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<title>Embedded C++/Hybrid Mapping Getting Started Guide</title>
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<div id="titlepage">
<div class="title" id="first-title">Embedded C++/Hybrid Mapping</div>
<div class="title" id="second-title">Getting Started Guide</div>
<p>Copyright © 2005-2009 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/hybrid/guide/index.xhtml">XHTML</a>,
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/hybrid/guide/cxx-hybrid-e-guide.pdf">PDF</a>, and
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/hybrid/guide/cxx-hybrid-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>
<tr><th>2.5</th><td><a href="#2.5">Adding Serialization</a></td></tr>
<tr><th>2.6</th><td><a href="#2.6">A Minimal Version</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>3</th><td><a href="#3">Mapping Configuration</a>
<table class="toc">
<tr><th>3.1</th><td><a href="#3.1">Standard Template Library</a></td></tr>
<tr><th>3.2</th><td><a href="#3.2">Input/Output Stream Library</a></td></tr>
<tr><th>3.3</th><td><a href="#3.3">C++ Exceptions</a></td></tr>
<tr><th>3.4</th><td><a href="#3.4">XML Schema Validation</a></td></tr>
<tr><th>3.5</th><td><a href="#3.5">64-bit Integer Type</a></td></tr>
<tr><th>3.6</th><td><a href="#3.6">Parser and Serializer Reuse</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>4</th><td><a href="#4">Working with Object Models</a>
<table class="toc">
<tr><th>4.1</th><td><a href="#4.1">Namespaces</a></td></tr>
<tr><th>4.2</th><td><a href="#4.2">Memory Management</a></td></tr>
<tr><th>4.3</th><td><a href="#4.3">Attributes and Elements</a></td></tr>
<tr><th>4.4</th><td><a href="#4.4">Compositors</a></td></tr>
<tr><th>4.5</th><td><a href="#4.5">Accessing the Object Model</a></td></tr>
<tr><th>4.6</th><td><a href="#4.6">Modifying the Object Model</a></td></tr>
<tr><th>4.7</th><td><a href="#4.7">Creating the Object Model from Scratch</a></td></tr>
<tr><th>4.8</th><td><a href="#4.8">Customizing the Object Model</a></td></tr>
</table>
</td>
</tr>
<tr>
<th>5</th><td><a href="#5">Mapping for Built-In XML Schema Types</a>
<table class="toc">
<tr><th>5.1</th><td><a href="#5.1">Mapping for <code>QName</code></a></td></tr>
<tr><th>5.2</th><td><a href="#5.2">Mapping for <code>NMTOKENS</code> and <code>IDREFS</code>s</a></td></tr>
<tr><th>5.3</th><td><a href="#5.3">Mapping for <code>base54Binary</code> and <code>hexBinary</code>s</a></td></tr>
<tr><th>5.4</th><td><a href="#5.4">Time Zone Representation</a></td></tr>
<tr><th>5.5</th><td><a href="#5.5">Mapping for <code>date</code></a></td></tr>
<tr><th>5.6</th><td><a href="#5.6">Mapping for <code>dateTime</code></a></td></tr>
<tr><th>5.7</th><td><a href="#5.7">Mapping for <code>duration</code></a></td></tr>
<tr><th>5.8</th><td><a href="#5.8">Mapping for <code>gDay</code></a></td></tr>
<tr><th>5.9</th><td><a href="#5.9">Mapping for <code>gMonth</code></a></td></tr>
<tr><th>5.10</th><td><a href="#5.10">Mapping for <code>gMonthDay</code></a></td></tr>
<tr><th>5.11</th><td><a href="#5.11">Mapping for <code>gYear</code></a></td></tr>
<tr><th>5.12</th><td><a href="#5.12">Mapping for <code>gYearMonth</code></a></td></tr>
<tr><th>5.13</th><td><a href="#5.13">Mapping for <code>time</code></a></td></tr>
</table>
</td>
</tr>
<tr>
<th>6</th><td><a href="#6">Parsing and Serialization</a>
<table class="toc">
<tr><th>6.1</th><td><a href="#6.1">Customizing Parsers and Serializers</a></td></tr>
</table>
</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++/Hybrid 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><a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/index.xhtml">Embedded
C++/Parser Mapping Getting Started Guide</a>. The C++/Hybrid
mapping uses C++/Parser for XML parsing.</li>
<li><a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/serializer/guide/index.xhtml">Embedded
C++/Serializer Mapping Getting Started Guide</a>. The C++/Hybrid
mapping uses C++/Serializer for XML serialization.</li>
<li>The <code>INSTALL</code> file in the XSD/e distribution provides
build instructions for various platforms.</li>
<li>The <code>examples/cxx/hybrid/</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++/Hybrid 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++/Hybrid mapping.
XSD/e is a validating XML parser/serializer and data binding generator
for mobile and embedded systems. Embedded C++/Hybrid is a W3C XML
Schema to C++ mapping that represents the data stored in XML as a
light-weight, statically-typed, in-memory object model.
</p>
<h2><a name="1.1">1.1 Mapping Overview</a></h2>
<p>Based on a formal description of an XML vocabulary (schema), the
C++/Hybrid mapping produces a tree-like data structure suitable
for in-memory processing. The core of the mapping consists of C++
classes that constitute the object model and are derived from
types defined in XML Schema. The C++/Hybrid mapping uses the
APIs provided by the
<a href="http://www.codesynthesis.com/products/xsde/c++/parser/">Embedded
C++/Parser</a> and
<a href="http://www.codesynthesis.com/products/xsde/c++/serializer/">Embedded
C++/Serializer</a>
mappings to perform validation and parsing of XML to the object
model and validation and serialization of the object model to
XML. The following diagram illustrates the high-level architecture
of the C++/Hybrid mapping:</p>
<!-- align=center is needed for html2ps -->
<div class="img" align="center"><img src="figure-1.png"/></div>
<p>The use of well-defined APIs presented by the C++/Parser and
C++/Serializer mappings for XML parsing and serialization
allows a number of advanced techniques, for example, customization
of parsing and serialization code, filtering of XML during
parsing or object model during serialization, as well as the hybrid,
partially event-driven, partially in-memory processing
where the XML document is delivered to the application as
parts of the object model. The last feature combines the
ease and convenience of the in-memory processing model
with the ability to minimize the use of RAM and process documents
that would otherwise not fit into memory.
</p>
<p>The Embedded C++/Hybrid mapping 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 parsing and serialization
code is 2-10 times faster than general-purpose XML processors
while at the same time maintaining extremely low static and
dynamic memory footprints. For example, an executable that
performs validating XML parsing and serialization can be as small
as 150KB in size. The size can be further reduced by disabling
support for parsing or serialization as well as 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 with the minimal use of C++ templates.</p>
<p>A typical application that uses the C++/Hybrid mapping for XML
processing performs the following three steps: it first
reads (parses) an XML document to an in-memory object model, it
then performs some useful computations on that object model which
may involve modification of the model, and finally it may write
(serialize) the modified object model back to XML. The next chapter
presents a simple application that performs these three steps. The
following chapters describe the Embedded C++/Hybrid 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>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 and inefficient use of resources due to
the data being represented as text.</li>
<li>Extra validation code that is not used by the application.</li>
<li>Resulting applications are hard to debug, change, and
maintain.</li>
</ul>
<p>In contrast, a light-weight, statically-typed, vocabulary-specific
object model produced by the Embedded C++/Hybrid mapping allows
you to operate in your domain terms instead of the generic elements,
attributes, and text. Native data types are used to store the XML
data (for example, integers are stored as integers, not as text).
Validation code is included 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, 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++/Hybrid object
model 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 parsing and serializing XML. This includes navigating
the structure and converting between the text representation and
data types suitable for manipulation by the application logic.</li>
<li><b>Natural representation.</b> The object representation allows
you to access the XML data using your domain vocabulary instead
of generic elements, attributes, and text.</li>
<li><b>Concise code.</b> With the object representation the
application implementation is simpler and thus easier
to read and understand.</li>
<li><b>Safety.</b> The generated object model is statically
typed and uses functions instead of strings to access the
information. 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 client code that need to be
changed.</li>
<li><b>Efficiency.</b> If the application makes repetitive use
of the data extracted from XML, then the C++/Hybrid object model
is more efficient because the navigation is performed using
function calls rather than string comparisons and the XML
data is extracted only once. The runtime memory
usage is also reduced due to more efficient data storage
(for instance, storing numeric data as integers instead of
strings) as well as the static knowledge of cardinality
constraints.
<p>Furthermore, the generated XML parsing and serialization code
combines validation and data-to-text conversion in a single step.
This makes the generated code much more efficient than traditional
architectures with separate stages for validation and data
conversion.</p>
</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, access, modify, and
serialize a very simple XML document using the generated
C++/Hybrid object model as well as the XML parser and serializer. The
code presented in this chapter is based on the <code>hello</code>
example which can be found in the <code>examples/cxx/hybrid/</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>earth</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 XML Schema, 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>unbounded</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 XML vocabulary; it tells
everybody what valid documents of our XML-based language should look
like. The next step is to compile the schema to generate the object
model and the parser.</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++.
To do this we invoke the XSD/e compiler from a terminal (UNIX) or
a command prompt (Windows):
</p>
<pre class="terminal">
$ xsde cxx-hybrid --generate-parser --generate-aggregate hello.xsd
</pre>
<p>This invocation of the XSD/e compiler produces three pairs of C++ files:
<code>hello.hxx</code> and <code>hello.cxx</code>,
<code>hello-pskel.hxx</code> and <code>hello-pskel.cxx</code>, as well as
<code>hello-pimpl.hxx</code> and <code>hello-pimpl.cxx</code>. The
first pair contains the object model classes. The second pair contains
parser skeletons. Parser skeletons are generated by the C++/Parser
mapping which is automatically invoked by C++/Hybrid.
For now we can ignore parser skeletons except that we need to compile
them and link the result to our application. The last pair of files
contains parser implementations. They implement the parser skeletons
to create and populate the object model types from XML data. The generation
of parser skeletons and parser implementations is requested with the
<code>--generate-parser</code> XSD/e compiler option.</p>
<p>You may be wondering what is the <code>--generate-aggregate</code>
option for. This option instructs the XSD/e compiler to generate
parser and, as we will see later, serializer aggregates. The
generated parser implementation files mentioned above contain
a separate parser implementation class for each type defined
in XML Schema. These parser implementations need to be
instantiated and connected before we can use them to parse an XML document.
