedness
checking, we can try to parse <code>hello-pskel.hxx</code>:</p>
<pre class="terminal">
$ ./driver hello-pskel.hxx
hello-pskel.hxx:1:0: not well-formed (invalid token)
</pre>
<p>We can also try to parse a valid XML but not from our
vocabulary, for example <code>hello.xsd</code>:</p>
<pre class="terminal">
$ ./driver hello.xsd
hello.xsd:2:57: unexpected element encountered
</pre>
<!-- Chapater 3 -->
<h1><a name="3">3 Parser Skeletons</a></h1>
<p>As we have seen in the previous chapter, the XSD/e compiler generates
a parser skeleton class for each type defined in XML Schema. In
this chapter we will take a closer look at different functions
that comprise a parser skeleton as well as the way to connect
our implementations of these parser skeletons to create a complete
parser.</p>
<p>In this and subsequent chapters we will use the following schema
that describes a collection of person records. We save it in
<code>people.xsd</code>:</p>
<pre class="xml">
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:simpleType name="gender">
<xs:restriction base="xs:string">
<xs:enumeration value="male"/>
<xs:enumeration value="female"/>
</xs:restriction>
</xs:simpleType>
<xs:complexType name="person">
<xs:sequence>
<xs:element name="first-name" type="xs:string"/>
<xs:element name="last-name" type="xs:string"/>
<xs:element name="gender" type="gender"/>
<xs:element name="age" type="xs:short"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="people">
<xs:sequence>
<xs:element name="person" type="person" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
<xs:element name="people" type="people"/>
</xs:schema>
</pre>
<p>A sample XML instance to go along with this schema is saved
in <code>people.xml</code>:</p>
<pre class="xml">
<?xml version="1.0"?>
<people>
<person>
<first-name>John</first-name>
<last-name>Doe</last-name>
<gender>male</gender>
<age>32</age>
</person>
<person>
<first-name>Jane</first-name>
<last-name>Doe</last-name>
<gender>female</gender>
<age>28</age>
</person>
</people>
</pre>
<p>Compiling <code>people.xsd</code> with the XSD/e compiler results
in three parser skeletons being generated: <code>gender_pskel</code>,
<code>person_pskel</code>, and <code>people_pskel</code>. We are going
to examine and implement each of them in the subsequent sections.</p>
<h2><a name="3.1">3.1 Implementing the Gender Parser</a></h2>
<p>The generated <code>gender_pskel</code> parser skeleton looks like
this:</p>
<pre class="c++">
class gender_pskel: public xml_schema::string_pskel
{
public:
gender_pskel (xml_schema::string_pskel* base_impl);
// Parser callbacks. Override them in your implementation.
//
virtual void
pre ();
virtual void
post_gender ();
};
</pre>
<p>Notice that <code>gender_pskel</code> inherits from
<code>xml_schema::string_pskel</code> which is a parser skeleton
for built-in XML Schema type <code>string</code> and is
predefined in the XSD/e runtime library. This is an example
of the general rule that parser skeletons follow: if a type
in XML Schema inherits from another then there will be an
equivalent inheritance between the corresponding parser
skeleton classes. The <code>gender_pskel</code> class also
declares a constructor which expects a pointer to the base
parser skeleton. We will discuss the purpose of this
constructor shortly.</p>
<p>The <code>pre()</code> and <code>post_gender()</code> callbacks
should look familiar from the previous chapter. Let's now
implement the parser. Our implementation will simply print
the gender to <code>cout</code>:</p>
<pre class="c++">
class gender_pimpl: public gender_pskel
{
public:
gender_pimpl ()
: gender_pskel (&base_impl_)
{
}
virtual void
post_gender ()
{
std::string s = post_string ();
cout << "gender: " << s << endl;
}
private:
xml_schema::string_pimpl base_impl_;
};
</pre>
<p>While the code is quite short, there is a lot going on. First,
notice that we define a member variable <code>base_impl_</code>
of type <code>xml_schema::string_pimpl</code> and then pass
it to the <code>gender_pskel</code>'s constructor. We have
encountered <code>xml_schema::string_pimpl</code> already; it is an
implementation of the <code>xml_schema::string_pskel</code> parser
skeleton for built-in XML Schema type <code>string</code>. By
passing <code>base_impl_</code> to the <code>gender_pskel</code>'s
constructor we provide an implementation for the part of the
parser skeleton that is inherited from <code>string_pskel</code>.</p>
<p>This is another common theme in the C++/Parser programming model:
reusing implementations of the base parsers in the derived ones.
In our case, <code>string_pimpl</code> will do all the dirty work
of extracting the data and we can just get it at the end with the
call to <code>post_string()</code>. For more information on parser
implementation reuse refer to <a href="#5.6">Section 5.6,
"Parser Reuse"</a>.</p>
<p>In case you are curious, here are the definitions for
<code>xml_schema::string_pskel</code> and
<code>xml_schema::string_pimpl</code>:</p>
<pre class="c++">
namespace xml_schema
{
class string_pskel: public parser_simple_content
{
public:
virtual std::string
post_string () = 0;
};
class string_pimpl: public string_pskel
{
public:
virtual void
_pre ();
virtual void
_characters (const xml_schema::ro_string&);
virtual std::string
post_string ();
protected:
std::string str_;
};
}
</pre>
<p>There are three new pieces in this code that we haven't seen yet.
Those are the <code>parser_simple_content</code> class and
the <code>_pre()</code> and <code>_characters()</code> functions.
The <code>parser_simple_content</code> class is defined in the XSD/e
runtime and is a base class for all parser skeletons that conform
to the simple content model in XML Schema. Types with the
simple content model cannot have nested elements—only text
and attributes. There is also the <code>parser_complex_content</code>
class which corresponds to the complex content mode (types with
nested elements, for example, <code>person</code> from
<code>people.xsd</code>).</p>
<p>The <code>_pre()</code> function is a parser callback. Remember we
talked about the <code>pre()</code> and <code>post_*()</code> callbacks
in the previous chapter? There are actually two more callbacks
with similar roles: <code>_pre()</code> and <code>_post ()</code>.
As a result, each parser skeleton has four special callbacks:</p>
<pre class="c++">
virtual void
pre ();
virtual void
_pre ();
virtual void
_post ();
virtual void
post_name ();
</pre>
<p><code>pre()</code> and <code>_pre()</code> are initialization
callbacks. They get called in that order before a new instance of the type
is about to be parsed. The difference between <code>pre()</code> and
<code>_pre()</code> is conventional: <code>pre()</code> can
be completely overridden by a derived parser. The derived
parser can also override <code>_pre()</code> but has to always call
the original version. This allows you to partition initialization
into customizable and required parts.</p>
<p>Similarly, <code>_post()</code> and <code>post_name()</code> are
finalization callbacks with exactly the same semantics:
<code>post_name()</code> can be completely overridden by the derived
parser while the original <code>_post()</code> should always be called.
</p>
<p>The final bit we need to discuss in this section is the
<code>_characters()</code> function. As you might have guessed, it
is also a callback. A low-level one that delivers raw character content
for the type being parsed. You will seldom need to use this callback
directly. Using implementations for the built-in parsers provided by
the XSD/e runtime is usually a simpler and more convenient
alternative.</p>
<p>At this point you might be wondering why some <code>post_*()</code>
callbacks, for example <code>post_string()</code>, return some data
while others, for example <code>post_gender()</code>, have
<code>void</code> as a return type. This is a valid concern
and it will be addressed in the next chapter.</p>
<h2><a name="3.2">3.2 Implementing the Person Parser</a></h2>
<p>The generated <code>person_pskel</code> parser skeleton looks like
this:</p>
<pre class="c++">
class person_pskel: public xml_schema::parser_complex_content
{
public:
// Parser callbacks. Override them in your implementation.
//
virtual void
pre ();
virtual void
first_name (const std::string&);
virtual void
last_name (const std::string&);
virtual void
gender ();
virtual void
age (short);
virtual void
post_person ();
// Parser construction API.
//
void
first_name_parser (xml_schema::string_pskel&);
void
last_name_parser (xml_schema::string_pskel&);
void
gender_parser (gender_pskel&);
void
age_parser (xml_schema::short_pskel&);
void
parsers (xml_schema::string_pskel& /* first-name */,
xml_schema::string_pskel& /* last-name */,
gender_pskel& /* gender */,
xml_schema::short_pskel& /* age */);
};
</pre>
<p>As you can see, we have a parser callback for each of the nested
elements found in the <code>person</code> XML Schema type.
The implementation of this parser is straightforward:</p>
<pre class="c++">
class person_pimpl: public person_pskel
{
public:
virtual void
first_name (const std::string& n)
{
cout << "first: " << f << endl;
}
virtual void
last_name (const std::string& l)
{
cout << "last: " << l << endl;
}
virtual void
age (short a)
{
cout << "age: " << a << endl;
}
};
</pre>
<p>Notice that we didn't override the <code>gender()</code> callback
because all the printing is done by <code>gender_pimpl</code>.</p>
<h2><a name="3.3">3.3 Implementing the People Parser</a></h2>
<p>The generated <code>people_pskel</code> parser skeleton looks like
this:</p>
<pre class="c++">
class people_pskel: public xml_schema::parser_complex_content
{
public:
// Parser callbacks. Override them in your implementation.
//
virtual void
pre ();
virtual void
person ();
virtual void
post_people ();
// Parser construction API.
//
void
person_parser (person_pskel&);
void
parsers (person_pskel& /* person */);
};
</pre>
<p>The <code>person()</code> callback will be called after parsing each
<code>person</code> element. While <code>person_pimpl</code> does
all the printing, one useful thing we can do in this callback is to
print an extra newline after each person record so that our
output is more readable:</p>
<pre class="c++">
class people_pimpl: public people_pskel
{
public:
virtual void
person ()
{
cout << endl;
}
};
</pre>
<p>Now it is time to put everything together.</p>
<h2><a name="3.4">3.4 Connecting the Parsers Together</a></h2>
<p>At this point we have all the individual parsers implemented
and can proceed to assemble them into a complete parser
for our XML vocabulary. The first step is to instantiate
all the individual parsers that we will need:</p>
<pre class="c++">
xml_schema::short_pimpl short_p;
xml_schema::string_pimpl string_p;
gender_pimpl gender_p;
person_pimpl person_p;
people_pimpl people_p;
</pre>
<p>Notice that our schema uses two built-in XML Schema types:
<code>string</code> for the <code>first-name</code> and
<code>last-name</code> elements as well as <code>short</code>
for <code>age</code>. We will use predefined parsers that
come with the XSD/e runtime to handle these types. The next
step is to connect all the individual parsers. We do this
with the help of functions defined in the parser
skeletons and marked with the "Parser Construction API"
comment. One way to do it is to connect each individual
parser by calling the <code>*_parser()</code> functions:</p>
<pre class="c++">
person_p.first_name_parser (string_p);
person_p.last_name_parser (string_p);
person_p.gender_parser (gender_p);
person_p.age_parser (short_p);
people_p.person_parser (person_p);
</pre>
<p>You might be wondering what happens if you do not provide
a parser by not calling one of the <code>*_parser()</code> functions.
In that case the corresponding XML content will be skipped,
including validation. This is an efficient way to ignore parts
of the document that you are not interested in.</p>
<p>An alternative, shorter, way to connect the parsers is by using
the <code>parsers()</code> functions which connects all the parsers
for a given type at once:</p>
<pre class="c++">
person_p.parsers (string_p, string_p, gender_p, short_p);
people_p.parsers (person_p);
</pre>
<p>The following figure illustrates the resulting connections. Notice
the correspondence between return types of the <code>post_*()</code>
functions and argument types of element callbacks that are connected
by the arrows.</p>
<!-- align=center is needed for html2ps -->
<div class="img" align="center"><img src="figure-1.png"/></div>
<p>The last step is the construction of the document parser and
invocation of the complete parser on our sample XML instance:</p>
<pre class="c++">
xml_schema::document_pimpl doc_p (people_p, "people");
people_p.pre ();
doc_p.parse ("people.xml");
people_p.post_people ();
</pre>
<p>Let's consider <code>xml_schema::document_pimpl</code> in
more detail. While the exact definition of this class
varies depending on the mapping configuration, here is
the part relevant to our example:</p>
<pre class="c++">
namespace xml_schema
{
class document_pimpl
{
public:
document_pimpl (xml_schema::parser_base&,
const std::string& root_element_name);
document_pimpl (xml_schema::parser_base&,
const std::string& root_element_namespace,
const std::string& root_element_name);
void
parse (const std::string& file);
void
parse (std::istream&);
void
parse (const void* data, size_t size, bool last);
};
}
</pre>
<p><code>xml_schema::document_pimpl</code> is a root parser for
the vocabulary. The first argument to its constructors is the
parser for the type of the root element (<code>people_pimpl</code>
in our case). Because a type parser is only concerned with
the element's content and not with the element's name, we need
to specify the root element name somewhere. That's
what is passed as the second and third arguments to the
<code>document_pimpl</code>'s constructors.</p>
<p>There are also three overloaded <code>parse()</code> function
defined in the <code>document_pimpl</code> class. The first version
parses a local file identified by a name. The second version
reads the data from an input stream. The last version allows
you to parse the data directly from a buffer, one chunk at a
time. You can call this function multiple times with the final
call having the <code>last</code> argument set to true. For more
information on the <code>xml_schema::document_pimpl</code> class
refer to <a href="#7">Chapter 7, "Document Parser and Error
Handling"</a>.</p>
<p>Let's now consider a step-by-step list of actions that happen
as we parse through <code>people.xml</code>. The content of
<code>people.xml</code> is repeated below for convenience.</p>
<pre class="xml">
<?xml version="1.0"?>
<people>
<person>
<first-name>John</first-name>
<last-name>Doe</last-name>
<gender>male</gender>
<age>32</age>
</person>
<person>
<first-name>Jane</first-name>
<last-name>Doe</last-name>
<gender>female</gender>
<age>28</age>
</person>
</people>
</pre>
<ol class="steps">
<li><code>people_p.pre()</code> is called from
<code>main()</code>. We did not provide any implementation
for this callback so this call is a no-op.</li>
<li><code>doc_p.parse("people.xml")</code> is called from
<code>main()</code>. The parser opens the file and starts
parsing its content.</li>
<li>The parser encounters the root element. <code>doc_p</code>
verifies that the root element is correct and calls
<code>_pre()</code> on <code>people_p</code> which is also
a no-op. Parsing is now delegated to <code>people_p</code>.</li>
<li>The parser encounters the <code>person</code> element.
