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CFile::LockRange

Visual Studio 2008

Locks a range of bytes in an open file, throwing an exception if the file is already locked.

virtual void LockRange( 
   ULONGLONG dwPos, 
   ULONGLONG dwCount  
);

Parameters

dwPos: The byte offset of the start of the byte range to lock.
dwCount: The number of bytes in the range to lock.

Remarks

Locking bytes in a file prevents access to those bytes by other processes. You can lock more than one region of a file, but no overlapping regions are allowed.

When you unlock the region, using the UnlockRange member function, the byte range must correspond exactly to the region that was previously locked. The LockRange function does not merge adjacent regions; if two locked regions are adjacent, you must unlock each region separately.

Note:
This function is not available for the CMemFile-derived class.

Example

C++

CFile cfile;
cfile.Open(_T("LockRange_File.dat"), CFile::modeCreate |
   CFile::modeReadWrite);
ULONGLONG dwPos = 10;
ULONGLONG dwCount = 100;
cfile.LockRange(dwPos, dwCount);

// do something with the file

cfile.UnlockRange(dwPos, dwCount);

Requirements

Header: afx.h

Reference

CFile Class

Hierarchy Chart

CFile::UnlockRange

Other Resources

CFile Members

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