findfp.c revision 53459 
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 53459 1999-11-20 14:01:48Z dt $";
43#endif /* LIBC_SCCS and not lint */
44
45#include <sys/param.h>
46#include <unistd.h>
47#include <stdio.h>
48#include <errno.h>
49#include <stdlib.h>
50#include <string.h>
51
52#include <libc_private.h>
53#include <spinlock.h>
54
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 = { 0, 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 };
76
77static struct glue *	moreglue __P((int));
78
79static spinlock_t thread_lock = _SPINLOCK_INITIALIZER;
80#define THREAD_LOCK()	if (__isthreaded) _SPINLOCK(&thread_lock)
81#define THREAD_UNLOCK()	if (__isthreaded) _SPINUNLOCK(&thread_lock)
82
83static struct glue *
84moreglue(n)
85	register int n;
86{
87	register struct glue *g;
88	register FILE *p;
89	static FILE empty;
90
91	g = (struct glue *)malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE));
92	if (g == NULL)
93		return (NULL);
94	p = (FILE *)ALIGN(g + 1);
95	g->next = NULL;
96	g->niobs = n;
97	g->iobs = p;
98	while (--n >= 0)
99		*p++ = empty;
100	return (g);
101}
102
103/*
104 * Find a free FILE for fopen et al.
105 */
106FILE *
107__sfp()
108{
109	register FILE *fp;
110	register int n;
111	register struct glue *g;
112
113	if (!__sdidinit)
114		__sinit();
115	THREAD_LOCK();
116	for (g = &__sglue;; g = g->next) {
117		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
118			if (fp->_flags == 0)
119				goto found;
120		if (g->next == NULL && (g->next = moreglue(NDYNAMIC)) == NULL)
121			break;
122	}
123	THREAD_UNLOCK();
124	return (NULL);
125found:
126	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
127	THREAD_UNLOCK();
128	fp->_p = NULL;		/* no current pointer */
129	fp->_w = 0;		/* nothing to read or write */
130	fp->_r = 0;
131	fp->_bf._base = NULL;	/* no buffer */
132	fp->_bf._size = 0;
133	fp->_lbfsize = 0;	/* not line buffered */
134	fp->_file = -1;		/* no file */
135/*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
136	fp->_ub._base = NULL;	/* no ungetc buffer */
137	fp->_ub._size = 0;
138	fp->_lb._base = NULL;	/* no line buffer */
139	fp->_lb._size = 0;
140	return (fp);
141}
142
143/*
144 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
145 * but documented historically for certain applications.  Bad applications.
146 */
147__warn_references(f_prealloc,
148	"warning: this program uses f_prealloc(), which is stupid.");
149
150void
151f_prealloc()
152{
153	register struct glue *g;
154	int n;
155
156	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
157	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
158		/* void */;
159	if (n > 0)
160		g->next = moreglue(n);
161}
162
163/*
164 * exit() calls _cleanup() through *__cleanup, set whenever we
165 * open or buffer a file.  This chicanery is done so that programs
166 * that do not use stdio need not link it all in.
167 *
168 * The name `_cleanup' is, alas, fairly well known outside stdio.
169 */
170void
171_cleanup()
172{
173	/* (void) _fwalk(fclose); */
174	(void) _fwalk(__sflush);		/* `cheating' */
175}
176
177/*
178 * __sinit() is called whenever stdio's internal variables must be set up.
179 */
180void
181__sinit()
182{
183	/* make sure we clean up on exit */
184	__cleanup = _cleanup;		/* conservative */
185	__sdidinit = 1;
186}
187