alloc.c revision 1.5
1 /* $NetBSD: alloc.c,v 1.5 1997/01/22 01:18:23 cgd 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 89 /* 90 * Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated 91 * to it, as follows: 92 * 93 * 0 ... (sizeof(unsigned) - 1) 94 * allocated or unallocated: holds size of user-data part of block. 95 * 96 * sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1) 97 * allocated: unused 98 * unallocated: depends on packing of struct fl 99 * 100 * ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1) 101 * allocated: user data 102 * unallocated: depends on packing of struct fl 103 * 104 * 'next' is only used when the block is unallocated (i.e. on the free list). 105 * However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must 106 * be at least 'sizeof(struct fl)', so that blocks can be used as structures 107 * when on the free list. 108 */ 109 struct fl { 110 unsigned size; 111 struct fl *next; 112 } *freelist = (struct fl *)0; 113 114 #ifdef HEAP_START 115 static char *top = (char*)HEAP_START; 116 #else 117 extern char end[]; 118 static char *top = end; 119 #endif 120 121 void * 122 alloc(size) 123 unsigned size; 124 { 125 register struct fl **f = &freelist, **bestf; 126 unsigned bestsize = 0xffffffff; /* greater than any real size */ 127 char *help; 128 int failed; 129 130 #ifdef ALLOC_TRACE 131 printf("alloc(%u)", size); 132 #endif 133 134 #ifdef ALLOC_FIRST_FIT 135 while (*f != (struct fl *)0 && (*f)->size < size) 136 f = &((*f)->next); 137 bestf = f; 138 failed = (*bestf == (struct fl *)0); 139 #else 140 /* scan freelist */ 141 while (*f) { 142 if ((*f)->size >= size) { 143 if ((*f)->size == size) /* exact match */ 144 goto found; 145 146 if ((*f)->size < bestsize) { 147 /* keep best fit */ 148 bestf = f; 149 bestsize = (*f)->size; 150 } 151 } 152 f = &((*f)->next); 153 } 154 155 /* no match in freelist if bestsize unchanged */ 156 failed = (bestsize == 0xffffffff); 157 #endif 158 159 if (failed) { /* nothing found */ 160 /* 161 * allocate from heap, keep chunk len in 162 * first word 163 */ 164 help = top; 165 166 /* make _sure_ the region can hold a struct fl. */ 167 if (size < ALIGN(sizeof (struct fl *))) 168 size = ALIGN(sizeof (struct fl *)); 169 top += ALIGN(sizeof(unsigned)) + ALIGN(size); 170 #ifdef HEAP_LIMIT 171 if (top > (char*)HEAP_LIMIT) 172 panic("heap full (0x%lx+%u)", help, size); 173 #endif 174 *(unsigned *)help = ALIGN(size); 175 #ifdef ALLOC_TRACE 176 printf("=%x\n", help + ALIGN(sizeof(unsigned))); 177 #endif 178 return(help + ALIGN(sizeof(unsigned))); 179 } 180 181 /* we take the best fit */ 182 f = bestf; 183 184 found: 185 /* remove from freelist */ 186 help = (char*)*f; 187 *f = (*f)->next; 188 #ifdef ALLOC_TRACE 189 printf("=%lx (origsize %u)\n", help + ALIGN(sizeof(unsigned)), 190 *(unsigned *)help); 191 #endif 192 return(help + ALIGN(sizeof(unsigned))); 193 } 194 195 void 196 free(ptr, size) 197 void *ptr; 198 unsigned size; /* only for consistence check */ 199 { 200 register struct fl *f = 201 (struct fl *)((char*)ptr - ALIGN(sizeof(unsigned))); 202 #ifdef ALLOC_TRACE 203 printf("free(%lx, %u) (origsize %u)\n", ptr, size, f->size); 204 #endif 205 #ifdef DEBUG 206 if (size > f->size) 207 printf("free %u bytes @%lx, should be <=%u\n", 208 size, ptr, f->size); 209 #endif 210 /* put into freelist */ 211 f->next = freelist; 212 freelist = f; 213 } 214
Indexes created Mon Sep 22 13:09:51 GMT 2025