std::filesystem::equivalent

equivalent.cpp

#include <vcruntime.h>

__std_win32_error __std_fs_equivalent(bool * _Result, const wchar_t *_Path1, const wchar_t *_Path2) noexcept
	{	// test for equivalent file names
	const __vcp_unique_handle _Handle1(_FilesysOpenFile(_Path1, FILE_READ_ATTRIBUTES,
		FILE_FLAG_BACKUP_SEMANTICS));
	if (!_Handle1.is_valid())
		{
		*_Result = false;
		return (GetLastError());
		}

	const __vcp_unique_handle _Handle2(_FilesysOpenFile(_Path2, FILE_READ_ATTRIBUTES,
		FILE_FLAG_BACKUP_SEMANTICS));
	if (!_Handle2.is_valid())
		{
		*_Result = false;
		return (GetLastError());
		}

	if (__vcp_has_GetFileInformationByHandleEx())
		{
		_FILE_ID_INFO _Info1;
		if (__vcp_GetFileInformationByHandleEx(_Handle1.get(), FileIdInfo, &_Info1, sizeof(_Info1)) == 0)
			{
			DWORD _LastError = GetLastError();
			if (_LastError == ERROR_INVALID_PARAMETER)
				{	// Windows Vista through Windows 7 don't support FileIdInfo
				goto tryGetFileInformationByHandle;
				}
			
			*_Result = false;
			return (_LastError);
			}

		_FILE_ID_INFO _Info2;
		if (__vcp_GetFileInformationByHandleEx(_Handle2.get(), FileIdInfo, &_Info2, sizeof(_Info2)) == 0)
			{
			*_Result = false;
			return (GetLastError());
			}

		static_assert(sizeof(_Info1) == sizeof(_Info1.VolumeSerialNumber) + sizeof(_Info1.FileId),
			"cannot combine comparisons");
		*_Result = memcmp(&_Info1, &_Info2, sizeof(_Info1)) == 0;
		return (__std_win32_success);
		}
		
tryGetFileInformationByHandle:
	if (__vcp_has_GetFileInformationByHandle())
		{
		BY_HANDLE_FILE_INFORMATION _Info1;
		if (__vcp_GetFileInformationByHandle(_Handle1.get(), &_Info1) == 0)
			{
			*_Result = false;
			return (GetLastError());
			}

		BY_HANDLE_FILE_INFORMATION _Info2;
		if (__vcp_GetFileInformationByHandle(_Handle2.get(), &_Info2) == 0)
			{
			*_Result = false;
			return (GetLastError());
			}

		*_Result = _Info1.dwVolumeSerialNumber == _Info2.dwVolumeSerialNumber
			&& _Info1.nFileIndexHigh == _Info2.nFileIndexHigh
			&& _Info1.nFileIndexLow == _Info2.nFileIndexLow;
		return (__std_win32_success);
		}

	return (ERROR_NOT_SUPPORTED);
	}