findfp.c revision 331722 
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/11/lib/libc/stdio/findfp.c 331722 2018-03-29 02:50:57Z eadler $");
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 <stdint.h>
45#include <string.h>
46
47#include <spinlock.h>
48
49#include "libc_private.h"
50#include "local.h"
51#include "glue.h"
52
53int	__sdidinit;
54
55#define	NDYNAMIC 10		/* add ten more whenever necessary */
56
57#define	std(flags, file) {		\
58	._flags = (flags),		\
59	._file = (file),		\
60	._cookie = __sF + (file),	\
61	._close = __sclose,		\
62	._read = __sread,		\
63	._seek = __sseek,		\
64	._write = __swrite,		\
65	._fl_mutex = PTHREAD_MUTEX_INITIALIZER, \
66}
67				/* the usual - (stdin + stdout + stderr) */
68static FILE usual[FOPEN_MAX - 3];
69static struct glue uglue = { NULL, FOPEN_MAX - 3, usual };
70
71static FILE __sF[3] = {
72	std(__SRD, STDIN_FILENO),
73	std(__SWR, STDOUT_FILENO),
74	std(__SWR|__SNBF, STDERR_FILENO)
75};
76
77FILE *__stdinp = &__sF[0];
78FILE *__stdoutp = &__sF[1];
79FILE *__stderrp = &__sF[2];
80
81struct glue __sglue = { &uglue, 3, __sF };
82static struct glue *lastglue = &uglue;
83
84static struct glue *	moreglue(int);
85
86spinlock_t __stdio_thread_lock = _SPINLOCK_INITIALIZER;
87
88#if NOT_YET
89#define	SET_GLUE_PTR(ptr, val)	atomic_set_rel_ptr(&(ptr), (uintptr_t)(val))
90#else
91#define	SET_GLUE_PTR(ptr, val)	ptr = val
92#endif
93
94static struct glue *
95moreglue(int n)
96{
97	struct glue *g;
98	static FILE empty = { ._fl_mutex = PTHREAD_MUTEX_INITIALIZER };
99	FILE *p;
100	size_t align;
101
102	align = __alignof__(FILE);
103	g = (struct glue *)malloc(sizeof(*g) + align + n * sizeof(FILE));
104	if (g == NULL)
105		return (NULL);
106	p = (FILE *)roundup((uintptr_t)(g + 1), align);
107	g->next = NULL;
108	g->niobs = n;
109	g->iobs = p;
110	while (--n >= 0)
111		*p++ = empty;
112	return (g);
113}
114
115/*
116 * Find a free FILE for fopen et al.
117 */
118FILE *
119__sfp(void)
120{
121	FILE	*fp;
122	int	n;
123	struct glue *g;
124
125	if (!__sdidinit)
126		__sinit();
127	/*
128	 * The list must be locked because a FILE may be updated.
129	 */
130	STDIO_THREAD_LOCK();
131	for (g = &__sglue; g != NULL; g = g->next) {
132		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
133			if (fp->_flags == 0)
134				goto found;
135	}
136	STDIO_THREAD_UNLOCK();	/* don't hold lock while malloc()ing. */
137	if ((g = moreglue(NDYNAMIC)) == NULL)
138		return (NULL);
139	STDIO_THREAD_LOCK();	/* reacquire the lock */
140	SET_GLUE_PTR(lastglue->next, g); /* atomically append glue to list */
141	lastglue = g;		/* not atomic; only accessed when locked */
142	fp = g->iobs;
143found:
144	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
145	STDIO_THREAD_UNLOCK();
146	fp->_p = NULL;		/* no current pointer */
147	fp->_w = 0;		/* nothing to read or write */
148	fp->_r = 0;
149	fp->_bf._base = NULL;	/* no buffer */
150	fp->_bf._size = 0;
151	fp->_lbfsize = 0;	/* not line buffered */
152	fp->_file = -1;		/* no file */
153/*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
154	fp->_ub._base = NULL;	/* no ungetc buffer */
155	fp->_ub._size = 0;
156	fp->_lb._base = NULL;	/* no line buffer */
157	fp->_lb._size = 0;
158/*	fp->_fl_mutex = NULL; */ /* once set always set (reused) */
159	fp->_orientation = 0;
160	memset(&fp->_mbstate, 0, sizeof(mbstate_t));
161	fp->_flags2 = 0;
162	return (fp);
163}
164
165/*
166 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
167 * but documented historically for certain applications.  Bad applications.
168 */
169__warn_references(f_prealloc,
170	"warning: this program uses f_prealloc(), which is not recommended.");
171void f_prealloc(void);
172
173void
174f_prealloc(void)
175{
176	struct glue *g;
177	int n;
178
179	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
180	/*
181	 * It should be safe to walk the list without locking it;
182	 * new nodes are only added to the end and none are ever
183	 * removed.
184	 */
185	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
186		/* void */;
187	if ((n > 0) && ((g = moreglue(n)) != NULL)) {
188		STDIO_THREAD_LOCK();
189		SET_GLUE_PTR(lastglue->next, g);
190		lastglue = g;
191		STDIO_THREAD_UNLOCK();
192	}
193}
194
195/*
196 * exit() calls _cleanup() through *__cleanup, set whenever we
197 * open or buffer a file.  This chicanery is done so that programs
198 * that do not use stdio need not link it all in.
199 *
200 * The name `_cleanup' is, alas, fairly well known outside stdio.
201 */
202void
203_cleanup(void)
204{
205	/* (void) _fwalk(fclose); */
206	(void) _fwalk(__sflush);		/* `cheating' */
207}
208
209/*
210 * __sinit() is called whenever stdio's internal variables must be set up.
211 */
212void
213__sinit(void)
214{
215
216	/* Make sure we clean up on exit. */
217	__cleanup = _cleanup;		/* conservative */
218	__sdidinit = 1;
219}
220