UnlockFileEx function

Unlocks a region in the specified file. This function can operate either synchronously or asynchronously.

Syntax

BOOL WINAPI UnlockFileEx(
  _In_       HANDLE       hFile,
  _Reserved_ DWORD        dwReserved,
  _In_       DWORD        nNumberOfBytesToUnlockLow,
  _In_       DWORD        nNumberOfBytesToUnlockHigh,
  _Inout_    LPOVERLAPPED lpOverlapped
);

Parameters

hFile [in]

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.

nNumberOfBytesToUnlockLow [in]

The low-order part of the length of the byte range to unlock.

nNumberOfBytesToUnlockHigh [in]

The high-order part of the length of the byte range to unlock.

lpOverlapped [in, out]

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 value

If 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.

Remarks

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.

Requirements

See also

CreateFile

File Management Functions

LockFile

LockFileEx

OVERLAPPED

Synchronous and Asynchronous I/O

UnlockFile