findfp.c revision 106721 
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)
38static 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: head/lib/libc/stdio/findfp.c 106721 2002-11-10 08:44:38Z imp $");
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
56int	__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) */
66static FILE usual[FOPEN_MAX - 3];
67static struct __sFILEX usual_extra[FOPEN_MAX - 3];
68static struct glue uglue = { NULL, FOPEN_MAX - 3, usual };
69
70static struct __sFILEX __sFX[3];
71
72#if LIBC_MAJOR >= 6
73static
74#endif
75FILE __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 */
88FILE *__stdinp = &__sF[0];
89FILE *__stdoutp = &__sF[1];
90FILE *__stderrp = &__sF[2];
91
92struct glue __sglue = { &uglue, 3, __sF };
93static struct glue *lastglue = &uglue;
94
95static struct glue *	moreglue(int);
96
97static 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
107static struct glue *
108moreglue(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 */
138FILE *
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;
163found:
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	fp->_extra->orientation = 0;
180#ifdef notdef
181	/* Stateful encoding/decoding is not yet supported. */
182	memset(&fp->_extra->wstate, 0, sizeof(mbstate_t));
183	memset(&fp->_extra->rstate, 0, sizeof(mbstate_t));
184#endif
185	return (fp);
186}
187
188/*
189 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
190 * but documented historically for certain applications.  Bad applications.
191 */
192__warn_references(f_prealloc,
193	"warning: this program uses f_prealloc(), which is not recommended.");
194
195void
196f_prealloc()
197{
198	struct glue *g;
199	int n;
200
201	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
202	/*
203	 * It should be safe to walk the list without locking it;
204	 * new nodes are only added to the end and none are ever
205	 * removed.
206	 */
207	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
208		/* void */;
209	if ((n > 0) && ((g = moreglue(n)) != NULL)) {
210		THREAD_LOCK();
211		SET_GLUE_PTR(lastglue->next, g);
212		lastglue = g;
213		THREAD_UNLOCK();
214	}
215}
216
217/*
218 * exit() calls _cleanup() through *__cleanup, set whenever we
219 * open or buffer a file.  This chicanery is done so that programs
220 * that do not use stdio need not link it all in.
221 *
222 * The name `_cleanup' is, alas, fairly well known outside stdio.
223 */
224void
225_cleanup()
226{
227	/* (void) _fwalk(fclose); */
228	(void) _fwalk(__sflush);		/* `cheating' */
229}
230
231/*
232 * __sinit() is called whenever stdio's internal variables must be set up.
233 */
234void
235__sinit()
236{
237	int	i;
238
239	THREAD_LOCK();
240	if (__sdidinit == 0) {
241		/* Set _extra for the usual suspects. */
242		for (i = 0; i < FOPEN_MAX - 3; i++)
243			usual[i]._extra = &usual_extra[i];
244
245		/* Make sure we clean up on exit. */
246		__cleanup = _cleanup;		/* conservative */
247		__sdidinit = 1;
248	}
249	THREAD_UNLOCK();
250}
251