findfp.c revision 290544 
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. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)findfp.c	8.2 (Berkeley) 1/4/94";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/10/lib/libc/stdio/findfp.c 290544 2015-11-08 13:37:16Z ache $");
38
39#include <sys/param.h>
40#include <machine/atomic.h>
41#include <unistd.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45
46#include <spinlock.h>
47
48#include "libc_private.h"
49#include "local.h"
50#include "glue.h"
51
52int	__sdidinit;
53
54#define	NDYNAMIC 10		/* add ten more whenever necessary */
55
56#define	std(flags, file) {		\
57	._flags = (flags),		\
58	._file = (file),		\
59	._cookie = __sF + (file),	\
60	._close = __sclose,		\
61	._read = __sread,		\
62	._seek = __sseek,		\
63	._write = __swrite,		\
64	._fl_mutex = PTHREAD_MUTEX_INITIALIZER, \
65}
66				/* the usual - (stdin + stdout + stderr) */
67static FILE usual[FOPEN_MAX - 3];
68static struct glue uglue = { NULL, FOPEN_MAX - 3, usual };
69
70static FILE __sF[3] = {
71	std(__SRD, STDIN_FILENO),
72	std(__SWR, STDOUT_FILENO),
73	std(__SWR|__SNBF, STDERR_FILENO)
74};
75
76FILE *__stdinp = &__sF[0];
77FILE *__stdoutp = &__sF[1];
78FILE *__stderrp = &__sF[2];
79
80struct glue __sglue = { &uglue, 3, __sF };
81static struct glue *lastglue = &uglue;
82
83static struct glue *	moreglue(int);
84
85spinlock_t __stdio_thread_lock = _SPINLOCK_INITIALIZER;
86
87#if NOT_YET
88#define	SET_GLUE_PTR(ptr, val)	atomic_set_rel_ptr(&(ptr), (uintptr_t)(val))
89#else
90#define	SET_GLUE_PTR(ptr, val)	ptr = val
91#endif
92
93static struct glue *
94moreglue(int n)
95{
96	struct glue *g;
97	static FILE empty = { ._fl_mutex = PTHREAD_MUTEX_INITIALIZER };
98	FILE *p;
99
100	g = (struct glue *)malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE));
101	if (g == NULL)
102		return (NULL);
103	p = (FILE *)ALIGN(g + 1);
104	g->next = NULL;
105	g->niobs = n;
106	g->iobs = p;
107	while (--n >= 0)
108		*p++ = empty;
109	return (g);
110}
111
112/*
113 * Find a free FILE for fopen et al.
114 */
115FILE *
116__sfp()
117{
118	FILE	*fp;
119	int	n;
120	struct glue *g;
121
122	if (!__sdidinit)
123		__sinit();
124	/*
125	 * The list must be locked because a FILE may be updated.
126	 */
127	STDIO_THREAD_LOCK();
128	for (g = &__sglue; g != NULL; g = g->next) {
129		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
130			if (fp->_flags == 0)
131				goto found;
132	}
133	STDIO_THREAD_UNLOCK();	/* don't hold lock while malloc()ing. */
134	if ((g = moreglue(NDYNAMIC)) == NULL)
135		return (NULL);
136	STDIO_THREAD_LOCK();	/* reacquire the lock */
137	SET_GLUE_PTR(lastglue->next, g); /* atomically append glue to list */
138	lastglue = g;		/* not atomic; only accessed when locked */
139	fp = g->iobs;
140found:
141	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
142	STDIO_THREAD_UNLOCK();
143	fp->_p = NULL;		/* no current pointer */
144	fp->_w = 0;		/* nothing to read or write */
145	fp->_r = 0;
146	fp->_bf._base = NULL;	/* no buffer */
147	fp->_bf._size = 0;
148	fp->_lbfsize = 0;	/* not line buffered */
149	fp->_file = -1;		/* no file */
150/*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
151	fp->_ub._base = NULL;	/* no ungetc buffer */
152	fp->_ub._size = 0;
153	fp->_lb._base = NULL;	/* no line buffer */
154	fp->_lb._size = 0;
155/*	fp->_fl_mutex = NULL; */ /* once set always set (reused) */
156	fp->_orientation = 0;
157	memset(&fp->_mbstate, 0, sizeof(mbstate_t));
158	fp->_flags2 = 0;
159	return (fp);
160}
161
162/*
163 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
164 * but documented historically for certain applications.  Bad applications.
165 */
166__warn_references(f_prealloc,
167	"warning: this program uses f_prealloc(), which is not recommended.");
168
169void
170f_prealloc(void)
171{
172	struct glue *g;
173	int n;
174
175	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
176	/*
177	 * It should be safe to walk the list without locking it;
178	 * new nodes are only added to the end and none are ever
179	 * removed.
180	 */
181	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
182		/* void */;
183	if ((n > 0) && ((g = moreglue(n)) != NULL)) {
184		STDIO_THREAD_LOCK();
185		SET_GLUE_PTR(lastglue->next, g);
186		lastglue = g;
187		STDIO_THREAD_UNLOCK();
188	}
189}
190
191/*
192 * exit() calls _cleanup() through *__cleanup, set whenever we
193 * open or buffer a file.  This chicanery is done so that programs
194 * that do not use stdio need not link it all in.
195 *
196 * The name `_cleanup' is, alas, fairly well known outside stdio.
197 */
198void
199_cleanup()
200{
201	/* (void) _fwalk(fclose); */
202	(void) _fwalk(__sflush);		/* `cheating' */
203}
204
205/*
206 * __sinit() is called whenever stdio's internal variables must be set up.
207 */
208void
209__sinit()
210{
211
212	/* Make sure we clean up on exit. */
213	__cleanup = _cleanup;		/* conservative */
214	__sdidinit = 1;
215}
216