xref: /freebsd/lib/libc/stdio/findfp.c (revision 42c159fe388a3765f69860c84183700af37aca8a)
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 #if LIBC_MAJOR >= 6
73 static
74 #endif
75 FILE __sF[3] = {
76 	std(__SRD, STDIN_FILENO),
77 	std(__SWR, STDOUT_FILENO),
78 	std(__SWR|__SNBF, STDERR_FILENO)
79 };
80 
81 /*
82  * The following kludge is done to ensure enough binary compatibility
83  * with future versions of libc.  Or rather it allows us to work with
84  * libraries that have been built with a newer libc that defines these
85  * symbols and expects libc to provide them.  We only have need to support
86  * i386 and alpha because they are the only "old" systems we have deployed.
87  */
88 FILE *__stdinp = &__sF[0];
89 FILE *__stdoutp = &__sF[1];
90 FILE *__stderrp = &__sF[2];
91 
92 struct glue __sglue = { &uglue, 3, __sF };
93 static struct glue *lastglue = &uglue;
94 
95 static struct glue *	moreglue(int);
96 
97 static spinlock_t thread_lock = _SPINLOCK_INITIALIZER;
98 #define THREAD_LOCK()	if (__isthreaded) _SPINLOCK(&thread_lock)
99 #define THREAD_UNLOCK()	if (__isthreaded) _SPINUNLOCK(&thread_lock)
100 
101 #if NOT_YET
102 #define	SET_GLUE_PTR(ptr, val)	atomic_set_rel_ptr(&(ptr), (uintptr_t)(val))
103 #else
104 #define	SET_GLUE_PTR(ptr, val)	ptr = val
105 #endif
106 
107 static struct glue *
108 moreglue(n)
109 	int n;
110 {
111 	struct glue *g;
112 	static FILE empty;
113 	static struct __sFILEX emptyx;
114 	FILE *p;
115 	struct __sFILEX *fx;
116 
117 	g = (struct glue *)malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE) +
118 	    n * sizeof(struct __sFILEX));
119 	if (g == NULL)
120 		return (NULL);
121 	p = (FILE *)ALIGN(g + 1);
122 	fx = (struct __sFILEX *)&p[n];
123 	g->next = NULL;
124 	g->niobs = n;
125 	g->iobs = p;
126 	while (--n >= 0) {
127 		*p = empty;
128 		p->_extra = fx;
129 		*p->_extra = emptyx;
130 		p++, fx++;
131 	}
132 	return (g);
133 }
134 
135 /*
136  * Find a free FILE for fopen et al.
137  */
138 FILE *
139 __sfp()
140 {
141 	FILE	*fp;
142 	int	n;
143 	struct glue *g;
144 
145 	if (!__sdidinit)
146 		__sinit();
147 	/*
148 	 * The list must be locked because a FILE may be updated.
149 	 */
150 	THREAD_LOCK();
151 	for (g = &__sglue; g != NULL; g = g->next) {
152 		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
153 			if (fp->_flags == 0)
154 				goto found;
155 	}
156 	THREAD_UNLOCK();	/* don't hold lock while malloc()ing. */
157 	if ((g = moreglue(NDYNAMIC)) == NULL)
158 		return (NULL);
159 	THREAD_LOCK();		/* reacquire the lock */
160 	SET_GLUE_PTR(lastglue->next, g); /* atomically append glue to list */
161 	lastglue = g;		/* not atomic; only accessed when locked */
162 	fp = g->iobs;
163 found:
164 	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
165 	THREAD_UNLOCK();
166 	fp->_p = NULL;		/* no current pointer */
167 	fp->_w = 0;		/* nothing to read or write */
168 	fp->_r = 0;
169 	fp->_bf._base = NULL;	/* no buffer */
170 	fp->_bf._size = 0;
171 	fp->_lbfsize = 0;	/* not line buffered */
172 	fp->_file = -1;		/* no file */
173 /*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
174 	fp->_ub._base = NULL;	/* no ungetc buffer */
175 	fp->_ub._size = 0;
176 	fp->_lb._base = NULL;	/* no line buffer */
177 	fp->_lb._size = 0;
178 /*	fp->_lock = NULL; */	/* once set always set (reused) */
179 	return (fp);
180 }
181 
182 /*
183  * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
184  * but documented historically for certain applications.  Bad applications.
185  */
186 __warn_references(f_prealloc,
187 	"warning: this program uses f_prealloc(), which is not recommended.");
188 
189 void
190 f_prealloc()
191 {
192 	struct glue *g;
193 	int n;
194 
195 	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
196 	/*
197 	 * It should be safe to walk the list without locking it;
198 	 * new nodes are only added to the end and none are ever
199 	 * removed.
200 	 */
201 	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
202 		/* void */;
203 	if ((n > 0) && ((g = moreglue(n)) != NULL)) {
204 		THREAD_LOCK();
205 		SET_GLUE_PTR(lastglue->next, g);
206 		lastglue = g;
207 		THREAD_UNLOCK();
208 	}
209 }
210 
211 /*
212  * exit() calls _cleanup() through *__cleanup, set whenever we
213  * open or buffer a file.  This chicanery is done so that programs
214  * that do not use stdio need not link it all in.
215  *
216  * The name `_cleanup' is, alas, fairly well known outside stdio.
217  */
218 void
219 _cleanup()
220 {
221 	/* (void) _fwalk(fclose); */
222 	(void) _fwalk(__sflush);		/* `cheating' */
223 }
224 
225 /*
226  * __sinit() is called whenever stdio's internal variables must be set up.
227  */
228 void
229 __sinit()
230 {
231 	int	i;
232 
233 	THREAD_LOCK();
234 	if (__sdidinit == 0) {
235 		/* Set _extra for the usual suspects. */
236 		for (i = 0; i < FOPEN_MAX - 3; i++)
237 			usual[i]._extra = &usual_extra[i];
238 
239 		/* Make sure we clean up on exit. */
240 		__cleanup = _cleanup;		/* conservative */
241 		__sdidinit = 1;
242 	}
243 	THREAD_UNLOCK();
244 }
245