<code>people_p</code> determines that <code>person_p</code>
is responsible for parsing this element. <code>pre()</code>
and <code>_pre()</code> callbacks are called on <code>person_p</code>.
Parsing is now delegated to <code>person_p</code>.</li>
<li>The parser encounters the <code>first-name</code> element.
<code>person_p</code> determines that <code>string_p</code>
is responsible for parsing this element. <code>pre()</code>
and <code>_pre()</code> callbacks are called on <code>string_p</code>.
Parsing is now delegated to <code>string_p</code>.</li>
<li>The parser encounters character content consisting of
<code>"John"</code>. The <code>_characters()</code> callback is
called on <code>string_p</code>.</li>
<li>The parser encounters the end of <code>first-name</code>
element. The <code>_post()</code> and <code>post_string()</code>
callbacks are called on <code>string_p</code>. The
<code>first_name()</code> callback is called on <code>person_p</code>
with the return value of <code>post_string()</code>. The
<code>first_name()</code> implementation prints
<code>"first: John"</code> to <code>cout</code>.
Parsing is now returned to <code>person_p</code>.</li>
<li>Steps analogous to 5-7 are performed for the <code>last-name</code>,
<code>gender</code>, and <code>age</code> elements.</li>
<li>The parser encounters the end of <code>person</code>
element. The <code>_post()</code> and <code>post_person()</code>
callbacks are called on <code>person_p</code>. The
<code>person()</code> callback is called on <code>people_p</code>.
The <code>person()</code> implementation prints a new line
to <code>cout</code>. Parsing is now returned to
<code>people_p</code>.</li>
<li>Steps 4-9 are performed for the second <code>person</code>
element.</li>
<li>The parser encounters the end of <code>people</code>
element. The <code>_post()</code> callback is called on
<code>people_p</code>. The <code>doc_p.parse("people.xml")</code>
call returns to <code>main()</code>.</li>
<li><code>people_p.post_people()</code> is called from
<code>main()</code> which is a no-op.</li>
</ol>
<!-- Chpater 4 -->
<h1><a name="4">4 Type Maps</a></h1>
<p>There are many useful things you can do inside parser callbacks as they
are right now. There are, however, times when you want to propagate
some information from one parser to another or to the caller of the
parser. One common task that would greatly benefit from such a
possibility is building a tree-like in-memory object model of the
data stored in XML. During execution, each individual sub-parser
would create a sub-tree and return it to its <em>parent</em> parser
which can then incorporate this sub-tree into the whole tree.</p>
<p>In this chapter we will discuss the mechanisms offered by the
C++/Parser mapping for returning information from individual
parsers and see how to use them to build an object model
of our people vocabulary.</p>
<h2><a name="4.1">4.1 Object Model</a></h2>
<p>An object model for our person record example could
look like this (saved in the <code>people.hxx</code> file):</p>
<pre class="c++">
#include <string>
#include <vector>
enum gender
{
male,
female
};
class person
{
public:
person (const std::string& first,
const std::string& last,
::gender gender,
short age)
: first_ (first), last_ (last),
gender_ (gender), age_ (age)
{
}
const std::string&
first () const
{
return first_;
}
const std::string&
last () const
{
return last_;
}
::gender
gender () const
{
return gender_;
}
short
age () const
{
return age_;
}
private:
std::string first_;
std::string last_;
::gender gender_;
short age_;
};
typedef std::vector<person> people;
</pre>
<p>While it is clear which parser is responsible for which part of
the object model, it is not exactly clear how, for
example, <code>gender_pimpl</code> will deliver <code>gender</code>
to <code>person_pimpl</code>. You might have noticed that
<code>string_pimpl</code> manages to deliver its value to the
<code>first_name()</code> callback of <code>person_pimpl</code>. Let's
see how we can utilize the same mechanism to propagate our
own data.</p>
<p>There is a way to tell the XSD/e compiler that you want to
exchange data between parsers. More precisely, for each
type defined in XML Schema, you can tell the compiler two things.
First, the return type of the <code>post_*()</code> callback
in the parser skeleton generated for this type. And, second,
the argument type for callbacks corresponding to elements and
attributes of this type. For example, for XML Schema type
<code>gender</code> we can specify the return type for
<code>post_gender()</code> in the <code>gender_pskel</code>
skeleton and the argument type for the <code>gender()</code> callback
in the <code>person_pskel</code> skeleton. As you might have guessed,
the generated code will then pass the return value from the
<code>post_*()</code> callback as an argument to the element or
attribute callback.</p>
<p>The way to tell the XSD/e compiler about these XML Schema to
C++ mappings is with type map files. Here is a simple type
map for the <code>gender</code> type from the previous paragraph.</p>
<pre class="type-map">
include "people.hxx";
gender ::gender ::gender;
</pre>
<p>The first line indicates that the generated code must include
<code>people.hxx</code> in order to get the definition for the
<code>gender</code> type. The second line specifies that both
argument and return types for the <code>gender</code>
XML Schema type should be the <code>::gender</code> C++ enum
(we use fully-qualified C++ names to avoid name clashes).
The next section will describe the type map format in detail.
We save this type map in <code>people.map</code> and
then translate our schemas with the <code>--type-map</code>
option to let the XSD/e compiler know about our type map:</p>
<pre class="terminal">
$ xsde cxx-parser --type-map people.map people.xsd
</pre>
<p>If we now look at the generated <code>people-pskel.hxx</code>,
we will see the following changes in the <code>gender_pskel</code> and
<code>person_pskel</code> skeletons:</p>
<pre class="c++">
#include "people.hxx"
class gender_pskel: public xml_schema::string_pskel
{
virtual ::gender
post_gender () = 0;
...
};
class person_pskel: public xml_schema::parser_complex_content
{
virtual void
gender (::gender);
...
};
</pre>
<p>Notice that <code>#include "people.hxx"</code> was added to
the generated header file from the type map to provide the
definition for the <code>gender</code> enum.</p>
<h2><a name="4.2">4.2 Type Map File Format</a></h2>
<p>Type map files are used to define a mapping between XML Schema
and C++ types. The compiler uses this information
to determine return types of <code>post_*()</code>
callbacks in parser skeletons corresponding to XML Schema
types as well as argument types for callbacks corresponding
to elements and attributes of these types.</p>
<p>The compiler has a set of predefined mapping rules that map the
built-in XML Schema types to suitable C++ types (discussed
below) and all other types to <code>void</code>.
By providing your own type maps you can override these predefined
rules. The format of the type map file is presented below:
</p>
<pre class="type-map">
namespace <schema-namespace> [<cxx-namespace>]
{
(include <file-name>;)*
([type] <schema-type> <cxx-ret-type> [<cxx-arg-type>];)*
}
</pre>
<p>Both <code><i><schema-namespace></i></code> and
<code><i><schema-type></i></code> are regex patterns while
<code><i><cxx-namespace></i></code>,
<code><i><cxx-ret-type></i></code>, and
<code><i><cxx-arg-type></i></code> are regex pattern
substitutions. All names can be optionally enclosed in
<code>" "</code>, for example, to include white-spaces.</p>
<p><code><i><schema-namespace></i></code> determines XML
Schema namespace. Optional <code><i><cxx-namespace></i></code>
is prefixed to every C++ type name in this namespace declaration.
<code><i><cxx-ret-type></i></code> is a C++ type name that is
used as a return type for the <code>post_*()</code> callback.
Optional <code><i><cxx-arg-type></i></code> is an argument
type for callbacks corresponding to elements and attributes
of this type. If <code><i><cxx-arg-type></i></code> is not
specified, it defaults to <code><i><cxx-ret-type></i></code>
if <code><i><cxx-ret-type></i></code> ends with <code>*</code> or
<code>&</code> (that is, it is a pointer or a reference) and
<code>const <i><cxx-ret-type></i>&</code>
otherwise.
<code><i><file-name></i></code> is a file name either in the
<code>" "</code> or <code>< ></code> format
and is added with the <code>#include</code> directive to
the generated code.</p>
<p>The <code><b>#</b></code> character starts a comment that ends
with a new line or end of file. To specify a name that contains
<code><b>#</b></code> enclose it in <code><b>" "</b></code>.
For example:</p>
<pre>
namespace http://www.example.com/xmlns/my my
{
include "my.hxx";
# Pass apples by value.
#
apple apple;
# Pass oranges as pointers.
#
orange orange_t*;
}
</pre>
<p>In the example above, for the
<code>http://www.example.com/xmlns/my#orange</code>
XML Schema type, the <code>my::orange_t*</code> C++ type will
be used as both return and argument types.</p>
<p>Several namespace declarations can be specified in a single
file. The namespace declaration can also be completely
omitted to map types in a schema without a namespace. For
instance:</p>
<pre class="type-map">
include "my.hxx";
apple apple;
namespace http://www.example.com/xmlns/my
{
orange "const orange_t*";
}
</pre>
<p>The compiler has a number of predefined mapping rules for
the built-in XML Schema types which can be presented as the
following map files:</p>
<pre class="type-map">
namespace http://www.w3.org/2001/XMLSchema
{
boolean bool bool;
byte "signed char" "signed char";
unsignedByte "unsigned char" "unsigned char";
short short short;
unsignedShort "unsigned short" "unsigned short";
int int int;
unsignedInt "unsigned int" "unsigned int";
long "long long" "long long";
unsignedLong "unsigned long long" "unsigned long long";
integer long long;
negativeInteger long long;
nonPositiveInteger long long;
positiveInteger "unsigned long" "unsigned long";
nonNegativeInteger "unsigned long" "unsigned long";
float float float;
double double double;
decimal double double;
NMTOKENS xml_schema::string_sequence*;
IDREFS xml_schema::string_sequence*;
base64Binary xml_schema::buffer*;
hexBinary xml_schema::buffer*;
date xml_schema::date;
dateTime xml_schema::date_time;
duration xml_schema::duration;
gDay xml_schema::gday;
gMonth xml_schema::gmonth;
gMonthDay xml_schema::gmonth_day;
gYear xml_schema::gyear;
gYearMonth xml_schema::gyear_month;
time xml_schema::time;
}
</pre>
<p>If STL is enabled (<a href="#5.1">Section 5.1, "Standard Template
Library"</a>), the following mapping is used for the string-based
XML Schema built-in types:</p>
<pre class="type-map">
namespace http://www.w3.org/2001/XMLSchema
{
include <string>;
anySimpleType std::string;
string std::string;
normalizedString std::string;
token std::string;
Name std::string;
NMTOKEN std::string;
NCName std::string;
ID std::string;
IDREF std::string;
language std::string;
anyURI std::string;
QName xml_schema::qname;
}
</pre>
<p>Otherwise, a C string-based mapping is used:</p>
<pre class="type-map">
namespace http://www.w3.org/2001/XMLSchema
{
anySimpleType char*;
string char*;
normalizedString char*;
token char*;
Name char*;
NMTOKEN char*;
NCName char*;
ID char*;
IDREF char*;
language char*;
anyURI char*;
QName xml_schema::qname*;
}
</pre>
<p>For more information about the mapping of the built-in XML Schema types
to C++ types refer to <a href="#6">Chapter 6, "Built-In XML Schema Type
Parsers"</a>. The last predefined rule maps anything that wasn't
mapped by previous rules to <code>void</code>:</p>
<pre class="type-map">
namespace .*
{
.* void void;
}
</pre>
<p>When you provide your own type maps with the
<code>--type-map</code> option, they are evaluated first. This
allows you to selectively override any
of the predefined rules. Note also that if you change the mapping
of a built-in XML Schema type then it becomes your responsibility
to provide the corresponding parser skeleton and implementation
in the <code>xml_schema</code> namespace. You can include the
custom definitions into the generated header file using the
<code>--hxx-prologue-*</code> options.</p>
<h2><a name="4.3">4.3 Parser Implementations</a></h2>
<p>With the knowledge from the previous section, we can proceed
with creating a type map that maps types in the <code>people.xsd</code>
schema to our object model classes in
<code>people.hxx</code>. In fact, we already have the beginning
of our type map file in <code>people.map</code>. Let's extend
it with the rest of the types:</p>
<pre class="type-map">
include "people.hxx";
gender ::gender ::gender;
person ::person;
people ::people;
</pre>
<p>A few things to note about this type map. We did not
provide the argument types for <code>person</code> and
<code>people</code> because the default constant reference is
exactly what we need. We also did not provide any mappings
for built-in XML Schema types <code>string</code> and
<code>short</code> because they are handled by the predefined
rules and we are happy with the result. Note also that
all C++ types are fully qualified. This is done to avoid
potential name conflicts in the generated code. Now we can
recompile our schema and move on to implementing the parsers:</p>
<pre class="terminal">
$ xsde cxx-parser --type-map people.map people.xsd
</pre>
<p>Here is the implementation of our three parsers in full. One
way to save typing when implementing your own parsers is
to open the generated code and copy the signatures of parser
callbacks into your code. Or you could always auto generate the
sample implementations and fill them with your code.</p>
<pre class="c++">
#include "people-pskel.hxx"
class gender_pimpl: public gender_pskel
{
public:
gender_pimpl ()
: gender_pskel (&base_impl_)
{
}
virtual ::gender
post_gender ()
{
return post_string () == "male" ? male : female;
}
private:
xml_schema::string_pimpl base_impl_;
};
class person_pimpl: public person_pskel
{
public:
virtual void
first_name (const std::string& f)
{
first_ = f;
}
virtual void
last_name (const std::string& l)
{
last_ = l;
}
virtual void
gender (::gender g)
{
gender_ = g;
}
virtual void
age (short a)
{
age_ = a;
}
virtual ::person
post_person ()
{
return ::person (first_, last_, gender_, age_);
}
private:
std::string first_;
std::string last_;
::gender gender_;
short age_;
};
class people_pimpl: public people_pskel
{
public:
virtual void
person (const ::person& p)
{
people_.push_back (p);
}
virtual ::people
post_people ()
{
::people r;
r.swap (people_);
return r;
}
private:
::people people_;
};
</pre>
<p>This code fragment should look familiar by now. Just note that
all the <code>post_*()</code> callbacks now have return types instead
of <code>void</code>. Here is the implementation of the test
driver for this example:</p>
<pre class="c++">
#include <iostream>
using namespace std;
int
main (int argc, char* argv[])
{
// Construct the parser.
