Category : C Source Code
Archive   : FILE_IO.ZIP
Filename : COMMIT.C

Output of file : COMMIT.C contained in archive : FILE_IO.ZIP
Copyright 1991 by David Thielen, All Rights Reserved.

This code example is from a commercial product and has restricted
rights. This code, or any code derived from this code may be
incorporated into any programs with the following restrictions;
1) It cannot be sold as source code, and 2) It cannot be sold in a
product which provides this code as an API.

#include "file_io.h"

// Keep in mind that a disk caching program may ignore the below so
// that while the file is flushed from DOS, it may still be in the
// buffers of the cache. Unfortunately, there is no way around this.

// fOpenCommit is true if the file was opened with the commit bit set.

unsigned FileCommit (int hFil,int fOpenCommit)
int hTmp;
unsigned uRtn=0;

// If we opened with commit & we are on DOS 4.0+, we don't need to
// do anything.
// OS/2 is DOS version 10 - we treat that like DOS 3.3
if ((fOpenCommit) && (DosMajVer >= 4) && (DosMajVer != 10))
return (0);

// If we are on version 3.3+, we can use file commit
if ((DosMajVer > 3) || ((DosMajVer == 3) && (DosMinVer >= 3)))
mov ah, 68h
mov bx, [hFil]
int 21h
jnc Ok
mov [uRtn], ax
return (uRtn);

// We now have 3 options. The first is to create a dup handle & then
// close it. However, this will fail if there are no available
// handles. The second option is to close the file & then re-open it
// but that requires we store the file name - which we will only need
// for DOS < 3.3 AND no available handles. Finally, we can reset the
// disk which will flush all buffers but won't update the directory
// entry (which means the size & date of the file MAY be wrong).

// If you are VERY concerned about this, there are 3 changes you can
// make in this code. 1) You can require DOS 3.3 or greater. 2) You
// can store the FULL name of the file. 3) You could close handle 0
// (which is generally CON) and then perform the dup/close, then re-open
// CON. Be careful on the final choice that you re-open whatever was
// truly on handle 0 - which in the case of re-directed I/O, may be
// a file.

// Lets try a dup
if ((hTmp = FileDup (hFil)) >= 0)
// ok close the dup & return
uRtn = FileClose (hTmp);

return (uRtn);

// We're fucked - all we can do is flush the buffers
// The directory entry WON'T be updated (which is only a problem
// if the file has grown since it was last closed/flushed).
// If you are using a file for transaction processing & it has a
// maximum size that's reasonable, open the file, write 0 bytes at
// the limit to size it, close & re-open it & then the below flush
// will always be sufficient.
mov ah, 0Dh
int 21h

return (0);

  3 Responses to “Category : C Source Code
Archive   : FILE_IO.ZIP
Filename : COMMIT.C

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

  2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

  3. But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: