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138 lines
3.6 KiB
138 lines
3.6 KiB
/* $Id: malloc.c,v 1.1.1.1 2006/09/14 01:59:06 root Exp $ */
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/*
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* Copyright (c) 2000-2002 Opsycon AB (www.opsycon.se)
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Opsycon AB.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
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* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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*/
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#include <sys/types.h>
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#include <stdlib.h>
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#include <unistd.h>
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typedef double ALIGN;
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int allocsize __P((void *));
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union header {
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struct {
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union header *ptr;
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unsigned size;
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} s;
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ALIGN x;
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};
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typedef union header HEADER;
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static HEADER base;
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static HEADER *allocp; /* K&R called allocp, freep */
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#define NULL 0
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#define NALLOC 128
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/* The rest of this file is from pages 185-189 of K & R Edition 2 */
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static HEADER *morecore __P((u_int32_t));
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void *
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malloc(size_t nbytes)
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{
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HEADER *p, *q; /* K&R called q, prevp */
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unsigned nunits;
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nunits = (nbytes + sizeof (HEADER) - 1) / sizeof (HEADER) + 1;
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if ((q = allocp) == NULL) { /* no free list yet */
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base.s.ptr = allocp = q = &base;
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base.s.size = 0;
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}
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for (p = q->s.ptr;; q = p, p = p->s.ptr) {
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if (p->s.size >= nunits) { /* big enough */
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if (p->s.size == nunits) /* exactly */
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q->s.ptr = p->s.ptr;
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else { /* allocate tail end */
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p->s.size -= nunits;
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p += p->s.size;
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p->s.size = nunits;
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}
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allocp = q;
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return ((char *)(p + 1));
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}
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if (p == allocp)
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if ((p = morecore (nunits)) == NULL)
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return (NULL);
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}
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}
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static HEADER *
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morecore(u_int32_t nu)
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{
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char *cp;
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HEADER *up;
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int rnu;
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rnu = NALLOC * ((nu + NALLOC - 1) / NALLOC);
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cp = sbrk (rnu * sizeof (HEADER));
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if ((int)cp == NULL)
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return (NULL);
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up = (HEADER *) cp;
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up->s.size = rnu;
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free ((char *)(up + 1));
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return (allocp);
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}
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void
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free(void *ap)
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{
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HEADER *p, *q;
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p = (HEADER *) ap - 1;
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for (q = allocp; !(p > q && p < q->s.ptr); q = q->s.ptr)
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if (q >= q->s.ptr && (p > q || p < q->s.ptr))
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break;
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if (p + p->s.size == q->s.ptr) {
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p->s.size += q->s.ptr->s.size;
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p->s.ptr = q->s.ptr->s.ptr;
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} else
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p->s.ptr = q->s.ptr;
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if (q + q->s.size == p) {
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q->s.size += p->s.size;
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q->s.ptr = p->s.ptr;
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} else
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q->s.ptr = p;
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allocp = q;
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}
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int
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allocsize(void *ap)
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{
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HEADER *p;
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p = (HEADER *) ap - 1;
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return (p->s.size * sizeof (HEADER));
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}
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