101 lines
2.2 KiB
C
101 lines
2.2 KiB
C
/*
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* File: - dis.c
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*
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* dispose() built in standard procedure in Pascal (6.6.5.3)
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*
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* Re-implementation of storage allocator for Ack Pascal compiler
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* under Linux, and other UNIX-like systems.
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*
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* Written by Erik Backerud, 2010-10-01
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*
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* Original copyright and author info below:
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*/
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/* $Id$ */
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/*
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* (c) copyright 1983 by the Vrije Universiteit, Amsterdam, The Netherlands.
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*
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* This product is part of the Amsterdam Compiler Kit.
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*
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* Permission to use, sell, duplicate or disclose this software must be
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* obtained in writing. Requests for such permissions may be sent to
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*
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* Dr. Andrew S. Tanenbaum
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* Wiskundig Seminarium
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* Vrije Universiteit
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* Postbox 7161
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* 1007 MC Amsterdam
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* The Netherlands
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*
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*/
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/* Author: J.W. Stevenson */
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#include <pc_err.h>
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#define assert() /* nothing */
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/*
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* use a singly linked list of free blocks.
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*/
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struct adm {
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struct adm *next;
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int size;
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};
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struct adm *freep = 0; /* first element on free list */
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extern void _trp(int);
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/*
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* Dispose
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* Called with two arguments:
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* n the size of the block to be freed, in bytes,
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* pp address of pointer to data.
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*/
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void
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_dis(int n, struct adm **pp)
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{
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struct adm *block; /* the block of data being freed (inc. header) */
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struct adm *p, *q;
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if (*pp == 0) {
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_trp(EFREE);
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}
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block = *pp - 1;
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if (freep == 0) {
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freep = block;
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block->next = 0;
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} else {
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q = 0; /* trail one behind */
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for (p = freep; p < block; p = p->next) {
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if (p == 0) { /* We reached the end of the free list. */
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break;
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}
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q = p;
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/* check if block is contained in the free block p */
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if (p+p->size > block) {
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_trp(EFREE);
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}
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}
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if (p == block) { /* this block already freed */
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_trp(EFREE);
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}
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if (q == 0) { /* block is first */
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freep = block;
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block->next = p;
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} else {
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q->next = block;
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}
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block->next = p;
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/* merge with successor on free list? */
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if (block + block->size == p) {
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block->size = block->size + p->size;
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block->next = p->next;
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}
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/* merge with preceding block on free list? */
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if (q != 0 && q+q->size == block) {
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q->size = q->size + block->size;
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q->next = block->next;
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}
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}
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} /* _dis */
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