openosfh.gml

开放源码的编译器open watcom 1.6.0版的源代码

.func _open_osfhandle
#include <&iohdr>
int _open_osfhandle( long osfhandle, int access );
.funcend
.desc begin
The &func function allocates a POSIX-level file handle and sets it to
point to the operating system's internal file handle specified by
.arg osfhandle.
The value returned by
.kw _get_osfhandle
can be used as an argument to the &func function.
.im openacc
.np
When two or more manifest constants are used to form the
.arg flags
argument, the constants are combined with the bitwise-OR operator (|).
.np
The example below demonstrates the use of the
.kw _get_osfhandle
and &func functions.
Note that the example shows how the
.kw dup2
function can be used to obtain almost identical functionality.
.np
When the POSIX-level file handles associated with one OS file handle
are closed, the first one closes successfully but the others return
an error (since the first call close the file and released the OS file
handle).
So it is important to call
.kw close
at the right time, i.e., after all I/O operations are completed to the
file.
.desc end
.return begin
If successful, &func returns a POSIX-style file handle.
Otherwise, it returns -1.
.return end
.see begin
.seelist &function. close _dos_open dup2 fdopen fopen freopen _fsopen
.seelist &function. _get_osfhandle _grow_handles _hdopen open
.seelist &function. _open_osfhandle _os_handle _popen sopen
.see end
.exmp begin
#include <stdio.h>
#include <stdlib.h>
#include <&iohdr>
#include <fcntl.h>

void main()
{
    long os_handle;
    int fh1, fh2, rc;
.exmp break
    fh1 = open( "file",
                O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
                S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP );
    if( fh1 == -1 ) {
        printf( "Could not open output file\n" );
        exit( EXIT_FAILURE );
    }
    printf( "First POSIX handle %d\n", fh1 );
.exmp break
#if defined(USE_DUP2)
    fh2 = 6;
    if( dup2( fh1, fh2 ) == -1 ) fh2 = -1;
#else
    os_handle = _get_osfhandle( fh1 );
    printf( "OS Handle %ld\n", os_handle );

    fh2 = _open_osfhandle( os_handle, O_WRONLY |
                                      O_BINARY );
#endif
    if( fh2 == -1 ) {
        printf( "Could not open with second handle\n" );
        exit( EXIT_FAILURE );
    }
    printf( "Second POSIX handle %d\n", fh2 );
.exmp break
    rc = write( fh2, "trash\x0d\x0a", 7 );
    printf( "Write file using second handle %d\n", rc );

    rc = close( fh2 );
    printf( "Closing second handle %d\n", rc );
    rc = close( fh1 );
    printf( "Closing first handle %d\n", rc );
}
.exmp end
.class WATCOM
.system