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