//
xml_schema::short_pimpl short_p;
xml_schema::string_pimpl string_p;
gender_pimpl gender_p;
person_pimpl person_p;
people_pimpl people_p;
person_p.parsers (string_p, string_p, gender_p, short_p);
people_p.parsers (person_p);
// Parse the document to obtain the object model.
//
xml_schema::document_pimpl doc_p (people_p, "people");
people_p.pre ();
doc_p.parse (argv[1]);
people ppl = people_p.post_people ();
// Print the object model.
//
for (people::iterator i (ppl.begin ()); i != ppl.end (); ++i)
{
cout << "first: " << i->first () << endl
<< "last: " << i->last () << endl
<< "gender: " << (i->gender () == male ? "male" : "female") << endl
<< "age: " << i->age () << endl
<< endl;
}
}
</pre>
<p>The parser creation and assembly part is exactly the same as in
the previous chapter. The parsing part is a bit different:
<code>post_people()</code> now has a return value which is the
complete object model. We store it in the
<code>ppl</code> variable. The last bit of the code simply iterates
over the <code>people</code> vector and prints the information
for each person. We save the last two code fragments to
<code>driver.cxx</code> and proceed to compile and test
our new application:</p>
<pre class="terminal">
$ c++ -I.../libxsde -c driver.cxx people-pskel.cxx
$ c++ -o driver driver.o people-pskel.o .../libxsde/xsde/libxsde.a
$ ./driver people.xml
first: John
last: Doe
gender: male
age: 32
first: Jane
last: Doe
gender: female
age: 28
</pre>
<!-- Mapping Configuration -->
<h1><a name="5">5 Mapping Configuration</a></h1>
<p>The Embedded C++/Parser mapping has a number of configuration
parameters that determine the overall properties and behavior
of the generated code, such as the use of Standard Template
Library (STL), Input/Output Stream Library (iostream), C++
exceptions, XML Schema validation, 64-bit integer types, parser
implementation reuse styles, and support for XML Schema polymorphism.
Previous chapters assumed that the use of STL, iostream, C++
exceptions, and XML Schema validation were enabled.
This chapter will discuss the changes in the Embedded C++/Parser
programming model that result from the changes to these configuration
parameters. A complete example that uses the minimal mapping
configuration is presented at the end of this chapter.</p>
<p>In order to enable or disable a particular feature, the corresponding
configuration parameter should be set accordingly in the XSD/e runtime
library as well as specified during schema compilation with the XSD/e
command line options as described in the
<a href="http://www.codesynthesis.com/projects/xsde/documentation/xsde.xhtml">XSD/e
Compiler Command Line Manual</a>.
</p>
<p>While the XML documents can use various encodings, the Embedded
C++/Parser mapping always delivers character data to the application
in the same encoding. The application encoding can either be UTF-8
(default) or ISO-8859-1. To select a particular encoding, configure
the XSD/e runtime library accordingly and pass the <code>--char-encoding</code>
option to the XSD/e compiler when translating your schemas.</p>
<p>When using ISO-8859-1 as the application encoding, XML documents
being parsed may contain characters with Unicode values greater
than 0xFF which are unrepresentable in the ISO-8859-1 encoding.
By default, in such situations parsing will terminate with
an error. However, you can suppress the error by providing a
replacement character that should be used instead of
unrepresentable characters, for example:</p>
<pre class="c++">
xml_schema::iso8859_1::unrep_char ('?');
</pre>
<p>To revert to the default behavior, set the replacement character
to <code>'\0'</code>.</p>
<p>The Embedded C++/Parser mapping includes built-in support for XML
documents encoded in UTF-8, UTF-16, ISO-8859-1, and US-ASCII.
Other encodings can be supported by providing application-specific
decoder functions.</p>
<h2><a name="5.1">5.1 Standard Template Library</a></h2>
<p>To disable the use of STL you will need to configure the XSD/e
runtime without support for STL as well as pass the
<code>--no-stl</code> option to the XSD/e compiler when
translating your schemas. When STL is disabled, all string-based
XML Schema types are mapped to C-style <code>char*</code> instead
of <code>std::string</code>, as described in
<a href="#4.2">Section 4.2, "Type Map File Format"</a>. The
following code fragment shows changes in the
signatures of <code>first_name()</code> and <code>last_name()</code>
callbacks from the person record example.</p>
<pre class="c++">
class person_pskel
{
public:
virtual void
first_name (char*);
virtual void
last_name (char*);
...
};
</pre>
<p>Note that it is your responsibility to eventually release the memory
associated with these strings using operator <code>delete[]</code>.
</p>
<h2><a name="5.2">5.2 Input/Output Stream Library</a></h2>
<p>To disable the use of iostream you will need to configure the
XSD/e runtime library without support for iostream as well as
pass the <code>--no-iostream</code> option to the XSD/e compiler
when translating your schemas. When iostream is disabled, the
following two <code>parse()</code> functions in the
<code>xml_schema::document_pimpl</code> class become unavailable:</p>
<pre class="c++">
void
parse (const std::string& file);
void
parse (std::istream&);
</pre>
<p>Leaving you with only one function in the form:</p>
<pre class="c++">
void
parse (const void* data, size_t size, bool last);
</pre>
<p>See <a href="#7.1">Section 7.1, "Document Parser"</a>
for more information on the semantics of these functions.</p>
<h2><a name="5.3">5.3 C++ Exceptions</a></h2>
<p>To disable the use of C++ exceptions, you will need to configure
the XSD/e runtime without support for exceptions as well as pass
the <code>--no-exceptions</code> option to the XSD/e compiler
when translating your schemas. When C++ exceptions are disabled,
the error conditions are indicated with error codes instead of
exceptions, as described in <a href="#7.3">Section 7.3,
"Error Codes"</a>.
</p>
<h2><a name="5.4">5.4 XML Schema Validation</a></h2>
<p>To disable support for XML Schema validation, you will need to
configure the XSD/e runtime accordingly as well as pass
the <code>--suppress-validation</code> option to the XSD/e compiler
when translating your schemas. Disabling XML Schema validation
allows to further increase the parsing performance and
reduce footprint in cases where XML instances are known to be
valid.
</p>
<h2><a name="5.5">5.5 64-bit Integer Type</a></h2>
<p>By default the 64-bit <code>long</code> and <code>unsignedLong</code>
XML Schema built-in types are mapped to the 64-bit <code>long long</code>
and <code>unsigned long long</code> fundamental C++ types. To
disable the use of these types in the mapping you will need to
configure the XSD/e runtime accordingly as well as pass
the <code>--no-long-long</code> option to the XSD/e compiler
when translating your schemas. When the use of 64-bit integral
C++ types is disabled the <code>long</code> and
<code>unsignedLong</code> XML Schema built-in types are mapped
to <code>long</code> and <code>unsigned long</code> fundamental
C++ types.</p>
<h2><a name="5.6">5.6 Parser Reuse</a></h2>
<p>When one type in XML Schema inherits from another, it is
often desirable to be able to reuse the parser implementation
corresponding to the base type in the parser implementation
corresponding to the derived type. XSD/e provides support
for two parser reuse styles: the so-called <em>mixin</em>
(generated when the <code>--reuse-style-mixin</code> option
is specified) and <em>tiein</em> (generated by default) styles.</p>
<p>The compiler can also be instructed not to generate any support
for parser reuse with the <code>--reuse-style-none</code> option.
This is mainly useful to further reduce the generated code size
when your vocabulary does not use inheritance or when you plan
to implement each parser from scratch. Note also that the
XSD/e runtime should be configured in accordance with the
parser reuse style used in the generated code. The remainder
of this section discusses the mixin and tiein parser reuse
styles in more detail.</p>
<p>To provide concrete examples for each reuse style we will use the
following schema fragment:</p>
<pre class="xml">
<xs:complexType name="person">
<xs:sequence>
<xs:element name="first-name" type="xs:string"/>
<xs:element name="last-name" type="xs:string"/>
<xs:element name="age" type="xs:short"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="emplyee">
<complexContent>
<extension base="person">
<xs:sequence>
<xs:element name="position" type="xs:string"/>
<xs:element name="salary" type="xs:unsignedLong"/>
</xs:sequence>
</extension>
</complexContent>
</xs:complexType>
</pre>
<p>The mixin parser reuse style uses the C++ mixin idiom that
relies on multiple and virtual inheritance. Because
virtual inheritance can result in a significant object
code size increase, this reuse style should be considered
when such an overhead is acceptable and/or the vocabulary
consists of only a handful of types. When the mixin reuse
style is used, the generated parser skeletons use virtual
inheritance, for example:</p>
<pre class="c++">
class person_pskel: public virtual parser_complex_content
{
...
};
class employee_pskel: public virtual person_pskel
{
...
};
</pre>
<p>When you implement the base parser you also need to use
virtual inheritance. The derived parser is implemented
by inheriting from both the derived parser skeleton and
the base parser implementation (that is, <em>mixing in</em>
the base parser implementation), for example:</p>
<pre class="c++">
class person_pimpl: public virtual person_pskel
{
...
};
class employee_pimpl: public employee_pskel,
public person_pimpl
{
...
};
</pre>
<p>The tiein parser reuse style uses delegation and normally
results in a significantly smaller object code while being
almost as convenient to use as the mixin style. When the
tiein reuse style is used, the generated derived parser
skeleton declares a constructor which allows you to specify
the implementation of the base parser:</p>
<pre class="c++">
class person_pskel: public parser_complex_content
{
...
};
class employee_pskel: public person_pskel
{
public:
employee_pskel (person_pskel* base_impl)
...
};
</pre>
<p>If you pass the implementation of the base parser to this
constructor then the generated code will transparently
forward all the callbacks corresponding to the base parser
skeleton to this implementation. You can also pass
<code>0</code> to this constructor in which case you will
need to implement the derived parser from scratch. The
following example shows how we could implement the
<code>person</code> and <code>employee</code> parsers
using the tiein style:</p>
<pre class="c++">
class person_pimpl: public person_pskel
{
...
};
class employee_pimpl: public employee_pskel
{
public:
employee_pimpl ()
: employee_pskel (&base_impl_)
{
}
...
private:
person_pimpl base_impl_;
};
</pre>
<p>Note that you cannot use the <em>tied in</em> base parser
instance (<code>base_impl_</code> in the above code) for
parsing anything except the derived type.</p>
<p>The ability to override the base parser callbacks in the
derived parser is also available in the tiein style. For
example, the following code fragment shows how we can
override the <code>age()</code> callback if we didn't
like the implementation provided by the base parser:</p>
<pre class="c++">
class employee_pimpl: public employee_pskel
{
public:
employee_pimpl ()
: employee_pskel (&base_impl_)
{
}
virtual void
age (short a)
{
...