When you specify the <code>--generate-aggregate</code> option,
the XSD/e compiler generates a class (in the parser implementation
files), called parser aggregate, for each global element defined
in the schema (you can also generate a parser aggregate for a type
as well as control for which global elements parser aggregates
are generated, see the
<a href="http://www.codesynthesis.com/projects/xsde/documentation/xsde.xhtml">XSD/e
Compiler Command Line Manual</a> for more information). A parser
aggregate instantiates and connects all the necessary parser
implementations needed to parse an XML document with a given root
element. We will see how to use the parser aggregate for the
<code>hello</code> root element in the next section.</p>
<p>The following code fragment is taken from <code>hello.hxx</code>; it
shows what the C++ object model for our "Hello World" XML vocabulary
looks like:
</p>
<pre class="c++">
class hello
{
public:
hello ();
// greeting
//
const std::string&
greeting () const;
std::string&
greeting ();
void
greeting (const std::string&);
// name
//
typedef xsde::string_sequence name_sequence;
typedef name_sequence::iterator name_iterator;
typedef name_sequence::const_iterator name_const_iterator;
const name_sequence&
name () const;
name_sequence&
name ();
private:
...
};
</pre>
<p>The <code>hello</code> C++ class corresponds to the
<code>hello</code> XML Schema type. For each element
in this type a set of accessor and modifier functions
are generated inside the <code>hello</code> class. Note
that the member functions for the <code>greeting</code> and
<code>name</code> elements are different because of the
different cardinalities these two elements have
(<code>greeting</code> is a required single element and
<code>name</code> is a sequence of elements).</p>
<p>It is also evident that the built-in XML Schema type
<code>string</code> is mapped to <code>std::string</code>.
The internal <code>string_sequence</code> class that
is used in the <code>name_sequence</code> type definition
has an interface similar to <code>std::vector</code>. The
mapping between the built-in XML Schema types and C++ types
is described in more detail in <a href="#5">Chapter 5,
"Mapping for Built-in XML Schema Types"</a>.</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 our XML document:
</p>
<pre class="c++">
#include <iostream>
#include "hello.hxx"
#include "hello-pimpl.hxx"
using namespace std;
int
main (int argc, char* argv[])
{
try
{
// Parse.
//
hello_paggr hello_p;
xml_schema::document_pimpl doc_p (hello_p.root_parser (),
hello_p.root_name ());
hello_p.pre ();
doc_p.parse (argv[1]);
hello* h = hello_p.post ();
// Print what we've got.
//
for (hello::name_const_iterator i = h->name ().begin ();
i != h->name ().end ();
++i)
{
cout << h->greeting () << ", " << *i << "!" << endl;
}
delete h;
}
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 our application creates a document parser
and parses the XML file specified in the command line to the
object model. The <code>hello_paggr</code> class is the parser
aggregate class we discussed earlier. Parsing is covered in more
detail in <a href="#6">Chapter 6, "Parsing and Serialization"</a>.
The second part uses the returned object model to iterate over
names and print a greeting line for each of them. We also catch
and print the <code>xml_schema::parser_exception</code> exception
in case something goes wrong.
</p>
<h2><a name="2.4">2.4 Compiling and Running</a></h2>
<p>After saving our application from the previous section in
<code>driver.cxx</code>, we are ready to compile our first
program 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 hello-pimpl.cxx
$ c++ -o driver driver.o hello-pskel.o hello-pimpl.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.</p>
<p>We can also test the error handling. To test XML well-formedness
checking, we can try to parse <code>hello.hxx</code>:</p>
<pre class="terminal">
$ ./driver hello.hxx
hello.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>
<h2><a name="2.5">2.5 Adding Serialization</a></h2>
<p>While parsing and accessing the XML data may be everything
you need, there are applications that require creating new
or modifying existing XML documents. To request the generation
of serialization support we will need to add the
<code>--generate-serializer</code> option to our XSD/e
compiler invocation:</p>
<pre class="terminal">
$ xsde cxx-hybrid --generate-parser --generate-serializer \
--generate-aggregate hello.xsd
</pre>
<p>This will result in two additional pairs of C++ files:
<code>hello-sskel.hxx</code> and <code>hello-sskel.cxx</code>, as well as
<code>hello-simpl.hxx</code> and <code>hello-simpl.cxx</code>.
Similar to the parser files, the first pair contains serializer
skeletons (generated by the C++/Serializer mapping) and the second
pair contains serializer implementations as well as the serializer
aggregate for the <code>hello</code> root element.</p>
<p>Let us first examine an application that modifies an existing
object model and serializes it back to XML:</p>
<pre class="c++">
#include <iostream>
#include "hello.hxx"
#include "hello-pimpl.hxx"
#include "hello-simpl.hxx"
using namespace std;
int
main (int argc, char* argv[])
{
try
{
// Parse.
//
hello_paggr hello_p;
xml_schema::document_pimpl doc_p (hello_p.root_parser (),
hello_p.root_name ());
hello_p.pre ();
doc_p.parse (argv[1]);
hello* h = hello_p.post ();
// Change the greeting phrase.
//
h->greeting ("Hi");
// Add another entry to the name sequence.
//
h->name ().push_back ("mars");
// Serialize the modified object model to XML.
//
hello_saggr hello_s;
xml_schema::document_simpl doc_s (hello_s.root_serializer (),
hello_s.root_name ());
hello_s.pre (*h);
doc_s.serialize (cout);
hello_s.post ();
delete h;
}
catch (const xml_schema::parser_exception& e)
{
cerr << argv[1] << ":" << e.line () << ":" << e.column ()
<< ": " << e.text () << endl;
return 1;
}
catch (const xml_schema::serializer_exception& e)
{
cerr << "error: " << e.text () << endl;
return 1;
}
}
</pre>
<p>First, our application parses an XML document and obtains its
object model as in the previous example. Then it changes the
greeting string and adds another entry to the list of names.
Finally, it creates a document serializer and serializes the
object model back to XML. The resulting XML is written to
the standard output (<code>cout</code>) for us to inspect.
We could have also written the result to a file or memory
buffer by creating an instance of <code>std::ofstream</code>
or <code>std::ostringstream</code> and passing it to
<code>serialize()</code> instead of <code>cout</code>.
The <code>hello_saggr</code> class is the serializer aggregate
class we discussed earlier. Serialization is covered in more
detail in <a href="#6">Chapter 6, "Parsing and Serialization"</a>.</p>
<p>If we now compile and run this application (don't forget to
compile and link <code>hello-sskel.cxx</code> and
<code>hello-simpl.cxx</code>), we will see the
output as shown in the following listing:</p>
<pre class="xml">
<hello>
<greeting>Hi</greeting>
<name>sun</name>
<name>earth</name>
<name>world</name>
<name>mars</name>
</hello>
</pre>
<p>
We can also test XML Schema validation. We can "accidently"
remove all the names from the object model by adding the following
after: <code>push_back ("mars")</code>:</p>
<pre class="c++">
h->name ().clear ();
</pre>
<p>This will violate our vocabulary specification which requires
at least one <code>name</code> element to be present. If we
make the above change and recompile our application, we will
get the following output:</p>
<pre class="terminal">
$ ./driver hello.xml
error: expected element not encountered
</pre>
<p>It is also possible to create and serialize an object model from
scratch as shown in the following example. For this case we
can remove the <code>--generate-parser</code> option since
we don't need support for XML parsing.</p>
<pre class="c++">
#include <sstream>
#include <iostream>
#include "hello.hxx"
#include "hello-simpl.hxx"
using namespace std;
int
main (int argc, char* argv[])
{
try
{
hello h;
h.greeting ("Hi");
hello::name_sequence& ns = h.name ();
ns.push_back ("Jane");
ns.push_back ("John");
// Serialize the object model to XML.
//
hello_saggr hello_s;
xml_schema::document_simpl doc_s (hello_s.root_serializer (),
hello_s.root_name ());
ostringstream ostr;
hello_s.pre (*h);
doc_s.serialize (ostr);
hello_s.post ();
delete h;
cout << ostr.c_str () << endl;
}
catch (const xml_schema::serializer_exception& e)
{
cerr << "error: " << e.text () << endl;
return 1;
}
}
</pre>
<p>In this example we used the generated default constructor to
create an empty instance of type <code>hello</code>. We then
set greeting and, to reduce typing, we obtained a reference to
the name sequence which we used to add a few names. The
serialization part is identical to the previous example except
this time we first save the XML representation into a string.
If we compile and run this program, it produces the following
output:</p>
<pre class="xml">
<hello>
<greeting>Hi</greeting>
<name>Jane</name>
<name>John</name>
</hello>
</pre>
<h2><a name="2.6">2.6 A Minimal Version</a></h2>
<p>The previous sections showed a number of examples that relied
on STL for strings, iostream of input/output and C++ exceptions
for error handling.
As was mentioned in the introduction and will be discussed
in further detail in the next chapter, the C++/Hybrid mapping
can be configured only to rely on the minimal subset of C++.
In this section we will implement an example that parses,
prints, modifies and serializes the object model without
relying on STL, iostream, or C++ exceptions.</p>
<p>The first step is to instruct the XSD/e compiler not to use
any of the above features in the generated code. You may also
need to re-configure and rebuild the XSD/e runtime library
(<code>libxsde.a</code>) to disable STL, iostream, and
exceptions.</p>
<pre class="terminal">
$ xsde cxx-hybrid --no-stl --no-iostream --no-exceptions \
--generate-parser --generate-serializer --generate-aggregate \
hello.xsd
</pre>
<p>If you now study the generated <code>hello.hxx</code> file,
you will notice that the use of <code>std::string</code> type
is replaced with <code>char*</code>. When STL is disabled,
built-in XML Schema type <code>string</code> is mapped to a
C string. The following listing presents the content of
<code>driver.cxx</code> in full:</p>
<pre class="c++">
#include <stdio.h>
#include "people.hxx"
#include "people-pimpl.hxx"
#include "people-simpl.hxx"
using namespace std;
struct writer: xml_schema::writer
{
virtual bool
write (const char* s, size_t n)
{
return fwrite (s, n, 1, stdout) == 1;
}
virtual bool
flush ()
{
return fflush (stdout) == 0;
}
};
int
main (int argc, char* argv[])
{
// Open the file or use STDIN.
//
FILE* f = fopen (argv[1], "rb");
if (f == 0)
{
fprintf (stderr, "%s: unable to open\n", argc);
return 1;
}
// Parse.
//
using xml_schema::parser_error;
parser_error pe;
bool io_error = false;
hello* h = 0;
do
{
hello_paggr hello_p;
xml_schema::document_pimpl doc_p (hello_p.root_parser (),
hello_p.root_name ());
if (pe = doc_p._error ())
break;
hello_p.pre ();
if (pe = hello_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);
pe = doc_p._error ();
} while (!pe && !feof (f));
if (io_error || pe)
break;
h = hello_p.post ();
pe = hello_p._error ();
} while (false);
fclose (f);
// Handle parsing errors.
