alloc.c revision 1.15
1 /* $NetBSD: alloc.c,v 1.15 2000/03/30 12:19:47 augustss Exp $ */ 2 3 /* 4 * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved. 5 * Copyright (c) 1996 6 * Matthias Drochner. All rights reserved. 7 * Copyright (c) 1993 8 * The Regents of the University of California. All rights reserved. 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * @(#)alloc.c 8.1 (Berkeley) 6/11/93 42 * 43 * 44 * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University 45 * All Rights Reserved. 46 * 47 * Author: Alessandro Forin 48 * 49 * Permission to use, copy, modify and distribute this software and its 50 * documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR 57 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution (at) CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * Dynamic memory allocator. 72 * 73 * Compile options: 74 * 75 * ALLOC_TRACE enable tracing of allocations/deallocations 76 77 * ALLOC_FIRST_FIT use a first-fit allocation algorithm, rather than 78 * the default best-fit algorithm. 79 * 80 * HEAP_LIMIT heap limit address (defaults to "no limit"). 81 * 82 * HEAP_START start address of heap (defaults to '&end'). 83 * 84 * DEBUG enable debugging sanity checks. 85 */ 86 87 #include <sys/param.h> 88 #include "stand.h" 89 90 /* 91 * Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated 92 * to it, as follows: 93 * 94 * 0 ... (sizeof(unsigned) - 1) 95 * allocated or unallocated: holds size of user-data part of block. 96 * 97 * sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1) 98 * allocated: unused 99 * unallocated: depends on packing of struct fl 100 * 101 * ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1) 102 * allocated: user data 103 * unallocated: depends on packing of struct fl 104 * 105 * 'next' is only used when the block is unallocated (i.e. on the free list). 106 * However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must 107 * be at least 'sizeof(struct fl)', so that blocks can be used as structures 108 * when on the free list. 109 */ 110 struct fl { 111 unsigned size; 112 struct fl *next; 113 } *freelist; 114 115 #ifdef HEAP_VARIABLE 116 static char *top, *heapstart, *heaplimit; 117 void setheap(start, limit) 118 void *start, *limit; 119 { 120 heapstart = top = start; 121 heaplimit = limit; 122 } 123 #define HEAP_START heapstart 124 #define HEAP_LIMIT heaplimit 125 #else /* !HEAP_VARIABLE */ 126 #ifndef HEAP_START 127 extern char end[]; 128 #define HEAP_START end 129 #endif 130 static char *top = (char*)HEAP_START; 131 #endif /* HEAP_VARIABLE */ 132 133 void * 134 alloc(size) 135 unsigned size; 136 { 137 struct fl **f = &freelist, **bestf = NULL; 138 #ifndef ALLOC_FIRST_FIT 139 unsigned bestsize = 0xffffffff; /* greater than any real size */ 140 #endif 141 char *help; 142 int failed; 143 144 #ifdef ALLOC_TRACE 145 printf("alloc(%u)", size); 146 #endif 147 148 #ifdef ALLOC_FIRST_FIT 149 while (*f != (struct fl *)0 && (*f)->size < size) 150 f = &((*f)->next); 151 bestf = f; 152 failed = (*bestf == (struct fl *)0); 153 #else 154 /* scan freelist */ 155 while (*f) { 156 if ((*f)->size >= size) { 157 if ((*f)->size == size) /* exact match */ 158 goto found; 159 160 if ((*f)->size < bestsize) { 161 /* keep best fit */ 162 bestf = f; 163 bestsize = (*f)->size; 164 } 165 } 166 f = &((*f)->next); 167 } 168 169 /* no match in freelist if bestsize unchanged */ 170 failed = (bestsize == 0xffffffff); 171 #endif 172 173 if (failed) { /* nothing found */ 174 /* 175 * allocate from heap, keep chunk len in 176 * first word 177 */ 178 help = top; 179 180 /* make _sure_ the region can hold a struct fl. */ 181 if (size < ALIGN(sizeof (struct fl *))) 182 size = ALIGN(sizeof (struct fl *)); 183 top += ALIGN(sizeof(unsigned)) + ALIGN(size); 184 #ifdef HEAP_LIMIT 185 if (top > (char*)HEAP_LIMIT) 186 panic("heap full (0x%lx+%u)", help, size); 187 #endif 188 *(unsigned *)help = ALIGN(size); 189 #ifdef ALLOC_TRACE 190 printf("=%lx\n", (u_long)help + ALIGN(sizeof(unsigned))); 191 #endif 192 return(help + ALIGN(sizeof(unsigned))); 193 } 194 195 /* we take the best fit */ 196 f = bestf; 197 198 #ifndef ALLOC_FIRST_FIT 199 found: 200 #endif 201 /* remove from freelist */ 202 help = (char*)*f; 203 *f = (*f)->next; 204 #ifdef ALLOC_TRACE 205 printf("=%lx (origsize %u)\n", (u_long)help + ALIGN(sizeof(unsigned)), 206 *(unsigned *)help); 207 #endif 208 return(help + ALIGN(sizeof(unsigned))); 209 } 210 211 void 212 free(ptr, size) 213 void *ptr; 214 unsigned size; /* only for consistence check */ 215 { 216 struct fl *f = 217 (struct fl *)((char*)ptr - ALIGN(sizeof(unsigned))); 218 #ifdef ALLOC_TRACE 219 printf("free(%lx, %u) (origsize %u)\n", (u_long)ptr, size, f->size); 220 #endif 221 #ifdef DEBUG 222 if (size > f->size) 223 printf("free %u bytes @%lx, should be <=%u\n", 224 size, (u_long)ptr, f->size); 225 226 if (ptr < (void *)HEAP_START) 227 printf("free: %lx before start of heap.\n", (u_long)ptr); 228 229 #ifdef HEAP_LIMIT 230 if (ptr > (void *)HEAP_LIMIT) 231 printf("free: %lx beyond end of heap.\n", (u_long)ptr); 232 #endif 233 #endif /* DEBUG */ 234 /* put into freelist */ 235 f->next = freelist; 236 freelist = f; 237 } 238
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