}
...
private:
person_pimpl base_impl_;
};
</pre>
<p>In the above example the <code>age</code> element will be
handled by <code>emplyee_pimpl</code> while the <code>first-name</code>
and <code>last-name</code> callbacks will still go to
<code>base_impl_</code>.</p>
<p>It is also possible to inherit from the base parser implementation
instead of declaring it as a member variable. This can be useful
if you need to access protected members in the base implementation
or need to override a virtual function that is not part of
the parser skeleton interface. Note, however, that in this case
you will need to resolve a number of ambiguities with explicit
qualifications or using-declarations. For example:</p>
<pre class="c++">
class person_pimpl: public person_pskel
{
...
protected:
virtual person*
create ()
{
return new person ();
}
};
class employee_pimpl: public employee_pskel,
public person_pimpl
{
public:
employee_pimpl ()
: employee_pskel (static_cast<person_pimpl*> (this))
{
}
// Resolve ambiguities.
//
using emplyee_pskel::parsers;
...
protected:
virtual employee*
create ()
{
return new employee ();
}
};
</pre>
<h2><a name="5.7">5.7 Support for Polymorphism</a></h2>
<p>By default the XSD/e compiler generates non-polymorphic code. If your
vocabulary uses XML Schema polymorphism in the form of <code>xsi:type</code>
and/or substitution groups, then you will need to configure the XSD/e
runtime with support for polymorphism, compile your schemas with the
<code>--generate-polymorphic</code> option to produce polymorphism-aware
code, as well as pass <code>true</code> as the last argument to the
<code>xml_schema::document_pimpl</code>'s constructors. If some of your
schemas do not require support for polymorphism then you can compile
them with the <code>--runtime-polymorphic</code> option and still
use the XSD/e runtime configured with polymorphism support.
</p>
<p>When using the polymorphism-aware generated code, you can specify
several parsers for a single element by passing a parser map
instead of an individual parser to the parser connection function
for the element. One of the parsers will then be looked up and used
depending on the <code>xsi:type</code> attribute value or an element
name from a substitution group. Consider the following schema as an
example:</p>
<pre class="xml">
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:complexType name="person">
<xs:sequence>
<xs:element name="name" type="xs:string"/>
</xs:sequence>
</xs:complexType>
<!-- substitution group root -->
<xs:element name="person" type="person"/>
<xs:complexType name="superman">
<xs:complexContent>
<xs:extension base="person">
<xs:attribute name="can-fly" type="xs:boolean"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="superman"
type="superman"
substitutionGroup="person"/>
<xs:complexType name="batman">
<xs:complexContent>
<xs:extension base="superman">
<xs:attribute name="wing-span" type="xs:unsignedInt"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="batman"
type="batman"
substitutionGroup="superman"/>
<xs:complexType name="supermen">
<xs:sequence>
<xs:element ref="person" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
<xs:element name="supermen" type="supermen"/>
</xs:schema>
</pre>
<p>Conforming XML documents can use the <code>superman</code>
and <code>batman</code> types in place of the <code>person</code>
type either by specifying the type with the <code>xsi:type</code>
attributes or by using the elements from the substitution
group, for instance:</p>
<pre class="xml">
<supermen xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<person>
<name>John Doe</name>
</person>
<superman can-fly="false">
<name>James "007" Bond</name>
</superman>
<superman can-fly="true" wing-span="10" xsi:type="batman">
<name>Bruce Wayne</name>
</superman>
</supermen>
</pre>
<p>To print the data stored in such XML documents we can implement
the parsers as follows:</p>
<pre class="c++">
class person_pimpl: public person_pskel
{
public:
virtual void
pre ()
{
cout << "starting to parse person" << endl;
}
virtual void
name (const std::string& v)
{
cout << "name: " << v << endl;
}
virtual void
post_person ()
{
cout << "finished parsing person" << endl;
}
};
class superman_pimpl: public superman_pskel
{
public:
superman_pimpl ()
: superman_pskel (&base_impl_)
{
}
virtual void
pre ()
{
cout << "starting to parse superman" << endl;
}
virtual void
can_fly (bool v)
{
cout << "can-fly: " << v << endl;
}
virtual void
post_person ()
{
post_superman ();
}
virtual void
post_superman ()
{
cout << "finished parsing superman" << endl
}
private:
person_pimpl base_impl_;
};
class batman_pimpl: public batman_pskel
{
public:
batman_pimpl ()
: batman_pskel (&base_impl_)
{
}
virtual void
pre ()
{
cout << "starting to parse batman" << endl;
}
virtual void
wing_span (unsigned int v)
{
cout << "wing-span: " << v << endl;
}
virtual void
post_person ()
{
post_superman ();
}
virtual void
post_superman ()
{
post_batman ();
}
virtual void
post_batman ()
{
cout << "finished parsing batman" << endl;
}
private:
superman_pimpl base_impl_;
};
</pre>
<p>Note that because the derived type parsers (<code>superman_pskel</code>
and <code>batman_pskel</code>) are called via the <code>person_pskel</code>
interface, we have to override the <code>post_person()</code> virtual
function in <code>superman_pimpl</code> and <code>batman_pimpl</code>
to call <code>post_superman()</code> and the <code>post_superman()</code>
virtual function in <code>batman_pimpl</code> to call
<code>post_batman()</code> (when the mixin parser reuse style is used
it is not necessary to override <code>post_person()</code>
in <code>batman_pimpl</code> since the suitable implementation
is inherited from <code>superman_pimpl</code>).</p>
<p>The following code fragment shows how to connect the parsers together.
Notice that for the <code>person</code> element in the <code>supermen_p</code>
parser we specify a parser map instead of a specific parser and we pass
<code>true</code> as the last argument to the document parser constructor
to indicate that we are parsing potentially-polymorphic XML documents:</p>
<pre class="c++">
int
main (int argc, char* argv[])
{
// Construct the parser.
//
xml_schema::string_pimpl string_p;
xml_schema::boolean_pimpl boolean_p;
xml_schema::unsigned_int_pimpl unsigned_int_p;
person_pimpl person_p;
superman_pimpl superman_p;
batman_pimpl batman_p;
xml_schema::parser_map_impl person_map (5); // 5 hashtable buckets
supermen_pimpl supermen_p;
person_p.parsers (string_p);
superman_p.parsers (string_p, boolean_p);
batman_p.parsers (string_p, boolean_p, unsigned_int_p);
// Here we are specifying several parsers that can be used to
// parse the person element.
//
person_map.insert (person_p);
person_map.insert (superman_p);
person_map.insert (batman_p);
supermen_p.person_parser (person_map);
// Parse the XML document. The last argument to the document's
// constructor indicates that we are parsing polymorphic XML
// documents.
//
xml_schema::document_pimpl doc_p (supermen_p, "supermen", true);
supermen_p.pre ();
doc_p.parse (argv[1]);
supermen_p.post_supermen ();
}
</pre>
<p>When polymorphism-aware code is generated, each element's
<code>*_parser()</code> function is overloaded to also accept
an object of the <code>xml_schema::parser_map</code> type.
For example, the <code>supermen_pskel</code> class from the
above example looks like this:</p>
<pre class="c++">
class supermen_pskel: public xml_schema::parser_complex_content
{
public:
...
// Parser construction API.
//
void
parsers (person_pskel&);
// Individual element parsers.
//
void
person_parser (person_pskel&);
void
person_parser (xml_schema::parser_map&);
...
};
</pre>
<p>Note that you can specify both the individual (static) parser and
the parser map. The individual parser will be used when the static
element type and the dynamic type of the object being parsed are
the same. This is the case, for example, when there is no
<code>xsi:type</code> attribute and the element hasn't been
substituted. Because the individual parser for an element is
cached and no map lookup is necessary, it makes sense to specify
both the individual parser and the parser map when most of the
objects being parsed are of the static type and optimal
performance is important. The following code fragment shows
how to change the above example to set both the individual
parser and the parser map:</p>
<pre class="c++">
int
main (int argc, char* argv[])
{
...
// Here we are specifying several parsers that can be used to
// parse the person element.
//
person_map.insert (superman_p);
person_map.insert (batman_p);
supermen_p.person_parser (person_p);
supermen_p.person_parser (person_map);
...
}
</pre>
<p>The <code>xml_schema::parser_map</code> interface and the
<code>xml_schema::parser_map_impl</code> default implementation
are presented below:</p>
<pre class="c++">
namespace xml_schema
{
class parser_map
{
public:
virtual parser_base*
find (const char* type) const = 0;
virtual void
reset () const = 0;
};
class parser_map_impl: public parser_map
{
public:
parser_map_impl (size_t buckets);
void
insert (parser_base&);
virtual parser_base*
find (const char* type) const;
virtual void
reset () const;
private:
parser_map_impl (const parser_map_impl&);
parser_map_impl&
operator= (const parser_map_impl&);
...
};
}
</pre>
<p>The <code>type</code> argument in the <code>find()</code> virtual
function is the type name and namespace from the xsi:type attribute
(the namespace prefix is resolved to the actual XML namespace)
or the type of an element from the substitution group in the form
<code>"<name> <namespace>"</code> with the space and the
namespace part absent if the type does not have a namespace.
You can obtain a parser's dynamic type in the same format
using the <code>_dynamic_type()</code> function. The static
type can be obtained by calling the static <code>_static_type()</code>
function, for example <code>person_pskel::_static_type()</code>.
Both functions return a C string (<code>const char*</code>) which
is valid for as long as the application is running. The
<code>reset()</code> virtual function is used to reset
the parsers contained in the map (as opposed to resetting or
clearing the map itself). For more information on parser
resetting refer to <a href="#7.4">Section 7.4, "Reusing Parsers
after an Error"</a>. The following example shows how we can
implement our own parser map using <code>std::map</code>:</p>
<pre class="c++">
#include <map>
#include <string>
class parser_map: public xml_schema::parser_map
{
public:
void
insert (xml_schema::parser_base& p)
{
map_[p._dynamic_type ()] = &p;
}
virtual xml_schema::parser_base*
find (const char* type) const
{
map::const_iterator i = map_.find (type);
return i != map_.end () ? i->second : 0;
}
virtual void
reset () const
{
for (map::const_iterator i (map_.begin ()), e (map_.end ());
i != e; ++i)
{
xml_schema::parser_base* p = i->second;
p->_reset ();
}
}
private:
typedef std::map<std::string, xml_schema::parser_base*> map;
map map_;
};
</pre>
<p>The XSD/e runtime provides the default implementation for the
<code>xml_schema::parser_map</code> interface,
<code>xml_schema::parser_map_impl</code>, which is a hashmap.
It requires that you specify the number of buckets it will contain
and it does not support automatic table resizing. To obtain good
performance the elements to buckets ratio should be between 0.7 and
0.9. It is also recommended to use prime numbers for bucket counts:
53, 97, 193, 389, 769, 1543, 3079, 6151, 12289, 24593, 49157, 98317,
196613, 393241.
</p>
<p>If C++ exceptions are disabled (<a href="#5.3">Section 5.3,
"C++ Exceptions"</a>), the <code>xml_schema::parser_map_impl</code>
class has the following additional error querying API. It can be used
to detect the out of memory errors after calls to the
<code>parser_map_impl</code>'s constructor and <code>insert()</code>
function.</p>
<pre class="c++">
namespace xml_schema
{
class parser_map_impl: public parser_map
{
public:
enum error
{
error_none,
error_no_memory
};
error
_error () const;
...
};
}
</pre>
<p>To support polymorphic parsing the XSD/e runtime and generated code
maintain a number of hashmaps that contain substitution and, if
XML Schema validation is enabled (<a href="#5.4">Section 5.4,
"XML Schema Validation"</a>), inheritance information. Because
the number of elements in these hashmaps depends on the schemas
being compiled and thus is fairly static, these hashmaps do not
perform automatic table resizing and instead the number of buckets
is specified when the XSD/e runtime is configured. To obtain good
performance the elements to buckets ratio in these hashmaps should
be between 0.7 and 0.9. The recommended way to ensure this range
is to add diagnostics code to your application as shown in the
following example:</p>
<pre class="c++">
int
main ()
{
// Check that the load in substitution and inheritance hashmaps
// is not too high.
//
#ifndef NDEBUG
float load = xml_schema::parser_smap_elements ();
load /= xml_schema::parser_smap_buckets ();
if (load > 0.8)
{
cerr << "substitution hashmap load is " << load << endl;
cerr << "time to increase XSDE_PARSER_SMAP_BUCKETS" << endl;
}
load = xml_schema::parser_imap_elements ();
load /= xml_schema::parser_imap_buckets ();
if (load > 0.8)
{
cerr << "inheritance hashmap load is " << load << endl;
cerr << "time to increase XSDE_PARSER_IMAP_BUCKETS" << endl;
}
#endif
...
}
</pre>
<p>Most of the code presented in this section is taken from the
<code>polymorphism</code> example which can be found in the
<code>examples/cxx/parser/</code> directory of the XSD/e distribution.
