newlib-cygwin/newlib/libc/stdio/freopen.c

163 lines
4.0 KiB
C

/*
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley. The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
/*
FUNCTION
<<freopen>>---open a file using an existing file descriptor
INDEX
freopen
ANSI_SYNOPSIS
#include <stdio.h>
FILE *freopen(const char *<[file]>, const char *<[mode]>,
FILE *<[fp]>);
TRAD_SYNOPSIS
#include <stdio.h>
FILE *freopen(<[file]>, <[mode]>, <[fp]>)
char *<[file]>;
char *<[mode]>;
FILE *<[fp]>;
DESCRIPTION
Use this variant of <<fopen>> if you wish to specify a particular file
descriptor <[fp]> (notably <<stdin>>, <<stdout>>, or <<stderr>>) for
the file.
If <[fp]> was associated with another file or stream, <<freopen>>
closes that other file or stream (but ignores any errors while closing
it).
<[file]> and <[mode]> are used just as in <<fopen>>.
RETURNS
If successful, the result is the same as the argument <[fp]>. If the
file cannot be opened as specified, the result is <<NULL>>.
PORTABILITY
ANSI C requires <<freopen>>.
Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
<<lseek>>, <<open>>, <<read>>, <<sbrk>>, <<write>>.
*/
#include <time.h>
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include "local.h"
/*
* Re-direct an existing, open (probably) file to some other file.
*/
FILE *
_DEFUN (freopen, (file, mode, fp),
_CONST char *file _AND
_CONST char *mode _AND
register FILE *fp)
{
register int f;
int flags, oflags, e;
struct _reent *ptr;
_flockfile(fp);
CHECK_INIT (fp);
ptr = fp->_data;
if ((flags = __sflags (ptr, mode, &oflags)) == 0)
{
(void) fclose (fp);
_funlockfile(fp);
return NULL;
}
/*
* Remember whether the stream was open to begin with, and
* which file descriptor (if any) was associated with it.
* If it was attached to a descriptor, defer closing it,
* so that, e.g., freopen("/dev/stdin", "r", stdin) works.
* This is unnecessary if it was not a Unix file.
*/
if (fp->_flags == 0)
fp->_flags = __SEOF; /* hold on to it */
else
{
if (fp->_flags & __SWR)
(void) fflush (fp);
/* if close is NULL, closing is a no-op, hence pointless */
if (fp->_close != NULL)
(void) (*fp->_close) (fp->_cookie);
}
/*
* Now get a new descriptor to refer to the new file.
*/
f = _open_r (ptr, (char *) file, oflags, 0666);
e = ptr->_errno;
/*
* Finish closing fp. Even if the open succeeded above,
* we cannot keep fp->_base: it may be the wrong size.
* This loses the effect of any setbuffer calls,
* but stdio has always done this before.
*/
if (fp->_flags & __SMBF)
_free_r (ptr, (char *) fp->_bf._base);
fp->_w = 0;
fp->_r = 0;
fp->_p = NULL;
fp->_bf._base = NULL;
fp->_bf._size = 0;
fp->_lbfsize = 0;
if (HASUB (fp))
FREEUB (fp);
fp->_ub._size = 0;
if (HASLB (fp))
FREELB (fp);
fp->_lb._size = 0;
if (f < 0)
{ /* did not get it after all */
fp->_flags = 0; /* set it free */
ptr->_errno = e; /* restore in case _close clobbered */
_funlockfile(fp);
return NULL;
}
fp->_flags = flags;
fp->_file = f;
fp->_cookie = (_PTR) fp;
fp->_read = __sread;
fp->_write = __swrite;
fp->_seek = __sseek;
fp->_close = __sclose;
#ifdef __SCLE
if (__stextmode(fp->_file))
fp->_flags |= __SCLE;
#endif
_funlockfile(fp);
return fp;
}