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