Handling of <code>xsi:type</code> and substitution groups when used
on root elements requires a number of special actions as shown in
the <code>polyroot</code> example.</p>
<h2><a name="5.8">5.8 Custom Allocators</a></h2>
<p>By default the XSD/e runtime and generated code use
the standard operators <code>new</code> and <code>delete</code>
to manage dynamic memory. However, it is possible to instead
use custom allocator functions provided by your application.
To achieve this, configure the XSD/e runtime library to use
custom allocator functions as well as pass the
<code>--custom-allocator</code> option to the XSD/e compiler
when translating your schemas. The signatures of the custom
allocator functions that should be provided by your application
are listed below. Their semantics should be equivalent to the
standard C <code>malloc()</code>, <code>realloc()</code>, and
<code>free()</code> functions.</p>
<pre class="c++">
extern "C" void*
xsde_alloc (size_t);
extern "C" void*
xsde_realloc (void*, size_t);
extern "C" void
xsde_free (void*);
</pre>
<p>Note also that when custom allocators are enabled, any
dynamically-allocated object of which the XSD/e runtime
or generated code assume ownership should be allocated
using the custom allocation function. Similarly, if your
application assumes ownership of any dynamically-allocated
object returned by the XSD/e runtime or the generated code,
then such an object should be disposed of using the custom
deallocation function. To help with these tasks the generated
<code>xml_schema</code> namespace defines the following two
helper functions and, if C++ exceptions are enabled, automatic
pointer class:</p>
<pre class="c++">
namespace xml_schema
{
void*
alloc (size_t);
void
free (void*);
struct alloc_guard
{
alloc_guard (void*);
~alloc_guard ();
void*
get () const;
void
release ();
private:
...
};
}
</pre>
<p>If C++ exceptions are disabled, these functions are equivalent
to <code>xsde_alloc()</code> and <code>xsde_free()</code>.
If exceptions are enabled, <code>xml_schema::alloc()</code>
throws <code>std::bad_alloc</code> on memory allocation failure.</p>
<p>The following code fragment shows how to create and destroy a
dynamically-allocated object with custom allocators when C++
exceptions are disabled:</p>
<pre class="c++">
void* v = xml_schema::alloc (sizeof (type));
if (v == 0)
{
// Handle out of memory condition.
}
type* x = new (v) type (1, 2);
...
if (x)
{
x->~type ();
xml_schema::free (x);
}
</pre>
<p>The equivalent code fragment for configurations with C++ exceptions
enabled is shown below:</p>
<pre class="c++">
xml_schema::alloc_guard g (xml_schema::alloc (sizeof (type)));
type* x = new (g.get ()) type (1, 2);
g.release ();
...
if (x)
{
x->~type ();
xml_schema::free (x);
}
</pre>
<h2><a name="5.9">5.9 A Minimal Example</a></h2>
<p>The following example is a re-implementation of the person
records example presented in <a href="#3">Chapter 3,
"Parser Skeletons"</a>. It is intended to work
without STL, iostream, and C++ exceptions. It can be found in
the <code>examples/cxx/parser/minimal/</code> directory of the
XSD/e distribution. The <code>people.xsd</code> schema is
compiled with the <code>--no-stl</code>, <code>--no-iostream</code>,
and <code>--no-exceptions</code> options. The following listing
presents the implementation of parser skeletons and the test
driver in full.</p>
<pre class="c++">
#include <stdio.h>
#include "people-pskel.hxx"
class gender_pimpl: public gender_pskel
{
public:
gender_pimpl ()
: gender_pskel (&base_impl_)
{
}
virtual void
post_gender ()
{
char* s = post_string ();
printf ("gender: %s\n", s);
delete[] s;
}
private:
xml_schema::string_pimpl base_impl_;
};
class person_pimpl: public person_pskel
{
public:
virtual void
first_name (char* n)
{
printf ("first: %s\n", n);
delete[] n;
}
virtual void
last_name (char* n)
{
printf ("last: %s\n", n);
delete[] n;
}
virtual void
age (short a)
{
printf ("age: %hd\n", a);
}
};
class people_pimpl: public people_pskel
{
public:
virtual void
person ()
{
// Add an extra newline after each person record.
//
printf ("\n");
}
};
int
main (int argc, char* argv[])
{
// Construct the parser.
//
xml_schema::short_pimpl short_p;
xml_schema::string_pimpl string_p;
gender_pimpl gender_p;
person_pimpl person_p;
people_pimpl people_p;
person_p.parsers (string_p, string_p, gender_p, short_p);
people_p.parsers (person_p);
// Open the file.
//
FILE* f = fopen (argv[1], "rb");
if (f == 0)
{
fprintf (stderr, "%s: unable to open\n", argv[1]);
return 1;
}
// Parse.
//
typedef xml_schema::parser_error error;
error e;
bool io_error = false;
do
{
xml_schema::document_pimpl doc_p (people_p, "people");
if (e = doc_p._error ())
break;
people_p.pre ();
if (e = people_p._error ())
break;
char buf[4096];
do
{
size_t s = fread (buf, 1, sizeof (buf), f);
if (s != sizeof (buf) && ferror (f))
{
io_error = true;
break;
}
doc_p.parse (buf, s, feof (f) != 0);
e = doc_p._error ();
} while (!e && !feof (f));
if (io_error || e)
break;
people_p.post_people ();
e = people_p._error ();
} while (false);
fclose (f);
// Handle errors.
//
if (io_error)
{
fprintf (stderr, "%s: read failure\n", argv[1]);
return 1;
}
if (e)
{
switch (e.type ())
{
case error::sys:
{
fprintf (stderr, "%s: %s\n", argv[1], e.sys_text ());
break;
}
case error::xml:
{
fprintf (stderr, "%s:%lu:%lu: %s\n",
argv[1], e.line (), e.column (), e.xml_text ());
break;
}
case error::schema:
{
fprintf (stderr, "%s:%lu:%lu: %s\n",
argv[1], e.line (), e.column (), e.schema_text ());
break;
}
case error::app:
{
fprintf (stderr, "%s:%lu:%lu: application error %d\n",
argv[1], e.line (), e.column (), e.app_code ());
break;
}
default:
break;
}
return 1;
}
return 0;
}
</pre>
<!-- Built-in XML Schema Type Parsers -->
<h1><a name="6">6 Built-In XML Schema Type Parsers</a></h1>
<p>The XSD/e runtime provides parser implementations for all built-in
XML Schema types as summarized in the following table. Declarations
for these types are automatically included into each generated
header file. As a result you don't need to include any headers
to gain access to these parser implementations.</p>
<!-- border="1" is necessary for html2ps -->
<table id="builtin" border="1">
<tr>
<th>XML Schema type</th>
<th>Parser implementation in the <code>xml_schema</code> namespace</th>
<th>Parser return type</th>
</tr>
<tr>
<th colspan="3">anyType and anySimpleType types</th>
</tr>
<tr>
<td><code>anyType</code></td>
<td><code>any_type_pimpl</code></td>
<td><code>void</code></td>
</tr>
<tr>
<td><code>anySimpleType</code></td>
<td><code>any_simple_type_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<th colspan="3">fixed-length integral types</th>
</tr>
<!-- 8-bit -->
<tr>
<td><code>byte</code></td>
<td><code>byte_pimpl</code></td>
<td><code>signed char</code></td>
</tr>
<tr>
<td><code>unsignedByte</code></td>
<td><code>unsigned_byte_pimpl</code></td>
<td><code>unsigned char</code></td>
</tr>
<!-- 16-bit -->
<tr>
<td><code>short</code></td>
<td><code>short_pimpl</code></td>
<td><code>short</code></td>
</tr>
<tr>
<td><code>unsignedShort</code></td>
<td><code>unsigned_short_pimpl</code></td>
<td><code>unsigned short</code></td>
</tr>
<!-- 32-bit -->
<tr>
<td><code>int</code></td>
<td><code>int_pimpl</code></td>
<td><code>int</code></td>
</tr>
<tr>
<td><code>unsignedInt</code></td>
<td><code>unsigned_int_pimpl</code></td>
<td><code>unsigned int</code></td>
</tr>
<!-- 64-bit -->
<tr>
<td><code>long</code></td>
<td><code>long_pimpl</code></td>
<td><code>long long</code> or <code>long</code><br/>
<a href="#5.5">Section 5.5, "64-bit Integer Type"</a></td>
</tr>
<tr>
<td><code>unsignedLong</code></td>
<td><code>unsigned_long_pimpl</code></td>
<td><code>unsigned long long</code> or
<code>unsigned long</code><br/>
<a href="#5.5">Section 5.5, "64-bit Integer Type"</a></td>
</tr>
<tr>
<th colspan="3">arbitrary-length integral types</th>
</tr>
<tr>
<td><code>integer</code></td>
<td><code>integer_pimpl</code></td>
<td><code>long</code></td>
</tr>
<tr>
<td><code>nonPositiveInteger</code></td>
<td><code>non_positive_integer_pimpl</code></td>
<td><code>long</code></td>
</tr>
<tr>
<td><code>nonNegativeInteger</code></td>
<td><code>non_negative_integer_pimpl</code></td>
<td><code>unsigned long</code></td>
</tr>
<tr>
<td><code>positiveInteger</code></td>
<td><code>positive_integer_pimpl</code></td>
<td><code>unsigned long</code></td>
</tr>
<tr>
<td><code>negativeInteger</code></td>
<td><code>negative_integer_pimpl</code></td>
<td><code>long</code></td>
</tr>
<tr>
<th colspan="3">boolean types</th>
</tr>
<tr>
<td><code>boolean</code></td>
<td><code>boolean_pimpl</code></td>
<td><code>bool</code></td>
</tr>
<tr>
<th colspan="3">fixed-precision floating-point types</th>
</tr>
<tr>
<td><code>float</code></td>
<td><code>float_pimpl</code></td>
<td><code>float</code></td>
</tr>
<tr>
<td><code>double</code></td>
<td><code>double_pimpl</code></td>
<td><code>double</code></td>
</tr>
<tr>
<th colspan="3">arbitrary-precision floating-point types</th>
</tr>
<tr>
<td><code>decimal</code></td>
<td><code>decimal_pimpl</code></td>
<td><code>double</code></td>
</tr>
<tr>
<th colspan="3">string-based types</th>
</tr>
<tr>
<td><code>string</code></td>
<td><code>string_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>normalizedString</code></td>
<td><code>normalized_string_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>token</code></td>
<td><code>token_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>Name</code></td>
<td><code>name_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>NMTOKEN</code></td>
<td><code>nmtoken_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>NCName</code></td>
<td><code>ncname_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>language</code></td>
<td><code>language_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<th colspan="3">qualified name</th>
</tr>
<tr>
<td><code>QName</code></td>
<td><code>qname_pimpl</code></td>
<td><code>xml_schema::qname</code> or <code>xml_schema::qname*</code><br/>
<a href="#6.1">Section 6.1, "<code>QName</code> Parser"</a></td>
</tr>
<tr>
<th colspan="3">ID/IDREF types</th>
</tr>
<tr>
<td><code>ID</code></td>
<td><code>id_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>IDREF</code></td>
<td><code>idref_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<th colspan="3">list types</th>
</tr>
<tr>
<td><code>NMTOKENS</code></td>
<td><code>nmtokens_pimpl</code></td>
<td><code>xml_schema::string_sequence*</code><br/><a href="#6.2">Section
6.2, "<code>NMTOKENS</code> and <code>IDREFS</code> Parsers"</a></td>
</tr>
<tr>
<td><code>IDREFS</code></td>
<td><code>idrefs_pimpl</code></td>
<td><code>xml_schema::string_sequence*</code><br/><a href="#6.2">Section
6.2, "<code>NMTOKENS</code> and <code>IDREFS</code> Parsers"</a></td>
</tr>
<tr>
<th colspan="3">URI types</th>
</tr>
<tr>
<td><code>anyURI</code></td>
<td><code>uri_pimpl</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#5.1">Section 5.1, "Standard Template Library"</a></td>
</tr>
<tr>
<th colspan="3">binary types</th>
</tr>
<tr>
<td><code>base64Binary</code></td>
<td><code>base64_binary_pimpl</code></td>
<td><code>xml_schema::buffer*</code><br/>
<a href="#6.3">Section 6.3, "<code>base64Binary</code> and
<code>hexBinary</code> Parsers"</a></td>
</tr>
<tr>
<td><code>hexBinary</code></td>
<td><code>hex_binary_pimpl</code></td>
<td><code>xml_schema::buffer*</code><br/>
<a href="#6.3">Section 6.3, "<code>base64Binary</code> and
<code>hexBinary</code> Parsers"</a></td>
</tr>
<tr>
<th colspan="3">date/time types</th>
</tr>
<tr>
<td><code>date</code></td>
<td><code>date_pimpl</code></td>
<td><code>xml_schema::date</code><br/><a href="#6.5">Section 6.5,
"<code>date</code> Parser"</a></td>
</tr>
<tr>
<td><code>dateTime</code></td>
<td><code>date_time_pimpl</code></td>
<td><code>xml_schema::date_time</code><br/><a href="#6.6">Section 6.6,
"<code>dateTime</code> Parser"</a></td>
</tr>
<tr>
<td><code>duration</code></td>
<td><code>duration_pimpl</code></td>
<td><code>xml_schema::duration</code><br/><a href="#6.7">Section 6.7,
"<code>duration</code> Parser"</a></td>
</tr>
<tr>
<td><code>gDay</code></td>
<td><code>gday_pimpl</code></td>
<td><code>xml_schema::gday</code><br/><a href="#6.8">Section 6.8,
"<code>gDay</code> Parser"</a></td>
</tr>
<tr>
<td><code>gMonth</code></td>
<td><code>gmonth_pimpl</code></td>
<td><code>xml_schema::gmonth</code><br/><a href="#6.9">Section 6.9,
"<code>gMonth</code> Parser"</a></td>
</tr>
<tr>
<td><code>gMonthDay</code></td>
<td><code>gmonth_day_pimpl</code></td>
<td><code>xml_schema::gmonth_day</code><br/><a href="#6.10">Section 6.10,
"<code>gMonthDay</code> Parser"</a></td>
</tr>
<tr>
<td><code>gYear</code></td>
<td><code>gyear_pimpl</code></td>
<td><code>xml_schema::gyear</code><br/><a href="#6.11">Section 6.11,
"<code>gYear</code> Parser"</a></td>
</tr>
<tr>
<td><code>gYearMonth</code></td>
<td><code>gyear_month_pimpl</code></td>
<td><code>xml_schema::gyear_month</code><br/><a href="#6.12">Section
6.12, "<code>gYearMonth</code> Parser"</a></td>
</tr>
<tr>
<td><code>time</code></td>
<td><code>time_pimpl</code></td>
<td><code>xml_schema::time</code><br/><a href="#6.13">Section 6.13,
"<code>time</code> Parser"</a></td>
</tr>
</table>
<h2><a name="6.1">6.1 <code>QName</code> Parser</a></h2>
<p>The return type of the <code>qname_pimpl</code> parser implementation
is either <code>xml_schema::qname</code> when STL is enabled
(<a href="#5.1">Section 5.1, "Standard Template Library"</a>) or
<code>xml_schema::qname*</code> when STL is disabled. The
<code>qname</code> class represents an XML qualified name. When the
return type is <code>xml_schema::qname*</code>, the returned
object is dynamically allocated with operator <code>new</code>
and should eventually be deallocated with operator <code>delete</code>.
With STL enabled, the <code>qname</code> type has the following
interface:</p>
<pre class="c++">
namespace xml_schema
{
class qname
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
qname ();
explicit
qname (const std::string& name);
qname (const std::string& prefix, const std::string& name);
void
swap (qname&);
const std::string&
prefix () const;
std::string&
prefix ();
void
prefix (const std::string&);
const std::string&
name () const;
std::string&
name ();
void
name (const std::string&);
};
bool
operator== (const qname&, const qname&);
bool
operator!= (const qname&, const qname&);
}
</pre>
<p>When STL is disabled and C++ exceptions are enabled
(<a href="#5.3">Section 5.3, "C++ Exceptions"</a>), the
<code>qname</code> type has the following interface:</p>
<pre class="c++">
namespace xml_schema
{
class qname
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
qname ();
explicit
qname (char* name);
qname (char* prefix, char* name);
void
swap (qname&);
private:
qname (const qname&);
qname&
operator= (const qname&);
public:
char*
prefix ();
const char*
prefix () const;
void
prefix (char*);
void
prefix_copy (const char*);
char*
prefix_detach ();
public:
char*
name ();
const char*
name () const;
void
name (char*);
void
name_copy (const char*);
char*
name_detach ();
};
bool
operator== (const qname&, const qname&);
bool
operator!= (const qname&, const qname&);
}
</pre>
<p>The modifier functions and constructors that have the <code>char*</code>
argument assume ownership of the passed strings which should be allocated
with operator <code>new char[]</code> and will be deallocated with
operator <code>delete[]</code> by the <code>qname</code> object.
If you detach the underlying prefix or name strings, then they
should eventually be deallocated with operator <code>delete[]</code>.
</p>
<p>Finally, if both STL and C++ exceptions are disabled, the
<code>qname</code> type has the following interface:</p>
<pre class="c++">
namespace xml_schema
{
class qname
{
public:
enum error
{
error_none,
error_no_memory
};
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
qname ();
explicit
qname (char* name);
qname (char* prefix, char* name);
void
swap (qname&);
private:
qname (const qname&);
qname&
operator= (const qname&);
public:
char*
prefix ();
const char*
prefix () const;
void
prefix (char*);
error
prefix_copy (const char*);
char*
prefix_detach ();
public:
char*
name ();
const char*
name () const;
void
name (char*);
error
name_copy (const char*);
char*
name_detach ();
};
bool
operator== (const qname&, const qname&);
bool
operator!= (const qname&, const qname&);
}
</pre>
<h2><a name="6.2">6.2 <code>NMTOKENS</code> and <code>IDREFS</code> Parsers</a></h2>
<p>The return type of the <code>nmtokens_pimpl</code> and
<code>idrefs_pimpl</code> parser implementations is
<code>xml_schema::string_sequence*</code>.
The returned object is dynamically allocated with operator
<code>new</code> and should eventually be deallocated with
operator <code>delete</code>. With STL and C++ exceptions enabled
(<a href="#5.1">Section 5.1, "Standard Template Library"</a>,
<a href="#5.3">Section 5.3, "C++ Exceptions"</a>), the
<code>string_sequence</code> type has the following interface:</p>
<pre class="c++">
namespace xml_schema
{
class string_sequence
{
public:
typedef std::string value_type;
typedef std::string* pointer;
typedef const std::string* const_pointer;
typedef std::string& reference;
typedef const std::string& const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef std::string* iterator;
typedef const std::string* const_iterator;
public:
string_sequence ();
void
swap (string_sequence&);
private:
string_sequence (string_sequence&);
string_sequence&
operator= (string_sequence&);
public:
iterator
begin ();
const_iterator
begin () const;
iterator
end ();
const_iterator
end () const;
std::string&
front ();
const std::string&
front () const;
std::string&
back ();
const std::string&
back () const;
std::string&
operator[] (size_t);
const std::string&
operator[] (size_t) const;
public:
bool
empty () const;
size_t
size () const;
size_t
capacity () const;
size_t
max_size () const;
public:
void
clear ();
void
pop_back ();
iterator
erase (iterator);
void
push_back (const std::string&);
iterator
insert (iterator, const std::string&);
void
reserve (size_t);
};
bool
operator== (const string_sequence&, const string_sequence&);
bool
operator!= (const string_sequence&, const string_sequence&);
}
</pre>
<p>When STL is enabled and C++ exceptions are disabled, the signatures
of the <code>push_back()</code>, <code>insert()</code>, and
<code>reserve()</code> functions change as follows:</p>
<pre class="c++">
namespace xml_schema
{
class string_sequence
{
public:
enum error
{
error_none,
error_no_memory
};
...
public:
error
push_back (const std::string&);
error
insert (iterator, const std::string&);
error
insert (iterator, const std::string&, iterator& result);
error
reserve (size_t);
};
}
</pre>
<p>When STL is disabled and C++ exceptions are enabled, the
<code>string_sequence</code> type has the following interface:</p>
<pre class="c++">
namespace xml_schema
{
class string_sequence
{
public:
typedef char* value_type;
typedef char** pointer;
typedef const char** const_pointer;
typedef char* reference;
typedef const char* const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef char** iterator;
typedef const char* const* const_iterator;
string_sequence ();
void
swap (string_sequence&);
private:
string_sequence (string_sequence&);
string_sequence&
operator= (string_sequence&);
public:
iterator
begin ();
const_iterator
begin () const;
iterator
end ();
const_iterator
end () const;
char*
front ();
const char*
front () const;
char*
back ();
const char*
back () const;
char*
operator[] (size_t);
const char*
operator[] (size_t) const;
public:
bool
empty () const;
size_t
size () const;
size_t
capacity () const;
size_t
max_size () const;
public:
void
clear ();
void
pop_back ();
iterator
erase (iterator);
void
push_back (char*);
void
push_back_copy (const char*);
iterator
insert (iterator, char*);
void
reserve (size_t);
// Detach a string from the sequence at a given position.
// The string pointer at this position in the sequence is
// set to 0.
//
char*
detach (iterator);
};
bool
operator== (const string_sequence&, const string_sequence&);
bool
operator!= (const string_sequence&, const string_sequence&);
}
</pre>
<p>The <code>push_back()</code> and <code>insert()</code> functions
assume ownership of the passed string which should be allocated
with operator <code>new char[]</code> and will be deallocated
with operator <code>delete[]</code> by the <code>string_sequence</code>
object. These two functions free the passed object if the reallocation
of the underlying sequence buffer fails. The <code>push_back_copy()</code>
function makes a copy of the passed string.
If you detach the underlying element string, then it should
eventually be deallocated with operator <code>delete[]</code>.</p>
<p>When both STL and C++ exceptions are disabled, the signatures
of the <code>push_back()</code>, <code>push_back_copy()</code>,
<code>insert()</code>, and <code>reserve()</code> functions change
as follows:</p>
<pre class="c++">
namespace xml_schema
{
class string_sequence
{
public:
enum error
{
error_none,
error_no_memory
};
...
public:
error
push_back (char*);
error
push_back_copy (const char*);
error
insert (iterator, char*);
error
insert (iterator, char*, iterator& result);
error
reserve (size_t);
};
}
</pre>
<h2><a name="6.3">6.3 <code>base64Binary</code> and <code>hexBinary</code> Parsers</a></h2>
<p>The return type of the <code>base64_binary_pimpl</code> and
<code>hex_binary_pimpl</code> parser implementations is
<code>xml_schema::buffer*</code>. The returned object is
dynamically allocated with operator <code>new</code> and
should eventually be deallocated with operator <code>delete</code>.
With C++ exceptions enabled (<a href="#5.3">Section 5.3, "C++
Exceptions"</a>), the <code>buffer</code> type has the following
interface:</p>
<pre class="c++">
namespace xml_schema
{
class buffer
{
public:
class bounds {}; // Out of bounds exception.
public:
buffer ();
explicit
buffer (size_t size);
buffer (size_t size, size_t capacity);
buffer (const void* data, size_t size);
buffer (const void* data, size_t size, size_t capacity);
enum ownership_value { assume_ownership };
// This constructor assumes ownership of the memory passed.
//
buffer (void* data, size_t size, size_t capacity, ownership_value);
private:
buffer (const buffer&);
buffer&
operator= (const buffer&);
public:
void
attach (void* data, size_t size, size_t capacity);
void*
detach ();
void
swap (buffer&);
public:
size_t
capacity () const;
bool
capacity (size_t);
public:
size_t
size () const;
bool
size (size_t);
public:
const char*
data () const;
char*
data ();
const char*
begin () const;
char*
begin ();
const char*
end () const;
char*
end ();
};
bool
operator== (const buffer&, const buffer&);
bool
operator!= (const buffer&, const buffer&);
}
</pre>
<p>The last constructor and the <code>attach()</code> member function
make the <code>buffer</code> instance assume the ownership of the
memory block pointed to by the <code>data</code> argument and
eventually release it by calling <code>operator delete()</code>.
The <code>detach()</code> member function detaches and returns the
underlying memory block which should eventually be released by
calling <code>operator delete()</code>.
