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1//
2// waccess.cpp
3//
4// Copyright (c) Microsoft Corporation. All rights reserved.
5//
6// The _waccess() and _waccess_s() functions, which test file accessibility.
7//
8#include <corecrt_internal.h>
9#include <io.h>
10
11
12
13// Tests whether the specified file can be accessed with the specified mode. The
14// access_mode must be one of: 0 (exist only), 2 (write), 4 (read), 6 (read and
15// write). Returns zero if the file can be accessed with the given mode; returns
16// an error code otherwise or if an error occurs.
17extern "C" errno_t __cdecl _waccess_s(wchar_t const* const path, int const access_mode)
18{
19 _VALIDATE_CLEAR_OSSERR_RETURN_ERRCODE(path != nullptr, EINVAL);
20 _VALIDATE_CLEAR_OSSERR_RETURN_ERRCODE((access_mode & (~6)) == 0, EINVAL);
21
22 WIN32_FILE_ATTRIBUTE_DATA attributes;
23 if (!GetFileAttributesExW(path, GetFileExInfoStandard, &attributes))
24 {
25 __acrt_errno_map_os_error(GetLastError());
26 return errno;
27 }
28
29 // All directories have both read and write access:
30 if (attributes.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
31 return 0;
32
33 // If we require write access, make sure the read only flag is not set:
34 bool const file_is_read_only = (attributes.dwFileAttributes & FILE_ATTRIBUTE_READONLY) != 0;
35 bool const mode_requires_write = (access_mode & 2) != 0;
36
37 if (file_is_read_only && mode_requires_write)
38 {
39 _doserrno = ERROR_ACCESS_DENIED;
40 errno = EACCES;
41 return errno;
42 }
43
44 // Otherwise, the file is accessible:
45 return 0;
46
47}
48
49
50
51// The same as _waccess_s, but transforms all errors into a -1 return value.
52extern "C" int __cdecl _waccess(wchar_t const* const path, int const access_mode)
53{
54 return _waccess_s(path, access_mode) == 0 ? 0 : -1;
55}