1 /* $OpenBSD: findfp.c,v 1.20 2021/11/29 03:20:37 deraadt Exp $ */
2 /*-
3 * Copyright (c) 1990, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #include <sys/param.h> /* ALIGN ALIGNBYTES */
35 #include <unistd.h>
36 #include <stdio.h>
37 #include <errno.h>
38 #include <stdlib.h>
39 #include <string.h>
40 #include "local.h"
41 #include "glue.h"
42 #include "thread_private.h"
43
44 int __sdidinit;
45
46 #define NDYNAMIC 10 /* add ten more whenever necessary */
47
48 #define std(flags, file) \
49 {0,0,0,flags,file,{0},0,__sF+file,__sclose,__sread,__sseek,__swrite, \
50 {(unsigned char *)(__sFext+file), 0}}
51 /* p r w flags file _bf z cookie close read seek write
52 ext */
53
54 /* the usual - (stdin + stdout + stderr) */
55 static FILE usual[FOPEN_MAX - 3];
56 static struct __sfileext usualext[FOPEN_MAX - 3];
57 static struct glue uglue = { 0, FOPEN_MAX - 3, usual };
58 static struct glue *lastglue = &uglue;
59 static void *sfp_mutex;
60
61 static struct __sfileext __sFext[3];
62 FILE __sF[3] = {
63 std(__SRD, STDIN_FILENO), /* stdin */
64 std(__SWR, STDOUT_FILENO), /* stdout */
65 std(__SWR|__SNBF, STDERR_FILENO) /* stderr */
66 };
67 struct glue __sglue = { &uglue, 3, __sF };
68
69 static struct glue *
moreglue(int n)70 moreglue(int n)
71 {
72 struct glue *g;
73 FILE *p;
74 struct __sfileext *pext;
75 static FILE empty;
76 char *data;
77
78 data = malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE)
79 + n * sizeof(struct __sfileext));
80 if (data == NULL)
81 return (NULL);
82 g = (struct glue *)data;
83 p = (FILE *)ALIGN(data + sizeof(*g));
84 pext = (struct __sfileext *)
85 (ALIGN(data + sizeof(*g)) + n * sizeof(FILE));
86 g->next = NULL;
87 g->niobs = n;
88 g->iobs = p;
89 while (--n >= 0) {
90 *p = empty;
91 _FILEEXT_SETUP(p, pext);
92 p++;
93 pext++;
94 }
95 return (g);
96 }
97
98 /*
99 * Find a free FILE for fopen et al.
100 */
101 FILE *
__sfp(void)102 __sfp(void)
103 {
104 FILE *fp;
105 int n;
106 struct glue *g;
107
108 if (!__sdidinit)
109 __sinit();
110
111 _MUTEX_LOCK(&sfp_mutex);
112 for (g = &__sglue; g != NULL; g = g->next) {
113 for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
114 if (fp->_flags == 0)
115 goto found;
116 }
117
118 /* release lock while mallocing */
119 _MUTEX_UNLOCK(&sfp_mutex);
120 if ((g = moreglue(NDYNAMIC)) == NULL)
121 return (NULL);
122 _MUTEX_LOCK(&sfp_mutex);
123 lastglue->next = g;
124 lastglue = g;
125 fp = g->iobs;
126 found:
127 fp->_flags = 1; /* reserve this slot; caller sets real flags */
128 _MUTEX_UNLOCK(&sfp_mutex);
129 fp->_p = NULL; /* no current pointer */
130 fp->_w = 0; /* nothing to read or write */
131 fp->_r = 0;
132 fp->_bf._base = NULL; /* no buffer */
133 fp->_bf._size = 0;
134 fp->_lbfsize = 0; /* not line buffered */
135 fp->_file = -1; /* no file */
136 /* fp->_cookie = <any>; */ /* caller sets cookie, _read/_write etc */
137 fp->_lb._base = NULL; /* no line buffer */
138 fp->_lb._size = 0;
139 _FILEEXT_INIT(fp);
140 return (fp);
141 }
142
143 /*
144 * exit() calls _cleanup() through the callback registered
145 * with __atexit_register_cleanup(), set whenever we open or buffer a
146 * file. This chicanery is done so that programs that do not use stdio
147 * need not link it all in.
148 *
149 * The name `_cleanup' is, alas, fairly well known outside stdio.
150 */
151 void
_cleanup(void)152 _cleanup(void)
153 {
154 /* (void) _fwalk(fclose); */
155 (void) _fwalk(__sflush); /* `cheating' */
156 }
157
158 /*
159 * __sinit() is called whenever stdio's internal variables must be set up.
160 */
161 void
__sinit(void)162 __sinit(void)
163 {
164 static void *sinit_mutex;
165 int i;
166
167 _MUTEX_LOCK(&sinit_mutex);
168 if (__sdidinit)
169 goto out; /* bail out if caller lost the race */
170 for (i = 0; i < FOPEN_MAX - 3; i++) {
171 _FILEEXT_SETUP(usual+i, usualext+i);
172 }
173 /* make sure we clean up on exit */
174 __atexit_register_cleanup(_cleanup); /* conservative */
175 __sdidinit = 1;
176 out:
177 _MUTEX_UNLOCK(&sinit_mutex);
178 }
179