//
if (io_error)
{
fprintf (stderr, "%s: read failure\n", argc);
return 1;
}
if (pe)
{
switch (pe.type ())
{
case parser_error::sys:
{
fprintf (stderr, "%s: %s\n", argc, pe.sys_text ());
break;
}
case parser_error::xml:
{
fprintf (stderr, "%s:%lu:%lu: %s\n",
argc, pe.line (), pe.column (), pe.xml_text ());
break;
}
case parser_error::schema:
{
fprintf (stderr, "%s:%lu:%lu: %s\n",
argc, pe.line (), pe.column (), pe.schema_text ());
break;
}
default:
break;
}
return 1;
}
// Print what we've got.
//
for (hello::name_const_iterator i = h->name ().begin ();
i != h->name ().end ();
++i)
{
printf ("%s, %s!\n", h->greeting (), *i);
}
using xml_schema::strdupx;
// Change the greeting phrase.
//
h->greeting (strdupx ("Hi"));
// Add another entry to the name sequence.
//
h->name ().push_back (strdupx ("mars"));
// Serialize.
//
using xml_schema::serializer_error;
serializer_error se;
writer w;
do
{
hello_saggr hello_s;
xml_schema::document_simpl doc_s (hello_s.root_serializer (),
hello_s.root_name ());
if (se = doc_s._error ())
break;
hello_s.pre (*h);
if (se = hello_s._error ())
break;
doc_s.serialize (w);
if (se = doc_s._error ())
break;
hello_s.post ();
se = hello_s._error ();
} while (false);
delete h;
// Handle serializer errors.
//
if (se)
{
switch (se.type ())
{
case serializer_error::sys:
{
fprintf (stderr, "error: %s\n", se.sys_text ());
break;
}
case serializer_error::xml:
{
fprintf (stderr, "error: %s\n", se.xml_text ());
break;
}
case serializer_error::schema:
{
fprintf (stderr, "error: %s\n", se.schema_text ());
break;
}
default:
break;
}
return 1;
}
}
</pre>
<p>The parsing and serialization parts of the above example got
quite a bit more complex due to the lack of exceptions and iostream
support. For more information on what's going on there, refer to
<a href="#6">Chapter 6, "Parsing and Serialization"</a>. On the other
hand, the access and modification of the object model stayed
relatively unchanged. The only noticeable change is the use
of the <code>xml_schema::strdupx</code> function to create
C strings from string literals. We have to use this function
because the object model assumes ownership of the strings
passed. We also cannot use the standard C <code>strdup</code>
because the object model expects the strings to be allocated
with C++ operator <code>new[]</code> while C <code>strdup</code>
uses <code>malloc</code> (on most implementations operator
<code>new</code> is implemented in terms of <code>malloc</code>
so you can probably use <code>strdup</code> if you really
want to).</p>
<!-- Mapping Configuration -->
<h1><a name="3">3 Mapping Configuration</a></h1>
<p>The Embedded C++/Hybrid 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, as well as
parser and serializer implementation reuse styles. In the previous
chapter we have already got an overview of the changes to the
generated code that happen when we disable STL, iostream, and C++
exceptions. In this chapter we will discuss these and other
configuration parameters in more detail.</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++/Hybrid mapping always delivers character data to the application
in the UTF-8 encoding. The underlying XML parser used by the 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. C++/Hybrid also expects character
data supplied by the application to be in the UTF-8 encoding. The
underlying XML serializer used by the mapping produces the resulting
XML in the UTF-8 encoding as well.</p>
<h2><a name="3.1">3.1 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.</p>
<p>When STL is disabled, all string-based XML Schema types
(see <a href="#5">Chapter 5, "Mapping for Built-In XML Schema
Types"</a>) are mapped to C-style <code>char*</code> instead of
<code>std::string</code>. In this configuration when you set an
element or attribute value of a string-based type, the object
model assumes ownership of the string and expects that it was
allocated with operator <code>new[]</code>. To simplify
creation of such strings from string literals, the generated
code provides the <code>strdupx</code> and <code>strndupx</code>
functions in the <code>xml_schema</code> namespace. These functions
are similar to C <code>strdup</code> and <code>strndup</code> except
that they use operator <code>new[]</code> instead of <code>malloc</code>
to allocate the string:</p>
<pre class="c++">
namespace xml_schema
{
char*
strdupx (const char*);
char*
strndupx (const char*, size_t);
}
</pre>
<h2><a name="3.2">3.2 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, a
number of overloaded <code>parse()</code> and <code>serialize()</code>
functions in the document parser (<code>xml_schema::document_pimpl</code>)
and document serializer (<code>xml_schema::document_simpl</code>) become
unavailable. See
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/index.xhtml#7">Chapter 7,
"Document Parser and Error Handling"</a> in the Embedded
C++/Parser Mapping Getting Started Guide and
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/serializer/guide/index.xhtml#8">Chapter 8,
"Document Serializer and Error Handling"</a> in the Embedded
C++/Serializer Mapping Getting Started Guide for details.
</p>
<h2><a name="3.3">3.3 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 that may arise while parsing, serializing,
and modifying the object model are indicated with error codes
instead of exceptions. For more information on error handling
during parsing, see
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/index.xhtml#7">Chapter 7,
"Document Parser and Error Handling"</a> in the Embedded C++/Parser
Mapping Getting Started Guide. For more information on error handling
during serialization, see
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/serializer/guide/index.xhtml#8">Chapter 8,
"Document Serializer and Error Handling"</a> in the Embedded
C++/Serializer Mapping Getting Started Guide. For more information on
error handling in the object model, see <a href="#4">Chapter 4, "Working
with Object Models"</a> below.
</p>
<h2><a name="3.4">3.4 XML Schema Validation</a></h2>
<p>By default, XML Schema validation is enabled during both parsing
and serialization. To disable validation during parsing, you will
need to configure the XSD/e runtime to disable support for validation
in the C++/Parser mapping as well as pass the <code>--suppress-parser-val</code>
option to the XSD/e compiler when translating your schemas. To disable
validation during serialization, you will need to configure the XSD/e
runtime to disable support for validation in the C++/Serializer mapping
as well as pass the <code>--suppress-serializer-val</code>
option to the XSD/e compiler when translating your schemas. If you
are disabling validation during both parsing and serialization, you
can use the <code>--suppress-validation</code> option instead of the
two options mentioned above.</p>
<p>Disabling XML Schema validation allows to further increase the
parsing and serialization performance as well as reduce footprint in
cases where the data being parsed and/or serialized is known
to be valid.</p>
<h2><a name="3.5">3.5 64-bit Integer Type</a></h2>
<p>By default the 64-bit <code>long</code> and <code>unsignedLong</code>
built-in XML Schema 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="3.6">3.6 Parser and Serializer Reuse</a></h2>
<p>When one type in XML Schema inherits from another, it is
often desirable to be able to reuse the parser and serializer
implementations corresponding to the base type in the parser
and serializer implementations corresponding to the derived type.
XSD/e provides support for two 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.
The XSD/e runtime should be configured in accordance with the
reuse style used in the generated code. See <a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/index.xhtml#5.6">Section 5.6,
"Parser Reuse"</a> in the Embedded C++/Parser Mapping Getting Started
Guide and
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/serializer/guide/index.xhtml#6.6">Section 6.6,
"Serializer Reuse"</a> in the Embedded C++/Serializer Mapping Getting
Started Guide for details.</p>
<!-- Chapater 4 -->
<h1><a name="4">4 Working with Object Models</a></h1>
<p>As we have seen in the previous chapters, the XSD/e compiler generates
a C++ class for each type defined in XML Schema. Together these classes
constitute an object model for an XML vocabulary. In this chapter we
will take a closer look at different parts that comprise an
object model class as well as how to create, access, and modify
object models.</p>
<p>In this chapter 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="middle-name" type="xs:string" minOccurs="0"/>
<xs:element name="last-name" type="xs:string"/>
<xs:element name="gender" type="gender"/>
<xs:element name="age" type="xs:unsignedShort"/>
</xs:sequence>
<xs:attribute name="id" type="xs:unsignedInt" use="required"/>
</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 id="1">
<first-name>John</first-name>
<last-name>Doe</last-name>
<gender>male</gender>
<age>32</age>
</person>
<person id="2">
<first-name>Jane</first-name>
<middle-name>Mary</middle-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 generated object model classes: <code>gender</code>,
<code>person</code> and <code>people</code>. Here is how they
look with STL enabled:</p>
<pre class="c++">
// gender (fixed-length)
//
class gender: public std::string
{
public:
gender ();
gender (const gender&);
gender& operator= (const gender&);
};
// person (fixed-length)
//
class person
{
public:
person ();
person (const person&);
person& operator= (const person&);
// id
//
unsigned int
id () const;
unsigned int&
id ();
void
id (unsigned int);
// first-name
//
const std::string&
first_name () const;
std::string&
first_name ();
void
first_name (const std::string&);
// middle-name
//
bool
middle_name_present () const;
void
middle_name_present (bool);
const std::string&
middle_name () const;
std::string&
middle_name ();
void
middle_name (const std::string&);
// last-name
//
const std::string&
last_name () const;
std::string&
last_name ();
void
last_name (const std::string&);
// gender
//
const ::gender&
gender () const;
::gender&
gender ();
void
gender (const ::gender&);
// age
//
unsigned short
age () const;
unsigned short&
age ();
void
age (unsigned short);
private:
...
};
// people (variable-length)
//
class people
{
public:
people ();
private:
people (const people&);
people& operator= (const people&);
public:
// person
//
typedef xsde::fix_sequence<person> person_sequence;
typedef person_sequence::iterator person_iterator;
typedef person_sequence::const_iterator person_const_iterator;
const person_sequence&
person () const;
person_sequence&
person ();
private:
...
