Annotation of src/lib/libc/stdio/freopen.c, revision 1.4

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 $
1.3       hmp        38:  * $DragonFly$
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 *
1.3       hmp        57: freopen(const char *file, const char *mode, FILE *fp)
1.1       dillon     58: {
                     59:        int f;
1.4     ! hmp        60:        int dflags, flags, isopen, oflags, sverrno, wantfd;
1.1       dillon     61: 
                     62:        if ((flags = __sflags(mode, &oflags)) == 0) {
                     63:                (void) fclose(fp);
                     64:                return (NULL);
                     65:        }
                     66: 
                     67:        FLOCKFILE(fp);
                     68: 
                     69:        if (!__sdidinit)
                     70:                __sinit();
                     71: 
1.4     ! hmp        72:        sverrno = 0;
        !            73: 
        !            74:        /*
        !            75:         * If the filename is a NULL pointer, the caller is asking us to
        !            76:         * re-open the same file with a different mode. We allow this only
        !            77:         * if the modes are compatible.
        !            78:         */
        !            79:        if (file == NULL) {
        !            80:                /* See comment below regarding freopen() of closed files. */
        !            81:                if (fp->_flags == 0) {
        !            82:                        FUNLOCKFILE(fp);
        !            83:                        errno = EINVAL;
        !            84:                        return (NULL);
        !            85:                }
        !            86:                if ((dflags = fcntl(fp->_file, F_GETFL)) < 0) {
        !            87:                        sverrno = errno;
        !            88:                        fclose(fp);
        !            89:                        FUNLOCKFILE(fp);
        !            90:                        errno = sverrno;
        !            91:                        return (NULL);
        !            92:                }
        !            93:                if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
        !            94:                    (oflags & O_ACCMODE)) {
        !            95:                        fclose(fp);
        !            96:                        FUNLOCKFILE(fp);
        !            97:                        errno = EINVAL;
        !            98:                        return (NULL);
        !            99:                }
        !           100:                if ((oflags ^ dflags) & O_APPEND) {
        !           101:                        dflags &= ~O_APPEND;
        !           102:                        dflags |= oflags & O_APPEND;
        !           103:                        if (fcntl(fp->_file, F_SETFL, dflags) < 0) {
        !           104:                                sverrno = errno;
        !           105:                                fclose(fp);
        !           106:                                FUNLOCKFILE(fp);
        !           107:                                errno = sverrno;
        !           108:                                return (NULL);
        !           109:                        }
        !           110:                }
        !           111:                if (oflags & O_TRUNC)
        !           112:                        ftruncate(fp->_file, 0);
        !           113:                if (fseeko(fp, 0, oflags & O_APPEND ? SEEK_END : SEEK_SET) < 0 &&
        !           114:                    errno != ESPIPE) {
        !           115:                        sverrno = errno;
        !           116:                        fclose(fp);
        !           117:                        FUNLOCKFILE(fp);
        !           118:                        errno = sverrno;
        !           119:                        return (NULL);
        !           120:                }
        !           121:                f = fp->_file;
        !           122:                isopen = 0;
        !           123:                wantfd = -1;
        !           124:                goto finish;
        !           125:        }
        !           126: 
1.1       dillon    127:        /*
                    128:         * There are actually programs that depend on being able to "freopen"
                    129:         * descriptors that weren't originally open.  Keep this from breaking.
                    130:         * Remember whether the stream was open to begin with, and which file
                    131:         * descriptor (if any) was associated with it.  If it was attached to
                    132:         * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
                    133:         * should work.  This is unnecessary if it was not a Unix file.
                    134:         */
                    135:        if (fp->_flags == 0) {
                    136:                fp->_flags = __SEOF;    /* hold on to it */
                    137:                isopen = 0;
                    138:                wantfd = -1;
                    139:        } else {
                    140:                /* flush the stream; ANSI doesn't require this. */
                    141:                if (fp->_flags & __SWR)
                    142:                        (void) __sflush(fp);
                    143:                /* if close is NULL, closing is a no-op, hence pointless */
                    144:                isopen = fp->_close != NULL;
                    145:                if ((wantfd = fp->_file) < 0 && isopen) {
                    146:                        (void) (*fp->_close)(fp->_cookie);
                    147:                        isopen = 0;
                    148:                }
                    149:        }
                    150: 
                    151:        /* Get a new descriptor to refer to the new file. */
                    152:        f = _open(file, oflags, DEFFILEMODE);
                    153:        if (f < 0 && isopen) {
                    154:                /* If out of fd's close the old one and try again. */
                    155:                if (errno == ENFILE || errno == EMFILE) {
                    156:                        (void) (*fp->_close)(fp->_cookie);
                    157:                        isopen = 0;
                    158:                        f = _open(file, oflags, DEFFILEMODE);
                    159:                }
                    160:        }
                    161:        sverrno = errno;
                    162: 
1.4     ! hmp       163: finish:
1.1       dillon    164:        /*
                    165:         * Finish closing fp.  Even if the open succeeded above, we cannot
                    166:         * keep fp->_base: it may be the wrong size.  This loses the effect
                    167:         * of any setbuffer calls, but stdio has always done this before.
                    168:         */
                    169:        if (isopen)
                    170:                (void) (*fp->_close)(fp->_cookie);
                    171:        if (fp->_flags & __SMBF)
                    172:                free((char *)fp->_bf._base);
                    173:        fp->_w = 0;
                    174:        fp->_r = 0;
                    175:        fp->_p = NULL;
                    176:        fp->_bf._base = NULL;
                    177:        fp->_bf._size = 0;
                    178:        fp->_lbfsize = 0;
                    179:        if (HASUB(fp))
                    180:                FREEUB(fp);
                    181:        fp->_ub._size = 0;
                    182:        if (HASLB(fp))
                    183:                FREELB(fp);
                    184:        fp->_lb._size = 0;
                    185: 
                    186:        if (f < 0) {                    /* did not get it after all */
                    187:                fp->_flags = 0;         /* set it free */
                    188:                errno = sverrno;        /* restore in case _close clobbered */
                    189:                FUNLOCKFILE(fp);
                    190:                return (NULL);
                    191:        }
                    192: 
                    193:        /*
                    194:         * If reopening something that was open before on a real file, try
                    195:         * to maintain the descriptor.  Various C library routines (perror)
                    196:         * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
                    197:         */
                    198:        if (wantfd >= 0 && f != wantfd) {
                    199:                if (dup2(f, wantfd) >= 0) {
                    200:                        (void)_close(f);
                    201:                        f = wantfd;
                    202:                }
                    203:        }
                    204: 
                    205:        fp->_flags = flags;
                    206:        fp->_file = f;
                    207:        fp->_cookie = fp;
                    208:        fp->_read = __sread;
                    209:        fp->_write = __swrite;
                    210:        fp->_seek = __sseek;
                    211:        fp->_close = __sclose;
                    212:        FUNLOCKFILE(fp);
                    213:        return (fp);
                    214: }