findfp.c revision 72394
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#if 0
39static char sccsid[] = "@(#)findfp.c	8.2 (Berkeley) 1/4/94";
40#endif
41static const char rcsid[] =
42  "$FreeBSD: head/lib/libc/stdio/findfp.c 72394 2001-02-12 03:31:23Z peter $";
43#endif /* LIBC_SCCS and not lint */
44
45#include <sys/param.h>
46#include <machine/atomic.h>
47#include <unistd.h>
48#include <stdio.h>
49#include <stdlib.h>
50#include <string.h>
51
52#include <spinlock.h>
53
54#include "libc_private.h"
55#include "local.h"
56#include "glue.h"
57
58int	__sdidinit;
59
60#define	NDYNAMIC 10		/* add ten more whenever necessary */
61
62#define	std(flags, file) \
63	{0,0,0,flags,file,{0},0,__sF+file,__sclose,__sread,__sseek,__swrite}
64/*	 p r w flags file _bf z  cookie      close    read    seek    write */
65
66				/* the usual - (stdin + stdout + stderr) */
67static FILE usual[FOPEN_MAX - 3];
68static struct glue uglue = { NULL, FOPEN_MAX - 3, usual };
69
70FILE __sF[3] = {
71	std(__SRD, STDIN_FILENO),		/* stdin */
72	std(__SWR, STDOUT_FILENO),		/* stdout */
73	std(__SWR|__SNBF, STDERR_FILENO)	/* stderr */
74};
75struct glue __sglue = { &uglue, 3, __sF };
76static struct glue *lastglue = &uglue;
77
78static struct glue *	moreglue __P((int));
79
80static spinlock_t thread_lock = _SPINLOCK_INITIALIZER;
81#define THREAD_LOCK()	if (__isthreaded) _SPINLOCK(&thread_lock)
82#define THREAD_UNLOCK()	if (__isthreaded) _SPINUNLOCK(&thread_lock)
83
84#if NOT_YET
85#define	SET_GLUE_PTR(ptr, val)	atomic_set_rel_ptr(&(ptr), (uintptr_t)(val))
86#else
87#define	SET_GLUE_PTR(ptr, val)	ptr = val
88#endif
89
90static struct glue *
91moreglue(n)
92	int n;
93{
94	struct glue *g;
95	FILE *p;
96	static FILE empty;
97
98	g = (struct glue *)malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE));
99	if (g == NULL)
100		return (NULL);
101	p = (FILE *)ALIGN(g + 1);
102	g->next = NULL;
103	g->niobs = n;
104	g->iobs = p;
105	while (--n >= 0)
106		*p++ = empty;
107	return (g);
108}
109
110/*
111 * Find a free FILE for fopen et al.
112 */
113FILE *
114__sfp()
115{
116	FILE	*fp;
117	int	n;
118	struct glue *g;
119
120	if (!__sdidinit)
121		__sinit();
122	/*
123	 * The list must be locked because a FILE may be updated.
124	 */
125	THREAD_LOCK();
126	for (g = &__sglue; g != NULL; g = g->next) {
127		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
128			if (fp->_flags == 0)
129				goto found;
130	}
131	THREAD_UNLOCK();	/* don't hold lock while malloc()ing. */
132	if ((g = moreglue(NDYNAMIC)) == NULL)
133		return (NULL);
134	THREAD_LOCK();		/* reacquire the lock */
135	SET_GLUE_PTR(lastglue->next, g); /* atomically append glue to list */
136	lastglue = g;		/* not atomic; only accessed when locked */
137	fp = g->iobs;
138found:
139	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
140	THREAD_UNLOCK();
141	fp->_p = NULL;		/* no current pointer */
142	fp->_w = 0;		/* nothing to read or write */
143	fp->_r = 0;
144	fp->_bf._base = NULL;	/* no buffer */
145	fp->_bf._size = 0;
146	fp->_lbfsize = 0;	/* not line buffered */
147	fp->_file = -1;		/* no file */
148/*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
149	fp->_ub._base = NULL;	/* no ungetc buffer */
150	fp->_ub._size = 0;
151	fp->_lb._base = NULL;	/* no line buffer */
152	fp->_lb._size = 0;
153/*	fp->_lock = NULL; */	/* once set always set (reused) */
154	return (fp);
155}
156
157/*
158 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
159 * but documented historically for certain applications.  Bad applications.
160 */
161__warn_references(f_prealloc,
162	"warning: this program uses f_prealloc(), which is stupid.");
163
164void
165f_prealloc()
166{
167	struct glue *g;
168	int n;
169
170	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
171	/*
172	 * It should be safe to walk the list without locking it;
173	 * new nodes are only added to the end and none are ever
174	 * removed.
175	 */
176	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
177		/* void */;
178	if ((n > 0) && ((g = moreglue(n)) != NULL)) {
179		THREAD_LOCK();
180		SET_GLUE_PTR(lastglue->next, g);
181		lastglue = g;
182		THREAD_UNLOCK();
183	}
184}
185
186/*
187 * exit() calls _cleanup() through *__cleanup, set whenever we
188 * open or buffer a file.  This chicanery is done so that programs
189 * that do not use stdio need not link it all in.
190 *
191 * The name `_cleanup' is, alas, fairly well known outside stdio.
192 */
193void
194_cleanup()
195{
196	/* (void) _fwalk(fclose); */
197	(void) _fwalk(__sflush);		/* `cheating' */
198}
199
200/*
201 * __sinit() is called whenever stdio's internal variables must be set up.
202 */
203void
204__sinit()
205{
206	/* Make sure we clean up on exit. */
207	__cleanup = _cleanup;		/* conservative */
208	__sdidinit = 1;
209}
210