};
</pre>
<p>We will examine these classes in detail in the subsequent
sections.</p>
<h2><a name="4.1">4.1 Namespaces</a></h2>
<p>XSD/e maps XML namespaces specified in the <code>targetNamespace</code>
attribute in XML Schema to one or more nested C++ namespaces. By
default, a namespace URI is mapped to a sequence of C++ namespace
names by removing the protocol and host parts and splitting the
rest into a sequence of names with <code>'/'</code> as the name
separator. For example, the <code>http://www.codesynthesis.com/cs/my</code>
XML namespace is mapped to the <code>cs::my</code> C++ namespace.</p>
<p>The default mapping of namespace URIs to C++ namespaces
can be altered using the <code>--namespace-map</code> and
<code>--namespace-regex</code> compiler options. For example,
to map the <code>http://www.codesynthesis.com/my</code> XML
namespace to the <code>cs::my</code> C++ namespace, we can use
the following option:</p>
<pre class="terminal">
--namespace-map http://www.codesynthesis.com/my=cs::my
</pre>
<p>A vocabulary without a namespace is mapped to the global scope. This
also can be altered with the above options by using an empty name
for the XML namespace. For example, we could place the generated
object model classes for the <code>people.xsd</code> schema
into the <code>records</code> C++ namespace by adding the following
option:</p>
<pre class="terminal">
--namespace-map =records
</pre>
<h2><a name="4.2">4.2 Memory Management</a></h2>
<p>To ensure that objects are allocated and passed efficiently,
the C++/Hybrid mapping divides all object model types into
fixed-length and variable-length. A type is variable-length
if any of the following is true:</p>
<ol class="list">
<li>it is an XML Schema <code>list</code> type</li>
<li>it is an XML Schema <code>union</code> type and STL is disabled</li>
<li>it derives from a variable-length type</li>
<li>it contains an element or attribute of a variable-length type</li>
<li>it contains an element or compositor (<code>sequence</code>
or <code>choice</code>) with <code>maxOccurs</code>
greater than one</li>
<li>it is recursive (that is, one of its elements contains
a reference, directly or indirectly, to the type itself)</li>
</ol>
<p>The following build-in XML Schema types are variable-length:
<code>base64Binary</code>, <code>hexBinary</code>, <code>NMTOKENS</code>,
and <code>IDREFS</code>. Furthermore, if STL is disabled, all
string-based build-in XML Schema types are variable-length,
namely: <code>string</code>, <code>normalizedString</code>,
<code>token</code>, <code>Name</code>, <code>NMTOKEN</code>,
<code>NCName</code>, <code>language</code>, <code>QName</code>,
<code>ID</code>, <code>IDFER</code>, and <code>anyURI</code>.</p>
<p>Otherwise, a type is fixed-length. As you might have noticed from
the previous code listings, the XSD/e compiler adds a comment before
each generated object model class that states whether it is fixed or
variable-length. For example, the <code>people</code> type is
variable-length because it contains a sequence of <code>person</code>
elements (<code>maxOccurs="unbounded"</code>). If we recompile
the <code>people.xsd</code> schema with the <code>--no-stl</code>
option, the first two types will also become variable-length
since <code>gender</code> inherits from and <code>person</code>
contains elements of the <code>string</code> built-in type. And
when STL is disabled, <code>string</code> is variable-length.</p>
<p>The object model uses different methods for storing and passing
around fixed-length and variable-length types. Instances of
fixed-length types are stored and passed by value since it is
cheaper to copy than to allocate them dynamically (in the
STL case, the <code>std::string</code> is expected to support the
referenced-counted copy-on-write optimization, which makes
copying cheap).</p>
<p>Variable-length types are always allocated dynamically and
are stored and passed as pointers. Because copying an instance
of a variable-length type can be expensive, such types make
their copy constructor and copy assignment operators unavailable.</p>
<p>When you set a value of an element or attribute of a
variable-length type, the object model assumes ownership of
the pointed to object. It expects you to allocate the object with
operator <code>new</code> and will eventually delete it
with operator <code>delete</code>. As an example, let us extend
our <code>people.xsd</code> schema with the following type:</p>
<pre class="xml">
<xs:complexType name="staff">
<xs:sequence>
<xs:element name="permanent" type="people"/>
<xs:element name="contract" type="people"/>
</xs:sequence>
</xs:complexType>
</pre>
<p>If we compile it with XSD/e, we will get the following C++
class:</p>
<pre class="c++">
// staff (variable-length)
//
class staff
{
public:
staff ();
private:
staff (const staff&);
staff& operator= (const staff&);
public:
// permanent
//
const people&
permanent () const;
people&
permanent ();
void
permanent (people*);
// contract
//
const people&
contract () const;
people&
contract ();
void
contract (people*);
private:
...
};
</pre>
<p>Notice that unlike, say, the <code>first_name()</code> modifier
function in the <code>person</code> class, the <code>permanent()</code>
and <code>contract()</code> modifiers expect a pointer to the
<code>people</code> object. The following listing shows how
we can create and populate an instance of the <code>staff</code>
class. The use of smart pointers to hold the results of dynamic
allocations is omitted for brevity:</p>
<pre class="c++">
people* per = new people;
people* con = new people;
// Populate per and con.
staff s;
s->permanent (per) // Assumes ownership or per.
s->contract (con) // Assumes ownership or con.
</pre>
<h2><a name="4.3">4.3 Attributes and Elements</a></h2>
<p>As we have seen before, XSD/e generates a different
set of member functions for elements with different cardinalities.
The C++/Hybrid mapping divides all the possible element and attribute
cardinalities into three cardinality classes:
<em>one</em>, <em>optional</em>, and <em>sequence</em>.</p>
<p>The <em>one</em> cardinality class covers all elements that should
occur exactly once as well as the required attributes. In our
example, the <code>first-name</code>, <code>last-name</code>,
<code>gender</code>, and <code>age</code> elements as well as
the <code>id</code> attribute belong to this cardinality class.
The following code fragment shows again the accessor and modifier
functions that are generated for the <code>first-name</code> element
in the <code>person</code> class:</p>
<pre class="c++">
class person
{
// first-name
//
const std::string&
first_name () const;
std::string&
first_name ();
void
first_name (const std::string&);
};
</pre>
<p>The first two accessor functions return read-only (constant) and
read-write references to the element's value, respectively. The
modifier function sets the new value for the element. Note that
the signature of the modifier function varies depending on
whether the element or attribute is of a fixed or variable-length
type, as was discussed in the previous section.</p>
<p>The <em>optional</em> cardinality class covers all elements that
can occur zero or one time as well as optional attributes. In our
example, the <code>middle-name</code> element belongs to this
cardinality class. The following code fragment shows again the
accessor and modifier functions that are generated for this element
in the <code>person</code> class:</p>
<pre class="c++">
class person
{
// middle-name
//
bool
middle_name_present () const;
void
middle_name_present (bool);
const std::string&
middle_name () const;
std::string&
middle_name ();
void
middle_name (const std::string&);
};
</pre>
<p>Compared to the <em>one</em> cardinality class, <em>optional</em> adds
two extra functions for querying and modifying the element's presence
status. The following example shows how we can use these functions:</p>
<pre class="c++">
person& p = ...
if (p.middle_name_present ())
{
cout << p.middle_name () << endl;
p.middle_name_present (false); // Reset to the "not present" state.
}
</pre>
<p>Finally, the <em>sequence</em> cardinality class covers all elements
that can occur more than once. In our example, the
<code>person</code> element in the <code>people</code> type
belongs to this cardinality class. The following code fragment shows
again the type definitions as well as the accessor and modifier
functions that are generated for this element in the <code>people</code>
class:</p>
<pre class="c++">
class people
{
// person
//
typedef xsde::fix_sequence<person> person_sequence;
typedef person_sequence::iterator person_iterator;
typedef person_sequence::const_iterator person_const_iterator;
const person_sequence&
person () const;
person_sequence&
person ();
};
</pre>
<p>The <code>person_sequence</code> type is a sequence container for the
element's values. It has an interface similar to <code>std::vector</code>
and we will discuss it in more detail shortly. The <code>person_iterator</code>
and <code>person_const_iterator</code> types are read-write and read-only
(constant) iterators for the <code>person_sequence</code>
container.</p>
<p>Unlike other two cardinality classes, the <em>sequence</em> class
only provides accessor functions that return read-only (constant)
and read-write references to the sequence container. The
modification of the element values is performed my manipulating
the returned sequence container and elements that it contains.</p>
<p>In the remainder of this section we will examine the interfaces
of the sequence containers which differ slightly depending on
whether the element type is fixed or variable-length and whether
C++ exceptions are enabled. Also, when STL is disabled, string
sequences have a special interface which is also discussed
below.</p>
<p>When exceptions are enabled, the fixed-length type sequences
are implemented in terms of the following class template:</p>
<pre class="c++">
template <typename T>
class fix_sequence
{
public:
typedef T value_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T& reference;
typedef const T& const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef T* iterator;
typedef const T* const_iterator;
public:
fix_sequence ();
void
swap (fix_sequence&);
private:
fix_sequence (const fix_sequence&);
fix_sequence&
operator= (fix_sequence&);
public:
iterator
begin ();
const_iterator
begin () const;
iterator
end ();
const_iterator
end () const;
T&
front ();
const T&
front () const;
T&
back ();
const T&
back () const;
T&
operator[] (size_t);
const T&
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 T&);
iterator
insert (iterator, const T&);
void
reserve (size_t);
};
</pre>
<p>When 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++">
template <typename T>
class fix_sequence
{
public:
enum error
{
error_none,
error_no_memory
};
...
public:
error
push_back (const T&);
error
insert (iterator, const T&);
error
insert (iterator, const T&, iterator& result);
error
reserve (size_t);
};
</pre>
<p>That is, the functions that may require memory allocation
now return an error code that you will need to check in
order to detect the out of memory condition.</p>
<p>When exceptions are enabled, the variable-length type sequences
are implemented in terms of the following class template:</p>
<pre class="c++">
template <typename T>
class var_sequence
{
public:
typedef T value_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T& reference;
typedef const T& const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef <implementation details> iterator;
typedef <implementation details> const_iterator;
public:
var_sequence ();
void
swap (var_sequence&);
private:
var_sequence (const var_sequence&);
var_sequence&
operator= (var_sequence&);
public:
iterator
begin ();
const_iterator
begin () const;
iterator
end ();
const_iterator
end () const;
T&
front ();
const T&
front () const;
T&
back ();
const T&
back () const;
T&
operator[] (size_t);
const T&
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 (T*);
iterator
insert (iterator, T*);
error
reserve (size_t);
};
</pre>
<p>Most of this interface is identical to the fixed-length type
version except for the <code>push_back()</code> and
<code>insert()</code> functions. Similar to the modifier
functions for elements and attributes of variable-length
types, these two functions expect a pointer to the
dynamically-allocated instance of the type and assume
ownership of the passed object. To simplify error handling,
these two functions delete the passed object if the reallocation
of the underlying sequence buffer fails.</p>
<p>When C++ exceptions are disabled, the <code>push_back()</code>,
<code>insert()</code>, and <code>reserve()</code> functions
return an error code to signal the out of memory condition:</p>
<pre class="c++">
template <typename T>
class var_sequence
{
public:
enum error
{
error_none,
error_no_memory
};
...
