Unlocks a region in the specified file. This function can operate either synchronously or asynchronously.
SyntaxBOOL UnlockFileEx(
[in] HANDLE hFile,
DWORD dwReserved,
[in] DWORD nNumberOfBytesToUnlockLow,
[in] DWORD nNumberOfBytesToUnlockHigh,
[in, out] LPOVERLAPPED lpOverlapped
);
Parameters
[in] hFile
A handle to the file. The handle must have been created with either the GENERIC_READ or GENERIC_WRITE access right. For more information, see File Security and Access Rights.
dwReserved
Reserved parameter; must be zero.
[in] nNumberOfBytesToUnlockLow
The low-order part of the length of the byte range to unlock.
[in] nNumberOfBytesToUnlockHigh
The high-order part of the length of the byte range to unlock.
[in, out] lpOverlapped
A pointer to an OVERLAPPED structure that the function uses with the unlocking request. This structure contains the file offset of the beginning of the unlock range. You must initialize the hEvent member to a valid handle or zero. For more information, see Synchronous and Asynchronous I/O.
Return valueIf the function succeeds, the return value is nonzero.
If the function fails, the return value is zero or NULL. To get extended error information, call GetLastError.
Unlocking a region of a file releases a previously acquired lock on the file. The region to unlock must correspond exactly to an existing locked region. Two adjacent regions of a file cannot be locked separately and then unlocked using a single region that spans both locked regions.
Locks are released before the CloseHandle function is finished processing.
In Windows 8 and Windows Server 2012, this function is supported by the following technologies.
Technology Supported Server Message Block (SMB) 3.0 protocol Yes SMB 3.0 Transparent Failover (TFO) Yes SMB 3.0 with Scale-out File Shares (SO) Yes Cluster Shared Volume File System (CsvFS) Yes Resilient File System (ReFS) Yes Requirements Requirement Value Minimum supported client Windows XP [desktop apps | UWP apps] Minimum supported server Windows Server 2003 [desktop apps | UWP apps] Target Platform Windows Header fileapi.h (include Windows.h) Library Kernel32.lib DLL Kernel32.dll See alsoLocking and Unlocking Byte Ranges in Files
Synchronous and Asynchronous I/O
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