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: }
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