public:
error
push_back (T*);
error
insert (iterator, T*);
error
insert (iterator, T*, iterator& result);
error
reserve (size_t);
};
</pre>
<p>When STL is enabled, the string sequence have the same
interface as <code>fix_sequence<std::string></code>. When
STL is disabled and strings are mapped to <code>char*</code>,
the string sequence has a special interface. When C++ exceptions are
enabled, it has the following definition:</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);
};
}
</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[]</code> and will be deallocated
with operator <code>delete[]</code> by the <code>string_sequence</code>
object. Similar to <code>var_sequence</code>, these two functions
free the passed string 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 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
in the <code>string_sequence</code> class 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="4.4">4.4 Compositors</a></h2>
<p>The XML Schema language provides three compositor constructs that
are used to group elements: <code>all</code>, <code>sequence</code>,
and <code>choice</code>. If a compositor has an <em>optional</em>
or <em>sequence</em> cardinality class (see <a href="#4.3">Section
4.3, "Attributes and Elements"</a>) or if a compositor is
inside <code>choice</code>, then the C++/Hybrid mapping generates
a nested class for such a compositor as well as a set of accessor
and modifier functions similar to the ones defined for elements
and attributes. Otherwise, the member functions, corresponding
to elements defined in a compositor, are generated directly in
the containing class.</p>
<p>Compositor classes are either fixed or variable-length and
obey the same storage and passing rules as object model
classes corresponding to XML Schema types (see <a href="#4.2">Section
4.2, "Memory Management"</a>). Consider the following schema
fragment as an example:</p>
<pre class="xml">
<complexType name="type">
<sequence>
<sequence minOccurs="0">
<element name="a" type="int"/>
<element name="b" type="string" maxOccurs="unbounded"/>
</sequence>
<sequence maxOccurs="unbounded">
<element name="c" type="int"/>
<element name="d" type="string"/>
</sequence>
</sequence>
</complexType>
</pre>
<p>The corresponding object model class is shown below:</p>
<pre class="c++">
// type (variable-length)
//
class type
{
public:
type ();
private:
type (const type&);
type& operator= (const type&);
public:
// sequence (variable-length)
//
class sequence_type
{
public:
sequence_type ();
private:
sequence_type (const sequence_type&);
sequence_type& operator= (const sequence_type&);
public:
// a
//
int
a () const;
int&
a ();
void
a (int);
// b
//
typedef xsde::string_sequence b_sequence;
typedef b_sequence::iterator b_iterator;
typedef b_sequence::const_iterator b_const_iterator;
const b_sequence&
b () const;
b_sequence&
b ();
private:
...
};
bool
sequence_present () const;
void
sequence_present (bool);
const sequence_type&
sequence () const;
sequence_type&
sequence ();
void
sequence (sequence_type*);
// sequence1 (fixed-length)
//
class sequence1_type
{
public:
sequence1_type ();
sequence1_type (const sequence1_type&);
sequence1_type& operator= (const sequence1_type&);
// c
//
int
c () const;
int&
c ();
void
c (int);
// d
//
const std::string&
d () const;
std::string&
d ();
void
d (const std::string&);
private:
...
};
typedef xsde::fix_sequence<sequence1_type> sequence1_sequence;
typedef sequence1_sequence::iterator sequence1_iterator;
typedef sequence1_sequence::const_iterator sequence1_const_iterator;
const sequence1_sequence&
sequence1 () const;
sequence1_sequence&
sequence1 ();
private:
...
};
</pre>
<p>The content of the outer <code>sequence</code> compositor is
generated in-line since this compositor belongs to the <em>one</em>
cardinality class. The first nested <code>sequence</code> compositor
is optional (<code>minOccurs="0"</code>), which results in a corresponding
nested class. Notice that the <code>sequence_type</code> is
variable-length and the accessor and modifier functions corresponding
to this <code>sequence</code> compositor are the same as for an
optional element or attribute. Similarly, the second nested
compositor is of the <em>sequence</em> cardinality class
(<code>maxOccurs="unbounded"</code>), which also results in a
nested class and a set of accessor functions.</p>
<p>Generated code corresponding to an <code>all</code> and
<code>sequence</code> compositor, whether in-line or as a
nested class, simply define accessor and modifier functions
for the elements that this compositor contains. For the
<code>choice</code> compositor, on the other hand,
additional types and functions are generated to support
querying and selecting the choice arm that is in effect.
Consider the following simple example:</p>
<pre class="xml">
<complexType name="type">
<choice>
<element name="a" type="int"/>
<element name="b" type="string"/>
<element name="c" type="boolean"/>
</choice>
</complexType>
</pre>
<p>The corresponding object model class is shown next:</p>
<pre class="c++">
// type (fixed-length)
//
class type
{
public:
type ();
type (const type&);
type& operator= (const type&);
// choice
//
enum choice_arm_tag
{
a_tag,
b_tag,
c_tag
};
choice_arm_tag
choice_arm () const;
void
choice_arm (choice_arm_tag);
// a
//
int
a () const;
int&
a ();
void
a (int);
// b
//
const std::string&
b () const;
std::string&
b ();
void
b (const std::string&);
// c
//
bool
c () const;
bool&
c ();
void
c (bool);
private:
...
};
</pre>
<p>The extra type is the <code>choice_arm_tag</code> enumeration
which defines a set of tags corresponding to each choice arm.
There are also the <code>choice_arm()</code> accessor and modifier
functions that can be used to query and set the current choice arm.
The following code fragment shows how we can use this class:</p>
<pre class="c++">
type& x = ...
switch (x.choice_arm ())
{
case type::a_tag:
{
cout << "a: " << x.a () << endl;
break;
}
case type::b_tag:
{
cout << "b: " << x.b () << endl;
break;
}
case type::c_tag:
{
cout << "c: " << x.c () << endl;
break;
}
}
// Modifiers automatically set the corresponding arm.
//
x.a (10);
// For accessors we need to select the arm explicitly.
//
x.choice_arm (type::b_tag);
x.b () = "b";
</pre>
<p>The following slightly more complex example triggers the generation of
nested classes for the <code>choice</code> compositor as well as for
the <code>sequence</code> compositor inside <code>choice</code>.
Notice that the nested class for <code>sequence</code> is generated
because it is in <code>choice</code> even though its cardinality
class is <em>one</em>.</p>
<pre class="xml">
<complexType name="type">
<choice maxOccurs="unbounded">
<sequence>
<element name="a" type="int"/>
<element name="b" type="string"/>
</sequence>
<element name="c" type="boolean"/>
</choice>
</complexType>
</pre>
<p>The corresponding object model class is shown next:</p>
<pre class="c++">
// type (variable-length)
//
class type
{
public:
type ();
private:
type (const type&);
type& operator= (const type&);
public:
// choice (fixed-length)
//
class choice_type
{
public:
choice_type ();
choice_type (const choice_type&);
choice_type& operator= (const choice_type&);
enum choice_arm_tag
{
sequence_tag,
c_tag
};
choice_arm_tag
choice_arm () const;
void
choice_arm (choice_arm_tag);
// sequence (fixed-length)
//
class sequence_type
{
public:
sequence_type ();
sequence_type (const sequence_type&);
sequence_type& operator= (const sequence_type&);
// a
//
int
a () const;
int&
a ();
void
a (int);
// b
//
const std::string&
b () const;
std::string&
b ();
void
b (const std::string&);
private:
...
};
const sequence_type&
sequence () const;
sequence_type&
sequence ();
void
sequence (const sequence_type&);
// c
//
bool
c () const;
bool&
c ();
void
c (bool);
private:
...
};
typedef xsde::fix_sequence<choice_type> choice_sequence;
typedef choice_sequence::iterator choice_iterator;
typedef choice_sequence::const_iterator choice_const_iterator;
const choice_sequence&
choice () const;
choice_sequence&
choice ();
private:
...
};
</pre>
<h2><a name="4.5">4.5 Accessing the Object Model</a></h2>
<p>In this section we will examine how to get to the information
stored in the object model for the person records vocabulary
introduced at the beginning of this chapter. The following
application accesses and prints the contents of the
<code>people.xml</code> file:</p>
<pre class="c++">
#include <memory>
#include <iostream>
#include "people.hxx"
#include "people-pimpl.hxx"
using namespace std;
int
main ()
{
// Parse.
//
people_paggr people_p;
xml_schema::document_pimpl doc_p (people_p.root_parser (),
people_p.root_name ());
people_p.pre ();
doc_p.parse ("people.xml");
auto_ptr<people> ppl (people_p.post ());
// Iterate over individual person records.
//
people::person_sequence& ps = ppl->person ();
for (people::person_iterator i = ps.begin (); i != ps.end (); ++i)
{
person& p = *i;
// Print names: first-name and last-name are required elements,
// middle-name is optional.
//
cout << "name: " << p.first_name () << " ";
if (p.middle_name_present ())
cout << p.middle_name () << " ";
cout << p.last_name () << endl;
// Print gender, age, and id which are all required.
//
cout << "gender: " << p.gender () << endl
<< "age: " << p.age () << endl
<< "id: " << p.id () << endl
<< endl;
}
}
</pre>
<p>This code shows common patterns of accessing elements and attributes
with different cardinality classes. For the sequence element
(<code>person</code> in the <code>people</code> type) we first obtain a
reference to the container and then iterate over individual
records. The values of elements and attributes with the
<em>one</em> cardinality class (<code>first-name</code>,
<code>last-name</code>, <code>gender</code>, <code>age</code>,
and <code>id</code>) can be obtained directly by calling the
corresponding accessor functions. For the optional
<code>middle-name</code> element we first check if the value is present
and only then call the corresponding accessor to retrieve it.</p>
<p>Note that when we want to reduce typing by creating a variable
representing a fragment of the object model that we are currently
working with (<code>ps</code> and <code>p</code> above), we obtain
a reference to that fragment instead of making a copy. This is
generally a good rule to follow when creating efficient
applications.</p>
<p>If we run the above application on our sample
<code>people.xml</code>, the output looks as follows:</p>
<pre class="terminal">
name: John Doe
gender: male
age: 32
id: 1
name: Jane Mary Doe
gender: female
age: 28
id: 2
</pre>
<h2><a name="4.6">4.6 Modifying the Object Model</a></h2>
<p>In this section we will examine how to modify the information
stored in the object model for our person records vocabulary.
The following application changes the contents of the
<code>people.xml</code> file:</p>
<pre class="c++">
#include <memory>
#include <iostream>
#include "people.hxx"
#include "people-pimpl.hxx"
#include "people-simpl.hxx"
using namespace std;
int
main ()
{
// Parse.
//
people_paggr people_p;
xml_schema::document_pimpl doc_p (people_p.root_parser (),
people_p.root_name ());
people_p.pre ();
doc_p.parse ("people.xml");
auto_ptr<people> ppl (people_p.post ());
// Iterate over individual person records and increment
// the age.
//
people::person_sequence& ps = ppl->person ();
for (people::person_iterator i = ps.begin (); i != ps.end (); ++i)
{
i->age ()++; // Alternative way: i->age (i->age () + 1)
}
// Add middle-name to the first record and remove it from
// the second.
//
person& john = ps[0];
person& jane = ps[1];
john.middle_name ("Mary");
jane.middle_name_present (false);
// Add another John record.
//
ps.push_back (john);
// Serialize the modified object model to XML.
