xref: /freebsd/lib/libc/stdio/findfp.c (revision cf04ed1bdf4e58fd2ae592a318788201feccd424)
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.
35  */
36 
37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)findfp.c	8.2 (Berkeley) 1/4/94";
39 #endif /* LIBC_SCCS and not lint */
40 #include <sys/cdefs.h>
41 __FBSDID("$FreeBSD$");
42 
43 #include <sys/param.h>
44 #include <machine/atomic.h>
45 #include <unistd.h>
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <string.h>
49 
50 #include <spinlock.h>
51 
52 #include "libc_private.h"
53 #include "local.h"
54 #include "glue.h"
55 
56 int	__sdidinit;
57 
58 #define	NDYNAMIC 10		/* add ten more whenever necessary */
59 
60 #define	std(flags, file) \
61   	{0,0,0,flags,file,{0},0,__sF+file,__sclose,__sread,__sseek,__swrite, \
62 	 {0}, __sFX + file}
63   /*	 p r w flags file _bf z  cookie      close    read    seek    write */
64   /*     _ub _extra */
65 				/* the usual - (stdin + stdout + stderr) */
66 static FILE usual[FOPEN_MAX - 3];
67 static struct __sFILEX usual_extra[FOPEN_MAX - 3];
68 static struct glue uglue = { NULL, FOPEN_MAX - 3, usual };
69 
70 static struct __sFILEX __sFX[3];
71 
72 /*
73  * We can't make this 'static' until 6.0-current due to binary
74  * compatibility concerns.  This also means we cannot change the
75  * sizeof(FILE) until that time either and must continue to use the
76  * __sFILEX stuff to add to FILE.
77  */
78 FILE __sF[3] = {
79 	std(__SRD, STDIN_FILENO),
80 	std(__SWR, STDOUT_FILENO),
81 	std(__SWR|__SNBF, STDERR_FILENO)
82 };
83 
84 /*
85  * The following kludge is done to ensure enough binary compatibility
86  * with future versions of libc.  Or rather it allows us to work with
87  * libraries that have been built with a newer libc that defines these
88  * symbols and expects libc to provide them.  We only have need to support
89  * i386 and alpha because they are the only "old" systems we have deployed.
90  */
91 FILE *__stdinp = &__sF[0];
92 FILE *__stdoutp = &__sF[1];
93 FILE *__stderrp = &__sF[2];
94 
95 struct glue __sglue = { &uglue, 3, __sF };
96 static struct glue *lastglue = &uglue;
97 
98 static struct glue *	moreglue(int);
99 
100 static spinlock_t thread_lock = _SPINLOCK_INITIALIZER;
101 #define THREAD_LOCK()	if (__isthreaded) _SPINLOCK(&thread_lock)
102 #define THREAD_UNLOCK()	if (__isthreaded) _SPINUNLOCK(&thread_lock)
103 
104 #if NOT_YET
105 #define	SET_GLUE_PTR(ptr, val)	atomic_set_rel_ptr(&(ptr), (uintptr_t)(val))
106 #else
107 #define	SET_GLUE_PTR(ptr, val)	ptr = val
108 #endif
109 
110 static struct glue *
111 moreglue(n)
112 	int n;
113 {
114 	struct glue *g;
115 	static FILE empty;
116 	static struct __sFILEX emptyx;
117 	FILE *p;
118 	struct __sFILEX *fx;
119 
120 	g = (struct glue *)malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE) +
121 	    n * sizeof(struct __sFILEX));
122 	if (g == NULL)
123 		return (NULL);
124 	p = (FILE *)ALIGN(g + 1);
125 	fx = (struct __sFILEX *)&p[n];
126 	g->next = NULL;
127 	g->niobs = n;
128 	g->iobs = p;
129 	while (--n >= 0) {
130 		*p = empty;
131 		p->_extra = fx;
132 		*p->_extra = emptyx;
133 		p++, fx++;
134 	}
135 	return (g);
136 }
137 
138 /*
139  * Find a free FILE for fopen et al.
