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)
        {
            _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);
        }

        DWORD _LastError = GetLastError();
        if (_LastError != ERROR_INVALID_PARAMETER)
        {	// Windows Vista through Windows 7 don't support FileIdInfo
            *_Result = false;
            return (_LastError);
        }
        goto tryGetFileInformationByHandle;
    }
    
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);
}