//
people_saggr people_s;
xml_schema::document_simpl doc_s (people_s.root_serializer (),
people_s.root_name ());
people_s.pre (*ppl);
doc_s.serialize (cout);
people_s.post ();
}
</pre>
<p>The first modification the above application performs is iterating
over person records and incrementing the age value. This code
fragment shows how to modify the value of a required attribute
or element. The next modification shows how to set a new value
for the optional <code>middle-name</code> element as well
as clear its value. Finally, the example adds a copy of the
John Doe record to the <code>person</code> element sequence.</p>
<p>Note that in this case using references for the <code>ps</code>,
<code>john</code>, and <code>jane</code> variables is no longer
a performance improvement but a requirement for the application
to function correctly. If we hadn't used references, all our changes
would have been made on copies without affecting the object model.</p>
<p>If we run the above application on our sample <code>people.xml</code>,
the output looks as follows:</p>
<pre class="xml">
<?xml version="1.0"?>
<people>
<person id="1">
<first-name>John</first-name>
<middle-name>Mary</middle-name>
<last-name>Doe</last-name>
<gender>male</gender>
<age>33</age>
</person>
<person id="2">
<first-name>Jane</first-name>
<last-name>Doe</last-name>
<gender>female</gender>
<age>29</age>
</person>
<person id="1">
<first-name>John</first-name>
<middle-name>Mary</middle-name>
<last-name>Doe</last-name>
<gender>male</gender>
<age>33</age>
</person>
</people>
</pre>
<h2><a name="4.7">4.7 Creating the Object Model from Scratch</a></h2>
<p>In this section we will examine how to create a new object model
for our person records vocabulary. The following application
recreates the content of the original <code>people.xml</code>
file:</p>
<pre class="c++">
#include <iostream>
#include "people.hxx"
#include "people-simpl.hxx"
using namespace std;
int
main ()
{
people ppl;
people::person_sequence& ps = ppl.person ();
// John
//
{
person p;
p.first_name ("John");
p.last_name ("Doe");
p.age (32);
p.id (1);
gender g;
g.assign ("male");
p.gender (g);
ps.push_back (p);
}
// Jane
//
{
person p;
p.first_name ("Jane");
p.middle_name ("Mary");
p.last_name ("Doe");
p.age (28);
p.id (2);
gender g;
g.assign ("male");
p.gender (g);
ps.push_back (p);
}
// Serialize the object model to XML.
//
people_saggr people_s;
xml_schema::document_simpl doc_s (people_s.root_serializer (),
people_s.root_name ());
people_s.pre (ppl);
doc_s.serialize (cout);
people_s.post ();
}
</pre>
<p>The only new part in the above application is the calls
to the <code>people</code> and <code>person</code>
constructors. As a general rule, a newly created instance
does not assign any values to its elements and attributes.
That is, members with the <em>one</em> cardinality
class are left uninitialized, members with the <em>optional</em>
cardinality class are set to the "not present" state,
and members with the <em>sequence</em> cardinality class
have empty containers. After the instance has been
created, we can set its element and attribute values
using the modifier functions.</p>
<p>The above application produces the following output:</p>
<pre class="xml">
<?xml version="1.0" ?>
<people>
<person id="1">
<first-name>John</first-name>
<last-name>Doe</last-name>
<gender>male</gender>
<age>32</age>
</person>
<person id="2">
<first-name>Jane</first-name>
<middle-name>Mary</middle-name>
<last-name>Doe</last-name>
<gender>female</gender>
<age>28</age>
</person>
</people>
</pre>
<h2><a name="4.8">4.8 Customizing the Object Model</a></h2>
<p>Sometimes it is desirable to be able to store extra,
application-specific data in some object model classes or
nested compositor classes. Cases where this functionality
may be required include handling of typeless content
matched by XML Schema wildcards as well as a need for
an application to pass extra data as part of the object
model. The C++/Hybrid mapping provides a light-weight
mechanism for storing custom data by allowing you to add
a sequence of opaque objects, stored as <code>void*</code>,
to select generated classes. It is also possible to
customize the parsing and serialization code for such
classes in order to populate the custom data sequence
during parsing and later serialize it to XML. See
<a href="#6.1">Section 6.1, "Customizing Parsers and
Serializers"</a> for details.</p>
<p>To instruct the XSD/e compiler to include custom data
in a specific object model class, we need to use the
<code>--custom-data</code> option with the corresponding
XML Schema type name as its argument. To include custom
data into a nested compositor class, use its qualified
name starting with the XML Schema type, for example
<code>type::sequence1</code>. If we would like to
add the ability to store custom data in the generated
<code>person</code> class for our person records
vocabulary, we can compile <code>people.xsd</code>
like this:</p>
<pre class="terminal">
$ xsde cxx-hybrid --custom-type person people.xsd
</pre>
<p>The resulting <code>person</code> class will have the
following extra set of type definitions and functions:</p>
<pre class="c++">
// person (variable-length)
//
class person
{
public:
...
// Custom data.
//
typedef xsde::data_sequence custom_data_sequence;
typedef custom_data_sequence::iterator custom_data_iterator;
typedef custom_data_sequence::const_iterator custom_data_const_iterator;
const custom_data_sequence&
custom_data () const;
custom_data_sequence&
custom_data ();
};
</pre>
<p>Notice also that the <code>person</code> class is now variable-length
since it contains a sequence. When C++ exceptions are enabled, the
custom data sequence has the following interface:</p>
<pre class="c++">
class data_sequence
{
public:
typedef void* value_type;
typedef void** pointer;
typedef const void** const_pointer;
typedef void* reference;
typedef const void* const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef void** iterator;
typedef const void* const* const_iterator;
typedef void (*destroy_func) (void* data, size_t pos);
public:
data_sequence ();
void
destructor (destroy_func);
void
swap (data_sequence&);
private:
data_sequence (const data_sequence&);
data_sequence&
operator= (data_sequence&);
public:
iterator
begin ();
const_iterator
begin () const;
iterator
end ();
const_iterator
end () const;
void*
front ();
const void*
front () const;
void*
back ();
const void*
back () const;
void*
operator[] (size_t);
const void*
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 (void*);
iterator
insert (iterator, void*);
void
reserve (size_t);
};
</pre>
<p>The <code>destructor()</code> modifier allows you to specify
the clean up function used to free the sequence elements.
The second argument in this clean up function is the position
of the element in the sequence that is being freed. This allows
you to store objects of different types in the same custom
data sequence. The <code>push_back()</code> and <code>insert()</code>
functions free the passed object if the reallocation of the
underlying sequence buffer fails.</p>
<p>When exceptions are disabled, the <code>push_back()</code>,
<code>insert()</code>, and <code>reserve()</code> functions
return an error code to signal the out of memory condition:</p>
<pre class="c++">
class data_sequence
{
public:
enum error
{
error_none,
error_no_memory
};
...
public:
error
push_back (void*);
error
insert (iterator, void*);
error
insert (iterator, void*, iterator& result);
error
reserve (size_t);
};
</pre>
<p>The following code fragment shows how we can store and retrieve
custom data in the <code>person</code> class:</p>
<pre class="c++">
class data
{
...
};
void
destroy_data (void* p, size_t)
{
delete static_cast<data*> (p);
}
person& = ...;
person::custom_data_sequence& cd = p.custom_data ();
cd.destructor (&destroy_data);
// Store.
//
data* d = new data;
cd.push_back (d);
// Retrieve.
//
for (person::custom_data_iterator i = cd.begin (); i != cd.end (); ++i)
{
data* d = static_cast<data*> (*i);
}
</pre>
<!-- Built-in XML Schema Type Parsers -->
<h1><a name="5">5 Mapping for Built-In XML Schema Types</a></h1>
<p>In XML Schema, built-in types, such as <code>int</code>,
<code>string</code>, etc., are defined in the XML Schema namespace.
By default this namespace is mapped to C++ namespace
<code>xml_schema</code> (this mapping can be altered
with the <code>--namespace-map</code> option). The following table
summarizes the mapping of XML Schema built-in types to C++ types
in the C++/Hybrid mapping. Declarations for these types are
automatically included into each generated header file.</p>
<!-- border="1" is necessary for html2ps -->
<table id="builtin" border="1">
<tr>
<th>XML Schema type</th>
<th>Alias in the <code>xml_schema</code> namespace</th>
<th>C++ type</th>
</tr>
<tr>
<th colspan="3">fixed-length integral types</th>
</tr>
<!-- 8-bit -->
<tr>
<td><code>byte</code></td>
<td><code>byte</code></td>
<td><code>signed char</code></td>
</tr>
<tr>
<td><code>unsignedByte</code></td>
<td><code>unsigned_byte</code></td>
<td><code>unsigned char</code></td>
</tr>
<!-- 16-bit -->
<tr>
<td><code>short</code></td>
<td><code>short_</code></td>
<td><code>short</code></td>
</tr>
<tr>
<td><code>unsignedShort</code></td>
<td><code>unsigned_short</code></td>
<td><code>unsigned short</code></td>
</tr>
<!-- 32-bit -->
<tr>
<td><code>int</code></td>
<td><code>int_</code></td>
<td><code>int</code></td>
</tr>
<tr>
<td><code>unsignedInt</code></td>
<td><code>unsigned_int</code></td>
<td><code>unsigned int</code></td>
</tr>
<!-- 64-bit -->
<tr>
<td><code>long</code></td>
<td><code>long_</code></td>
<td><code>long</code> or<br/> <code>long long</code><br/>
<a href="#3.5">Section 3.5, "64-bit Integer Type"</a></td>
</tr>
<tr>
<td><code>unsignedLong</code></td>
<td><code>unsigned_long</code></td>
<td><code>unsigned long</code> or
<code>unsigned long long</code><br/>
<a href="#3.5">Section 3.5, "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</code></td>
<td><code>long</code></td>
</tr>
<tr>
<td><code>nonPositiveInteger</code></td>
<td><code>non_positive_integer</code></td>
<td><code>long</code></td>
</tr>
<tr>
<td><code>nonNegativeInteger</code></td>
<td><code>non_negative_integer</code></td>
<td><code>unsigned long</code></td>
</tr>
<tr>
<td><code>positiveInteger</code></td>
<td><code>positive_integer</code></td>
<td><code>unsigned long</code></td>
</tr>
<tr>
<td><code>negativeInteger</code></td>
<td><code>negative_integer</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</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_</code></td>
<td><code>float</code></td>
</tr>
<tr>
<td><code>double</code></td>
<td><code>double_</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</code></td>
<td><code>double</code></td>
</tr>
<tr>
<th colspan="3">string types</th>
</tr>
<tr>
<td><code>string</code></td>
<td><code>string</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>normalizedString</code></td>
<td><code>normalized_string</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>token</code></td>
<td><code>token</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>Name</code></td>
<td><code>name</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>NMTOKEN</code></td>
