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Annotation of prex-old/usr/lib/libc/stdio/freopen.c, Revision 1.1.1.1

1.1       nbrk        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. Neither the name of the University nor the names of its contributors
                     17:  *    may be used to endorse or promote products derived from this software
                     18:  *    without specific prior written permission.
                     19:  *
                     20:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     21:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     22:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     23:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     24:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     25:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     26:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     27:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     28:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     29:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     30:  * SUCH DAMAGE.
                     31:  */
                     32:
                     33: #include <sys/types.h>
                     34: #include <sys/stat.h>
                     35: #include <fcntl.h>
                     36: #include <errno.h>
                     37: #include <unistd.h>
                     38: #include <stdio.h>
                     39: #include <stdlib.h>
                     40: #include "local.h"
                     41:
                     42: /*
                     43:  * Re-direct an existing, open (probably) file to some other file.
                     44:  * ANSI is written such that the original file gets closed if at
                     45:  * all possible, no matter what.
                     46:  */
                     47: FILE *
                     48: freopen(file, mode, fp)
                     49:        const char *file, *mode;
                     50:        FILE *fp;
                     51: {
                     52:        int f;
                     53:        int flags, isopen, oflags, sverrno, wantfd;
                     54:
                     55:        if ((flags = __sflags(mode, &oflags)) == 0) {
                     56:                (void) fclose(fp);
                     57:                return (NULL);
                     58:        }
                     59:
                     60:        if (!__sdidinit)
                     61:                __sinit();
                     62:
                     63:        /*
                     64:         * There are actually programs that depend on being able to "freopen"
                     65:         * descriptors that weren't originally open.  Keep this from breaking.
                     66:         * Remember whether the stream was open to begin with, and which file
                     67:         * descriptor (if any) was associated with it.  If it was attached to
                     68:         * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
                     69:         * should work.  This is unnecessary if it was not a Unix file.
                     70:         */
                     71:        if (fp->_flags == 0) {
                     72:                fp->_flags = __SEOF;    /* hold on to it */
                     73:                isopen = 0;
                     74:                wantfd = -1;
                     75:        } else {
                     76:                /* flush the stream; ANSI doesn't require this. */
                     77:                if (fp->_flags & __SWR)
                     78:                        (void) __sflush(fp);
                     79:                /* if close is NULL, closing is a no-op, hence pointless */
                     80:                isopen = 1;
                     81:                if ((wantfd = fp->_file) < 0 && isopen) {
                     82:                        (void) __sclose(fp);
                     83:                        isopen = 0;
                     84:                }
                     85:        }
                     86:
                     87:        /* Get a new descriptor to refer to the new file. */
                     88:        f = open(file, oflags, DEFFILEMODE);
                     89:        if (f < 0 && isopen) {
                     90:                /* If out of fd's close the old one and try again. */
                     91:                if (errno == ENFILE || errno == EMFILE) {
                     92:                        (void) __sclose(fp);
                     93:                        isopen = 0;
                     94:                        f = open(file, oflags, DEFFILEMODE);
                     95:                }
                     96:        }
                     97:        sverrno = errno;
                     98:
                     99:        /*
                    100:         * Finish closing fp.  Even if the open succeeded above, we cannot
                    101:         * keep fp->_base: it may be the wrong size.  This loses the effect
                    102:         * of any setbuffer calls, but stdio has always done this before.
                    103:         */
                    104:        if (isopen)
                    105:                (void) __sclose(fp);
                    106:        if (fp->_flags & __SMBF)
                    107:                free((char *)fp->_bf._base);
                    108:        fp->_w = 0;
                    109:        fp->_r = 0;
                    110:        fp->_p = NULL;
                    111:        fp->_bf._base = NULL;
                    112:        fp->_bf._size = 0;
                    113:        if (HASUB(fp))
                    114:                FREEUB(fp);
                    115:        fp->_ub._size = 0;
                    116:
                    117:        if (f < 0) {                    /* did not get it after all */
                    118:                fp->_flags = 0;         /* set it free */
                    119:                errno = sverrno;        /* restore in case _close clobbered */
                    120:                return (NULL);
                    121:        }
                    122:
                    123:        /*
                    124:         * If reopening something that was open before on a real file, try
                    125:         * to maintain the descriptor.  Various C library routines (perror)
                    126:         * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
                    127:         */
                    128:        if (wantfd >= 0 && f != wantfd) {
                    129:                if (dup2(f, wantfd) >= 0) {
                    130:                        (void) close(f);
                    131:                        f = wantfd;
                    132:                }
                    133:        }
                    134:
                    135:        fp->_flags = flags;
                    136:        fp->_file = f;
                    137:        return (fp);
                    138: }