Boost read/write XML file: how to change the characters encoding? - boost

Question

I'm trying to read/write an XML file, using Boost functions read_xml and write_xml.
The XML file original encoding is "windows-1252", but after the read/write operations, the encoding became "utf-8".
This is the XML original file:
<?xml version="1.0" encoding="windows-1252" standalone="no" ?>
<lot>
<name>Lot1</name>
<lot_id>123</lot_id>
<descr></descr>
<job>
<name>TEST</name>
<num_items>2</num_items>
<item>
<label>Item1</label>
<descr>Item First Test</descr>
</item>
<item>
<label>Item2</label>
<descr>Item Second Test</descr>
</item>
</job>
</lot>
And this is the output one:
<?xml version="1.0" encoding="utf-8"?>
<lot>
<name>Lot1</name>
<lot_id>123</lot_id>
<descr></descr>
<job>
<name>TEST</name>
<num_items>2</num_items>
<item>
<label>Item1</label>
<descr>Item First Test</descr>
</item>
<item>
<label>Item2</label>
<descr>Item Second Test</descr>
</item>
</job>
</lot>
This is my C++ code (just a test code):
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>
using boost::property_tree::ptree;
ptree xmlTree;
read_xml(FILE_XML, xmlTree);
for (auto it = xmlTreeChild.begin(); it != xmlTreeChild.end();)
{
std::string strItem = it->first.data();
if (strcmp(strItem.c_str(), "item") == 0)
{
std::string strLabel = it->second.get_child("label").data();
if (strcmp(strLabel.c_str(), "item3") != 0)
{
it = xmlTreeChild.erase(it);
}
}
++it;
}
auto settings = boost::property_tree::xml_writer_make_settings<std::string>('\t', 1);
write_xml(FILE_XML, xmlTree, std::locale(), settings);
I need to read and re-write the file using the same encoding from the original file.
I've tried also to change the Locale settings, using:
std::locale newlocale1("English_USA.1252");
read_xml(FILE_XML, xmlTree, 0, newlocale1);
...
auto settings = boost::property_tree::xml_writer_make_settings<std::string>('\t', 1);
write_xml(FILE_XML, xmlTree, newlocale1, settings);
but I've got the same result.
How can I be able to read and write, using the original file encoding, with Boost functions?
Thank you

Answer 1

You can pass an encoding via the writer settings:
auto settings = boost::property_tree::xml_writer_make_settings<std::string>(
'\t', 1, "windows-1252");
Of course, make sure key/values are in fact latin1/cp1252 compatible (this makes sense as long as you read all the information from the source file; however you have to take care when e.g. assigning user input to a property tree node; you might need to convert from the input encoding to cp1252 first).
Live On Coliru

Answer 2

To fix the problem you experience you have to replace this line:
read_xml(FILE_XML, xmlTree);
with
read_xml(FILE_XML,
xmlTree,
boost::property_tree::xml_parser::trim_whitespace);
as far as I know your issue cannot be fixed only by modifying the settings of the write_xml function.
I tried it and worked: when I compare the files ignoring the whitespaces, the input and output xml files are identical.

Answer 3

You can also write to a string stream as following:
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>
boost::property_tree::ptree pt;
std::ostringstream oss;
write_xml(
oss, pt,
boost::property_tree::xml_writer_make_settings<char>(
'\t', 0, "ASCII"));