<td><code>nmtoken</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>NMTOKENS</code></td>
<td><code>nmtokens</code></td>
<td><a href="#5.2">Section 5.2, "Mapping for <code>NMTOKENS</code> and <code>IDREFS</code>"</a></td>
</tr>
<tr>
<td><code>NCName</code></td>
<td><code>ncname</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>language</code></td>
<td><code>language</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<th colspan="3">qualified name</th>
</tr>
<tr>
<td><code>QName</code></td>
<td><code>qname</code></td>
<td><a href="#5.1">Section 5.1, "Mapping for <code>QName</code>"</a></td>
</tr>
<tr>
<th colspan="3">ID/IDREF types</th>
</tr>
<tr>
<td><code>ID</code></td>
<td><code>id</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>IDREF</code></td>
<td><code>idref</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<td><code>IDREFS</code></td>
<td><code>idrefs</code></td>
<td><a href="#5.2">Section 5.2, "Mapping for <code>NMTOKENS</code> and <code>IDREFS</code>"</a></td>
</tr>
<tr>
<th colspan="3">URI types</th>
</tr>
<tr>
<td><code>anyURI</code></td>
<td><code>uri</code></td>
<td><code>std::string</code> or <code>char*</code><br/>
<a href="#3.1">Section 3.1, "Standard Template Library"</a></td>
</tr>
<tr>
<th colspan="3">binary types</th>
</tr>
<tr>
<td><code>base64Binary</code></td>
<td><code>base64_binary</code></td>
<td><a href="#5.3">Section 5.3, "Mapping for <code>base64Binary</code> and <code>hexBinary</code>"</a></td>
</tr>
<tr>
<td><code>hexBinary</code></td>
<td><code>hex_binary</code></td>
<td><a href="#5.3">Section 5.3, "Mapping for <code>base64Binary</code> and <code>hexBinary</code>"</a></td>
</tr>
<tr>
<th colspan="3">date/time types</th>
</tr>
<tr>
<td><code>date</code></td>
<td><code>date</code></td>
<td><a href="#5.5">Section 5.5, "Mapping for <code>date</code>"</a></td>
</tr>
<tr>
<td><code>dateTime</code></td>
<td><code>date_time</code></td>
<td><a href="#5.6">Section 5.6, "Mapping for <code>dateTime</code>"</a></td>
</tr>
<tr>
<td><code>duration</code></td>
<td><code>duration</code></td>
<td><a href="#5.7">Section 5.7, "Mapping for <code>duration</code>"</a></td>
</tr>
<tr>
<td><code>gDay</code></td>
<td><code>gday</code></td>
<td><a href="#5.8">Section 5.8, "Mapping for <code>gDay</code>"</a></td>
</tr>
<tr>
<td><code>gMonth</code></td>
<td><code>gmonth</code></td>
<td><a href="#5.9">Section 5.9, "Mapping for <code>gMonth</code>"</a></td>
</tr>
<tr>
<td><code>gMonthDay</code></td>
<td><code>gmonth_day</code></td>
<td><a href="#5.10">Section 5.10, "Mapping for <code>gMonthDay</code>"</a></td>
</tr>
<tr>
<td><code>gYear</code></td>
<td><code>gyear</code></td>
<td><a href="#5.11">Section 5.11, "Mapping for <code>gYear</code>"</a></td>
</tr>
<tr>
<td><code>gYearMonth</code></td>
<td><code>gyear_month</code></td>
<td><a href="#5.12">Section 5.12, "Mapping for <code>gYearMonth</code>"</a></td>
</tr>
<tr>
<td><code>time</code></td>
<td><code>time</code></td>
<td><a href="#5.13">Section 5.13, "Mapping for <code>time</code>"</a></td>
</tr>
</table>
<p>As you can see from the table above a number of built-in
XML Schema types are mapped to fundamental C++ types such
as <code>int</code> or <code>bool</code>. All string-based
XML Schema types are mapped to either <code>std::string</code>
or <code>char*</code>, depending on whether the use of STL is
enabled or not. A number of built-in types, such as
<code>QName</code>, the binary types, and the date/time types,
do not have suitable fundamental or standard C++ types to map to.
These types are implemented from scratch in the XSD/e runtime
and are discussed in more detail in the subsequent sections.</p>
<p>In cases where the schema calls for an inheritance from a built-in
type which is mapped to a fundamental C++ type, a special base
type corresponding to the fundamental type and defined in the
<code>xml_schema</code> namespace is used (C++ does not allow
inheritance from fundamental types). For example:</p>
<pre class="xml">
<complexType name="measure">
<simpleContent>
<extension base="int">
<attribute name="unit" type="string" use="required"/>
</extension>
</simpleContent>
</complexType>
</pre>
<p>The corresponding object model class is shown below:</p>
<pre class="c++">
// measure (fixed-length)
//
class measure: public xml_schema::int_base
{
public:
measure ();
measure (const measure&);
measure& operator= (const measure&);
// unit
//
const std::string&
unit () const;
std::string&
unit ();
void
unit (const std::string&);
private:
...
};
</pre>
<p>The <code>xml_schema::int_base</code> class has the following
interface:</p>
<pre class="c++">
namespace xml_schema
{
class int_base
{
public:
int_base ();
int_base&
operator= (int);
public:
int
base_value () const;
int&
base_value ();
void
base_value (int);
operator const int& () const;
operator int& ();
};
}
</pre>
<p>All other base types for fundamental C++ types have similar
interfaces. The only exception is the base type for string
types when STL is disabled:</p>
<pre class="c++">
namespace xml_schema
{
class string_base
{
public:
string_base ();
string_base&
operator= (char* x)
public:
const char*
base_value () const;
char*
base_value ();
void
base_value (char* x);
operator const char* () const;
operator char* ();
};
}
</pre>
<p>Note that the <code>string_base</code> object assumes ownership
of the strings passed to the assignment operator and the
<code>base_value()</code> modifier.</p>
<h2><a name="5.1">5.1 Mapping for <code>QName</code></a></h2>
<p>The <code>QName</code> built-in XML Schema type is mapped to the
<code>qname</code> class which represents an XML qualified name.
With STL enabled (<a href="#3.1">Section 3.1, "Standard Template
Library"</a>), it 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="#3.3">Section 3.3, "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="5.2">5.2 Mapping for <code>NMTOKENS</code> and <code>IDREFS</code></a></h2>
<p>The <code>NMTOKENS</code> and <code>IDREFS</code> built-in
XML Schema types are mapped to the string sequence type which
is discussed in <a href="#4.3">Section 4.3, "Attributes and
Elements"</a>.</p>
<h2><a name="5.3">5.3 Mapping for <code>base64Binary</code> and <code>hexBinary</code></a></h2>
<p>The <code>base64Binary</code> and <code>hexBinary</code> built-in
XML Schema types are mapped to the <code>buffer</code> class.
With C++ exceptions enabled (<a href="#3.3">Section 3.3, "C++
Exceptions"</a>), it 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> class 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="5.4">5.4 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>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 "not specified"
state. If the time zone offset is negative then both hours and
minutes components should be negative.</p>
<h2><a name="5.5">5.5 Mapping for <code>date</code></a></h2>
<p>The <code>date</code> built-in XML Schema type is mapped to the
<code>date</code> class 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="#5.4">Section 5.4, "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="5.6">5.6 Mapping for <code>dateTime</code></a></h2>
<p>The <code>dateTime</code> built-in XML Schema type is mapped to the
<code>date_time</code> class 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="#5.4">Section
5.4, "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="5.7">5.7 Mapping for <code>duration</code></a></h2>
<p>The <code>duration</code> built-in XML Schema type is mapped to the
<code>duration</code> class 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="5.8">5.8 Mapping for <code>gDay</code></a></h2>
<p>The <code>gDay</code> built-in XML Schema type is mapped to the
<code>gday</code> class 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="#5.4">Section 5.4, "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="5.9">5.9 Mapping for <code>gMonth</code></a></h2>
<p>The <code>gMonth</code> built-in XML Schema type is mapped to the
<code>gmonth</code> class 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="#5.4">Section 5.4, "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="5.10">5.10 Mapping for <code>gMonthDay</code></a></h2>
<p>The <code>gMonthDay</code> built-in XML Schema type is mapped to the
<code>gmonth_day</code> class 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="#5.4">Section 5.4, "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="5.11">5.11 Mapping for <code>gYear</code></a></h2>
<p>The <code>gYear</code> built-in XML Schema type is mapped to the
<code>gyear</code> class 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="#5.4">Section 5.4, "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="5.12">5.12 Mapping for <code>gYearMonth</code></a></h2>
<p>The <code>gYearMonth</code> built-in XML Schema type is mapped to the
<code>gyear_month</code> class 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="#5.4">Section 5.4, "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="5.13">5.13 Mapping for <code>time</code></a></h2>
<p>The <code>time</code> built-in XML Schema type is mapped to the
<code>time</code> class 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="#5.4">Section 5.4, "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>
<!-- Parsing and Serialization -->
<h1><a name="6">6 Parsing and Serialization</a></h1>
<p>As was mentioned in the introduction, the C++/Hybrid mapping
uses the C++/Parser and C++/Serializer mappings for XML parsing
and serialization. If your parsing and serialization requirements
are fairly basic, for example, parsing from and serializing to
a file or a memory buffer, then you don't need to concern yourself
with these two underlying mappings. On the other hand, the C++/Parser
and C++/Serializer mappings provide well-defined APIs which allow
a great amount of flexibility that may be useful in certain situations.
In such cases, you may need to get an understanding of how the
C++/Parser and C++/Serializer mappings work. See the
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/index.xhtml">Embedded
C++/Parser Mapping Getting Started Guide</a> and the
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/serializer/guide/index.xhtml">Embedded
C++/Serializer Mapping Getting Started Guide</a> for more detailed
information on these mappings.</p>
<p>For each type defined in XML Schema, the C++/Parser and
C++/Serializer mappings generate a parser skeleton class and
serializer skeleton class, respectively. These classes manage
parsing/serialization state, convert data between text
and C++ types, and perform XML Schema validation, if enabled.
Parser skeletons deliver the parsed data and serializer
skeletons request the data to be serialized with callbacks.
These callbacks are implemented by parser and serializer
implementation classes that are derived from the skeletons.
If the application uses the C++/Parser and C++/Serializer
mappings directly, these implementation classes are normally
written by the application developer to perform some
application-specific actions. In case of the C++/Hybrid mapping,
these implementations are automatically generated by the XSD/e
compiler to parse XML to object models and to serialize object
models to XML.