140  */
141 FILE *
142 __sfp()
143 {
144 	FILE	*fp;
145 	int	n;
146 	struct glue *g;
147 
148 	if (!__sdidinit)
149 		__sinit();
150 	/*
151 	 * The list must be locked because a FILE may be updated.
152 	 */
153 	THREAD_LOCK();
154 	for (g = &__sglue; g != NULL; g = g->next) {
155 		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
156 			if (fp->_flags == 0)
157 				goto found;
158 	}
159 	THREAD_UNLOCK();	/* don't hold lock while malloc()ing. */
160 	if ((g = moreglue(NDYNAMIC)) == NULL)
161 		return (NULL);
162 	THREAD_LOCK();		/* reacquire the lock */
163 	SET_GLUE_PTR(lastglue->next, g); /* atomically append glue to list */
164 	lastglue = g;		/* not atomic; only accessed when locked */
165 	fp = g->iobs;
166 found:
167 	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
168 	THREAD_UNLOCK();
169 	fp->_p = NULL;		/* no current pointer */
170 	fp->_w = 0;		/* nothing to read or write */
171 	fp->_r = 0;
172 	fp->_bf._base = NULL;	/* no buffer */
173 	fp->_bf._size = 0;
174 	fp->_lbfsize = 0;	/* not line buffered */
175 	fp->_file = -1;		/* no file */
176 /*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
177 	fp->_ub._base = NULL;	/* no ungetc buffer */
178 	fp->_ub._size = 0;
179 	fp->_lb._base = NULL;	/* no line buffer */
180 	fp->_lb._size = 0;
181 /*	fp->_lock = NULL; */	/* once set always set (reused) */
182 	fp->_extra->orientation = 0;
183 #ifdef notdef
184 	/* Stateful encoding/decoding is not yet supported. */
185 	memset(&fp->_extra->wstate, 0, sizeof(mbstate_t));
186 	memset(&fp->_extra->rstate, 0, sizeof(mbstate_t));
187 #endif
188 	return (fp);
189 }
190 
191 /*
192  * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
193  * but documented historically for certain applications.  Bad applications.
194  */
195 __warn_references(f_prealloc,
196 	"warning: this program uses f_prealloc(), which is not recommended.");
197 
198 void
199 f_prealloc()
200 {
201 	struct glue *g;
202 	int n;
203 
204 	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
205 	/*
206 	 * It should be safe to walk the list without locking it;
207 	 * new nodes are only added to the end and none are ever
208 	 * removed.
209 	 */
210 	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
211 		/* void */;
212 	if ((n > 0) && ((g = moreglue(n)) != NULL)) {
213 		THREAD_LOCK();
214 		SET_GLUE_PTR(lastglue->next, g);
215 		lastglue = g;
216 		THREAD_UNLOCK();
217 	}
218 }
219 
220 /*
221  * exit() calls _cleanup() through *__cleanup, set whenever we
222  * open or buffer a file.  This chicanery is done so that programs
223  * that do not use stdio need not link it all in.
224  *
225  * The name `_cleanup' is, alas, fairly well known outside stdio.
226  */
227 void
228 _cleanup()
229 {
230 	/* (void) _fwalk(fclose); */
231 	(void) _fwalk(__sflush);		/* `cheating' */
232 }
233 
234 /*
235  * __sinit() is called whenever stdio's internal variables must be set up.
236  */
237 void
238 __sinit()
239 {
240 	int	i;
241 
242 	THREAD_LOCK();
243 	if (__sdidinit == 0) {
244 		/* Set _extra for the usual suspects. */
245 		for (i = 0; i < FOPEN_MAX - 3; i++)
246 			usual[i]._extra = &usual_extra[i];
247 
248 		/* Make sure we clean up on exit. */
249 		__cleanup = _cleanup;		/* conservative */
250 		__sdidinit = 1;
251 	}
252 	THREAD_UNLOCK();
253 }
254