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PathAllocCanonicalize function (pathcch.h)

Converts a path string into a canonical form.

This function differs from PathCchCanonicalize and PathCchCanonicalizeEx in that it returns the result on the heap. This means that the caller does not have to declare the size of the returned string and reduces stack use.

This function differs from PathCanonicalize in that it accepts paths with "\", "\?" and "\?\UNC" prefixes.

Note This function, PathCchCanonicalize, or PathCchCanonicalizeEx, should be used in place of PathCanonicalize.

Syntax

WINPATHCCHAPI HRESULT PathAllocCanonicalize(
  [in]  PCWSTR pszPathIn,
  [in]  ULONG  dwFlags,
  [out] PWSTR  *ppszPathOut
);

Parameters

[in] pszPathIn

A pointer to a buffer that contains the original string. This value cannot be NULL.

[in] dwFlags

One or more of the following flags:

Value Meaning
PATHCCH_NONE
0x0000000
 Do not allow for the construction of \\?\ paths (ie, long paths) longer than MAX_PATH .
PATHCCH_ALLOW_LONG_PATHS
0x00000001
 Allow the building of \\?\ paths longer than MAX_PATH .
PATHCCH_FORCE_ENABLE_LONG_NAME_PROCESS
0x00000002
 Forces the API to treat the caller as long path enabled, independent of the process's long name enabled state. This option can be used only when PATHCCH_ALLOW_LONG_PATHS is specified, and cannot be used with PATHCCH_FORCE_DISABLE_LONG_NAME_PROCESS.

Note This value is available starting in Windows 10, version 1703.
PATHCCH_FORCE_DISABLE_LONG_NAME_PROCESS
0x00000004
 Forces the API to treat the caller as long path disabled, independent of the process's long name enabled state. This option can be used only when PATHCCH_ALLOW_LONG_PATHS is specified, and cannot be used with PATHCCH_FORCE_ENABLE_LONG_NAME_PROCESS.

Note This value is available starting in Windows 10, version 1703.
PATHCCH_DO_NOT_NORMALIZE_SEGMENTS
0x00000008
 Disables the normalization of path segments that includes removing trailing dots and spaces. This enables access to paths that win32 path normalization will block.

Note  This value is available starting in Windows 10, version 1703.
PATHCCH_ENSURE_IS_EXTENDED_LENGTH_PATH
0x00000010
 Converts the input path into the extended length DOS device path form (with the \\?\ prefix) if not already in that form. This enables access to paths that are otherwise not addressable due to Win32 normalization rules (that can strip trailing dots and spaces) and path length limitations. This option implies the same behavior of PATHCCH_DO_NOT_NORMALIZE_SEGMENTS.

Note This value is available starting in Windows 10, version 1703.
PATHCCH_ENSURE_TRAILING_SLASH
0x00000020
 When combining or normalizing a path, ensure there is a trailing backslash.

Note This value is available starting in Windows 10, version 1703.
PATHCCH_CANONICALIZE_SLASHES
0x00000040
 Convert forward slashes to back slashes and collapse multiple slashes.

Note This value is available starting in Windows 11 (SDK version 10.0.22000.194).

[out] ppszPathOut

The address of a pointer to a buffer that, when this function returns successfully, receives the canonicalized path string. It is the responsibility of the caller to free this resource, when it is no longer needed, by calling the LocalFree function. This value cannot be NULL.

Return value

If this function succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

This function supports these alternate path forms:

  • \\?\
  • \\?\\UNC\
  • \\?\Volume{guid}\

This function does not convert forward slashes (/) into back slashes (\). With untrusted input, this function by itself, cannot be used to convert paths into a form that can be compared with other paths for sub-path or identity. Callers that need that ability should convert forward to back slashes before using this function.

Requirements

Requirement Value
Minimum supported client Windows 8 [desktop apps | UWP apps]
Minimum supported server Windows Server 2012 [desktop apps | UWP apps]
Target Platform Windows
Header pathcch.h
Library Pathcch.lib
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