findfp.c revision 11667 
125895Sjkh/*-
225895Sjkh * Copyright (c) 1990, 1993
325895Sjkh *	The Regents of the University of California.  All rights reserved.
425895Sjkh *
525895Sjkh * This code is derived from software contributed to Berkeley by
625895Sjkh * Chris Torek.
725895Sjkh *
825895Sjkh * Redistribution and use in source and binary forms, with or without
925895Sjkh * modification, are permitted provided that the following conditions
1025895Sjkh * are met:
1125895Sjkh * 1. Redistributions of source code must retain the above copyright
1225895Sjkh *    notice, this list of conditions and the following disclaimer.
1325895Sjkh * 2. Redistributions in binary form must reproduce the above copyright
1425895Sjkh *    notice, this list of conditions and the following disclaimer in the
1525895Sjkh *    documentation and/or other materials provided with the distribution.
1625895Sjkh * 3. All advertising materials mentioning features or use of this software
1725895Sjkh *    must display the following acknowledgement:
1825895Sjkh *	This product includes software developed by the University of
1925895Sjkh *	California, Berkeley and its contributors.
2025895Sjkh * 4. Neither the name of the University nor the names of its contributors
2125895Sjkh *    may be used to endorse or promote products derived from this software
2225895Sjkh *    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
41#include <sys/param.h>
42#include <unistd.h>
43#include <stdio.h>
44#include <errno.h>
45#include <stdlib.h>
46#include <string.h>
47#include "local.h"
48#include "glue.h"
49
50int	__sdidinit;
51
52#define	NDYNAMIC 10		/* add ten more whenever necessary */
53
54#define	std(flags, file) \
55	{0,0,0,flags,file,{0},0,__sF+file,__sclose,__sread,__sseek,__swrite}
56/*	 p r w flags file _bf z  cookie      close    read    seek    write */
57
58				/* the usual - (stdin + stdout + stderr) */
59static FILE usual[FOPEN_MAX - 3];
60static struct glue uglue = { 0, FOPEN_MAX - 3, usual };
61
62FILE __sF[3] = {
63	std(__SRD, STDIN_FILENO),		/* stdin */
64	std(__SWR, STDOUT_FILENO),		/* stdout */
65	std(__SWR|__SNBF, STDERR_FILENO)	/* stderr */
66};
67struct glue __sglue = { &uglue, 3, __sF };
68
69static struct glue *
70moreglue(n)
71	register int n;
72{
73	register struct glue *g;
74	register FILE *p;
75	static FILE empty;
76
77	g = (struct glue *)malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE));
78	if (g == NULL)
79		return (NULL);
80	p = (FILE *)ALIGN(g + 1);
81	g->next = NULL;
82	g->niobs = n;
83	g->iobs = p;
84	while (--n >= 0)
85		*p++ = empty;
86	return (g);
87}
88
89/*
90 * Find a free FILE for fopen et al.
91 */
92FILE *
93__sfp()
94{
95	register FILE *fp;
96	register int n;
97	register struct glue *g;
98
99	if (!__sdidinit)
100		__sinit();
101	for (g = &__sglue;; g = g->next) {
102		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
103			if (fp->_flags == 0)
104				goto found;
105		if (g->next == NULL && (g->next = moreglue(NDYNAMIC)) == NULL)
106			break;
107	}
108	return (NULL);
109found:
110	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
111	fp->_p = NULL;		/* no current pointer */
112	fp->_w = 0;		/* nothing to read or write */
113	fp->_r = 0;
114	fp->_bf._base = NULL;	/* no buffer */
115	fp->_bf._size = 0;
116	fp->_lbfsize = 0;	/* not line buffered */
117	fp->_file = -1;		/* no file */
118/*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
119	fp->_ub._base = NULL;	/* no ungetc buffer */
120	fp->_ub._size = 0;
121	fp->_lb._base = NULL;	/* no line buffer */
122	fp->_lb._size = 0;
123	return (fp);
124}
125
126/*
127 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
128 * but documented historically for certain applications.  Bad applications.
129 */
130__warn_references(f_prealloc,
131	"warning: this program uses f_prealloc(), which is stupid.");
132
133void
134f_prealloc()
135{
136	register struct glue *g;
137	int n;
138
139	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
140	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
141		/* void */;
142	if (n > 0)
143		g->next = moreglue(n);
144}
145
146/*
147 * exit() calls _cleanup() through *__cleanup, set whenever we
148 * open or buffer a file.  This chicanery is done so that programs
149 * that do not use stdio need not link it all in.
150 *
151 * The name `_cleanup' is, alas, fairly well known outside stdio.
152 */
153void
154_cleanup()
155{
156	/* (void) _fwalk(fclose); */
157	(void) _fwalk(__sflush);		/* `cheating' */
158}
159
160/*
161 * __sinit() is called whenever stdio's internal variables must be set up.
162 */
163void
164__sinit()
165{
166	/* make sure we clean up on exit */
167	__cleanup = _cleanup;		/* conservative */
168	__sdidinit = 1;
169}
170