pugixml/docs/samples/save_custom_writer.cpp

#include "pugixml.hpp"

#include <string>

#include <stdio.h>

struct xml_string_writer: pugi::xml_writer
{
	std::string result;

	virtual void write(const void* data, size_t size)
	{
		result += std::string(static_cast<const char*>(data), size);
	}
};

struct xml_memory_writer: pugi::xml_writer
{
	char* buffer;
	size_t capacity;

	size_t result;

	xml_memory_writer(): buffer(0), capacity(0), result(0)
	{
	}

	xml_memory_writer(char* buffer, size_t capacity): buffer(buffer), capacity(capacity), result(0)
	{
	}

	size_t written_size() const
	{
		return result < capacity ? result : capacity;
	}

	virtual void write(const void* data, size_t size)
	{
		if (result < capacity)
		{
			size_t chunk = (capacity - result < size) ? capacity - result : size;

			memcpy(buffer + result, data, chunk);
		}

		result += size;
	}
};

std::string node_to_string(pugi::xml_node node)
{
	xml_string_writer writer;
	node.print(writer);

	return writer.result;
}

char* node_to_buffer(pugi::xml_node node, char* buffer, size_t size)
{
	if (size == 0) return buffer;

	// leave one character for null terminator
	xml_memory_writer writer(buffer, size - 1);
	node.print(writer);

	// null terminate
	buffer[writer.written_size()] = 0;

	return buffer;
}

char* node_to_buffer_heap(pugi::xml_node node)
{
	// first pass: get required memory size
	xml_memory_writer counter;
	node.print(counter);

	// allocate necessary size (+1 for null termination)
	char* buffer = new char[counter.result + 1];

	// second pass: actual printing
	xml_memory_writer writer(buffer, counter.result);
	node.print(writer);

	// null terminate
	buffer[writer.written_size()] = 0;

	return buffer;
}

int main()
{
	// get a test document
	pugi::xml_document doc;
	doc.load("<foo bar='baz'>hey</foo>");

	// get contents as std::string (single pass)
	printf("contents: [%s]\n", node_to_string(doc).c_str());

	// get contents into fixed-size buffer (single pass)
	char large_buf[128];
	printf("contents: [%s]\n", node_to_buffer(doc, large_buf, sizeof(large_buf)));

	// get contents into fixed-size buffer (single pass, shows truncating behavior)
	char small_buf[22];
	printf("contents: [%s]\n", node_to_buffer(doc, small_buf, sizeof(small_buf)));

	// get contents into heap-allocated buffer (two passes)
	char* heap_buf = node_to_buffer_heap(doc);
	printf("contents: [%s]\n", heap_buf);
	delete[] heap_buf;
}