120 lines
2.5 KiB
C
120 lines
2.5 KiB
C
/*
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* File: - new.c
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*
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* new() 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 <em_abs.h>
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#include <pc_err.h>
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#define assert(x) /* nothing */
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#define UNDEF 0x8000
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#define NALLOC (1024) /* request this many units from OS */
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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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extern struct adm *freep;
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extern void _trp(int); /* called on error */
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extern void _dis(int, struct adm **);
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/*
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* Helper function to request 'nu' units of memory from the OS.
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* A storage unit is sizeof(struct adm). Typically 8 bytes
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* on a 32-bit machine like i386 etc.
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*/
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static struct adm *
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morecore(unsigned nu)
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{
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char *cp, *sbrk(int);
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struct adm *up;
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if (nu < NALLOC)
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nu = NALLOC;
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cp = sbrk(nu * sizeof(struct adm));
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if (cp == (char *) -1) /* no space at all */
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return 0;
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up = (struct adm*) cp;
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up->size = nu;
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up = up + 1;
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_dis((nu - 1) * sizeof(struct adm), &up);
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return freep;
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} /* morecore */
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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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_new(int n, struct adm **pp)
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{
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int nunits; /* the unit of storage is sizeof(struct adm) */
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struct adm *p,*q;
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/* round up size of request */
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nunits = (n + sizeof(struct adm) - 1) / sizeof(struct adm) + 1;
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q = 0;
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for (p = freep; ; p = p->next) {
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if (p == 0) {
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p = morecore(nunits);
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if (p == 0)
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_trp(EHEAP);
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q = 0;
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}
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if (p->size >= nunits) {
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if (p->size == nunits) { /* exact fit */
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if (q == 0) { /* first element on free list. */
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freep = p->next;
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} else {
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q->next = p->next;
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}
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} else { /* allocate tail end */
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q = p;
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q->size = q->size - nunits;
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p = q + q->size;
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p->next = 0;
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p->size = nunits;
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}
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break;
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}
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q = p;
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}
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*pp = p + 1;
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} /* _new */
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