From 9cb49187f65bea1a9ec0fd6b35295632d6a7e121 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 9 May 2014 18:33:25 -0700
Subject: Add 'processing' example that uses higher-level API

---
 examples/processing/driver.cxx | 145 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 examples/processing/driver.cxx

(limited to 'examples/processing/driver.cxx')

diff --git a/examples/processing/driver.cxx b/examples/processing/driver.cxx
new file mode 100644
index 0000000..e0f939d
--- /dev/null
+++ b/examples/processing/driver.cxx
@@ -0,0 +1,145 @@
+// file      : examples/processing/driver.cxx
+// copyright : not copyrighted - public domain
+
+#include <string>
+#include <fstream>
+#include <iostream>
+
+#include <xml/parser.hxx>
+#include <xml/serializer.hxx>
+#include <xml/value-traits.hxx>
+
+using namespace std;
+using namespace xml;
+
+enum object_type {building, mountain};
+
+// Specialization of xml::value_traits for object_type. This mechanism is
+// used to implements XML-specific value type parsing and serialization.
+// By default the parser and serializer fall back onto iostream insertion
+// and extraction operators.
+//
+// This code also shows how we can reuse the parsing exception to implement
+// our own diagnostics.
+//
+namespace xml
+{
+  template <>
+  struct value_traits<object_type>
+  {
+    static object_type
+    parse (string s, const parser& p)
+    {
+      if (s == "building")
+        return building;
+      else if (s == "mountain")
+        return mountain;
+      else
+        throw parsing (p, "invalid object type '" + s + "'");
+    }
+
+    static string
+    serialize (object_type x, const serializer&)
+    {
+      if (x == building)
+        return "building";
+      else
+        return "mountain";
+    }
+  };
+}
+
+int
+main (int argc, char* argv[])
+{
+  if (argc != 2)
+  {
+    cerr << "usage: " << argv[0] << " <xml-file>" << endl;
+    return 1;
+  }
+
+  try
+  {
+    // Parse the input document and compute the average object position.
+    //
+    ifstream ifs (argv[1]);
+    parser p (ifs, argv[1]);
+
+    p.next_expect (parser::start_element, "object", content::complex);
+
+    unsigned int id (p.attribute<unsigned int> ("id"));
+    string name (p.element ("name"));
+    object_type type (p.element<object_type> ("type"));
+
+    float alat (0), alon (0);
+    unsigned int count (0);
+
+    do
+    {
+      p.next_expect (parser::start_element, "position", content::empty);
+
+      float lat (p.attribute<float> ("lat"));
+      float lon (p.attribute<float> ("lon"));
+
+      p.next_expect (parser::end_element); // position
+
+      alat += lat;
+      alon += lon;
+      count++;
+
+    } while (p.peek () == parser::start_element);
+
+    // Here is another example of re-using the parsing exception to
+    // implement application-level diagnostics. Every object in our
+    // vocabulary should have at least two position samples.
+    //
+    if (count < 2)
+      throw parsing (p, "at least two position samples required");
+
+    alat /= count;
+    alon /= count;
+
+    p.next_expect (parser::end_element); // object
+
+    // Serialize an XML document with simulated positions based on the
+    // average we just calculated.
+    //
+    serializer s (cout, "output");
+    s.start_element ("object");
+
+    s.attribute ("id", id);
+    s.element ("name", name);
+    s.element ("type", type);
+
+    for (unsigned int i (0); i < 2; ++i)
+    {
+      for (unsigned int j (0); j < 2; ++j)
+      {
+        s.start_element ("position");
+
+        float lat (alat + (i % 2 ? 0.0001F : -0.0001F));
+        float lon (alon + (j % 2 ? -0.0001F : 0.0001F));
+
+        s.attribute ("lat", lat);
+        s.attribute ("lon", lon);
+
+        s.end_element (); // position
+      }
+    }
+
+    s.end_element (); // object
+  }
+  catch (const ios_base::failure&)
+  {
+    cerr << "io failure" << endl;
+    return 1;
+  }
+  // This handler will handle both parsing (xml::parsing) and serialization
+  // (xml::serialization) exceptions.
+  //
+  catch (const xml::exception& e)
+  {
+    cerr << e.what () << endl;
+    return 1;
+  }
+}
-- 
cgit v1.1