#include "stdafx.h"
#include "StringUtil.h"
#include <stdarg.h>

namespace zl
{
	namespace base
	{

#ifdef OS_WINDOWS
#define VADUP(aq, ap)    (backup_ap = ap)
#else
#define VADUP(aq, ap)    va_copy(backup_ap, ap)
#endif

		size_t stringFormatAppendImpl(std::string *dst, const char *format, va_list ap)
		{
			char space[1024];    // just try with a small fixed size buffer

			va_list backup_ap;       // see "man va_start"
			VADUP(backup_ap, ap);

			int result = vsnprintf(space, sizeof(space), format, backup_ap);
			va_end(backup_ap);
			if ((result >= 0) && (result < static_cast<int>(sizeof(space))))
			{
				dst->append(space, result);
				return result;
			}

			int length = sizeof(space);
			while (true)        // Repeatedly increase buffer size until it fits
			{
				if (result < 0)
				{
					length *= 2;
				}
				else
				{
					length = result + 1;
				}

				char* buf = new char[length];
				VADUP(backup_ap, ap);    // Restore the va_list before we use it again
				result = vsnprintf(buf, length, format, backup_ap);
				va_end(backup_ap);
				if ((result >= 0) && (result < length))
				{
					dst->append(buf, result);
					delete[] buf;
					break;
				}
				delete[] buf;
			}

			return result;
		}

		size_t stringFormatAppend(std::string *dst, const char *format, ...)
		{
			va_list ap;
			va_start(ap, format);
			size_t result = stringFormatAppendImpl(dst, format, ap);
			va_end(ap);
			return result;
		}

		size_t stringFormat(std::string *dst, const char *format, ...)
		{
			va_list ap;
			va_start(ap, format);
			dst->clear();
			size_t result = stringFormatAppendImpl(dst, format, ap);
			va_end(ap);
			return result;
		}

		std::string stringFormat(const char *format, ...)
		{
			va_list ap;
			va_start(ap, format);
			std::string result;
			stringFormatAppendImpl(&result, format, ap);
			va_end(ap);
			return result;
		}

	} // namespace base
} // namespace zl