unlock.gml

开放源码的编译器open watcom 1.6.0版的源代码

.func unlock
#include <&iohdr>
int unlock( int &fd,
            unsigned long offset,
            unsigned long nbytes );
.ixfunc2 '&OsIo' &func
.funcend
.desc begin
The &func function unlocks
.arg nbytes
amount of previously locked data in the file designated by
.arg &fd
starting at byte
.arg offset
in the file.
This allows other processes to lock this region of the file.
.np
Multiple regions of a file can be locked, but no overlapping regions
are allowed.
You cannot unlock multiple regions in the same call, even if the
regions are contiguous.
All locked regions of a file should be unlocked before closing a file
or exiting the program.
.if '&machsys' ne 'QNX' .do begin
.if '&machsys' ne 'PP' .do begin
.np
With DOS, locking is supported by version 3.0 or later.
Note that
.mono SHARE.COM
or
.mono SHARE.EXE
must be installed.
.do end
.do end
.desc end
.return begin
The &func function returns zero if successful, and &minus.1 when an
error occurs.
.im errnoref
.return end
.see begin
.seelist unlock lock locking open sopen
.see end
.exmp begin
#include <stdio.h>
#include <fcntl.h>
#include <&iohdr>

void main()
  {
    int &fd;
    char buffer[20];
.exmp break
.if '&machsys' eq 'PP' .do begin
    &fd = open( "file", O_RDWR );
.do end
.el .if '&machsys' eq 'QNX' .do begin
    &fd = open( "file", O_RDWR );
.do end
.el .do begin
    &fd = open( "file", O_RDWR | O_TEXT );
.do end
    if( &fd != -1 ) {
      if( lock( &fd, 0L, 20L ) ) {
        printf( "Lock failed\n" );
      } else {
        read( &fd, buffer, 20 );
        /* update the buffer here */
        lseek( &fd, 0L, SEEK_SET );
        write( &fd, buffer, 20 );
        unlock( &fd, 0L, 20L );
      }
      close( &fd );
    }
  }
.exmp end
.class WATCOM
.system