</p>
<p>The <code>capacity()</code> and <code>size()</code> modifier functions
return <code>true</code> if the underlying buffer has moved. The
<code>bounds</code> exception is thrown if the constructor or
<code>attach()</code> member function arguments violate the
<code>(size <= capacity)</code> constraint.</p>
<p>If C++ exceptions are disabled, the <code>buffer</code> type has
the following interface:</p>
<pre class="c++">
namespace xml_schema
{
class buffer
{
public:
enum error
{
error_none,
error_bounds,
error_no_memory
};
buffer ();
private:
buffer (const buffer&);
buffer&
operator= (const buffer&);
public:
error
attach (void* data, size_t size, size_t capacity);
void*
detach ();
void
swap (buffer&);
public:
size_t
capacity () const;
error
capacity (size_t);
error
capacity (size_t, bool& moved);
public:
size_t
size () const;
error
size (size_t);
error
size (size_t, bool& moved);
public:
const char*
data () const;
char*
data ();
const char*
begin () const;
char*
begin ();
const char*
end () const;
char*
end ();
};
bool
operator== (const buffer&, const buffer&);
bool
operator!= (const buffer&, const buffer&);
}
</pre>
<h2><a name="6.4">6.4 Time Zone Representation</a></h2>
<p>The <code>date</code>, <code>dateTime</code>, <code>gDay</code>,
<code>gMonth</code>, <code>gMonthDay</code>, <code>gYear</code>,
<code>gYearMonth</code>, and <code>time</code> XML Schema built-in
types all include an optional time zone component. The following
<code>xml_schema::time_zone</code> base class is used to represent
this information:</p>
<pre class="c++">
namespace xml_schema
{
class time_zone
{
public:
time_zone ();
time_zone (short hours, short minutes);
bool
zone_present () const;
void
zone_reset ();
short
zone_hours () const;
void
zone_hours (short);
short
zone_minutes () const;
void
zone_minutes (short);
};
bool
operator== (const time_zone&, const time_zone&);
bool
operator!= (const time_zone&, const time_zone&);
}
</pre>
<p>The <code>zone_present()</code> accessor function returns <code>true</code>
if the time zone is specified. The <code>zone_reset()</code> modifier
function resets the time zone object to the <em>not specified</em>
state. If the time zone offset is negative then both hours and
minutes components are represented as negative integers.</p>
<h2><a name="6.5">6.5 <code>date</code> Parser</a></h2>
<p>The return type of the <code>date_pimpl</code> parser implementation
is <code>xml_schema::date</code> which represents a year, a day, and a month
with an optional time zone. Its interface is presented below. For
more information on the base <code>xml_schema::time_zone</code>
class refer to <a href="#6.4">Section 6.4, "Time Zone
Representation"</a>.</p>
<pre class="c++">
namespace xml_schema
{
class date: public time_zone
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
date ();
date (int year, unsigned short month, unsigned short day);
date (int year, unsigned short month, unsigned short day,
short zone_hours, short zone_minutes);
int
year () const;
void
year (int);
unsigned short
month () const;
void
month (unsigned short);
unsigned short
day () const;
void
day (unsigned short);
};
bool
operator== (const date&, const date&);
bool
operator!= (const date&, const date&);
}
</pre>
<h2><a name="6.6">6.6 <code>dateTime</code> Parser</a></h2>
<p>The return type of the <code>date_time_pimpl</code> parser implementation
is <code>xml_schema::date_time</code> which represents a year, a month, a day,
hours, minutes, and seconds with an optional time zone. Its interface
is presented below. For more information on the base
<code>xml_schema::time_zone</code> class refer to <a href="#6.4">Section
6.4, "Time Zone Representation"</a>.</p>
<pre class="c++">
namespace xml_schema
{
class date_time: public time_zone
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
date_time ();
date_time (int year, unsigned short month, unsigned short day,
unsigned short hours, unsigned short minutes,
double seconds);
date_time (int year, unsigned short month, unsigned short day,
unsigned short hours, unsigned short minutes,
double seconds, short zone_hours, short zone_minutes);
int
year () const;
void
year (int);
unsigned short
month () const;
void
month (unsigned short);
unsigned short
day () const;
void
day (unsigned short);
unsigned short
hours () const;
void
hours (unsigned short);
unsigned short
minutes () const;
void
minutes (unsigned short);
double
seconds () const;
void
seconds (double);
};
bool
operator== (const date_time&, const date_time&);
bool
operator!= (const date_time&, const date_time&);
}
</pre>
<h2><a name="6.7">6.7 <code>duration</code> Parser</a></h2>
<p>The return type of the <code>duration_pimpl</code> parser implementation
is <code>xml_schema::duration</code> which represents a potentially
negative duration in the form of years, months, days, hours, minutes,
and seconds. Its interface is presented below.</p>
<pre class="c++">
namespace xml_schema
{
class duration
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
duration ();
duration (bool negative,
unsigned int years, unsigned int months, unsigned int days,
unsigned int hours, unsigned int minutes, double seconds);
bool
negative () const;
void
negative (bool);
unsigned int
years () const;
void
years (unsigned int);
unsigned int
months () const;
void
months (unsigned int);
unsigned int
days () const;
void
days (unsigned int);
unsigned int
hours () const;
void
hours (unsigned int);
unsigned int
minutes () const;
void
minutes (unsigned int);
double
seconds () const;
void
seconds (double);
};
bool
operator== (const duration&, const duration&);
bool
operator!= (const duration&, const duration&);
}
</pre>
<h2><a name="6.8">6.8 <code>gDay</code> Parser</a></h2>
<p>The return type of the <code>gday_pimpl</code> parser implementation
is <code>xml_schema::gday</code> which represents a day of the month with
an optional time zone. Its interface is presented below. For
more information on the base <code>xml_schema::time_zone</code>
class refer to <a href="#6.4">Section 6.4, "Time Zone
Representation"</a>.</p>
<pre class="c++">
namespace xml_schema
{
class gday: public time_zone
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
gday ();
explicit
gday (unsigned short day);
gday (unsigned short day, short zone_hours, short zone_minutes);
unsigned short
day () const;
void
day (unsigned short);
};
bool
operator== (const gday&, const gday&);
bool
operator!= (const gday&, const gday&);
}
</pre>
<h2><a name="6.9">6.9 <code>gMonth</code> Parser</a></h2>
<p>The return type of the <code>gmonth_pimpl</code> parser implementation
is <code>xml_schema::gmonth</code> which represents a month of the year
with an optional time zone. Its interface is presented below. For
more information on the base <code>xml_schema::time_zone</code>
class refer to <a href="#6.4">Section 6.4, "Time Zone
Representation"</a>.</p>
<pre class="c++">
namespace xml_schema
{
class gmonth: public time_zone
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
gmonth ();
explicit
gmonth (unsigned short month);
gmonth (unsigned short month,
short zone_hours, short zone_minutes);
unsigned short
month () const;
void
month (unsigned short);
};
bool
operator== (const gmonth&, const gmonth&);
bool
operator!= (const gmonth&, const gmonth&);
}
</pre>
<h2><a name="6.10">6.10 <code>gMonthDay</code> Parser</a></h2>
<p>The return type of the <code>gmonth_day_pimpl</code> parser implementation
is <code>xml_schema::gmonth_day</code> which represents a day and a month of
the year with an optional time zone. Its interface is presented below.
For more information on the base <code>xml_schema::time_zone</code>
class refer to <a href="#6.4">Section 6.4, "Time Zone
Representation"</a>.</p>
<pre class="c++">
namespace xml_schema
{
class gmonth_day: public time_zone
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
gmonth_day ();
gmonth_day (unsigned short month, unsigned short day);
gmonth_day (unsigned short month, unsigned short day,
short zone_hours, short zone_minutes);
unsigned short
month () const;
void
month (unsigned short);
unsigned short
day () const;
void
day (unsigned short);
};
bool
operator== (const gmonth_day&, const gmonth_day&);
bool
operator!= (const gmonth_day&, const gmonth_day&);
}
</pre>
<h2><a name="6.11">6.11 <code>gYear</code> Parser</a></h2>
<p>The return type of the <code>gyear_pimpl</code> parser implementation
is <code>xml_schema::gyear</code> which represents a year with
an optional time zone. Its interface is presented below.
For more information on the base <code>xml_schema::time_zone</code>
class refer to <a href="#6.4">Section 6.4, "Time Zone
Representation"</a>.</p>
<pre class="c++">
namespace xml_schema
{
class gyear: public time_zone
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
gyear ();
explicit
gyear (int year);
gyear (int year, short zone_hours, short zone_minutes);
int
year () const;
void
year (int);
};
bool
operator== (const gyear&, const gyear&);
bool
operator!= (const gyear&, const gyear&);
}
</pre>
<h2><a name="6.12">6.12 <code>gYearMonth</code> Parser</a></h2>
<p>The return type of the <code>gyear_month_pimpl</code> parser implementation
is <code>xml_schema::gyear_month</code> which represents a year and a month
with an optional time zone. Its interface is presented below.
For more information on the base <code>xml_schema::time_zone</code>
class refer to <a href="#6.4">Section 6.4, "Time Zone
Representation"</a>.</p>
<pre class="c++">
namespace xml_schema
{
class gyear_month: public time_zone
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
gyear_month ();
gyear_month (int year, unsigned short month);
gyear_month (int year, unsigned short month,
short zone_hours, short zone_minutes);
int
year () const;
void
year (int);
unsigned short
month () const;
void
month (unsigned short);
};
bool
operator== (const gyear_month&, const gyear_month&);
bool
operator!= (const gyear_month&, const gyear_month&);
}
</pre>
<h2><a name="6.13">6.13 <code>time</code> Parser</a></h2>
<p>The return type of the <code>time_pimpl</code> parser implementation
is <code>xml_schema::time</code> which represents hours, minutes,
and seconds with an optional time zone. Its interface is presented below.
For more information on the base <code>xml_schema::time_zone</code>
class refer to <a href="#6.4">Section 6.4, "Time Zone
Representation"</a>.</p>
<pre class="c++">
namespace xml_schema
{
class time: public time_zone
{
public:
// The default constructor creates an uninitialized object.
// Use modifiers to initialize it.
//
time ();
time (unsigned short hours, unsigned short minutes, double seconds);
time (unsigned short hours, unsigned short minutes, double seconds,
short zone_hours, short zone_minutes);
unsigned short
hours () const;
void
hours (unsigned short);
unsigned short
minutes () const;
void
minutes (unsigned short);
double
seconds () const;
void
seconds (double);
};
bool
operator== (const time&, const time&);
bool
operator!= (const time&, const time&);
}
</pre>
<!-- Error Handling -->
<h1><a name="7">7 Document Parser and Error Handling</a></h1>
<p>In this chapter we will discuss the <code>xml_schema::document_pimpl</code>
type, the error handling mechanisms provided by the mapping, as well
as how to reuse a parser after an error has occurred.</p>
<p>There are four categories of errors that can result from running
a parser on an XML instance: system, xml, schema, and application.
The system category contains memory allocation and file/stream
operation errors. The xml category is for XML parsing and
well-formedness checking errors. Similarly, the schema category is
for XML Schema validation errors. Finally, the application category
is for application logic errors that you may want to propagate
from parser implementations to the caller of the parser.
</p>
<p>The C++/Parser mapping supports two methods of reporting errors:
using C++ exceptions and with error codes. The method used depends
on whether or not you have configured the XSD/e runtime and
the generated code with C++ exceptions enabled, as described
in <a href="#5.3">Section 5.3, "C++ Exceptions"</a>.</p>
<h2><a name="7.1">7.1 Document Parser</a></h2>
<p>The <code>xml_schema::document_pimpl</code> parser is a root parser for
the vocabulary. As mentioned in <a href="#3.4">Section 3.4,
"Connecting the Parsers Together"</a>, its interface varies depending
on the mapping configuration (<a href="#5">Chapter 5, "Mapping
Configuration"</a>). When STL and the iostream library are
enabled, the <code>xml_schema::document_pimpl</code> class has the
following interface:</p>
<pre class="c++">
namespace xml_schema
{
class parser_base;
class document_pimpl
{
public:
document_pimpl (parser_base&,
const char* root_element_name);
document_pimpl (parser_base&,
const char* root_element_namespace,
const char* root_element_name);
document_pimpl (parser_base&,
const std::string& root_element_name);
document_pimpl (parser_base&,
const std::string& root_element_namespace,
const std::string& root_element_name);
public:
// Parse a local file. The file is accessed with std::ifstream
// in binary mode. The std::ios_base::failure exception is used
// to report io errors (badbit and failbit) if exceptions are
// enabled. Otherwise error codes are used.
//
void
parse (const char* file);
void
parse (const std::string& file);
// Parse std::istream. std::ios_base::failure exception is used
// to report io errors (badbit and failbit) if exceptions are
// enabled. Otherwise error codes are used.
//
void
parse (std::istream&);
// Parse a chunk of input. You can call this function multiple
// times with the last call having the last argument true.
//
void
parse (const void* data, size_t size, bool last);
// Low-level Expat-specific parsing API.
//
void
parse_begin (XML_Parser);
void
parse_end ();
};
}
</pre>
<p>When the use of STL is disabled, the constructors and the <code>parse()</code>
function that use <code>std::string</code> in their signatures
are not available. When the use of iostream is disabled, the
<code>parse()</code> functions that parse a local file and
<code>std::istream</code> are not available.</p>
<p>When support for XML Schema polymorphism is enabled, the
overloaded <code>document_pimpl</code> constructors have
additional arguments which control polymorphic parsing.
For more information refer to <a href="#5.7">Section 5.7,
"Support for Polymorphism"</a>.
</p>
<p>The first argument to all overloaded constructors is the
parser for the type of the root element. The <code>parser_base</code>
class is the base type for all parser skeletons. The second and
third arguments to the <code>document_pimpl</code>'s constructors are
the root element's name and namespace.</p>
<p>The <code>parse_begin()</code> and <code>parse_end()</code> functions
present a low-level, Expat-specific parsing API for maximum control.
A typical use case would look like this (pseudo-code):</p>
<pre class="c++">
xxx_pimpl root_p;
document_pimpl doc_p (root_p, "root");
root_p.pre ();
doc_p.parse_begin (xml_parser);
while (more_stuff_to_parse)
{
// Call XML_Parse or XML_ParseBuffer:
//
if (XML_Parse (...) != XML_STATUS_ERROR)
break;
}
doc_p.parse_end ();
result_type result (root_p.post_xxx ());
</pre>
<p>Note that if your vocabulary use XML namespaces, the
<code>XML_ParserCreateNS()</code> functions should be used to create
the XML parser. Space (<code>XML_Char (' ')</code>) should be used
as a separator (the second argument to <code>XML_ParserCreateNS()</code>).
