Annotation of src/lib/libc/stdio/freopen.c, revision 1.2

1.1       dillon      1: /*-
                      2:  * Copyright (c) 1990, 1993
                      3:  *     The Regents of the University of California.  All rights reserved.
                      4:  *
                      5:  * This code is derived from software contributed to Berkeley by
                      6:  * Chris Torek.
                      7:  *
                      8:  * Redistribution and use in source and binary forms, with or without
                      9:  * modification, are permitted provided that the following conditions
                     10:  * are met:
                     11:  * 1. Redistributions of source code must retain the above copyright
                     12:  *    notice, this list of conditions and the following disclaimer.
                     13:  * 2. Redistributions in binary form must reproduce the above copyright
                     14:  *    notice, this list of conditions and the following disclaimer in the
                     15:  *    documentation and/or other materials provided with the distribution.
                     16:  * 3. All advertising materials mentioning features or use of this software
                     17:  *    must display the following acknowledgement:
                     18:  *     This product includes software developed by the University of
                     19:  *     California, Berkeley and its contributors.
                     20:  * 4. Neither the name of the University nor the names of its contributors
                     21:  *    may be used to endorse or promote products derived from this software
                     22:  *    without specific prior written permission.
                     23:  *
                     24:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     25:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     26:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     27:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     28:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     29:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     30:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     31:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     32:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     33:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     34:  * SUCH DAMAGE.
1.2     ! dillon     35:  *
        !            36:  * @(#)freopen.c       8.1 (Berkeley) 6/4/93
        !            37:  * $FreeBSD: src/lib/libc/stdio/freopen.c,v 1.5.2.1 2001/03/05 10:54:53 obrien Exp $
        !            38:  * $DragonFly: src/lib/libc/stdio/freopen.c,v 1.1 2003/06/16 04:33:32 dillon Exp $
1.1       dillon     39:  */
                     40: 
                     41: #include <sys/types.h>
                     42: #include <sys/stat.h>
                     43: #include <fcntl.h>
                     44: #include <errno.h>
                     45: #include <unistd.h>
                     46: #include <stdio.h>
                     47: #include <stdlib.h>
                     48: #include "libc_private.h"
                     49: #include "local.h"
                     50: 
                     51: /*
                     52:  * Re-direct an existing, open (probably) file to some other file.
                     53:  * ANSI is written such that the original file gets closed if at
                     54:  * all possible, no matter what.
                     55:  */
                     56: FILE *
                     57: freopen(file, mode, fp)
                     58:        const char *file, *mode;
                     59:        FILE *fp;
                     60: {
                     61:        int f;
                     62:        int flags, isopen, oflags, sverrno, wantfd;
                     63: 
                     64:        if ((flags = __sflags(mode, &oflags)) == 0) {
                     65:                (void) fclose(fp);
                     66:                return (NULL);
                     67:        }
                     68: 
                     69:        FLOCKFILE(fp);
                     70: 
                     71:        if (!__sdidinit)
                     72:                __sinit();
                     73: 
                     74:        /*
                     75:         * There are actually programs that depend on being able to "freopen"
                     76:         * descriptors that weren't originally open.  Keep this from breaking.
                     77:         * Remember whether the stream was open to begin with, and which file
                     78:         * descriptor (if any) was associated with it.  If it was attached to
                     79:         * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
                     80:         * should work.  This is unnecessary if it was not a Unix file.
                     81:         */
                     82:        if (fp->_flags == 0) {
                     83:                fp->_flags = __SEOF;    /* hold on to it */
                     84:                isopen = 0;
                     85:                wantfd = -1;
                     86:        } else {
                     87:                /* flush the stream; ANSI doesn't require this. */
                     88:                if (fp->_flags & __SWR)
                     89:                        (void) __sflush(fp);
                     90:                /* if close is NULL, closing is a no-op, hence pointless */
                     91:                isopen = fp->_close != NULL;
                     92:                if ((wantfd = fp->_file) < 0 && isopen) {
                     93:                        (void) (*fp->_close)(fp->_cookie);
                     94:                        isopen = 0;
                     95:                }
                     96:        }
                     97: 
                     98:        /* Get a new descriptor to refer to the new file. */
                     99:        f = _open(file, oflags, DEFFILEMODE);
                    100:        if (f < 0 && isopen) {
                    101:                /* If out of fd's close the old one and try again. */
                    102:                if (errno == ENFILE || errno == EMFILE) {
                    103:                        (void) (*fp->_close)(fp->_cookie);
                    104:                        isopen = 0;
                    105:                        f = _open(file, oflags, DEFFILEMODE);
                    106:                }
                    107:        }
                    108:        sverrno = errno;
                    109: 
                    110:        /*
                    111:         * Finish closing fp.  Even if the open succeeded above, we cannot
                    112:         * keep fp->_base: it may be the wrong size.  This loses the effect
                    113:         * of any setbuffer calls, but stdio has always done this before.
                    114:         */
                    115:        if (isopen)
                    116:                (void) (*fp->_close)(fp->_cookie);
                    117:        if (fp->_flags & __SMBF)
                    118:                free((char *)fp->_bf._base);
                    119:        fp->_w = 0;
                    120:        fp->_r = 0;
                    121:        fp->_p = NULL;
                    122:        fp->_bf._base = NULL;
                    123:        fp->_bf._size = 0;
                    124:        fp->_lbfsize = 0;
                    125:        if (HASUB(fp))
                    126:                FREEUB(fp);
                    127:        fp->_ub._size = 0;
                    128:        if (HASLB(fp))
                    129:                FREELB(fp);
                    130:        fp->_lb._size = 0;
                    131: 
                    132:        if (f < 0) {                    /* did not get it after all */
                    133:                fp->_flags = 0;         /* set it free */
                    134:                errno = sverrno;        /* restore in case _close clobbered */
                    135:                FUNLOCKFILE(fp);
                    136:                return (NULL);
                    137:        }
                    138: 
                    139:        /*
                    140:         * If reopening something that was open before on a real file, try
                    141:         * to maintain the descriptor.  Various C library routines (perror)
                    142:         * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
                    143:         */
                    144:        if (wantfd >= 0 && f != wantfd) {
                    145:                if (dup2(f, wantfd) >= 0) {
                    146:                        (void)_close(f);
                    147:                        f = wantfd;
                    148:                }
                    149:        }
                    150: 
                    151:        fp->_flags = flags;
                    152:        fp->_file = f;
                    153:        fp->_cookie = fp;
                    154:        fp->_read = __sread;
                    155:        fp->_write = __swrite;
                    156:        fp->_seek = __sseek;
                    157:        fp->_close = __sclose;
                    158:        FUNLOCKFILE(fp);
                    159:        return (fp);
                    160: }