malloc.c

来自「把fortran语言编的程序转为c语言编的程序, 运行环境linux」· C语言 代码 · 共 167 行

/****************************************************************
Copyright 1990, 1994 by AT&T Bell Laboratories and Bellcore.

Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that the copyright notice and this
permission notice and warranty disclaimer appear in supporting
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specific, written prior permission.

AT&T and Bellcore disclaim all warranties with regard to this
software, including all implied warranties of merchantability
and fitness.  In no event shall AT&T or Bellcore be liable for
any special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits, whether
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#ifndef CRAY
#define STACKMIN 512
#define MINBLK (2*sizeof(struct mem) + 16)
#define F _malloc_free_
#define SBGULP 8192
#include "string.h"	/* for memcpy */

#ifdef KR_headers
#define Char char
#define Unsigned unsigned
#define Int /*int*/
#else
#define Char void
#define Unsigned size_t
#define Int int
#endif

typedef struct mem {
	struct mem *next;
	Unsigned len;
	} mem;

mem *F;

 Char *
#ifdef KR_headers
malloc(size)
	register Unsigned size;
#else
malloc(register Unsigned size)
#endif
{
	register mem *p, *q, *r, *s;
	unsigned register k, m;
	extern Char *sbrk(Int);
	char *top, *top1;

	size = (size+7) & ~7;
	r = (mem *) &F;
	for (p = F, q = 0; p; r = p, p = p->next) {
		if ((k = p->len) >= size && (!q || m > k)) {
			m = k;
			q = p;
			s = r;
			}
		}
	if (q) {
		if (q->len - size >= MINBLK) { /* split block */
			p = (mem *) (((char *) (q+1)) + size);
			p->next = q->next;
			p->len = q->len - size - sizeof(mem);
			s->next = p;
			q->len = size;
			}
		else
			s->next = q->next;
		}
	else {
		top = (Char *)(((long)sbrk(0) + 7) & ~7);
		if (F && (char *)(F+1) + F->len == top) {
			q = F;
			F = F->next;
			}
		else
			q = (mem *) top;
		top1 = (char *)(q+1) + size;
		if (sbrk((int)(top1-top+SBGULP)) == (Char *) -1)
			return 0;
		r = (mem *)top1;
		r->len = SBGULP - sizeof(mem);
		r->next = F;
		F = r;
		top1 += SBGULP;
		q->len = size;
		}
	return (Char *) (q+1);
	}

 void
#ifdef KR_headers
free(f)
	Char *f;
#else
free(Char *f)
#endif
{
	mem *p, *q, *r;
	char *pn, *qn;

	if (!f) return;
	q = (mem *) ((char *)f - sizeof(mem));
	qn = (char *)f + q->len;
	for (p = F, r = (mem *) &F; ; r = p, p = p->next) {
		if (qn == (Char *) p) {
			q->len += p->len + sizeof(mem);
			p = p->next;
			}
		pn = p ? ((char *) (p+1)) + p->len : 0;
		if (pn == (Char *) q) {
			p->len += sizeof(mem) + q->len;
			q->len = 0;
			q->next = p;
			r->next = p;
			break;
			}
		if (pn < (char *) q) {
			r->next = q;
			q->next = p;
			break;
			}
		}
	}

 Char *
#ifdef KR_headers
realloc(f, size)
	Char *f;
	Unsigned size;
#else
realloc(Char *f, Unsigned size)
#endif
{
	mem *p;
	Char *q, *f1;
	Unsigned s1;

	if (!f) return malloc(size);
	p = (mem *) ((char *)f - sizeof(mem));
	s1 = p->len;
	free(f);
	if (s1 > size)
		s1 = size + 7 & ~7;
	if (!p->len) {
		f1 = (Char *)(p->next + 1);
		memcpy(f1, f, s1);
		f = f1;
		}
	q = malloc(size);
	if (q && q != f)
		memcpy(q, f, s1);
	return q;
	}
#endif