The LockFile function locks a region in an open file. Locking a region prevents other processes from accessing the region.
BOOL LockFile(
HANDLE hFile, // handle of file to lock
DWORD dwFileOffsetLow, // low-order word of lock region offset
DWORD dwFileOffsetHigh, // high-order word of lock region offset
DWORD nNumberOfBytesToLockLow, // low-order word of length to lock
DWORD nNumberOfBytesToLockHigh // high-order word of length to lock
);
The UnlockFile function unlocks a region in an open file. Unlocking a region enables other processes to access the region.
BOOL UnlockFile(
HANDLE hFile, // handle of file to unlock
DWORD dwFileOffsetLow, // low-order word of lock region offset
DWORD dwFileOffsetHigh, // high-order word of lock region offset
DWORD nNumberOfBytesToUnlockLow, // low-order word of length to unlock
DWORD nNumberOfBytesToUnlockHigh // high-order word of length to unlock
);