Class xpath_string

external/pugixml/pugixml.cpp:5243–5366

namespace
{
	class xpath_string
	{
		const char_t* _buffer;
		bool _uses_heap;

		static char_t* duplicate_string(const char_t* string, size_t length, xpath_allocator* alloc)
		{
			char_t* result = static_cast<char_t*>(alloc->allocate((length + 1) * sizeof(char_t)));
			assert(result);

			memcpy(result, string, length * sizeof(char_t));
			result[length] = 0;

			return result;
		}

		static char_t* duplicate_string(const char_t* string, xpath_allocator* alloc)
		{
			return duplicate_string(string, strlength(string), alloc);
		}

	public:
		xpath_string(): _buffer(PUGIXML_TEXT("")), _uses_heap(false)
		{
		}

		explicit xpath_string(const char_t* str, xpath_allocator* alloc)
		{
			bool empty = (*str == 0);

			_buffer = empty ? PUGIXML_TEXT("") : duplicate_string(str, alloc);
			_uses_heap = !empty;
		}

		explicit xpath_string(const char_t* str, bool use_heap): _buffer(str), _uses_heap(use_heap)
		{
		}

		xpath_string(const char_t* begin, const char_t* end, xpath_allocator* alloc)
		{
			assert(begin <= end);

			bool empty = (begin == end);

			_buffer = empty ? PUGIXML_TEXT("") : duplicate_string(begin, static_cast<size_t>(end - begin), alloc);
			_uses_heap = !empty;
		}

		void append(const xpath_string& o, xpath_allocator* alloc)
		{
			// skip empty sources
			if (!*o._buffer) return;

			// fast append for constant empty target and constant source
			if (!*_buffer && !_uses_heap && !o._uses_heap)
			{
				_buffer = o._buffer;
			}