Method eval_string_concat

external/pugixml/pugixml.cpp:7669–7716

		}
		
		xpath_string eval_string_concat(const xpath_context& c, const xpath_stack& stack)
		{
			assert(_type == ast_func_concat);

			xpath_allocator_capture ct(stack.temp);

			// count the string number
			size_t count = 1;
			for (xpath_ast_node* nc = _right; nc; nc = nc->_next) count++;

			// gather all strings
			xpath_string static_buffer[4];
			xpath_string* buffer = static_buffer;

			// allocate on-heap for large concats
			if (count > sizeof(static_buffer) / sizeof(static_buffer[0]))
			{
				buffer = static_cast<xpath_string*>(stack.temp->allocate(count * sizeof(xpath_string)));
				assert(buffer);
			}

			// evaluate all strings to temporary stack
			xpath_stack swapped_stack = {stack.temp, stack.result};

			buffer[0] = _left->eval_string(c, swapped_stack);

			size_t pos = 1;
			for (xpath_ast_node* n = _right; n; n = n->_next, ++pos) buffer[pos] = n->eval_string(c, swapped_stack);
			assert(pos == count);

			// get total length
			size_t length = 0;
			for (size_t i = 0; i < count; ++i) length += buffer[i].length();

			// create final string
			char_t* result = static_cast<char_t*>(stack.result->allocate((length + 1) * sizeof(char_t)));
			assert(result);

			char_t* ri = result;

			for (size_t j = 0; j < count; ++j)
				for (const char_t* bi = buffer[j].c_str(); *bi; ++bi)
					*ri++ = *bi;

			*ri = 0;

			return xpath_string(result, true);
		}

		xpath_string eval_string(const xpath_context& c, const xpath_stack& stack)
		{