Furthermore, if XML_Parse or XML_ParseBuffer fail, call
<code>parse_end()</code> to determine the error which is indicated
either via exception or set as an error code.
</p>
<p>The error handling mechanisms employed by the <code>document_pimpl</code>
parser are described in <a href="#7.2">Section 7.2, "Exceptions"</a>
and <a href="#7.3">Section 7.3, "Error Codes"</a>.</p>
<h2><a name="7.2">7.2 Exceptions</a></h2>
<p>When C++ exceptions are used for error reporting, the system
errors are mapped to the standard exceptions. The out of memory
condition is indicated by throwing an instance
of <code>std::bad_alloc</code>. The stream operation errors
are reported by throwing an instance of
<code>std::ios_base::failure</code>.</p>
<p>The xml and schema errors are reported by throwing the
<code>xml_schema::parser_xml</code> and <code>xml_schema::parser_schema</code>
exceptions, respectively. These two exceptions derive from
<code>xml_schema::parser_exception</code> which, in turn, derives
from <code>std::exception</code>. As a result, you can handle
any error from these two categories by either catching
<code>std::exception</code>, <code>xml_schema::parser_exception</code>,
or individual exceptions. The further down the hierarchy you go
the more detailed error information is available to you. The
following listing shows the definitions of these exceptions:</p>
<pre class="c++">
namespace xml_schema
{
class parser_exception: public std::exception
{
public:
unsigned long
line () const;
unsigned long
column () const;
virtual const char*
text () const = 0;
...
};
std::ostream&
operator<< (std::ostream&, const parser_exception&);
typedef <implementation-details> parser_xml_error;
class parser_xml: public parser_exception
{
public:
parser_xml_error
code () const;
virtual const char*
text () const;
virtual const char*
what () const throw ();
...
};
typedef <implementation-details> parser_schema_error;
class parser_schema: public parser_exception
{
public:
parser_schema_error
code () const;
virtual const char*
text () const;
virtual const char*
what () const throw ();
...
};
}
</pre>
<p>The <code>parser_xml_error</code> and <code>parser_schema_error</code>
are implementation-specific error code types. The
<code>operator<<</code> defined for the <code>parser_exception</code>
class simply prints the error description as returned by the
<code>text()</code> function. The following example shows
how we can catch these exceptions:</p>
<pre class="c++">
int
main (int argc, char* argv[])
{
try
{
// Parse argv[1].
}
catch (const xml_schema::parser_exception& e)
{
cout << argv[1] << ":" << e.line () << ":" << e.column ()
<< ": error: " << e.text () << endl;
return 1;
}
}
</pre>
<p>Finally, for reporting application errors from parsing callbacks, you
can throw any exceptions of your choice. They are propagated to
the caller of the parser without any alterations.</p>
<h2><a name="7.3">7.3 Error Codes</a></h2>
<p>When C++ exceptions are not available, error codes are used to
report error conditions. Each parser skeleton and the root
<code>document_pimpl</code> parser have the following member
function for querying
the error status:</p>
<pre class="c++">
xml_schema::parser_error
_error () const;
</pre>
<p>To handle all possible error conditions, you will need to obtain
the error status after calls to: the <code>document_pimpl</code>'s
constructor (it performs memory allocations which may fail), the
root parser <code>pre()</code> callback, each call to the <code>parse()</code>
function, and, finally, the call to the root parser
<code>post_*()</code> callback. The definition of
<code>xml_schema::parser_error</code> class is presented below:</p>
<pre class="c++">
namespace xml_schema
{
class sys_error
{
public:
enum value
{
none,
no_memory,
open_failed,
read_failed,
write_failed
};
sys_error (value);
operator value () const;
static const char*
text (value);
...
};
typedef <implementation-details> parser_xml_error;
typedef <implementation-details> parser_schema_error;
class parser_error
{
public:
enum error_type
{
none,
sys,
xml,
schema,
app
};
error_type
type () const;
// Line and column are only available for xml, schema, and
// app errors.
//
unsigned long
line () const;
unsigned long
column () const;
// Returns true if there is an error so that you can write
// if (p.error ()) or if (error e = p.error ()).
//
typedef void (error::*bool_convertible) ();
operator bool_convertible () const;
// system
//
sys_error
sys_code () const;
const char*
sys_text () const;
// xml
//
parser_xml_error
xml_code () const;
const char*
xml_text () const;
// schema
//
parser_schema_error
schema_code () const;
const char*
schema_text () const;
// app
//
int
app_code () const;
...
};
}
</pre>
<p>The <code>parser_xml_error</code> and <code>parser_schema_error</code>
are implementation-specific error code types. The
<code>parser_error</code> class incorporates four categories of errors
which you can query by calling the <code>type()</code> function.
The following example shows how to handle error conditions with
error codes. It is based on the person record example presented
in <a href="#3">Chapter 3, "Parser Skeletons"</a>.</p>
<pre class="c++">
int
main (int argc, char* argv[])
{
// Construct the parser.
//
xml_schema::short_pimpl short_p;
xml_schema::string_pimpl string_p;
gender_pimpl gender_p;
person_pimpl person_p;
people_pimpl people_p;
person_p.parsers (string_p, string_p, gender_p, short_p);
people_p.parsers (person_p);
// Parse.
//
using xml_schema::parser_error;
parser_error e;
do
{
xml_schema::document_pimpl doc_p (people_p, "people");
if (e = doc_p._error ())
break;
people_p.pre ();
if (e = people_p._error ())
break;
doc_p.parse (argv[1]);
if (e = doc_p._error ())
break;
people_p.post_people ();
e = people_p._error ();
} while (false);
// Handle errors.
//
if (e)
{
switch (e.type ())
{
case parser_error::sys:
{
cerr << argv[1] << ": error: " << e.sys_text () << endl;
break;
}
case parser_error::xml:
{
cerr << argv[1] << ":" << e.line () << ":" << e.column ()
<< ": error: " << e.xml_text () << endl;
break;
}
case parser_error::schema:
{
cerr << argv[1] << ":" << e.line () << ":" << e.column ()
<< ": error: " << e.schema_text () << endl;
break;
}
case parser_error::app:
{
cerr << argv[1] << ":" << e.line () << ":" << e.column ()
<< ": application error " << e.app_code () << endl;
break;
}
}
return 1;
}
}
</pre>
<p>The error type for application errors is <code>int</code> with
the value <code>0</code> indicated the absence of error. You can
set the application error by calling the <code>_app_error()</code>
function inside a parser callback. For example, if it was invalid to
have a person younger than 18 in our people catalog, then we could
have implemented this check as follows: </p>
<pre class="c++">
class person_pimpl: public person_pskel
{
public:
virtual void
age (short a)
{
if (a < 18)
_app_error (1);
}
...
};
</pre>
<p>You can also set a system error by calling the <code>_sys_error()</code>
function inside a parser callback. This function has one argument of type
<code>xml_schema::sys_error</code> which was presented above. For
example:</p>
<pre class="c++">
class person_pimpl: public person_pskel
{
public:
virtual void
pre ()
{
p_ = new person ();
if (p_ == 0)
_sys_error (xml_schema::sys_error::no_memory);
}
...
private:
person* p_;
};
</pre>
<h2><a name="7.4">7.4 Reusing Parsers after an Error</a></h2>
<p>After a successful execution a parser returns into the initial
state and can be used to parse another document without any
extra actions. On the other hand, if an error occurred during
parsing and you would like to reuse the parser to parse another
document, you need to explicitly reset it into the initial
state as shown in the following code fragment:</p>
<pre class="c++">
int
main ()
{
...
std::vector<std::string> files = ...
xml_schema::document_pimpl doc_p (people_p, "people");
for (size_t i = 0; i < files.size (); ++i)
{
try
{
people_p.pre ();
doc_p.parse (files[i]);
people_p.post_people ();
}
catch (const xml_schema::parser_exception&)
{
doc_p.reset ();
}
}
}
</pre>
<p>If you do not need to reuse parsers after an error for example
because your application terminates or you create a new parser
instance in such situations, then you can avoid generating
parser reset code by specifying the <code>--suppress-reset</code>
XSD/e compiler option.</p>
<p>Your individual parser implementations may also require extra
actions in order to bring them into a usable state after an
error. To accomplish this you can override the <code>_reset()</code>
virtual function as shown below. Notice that when you override the
<code>_reset()</code> function in your implementation, you should
always call the base skeleton version to allow it to reset
its state:</p>
<pre class="c++">
class person_pimpl: public person_pskel
{
public:
virtual void
pre ()
{
p_ = new person ();
}
virtual void
_reset ()
{
person_pskel::_reset ();
delete p_;
p_ = 0;
}
...
private:
person* p_;
};
</pre>
<p>Note also that the <code>_reset()</code> mechanism is used only when
an error has occurred. To make sure that your parser implementations
arrive at the initial state during successful execution, use the
initialization (<code>pre()</code> and <code>_pre()</code>) and
finalization (<code>post_*()</code> and <code>_post()</code>)
callbacks.</p>
<!-- Appendix A -->
<h1><a name="A">Appendix A — Supported XML Schema Constructs</a></h1>
<p>The Embedded C++/Parser mapping supports validation of the following
W3C XML Schema constructs in the generated code.</p>
<!-- border="1" is necessary for html2ps -->
<table id="features" border="1">
<tr><th>Construct</th><th>Notes</th></tr>
<tr><th colspan="2">Structure</th></tr>
<tr><td>element</td><td></td></tr>
<tr><td>attribute</td><td></td></tr>
<tr><td>any</td><td></td></tr>
<tr><td>anyAttribute</td><td></td></tr>
<tr><td>all</td><td></td></tr>
<tr><td>sequence</td><td></td></tr>
<tr><td>choice</td><td></td></tr>
<tr><td>complex type, empty content</td><td></td></tr>
<tr><td>complex type, mixed content</td><td></td></tr>
<tr><td>complex type, simple content extension</td><td></td></tr>
<tr><td>complex type, simple content restriction</td><td></td></tr>
<tr><td>complex type, complex content extension</td><td></td></tr>
<tr><td>complex type, complex content restriction</td><td></td></tr>
<tr><td>list</td><td></td></tr>
<tr><th colspan="2">Facets</th></tr>
<tr><td>length</td><td>String-based types.</td></tr>
<tr><td>minLength</td><td>String-based types.</td></tr>
<tr><td>maxLength</td><td>String-based types.</td></tr>
<tr><td>pattern</td><td>String-based types.</td></tr>
<tr><td>whiteSpace</td><td>String-based types.</td></tr>
<tr><td>enumeration</td><td>String-based types.</td></tr>
<tr><td>minExclusive</td><td>Integer and floating-point types.</td></tr>
<tr><td>minInclusive</td><td>Integer and floating-point types.</td></tr>
<tr><td>maxExclusive</td><td>Integer and floating-point types.</td></tr>
<tr><td>maxInclusive</td><td>Integer and floating-point types.</td></tr>
<tr><th colspan="2">Datatypes</th></tr>
<tr><td>byte</td><td></td></tr>
<tr><td>unsignedByte</td><td></td></tr>
<tr><td>short</td><td></td></tr>
<tr><td>unsignedShort</td><td></td></tr>
<tr><td>int</td><td></td></tr>
<tr><td>unsignedInt</td><td></td></tr>
<tr><td>long</td><td></td></tr>
<tr><td>unsignedLong</td><td></td></tr>
<tr><td>integer</td><td></td></tr>
<tr><td>nonPositiveInteger</td><td></td></tr>
<tr><td>nonNegativeInteger</td><td></td></tr>
<tr><td>positiveInteger</td><td></td></tr>
<tr><td>negativeInteger</td><td></td></tr>
<tr><td>boolean</td><td></td></tr>
<tr><td>float</td><td></td></tr>
<tr><td>double</td><td></td></tr>
<tr><td>decimal</td><td></td></tr>
<tr><td>string</td><td></td></tr>
<tr><td>normalizedString</td><td></td></tr>
<tr><td>token</td><td></td></tr>
<tr><td>Name</td><td></td></tr>
<tr><td>NMTOKEN</td><td></td></tr>
<tr><td>NCName</td><td></td></tr>
<tr><td>language</td><td></td></tr>
<tr><td>anyURI</td><td></td></tr>
<tr><td>ID</td><td>Identity constraint is not enforced.</td></tr>
<tr><td>IDREF</td><td>Identity constraint is not enforced.</td></tr>
<tr><td>NMTOKENS</td><td></td></tr>
<tr><td>IDREFS</td><td>Identity constraint is not enforced.</td></tr>
<tr><td>QName</td><td></td></tr>
<tr><td>base64Binary</td><td></td></tr>
<tr><td>hexBinary</td><td></td></tr>
<tr><td>date</td><td></td></tr>
<tr><td>dateTime</td><td></td></tr>
<tr><td>duration</td><td></td></tr>
<tr><td>gDay</td><td></td></tr>
<tr><td>gMonth</td><td></td></tr>
<tr><td>gMonthDay</td><td></td></tr>
<tr><td>gYear</td><td></td></tr>
<tr><td>gYearMonth</td><td></td></tr>
<tr><td>time</td><td></td></tr>
</table>
</div>
</div>
</body>
</html>
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