To request the generation of parser skeletons and
implementations, you need to specify the <code>--generate-parser</code>
XSD/e command line option. Similarly, to generate serializer
skeletons and implementations, you will need to use the
<code>--generate-serializer</code> option.</p>
<p>Before an XML document can be parsed or serialized, the
individual parser and serializer implementations need to
be instantiated and connected to each other. Again, if the
application uses the C++/Parser and C++/Serializer mappings
directly, this is done by the application developer. While
you can also do this with the generated C++/Hybrid parser and
serializer implementations, it is easier to request the
generation of parser and serializer aggregate classes with
the <code>--generate-aggregate</code> options. Aggregate
classes instantiate and connect all the necessary individual
parser and serializer implementations for a particular root
element or type. Consider again the <code>hello.xsd</code>
schema from <a href="#2">Chapter 2, "Hello World Example"</a>:</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>If we compile this schema with the <code>--generate-parser</code>,
<code>--generate-serializer</code>, and <code>--generate-aggregate</code>
options, we will have two aggregate classes, <code>hello_paggr</code>
and <code>hello_saggr</code>, generated for the root <code>hello</code>
element. The interface of the <code>hello_paggr</code> class is
presented below:</p>
<pre class="c++">
class hello_paggr
{
public:
hello_paggr ();
void
pre ();
hello*
post ();
hello_pimpl&
root_parser ();
static const char*
root_name ();
static const char*
root_namespace ();
};
</pre>
<p>The <code>pre()</code> and <code>post()</code> functions
call the corresponding callbacks on the root parser
implementation. The <code>root_parser()</code> function
returns the root parser implementation. The <code>root_name()</code>
and <code>root_namespace()</code> functions return the
root element name and namespace, respectively.</p>
<p>As was shown in <a href="#2">Chapter 2, "Hello World Example"</a>,
we can use this parser aggregate to create the document parser
(supplied by the C++/Parser mapping) and perform the parsing:</p>
<pre class="c++">
hello_paggr hello_p;
xml_schema::document_pimpl doc_p (hello_p.root_parser (),
hello_p.root_name ());
hello_p.pre ();
doc_p.parse ("hello.xml");
hello* h = hello_p.post ();
</pre>
<p>For more information on the <code>document_pimpl</code> class,
including the other variants of the <code>parse()</code> function
as well as error handling during parsing, see
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/parser/guide/index.xhtml#7">Chapter 7,
"Document Parser and Error Handling"</a> in the Embedded C++/Parser
Mapping Getting Started Guide.</p>
<p>The interface of the <code>hello_saggr</code> serializer aggregate
mirrors that of <code>hello_paggr</code> and is presented below:</p>
<pre class="c++">
class hello_saggr
{
public:
hello_saggr ();
void
pre (const hello&);
void
post ();
hello_simpl&
root_serializer ();
static const char*
root_name ();
static const char*
root_namespace ();
};
</pre>
<p>The <code>pre()</code> and <code>post()</code> functions
call the corresponding callbacks on the root serializer
implementation. The <code>root_serializer()</code> function
returns the root serializer implementation. The
<code>root_name()</code> and <code>root_namespace()</code>
functions return the root element name and namespace,
respectively.</p>
<p>As was shown in <a href="#2">Chapter 2, "Hello World Example"</a>,
we can use this serializer aggregate to create the document
serializer (supplied by the C++/Serializer mapping) and perform
the serialization:</p>
<pre class="c++">
hello_saggr hello_s;
xml_schema::document_simpl doc_s (hello_s.root_serializer (),
hello_s.root_name ());
hello_s.pre (*h);
doc_s.serialize (std::cout);
hello_s.post ();
</pre>
<p>For more information on the <code>document_simpl</code> class,
including the other variants of the <code>serialize()</code>
function as well as error handling during serialization, see
<a href="http://www.codesynthesis.com/projects/xsde/documentation/cxx/serializer/guide/index.xhtml#8">Chapter 8,
"Document Serializer and Error Handling"</a> in the Embedded
C++/Serializer Mapping Getting Started Guide.</p>
<h2><a name="6.1">6.1 Customizing Parsers and Serializers</a></h2>
<p>The C++/Hybrid mapping allows you to customize the generated
parser and serializer implementations. This mechanism can be
used, for example, to implement filtering, partially
event-driven XML processing, as well as parsing of content
matched by XML Schema wildcards. Filtering allows only parts
of the XML document to be parsed into the object model or only
parts of the object model to be serialized to XML. With
partially event-driven parsing and serialization, we can
process parts of the document as they become available as
well as handle documents that are too large to fit into
memory. This section expects you to have an understanding
of the C++/Parser and C++/Serializer programming models.</p>
<p>To request customization of a parser or serializer
implementation, you will need to specify the
<code>--custom-parser</code> or <code>--custom-serializer</code>
option, respectively. The argument format for these two options
is <code>type[=base[/include]]</code>. The <code>type</code>
component is the XML Schema type name being customized. Optional
<code>base</code> is a C++ name that should be given to the
generated version. It is normally used as a base for the custom
implementation. Optional <code>include</code> is the header file
that defines the custom implementation. It is <code>#include</code>'ed
into the generated code immediately after (if <code>base</code>
is specified) or instead of the generated version. The following
examples show how we can use these options:</p>
<pre class="terminal">
--custom-parser foo
--custom-parser foo=foo_base_pimpl
--custom-parser foo=foo_base_pimpl/foo/foo-custom.hxx
--custom-parser foo=/foo/foo-custom.hxx
</pre>
<p>The first version instructs the XSD/e compiler not to generate
the parser implementation for the <code>foo</code> XML Schema
type. The second version instructs the compiler to generate
the parser implementation for type <code>foo</code> but call
it <code>foo_base_pimpl</code>. The third version is similar to the
second except that the compiler generates the <code>#include</code>
directive with the <code>foo/foo-custom.hxx</code> file (which
presumably defines <code>foo_pimpl</code>) right after the
<code>foo_base_pimpl</code> class. The last version instructs
the XSD/e compiler to include <code>foo/foo-custom.hxx</code>
instead of generating the parser implementation for
<code>foo</code>. If you omit the last component, then
you can include the custom parser/serializer definitions
using one of the prologue or epilogue XSD/e compiler options.
See the <a href="http://www.codesynthesis.com/projects/xsde/documentation/xsde.xhtml">XSD/e
Compiler Command Line Manual</a> for details.</p>
<p>Once you specify the <code>--custom-parser</code> or
<code>--custom-serializer</code> option, you will need to
provide the custom implementation. You have a choice of either
basing it on the generated version and overriding some
callbacks or implementing it from scratch.</p>
<p>In the remainder of this section we will examine how to
customize the <code>people</code> parser and serializer
implementations from the example presented in <a href="#4">Chapter 4,
"Working with Object Models"</a>. Our custom parser
implementation will filter the records being parsed
based on a person's age. Similarly, the serializer will
only serialize records of a specific gender. The code
presented below is taken from the <code>filter</code>
example in the XSD/e distribution. Other examples
related to parser/serializer customization are
<code>wildcard</code> and <code>streaming</code>.</p>
<p>First, we compile the <code>people.xsd</code> schema
and instruct the XSD/e compiler to customize the
parser and serializer implementations for the <code>people</code>
XML Schema type:</p>
<pre class="terminal">
$ xsde cxx-hybrid --generate-parser --generate-serializer \
--custom-parser people=people_base_pimpl/people-custom-pimpl.hxx \
--custom-serializer people=people_base_simpl/people-custom-simpl.hxx \
--generate-aggregate people.xsd
</pre>
<p>The custom <code>people_pimpl</code> parser implementation
is based on the generated version and is saved to
<code>people-custom-pimpl.hxx</code>:</p>
<pre class="c++">
class people_pimpl: public people_base_pimpl
{
public:
void
age_filter (unsigned short min, unsigned short max)
{
min_age_ = min;
max_age_ = max;
}
virtual void
person (const ::person& p)
{
// Check if the age constraints are met.
//
unsigned short age = p.age ();
if (age >= min_age_ && age <= max_age_)
people_base_pimpl::person (p);
}
private:
unsigned short min_age_;
unsigned short max_age_;
};
</pre>
<p>Here we override the <code>person()</code> callback and,
if the filter conditions are satisfied, call the original
version which adds the person record to the object model.
Note that if the <code>person</code> object model class
were variable-length, then the instance would be
dynamically allocated and passed as a pointer. In this
situation, if we don't use the object, we need to delete it,
for example:</p>
<pre class="c++">
virtual void
person (const ::person* p)
{
unsigned short age = p->age ();
if (age >= min_age_ && age <= max_age_)
people_base_pimpl::person (p);
else
delete p;
}
</pre>
<p>The custom <code>people_simpl</code> parser implementation
is also based on the generated version and is saved to
<code>people-custom-simpl.hxx</code>:</p>
<pre class="c++">
class people_simpl: public people_base_simpl
{
public:
void
gender_filter (gender g)
{
gender_ = g;
}
virtual bool
person_next ()
{
// See if we have any more person records with the gender we
// are interested in.
//
people::person_const_iterator& i = people_base_simpl_state_.person_;
people::person_const_iterator& e = people_base_simpl_state_.person_end_;
for (; i != e; ++i)
{
if (i->gender () == gender_)
break;
}
return i != e;
}
private:
gender gender_;
};
</pre>
<p>Here we override the <code>person_next()</code> callback
where we locate the next record that satisfies the filter
conditions. Note that we use the serialization state
provided by the generated <code>people_base_simpl</code>
implementation.</p>
<p>The following code fragment shows a test driver that uses
the above implementations to filter the data during parsing
and serialization:</p>
<pre class="c++">
#include <memory>
#include <iostream>
#include "people.hxx"
#include "people-pimpl.hxx"
#include "people-simpl.hxx"
using namespace std;
int
main (int argc, char* argv[])
{
// Parse.
//
people_paggr people_p;
people_pimpl& root_p = people_p.root_parser ();
// Initialize the filter.
//
root_p.age_filter (1, 30);
xml_schema::document_pimpl doc_p (root_p, people_p.root_name ());
people_p.pre ();
doc_p.parse (argv[1]);
auto_ptr<people> ppl (people_p.post ());
// Print what we've got.
//
people::person_sequence& ps = ppl->person ();
for (people::person_iterator i = ps.begin (); i != ps.end (); ++i)
{
cerr << "first: " << i->first_name () << endl
<< "last: " << i->last_name () << endl
<< "gender: " << i->gender () << endl
<< "age: " << i->age () << endl
<< endl;
}
// Serialize.
//
people_saggr people_s;
people_simpl& root_s = people_s.root_serializer ();
// Initialize the filter.
//
gender g;
g.assign ("female");
root_s.gender_filter (g);
xml_schema::document_simpl doc_s (root_s, people_s.root_name ());
people_s.pre (*ppl);
doc_s.serialize (cout);
people_s.post ();
}
</pre>
<p>If we run this test driver on the following XML document:</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>
<person>
<first-name>Joe</first-name>
<last-name>Dirt</last-name>
<gender>male</gender>
<age>25</age>
</person>
</people>
</pre>
<p>We will get the following output:</p>
<pre class="terminal">
first: Jane
last: Doe
gender: female
age: 28
first: Joe
last: Dirt
gender: male
age: 25
<people>
<person>
<first-name>Jane</first-name>
<last-name>Doe</last-name>
<gender>female</gender>
<age>28</age>
</person>
</people>
</pre>
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