alloc.c revision 1.8
1 /* $NetBSD: alloc.c,v 1.8 1997/06/13 14:28:52 drochner 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 = (struct fl *)0; 114 115 #ifdef HEAP_START 116 static char *top = (char*)HEAP_START; 117 #else 118 extern char end[]; 119 static char *top = end; 120 #endif 121 122 void * 123 alloc(size) 124 unsigned size; 125 { 126 register struct fl **f = &freelist, **bestf = NULL; 127 unsigned bestsize = 0xffffffff; /* greater than any real size */ 128 char *help; 129 int failed; 130 131 #ifdef ALLOC_TRACE 132 printf("alloc(%u)", size); 133 #endif 134 135 #ifdef ALLOC_FIRST_FIT 136 while (*f != (struct fl *)0 && (*f)->size < size) 137 f = &((*f)->next); 138 bestf = f; 139 failed = (*bestf == (struct fl *)0); 140 #else 141 /* scan freelist */ 142 while (*f) { 143 if ((*f)->size >= size) { 144 if ((*f)->size == size) /* exact match */ 145 goto found; 146 147 if ((*f)->size < bestsize) { 148 /* keep best fit */ 149 bestf = f; 150 bestsize = (*f)->size; 151 } 152 } 153 f = &((*f)->next); 154 } 155 156 /* no match in freelist if bestsize unchanged */ 157 failed = (bestsize == 0xffffffff); 158 #endif 159 160 if (failed) { /* nothing found */ 161 /* 162 * allocate from heap, keep chunk len in 163 * first word 164 */ 165 help = top; 166 167 /* make _sure_ the region can hold a struct fl. */ 168 if (size < ALIGN(sizeof (struct fl *))) 169 size = ALIGN(sizeof (struct fl *)); 170 top += ALIGN(sizeof(unsigned)) + ALIGN(size); 171 #ifdef HEAP_LIMIT 172 if (top > (char*)HEAP_LIMIT) 173 panic("heap full (0x%lx+%u)", help, size); 174 #endif 175 *(unsigned *)help = ALIGN(size); 176 #ifdef ALLOC_TRACE 177 printf("=%x\n", help + ALIGN(sizeof(unsigned))); 178 #endif 179 return(help + ALIGN(sizeof(unsigned))); 180 } 181 182 /* we take the best fit */ 183 f = bestf; 184 185 found: 186 /* remove from freelist */ 187 help = (char*)*f; 188 *f = (*f)->next; 189 #ifdef ALLOC_TRACE 190 printf("=%lx (origsize %u)\n", help + ALIGN(sizeof(unsigned)), 191 *(unsigned *)help); 192 #endif 193 return(help + ALIGN(sizeof(unsigned))); 194 } 195 196 void 197 free(ptr, size) 198 void *ptr; 199 unsigned size; /* only for consistence check */ 200 { 201 register struct fl *f = 202 (struct fl *)((char*)ptr - ALIGN(sizeof(unsigned))); 203 #ifdef ALLOC_TRACE 204 printf("free(%lx, %u) (origsize %u)\n", ptr, size, f->size); 205 #endif 206 #ifdef DEBUG 207 if (size > f->size) 208 printf("free %u bytes @%lx, should be <=%u\n", 209 size, ptr, f->size); 210 #ifdef HEAP_START 211 if (ptr < (void *)HEAP_START) 212 #else 213 if (ptr < (void *)end[]) 214 #endif 215 printf("free: %lx before start of heap.\n", (u_long)ptr); 216 217 #ifdef HEAP_LIMIT 218 if (ptr > (void *)HEAP_LIMIT) 219 printf("free: %lx beyond end of heap.\n", (u_long)ptr); 220 #endif 221 #endif /* DEBUG */ 222 /* put into freelist */ 223 f->next = freelist; 224 freelist = f; 225 } 226
Indexes created Tue Sep 23 01:09:51 GMT 2025