128 lines
3 KiB
C
128 lines
3 KiB
C
/*
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* (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
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* See the copyright notice in the ACK home directory, in the file "Copyright".
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*/
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/* $Header$ */
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#include <stdlib.h>
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#define CLICK_SIZE 4096
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#if EM_WSIZE == EM_PSIZE
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typedef unsigned int vir_bytes;
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#else
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typedef long vir_bytes;
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#endif
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#define ALIGN(x, a) (((x) + (a - 1)) & ~(a - 1))
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#define BUSY 1
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#define NEXT(p) (* (void **) (p))
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#ifdef pdp
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#define BUGFIX 64 /* cannot set break in top 64 bytes */
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#else
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#define BUGFIX 0
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#endif
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extern void bcopy(void *, void *, size_t);
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extern void *sbrk(unsigned int);
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extern void *brk(unsigned int);
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static void *bottom, *top;
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static int
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grow(size_t len)
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{
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register void *p;
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register int click = CLICK_SIZE;
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p = sbrk(0);
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len += (void *) ALIGN((vir_bytes) p, sizeof(void *)) - p;
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while (click >= 4) {
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size_t len1 = ALIGN((vir_bytes)p+len+sizeof(char *),click)-(vir_bytes)p;
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void *p1 = p;
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if (p + len1 + BUGFIX < p || (p1 = sbrk(len1)) == (void *) -1) {
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click >>= 1;
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continue;
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}
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p = p1;
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if (top + sizeof(void *) != p) {
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/* someone else has done an sbrk */
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NEXT(top) = (void *) ((vir_bytes) p | BUSY);
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} else {
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for (p = bottom; NEXT(p) != NULL; p = (void *) (* (vir_bytes *) p & ~BUSY))
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;
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}
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top = p + len1 - sizeof(void *);
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NEXT(p) = top;
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NEXT(top) = NULL;
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return 1;
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}
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return 0;
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}
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void *
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malloc(size_t size)
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{
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register void *p, *next, *new;
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register size_t len = ALIGN(size, sizeof(void *)) + sizeof(void *);
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if ((p = bottom) == NULL) {
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p = sbrk(sizeof(void *));
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sbrk((void *) ALIGN((vir_bytes) p, sizeof(void *)) - p);
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p = (void *) ALIGN((vir_bytes) p, sizeof(void *));
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top = bottom = p;
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NEXT(p) = NULL;
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}
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while ((next = NEXT(p)) != NULL)
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if ((vir_bytes) next & BUSY) /* already in use */
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p = (void *) ((vir_bytes) next & ~BUSY);
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else {
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while ((new = NEXT(next)) != NULL
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&& !((vir_bytes) new & BUSY))
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next = new;
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if (next - p >= len) { /* fits */
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if ((new = p + len) < next) /* too big */
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NEXT(new) = next;
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NEXT(p) = (void *) ((vir_bytes) new | BUSY);
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return(p + sizeof(void *));
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}
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p = next;
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}
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return grow(len) ? malloc(size) : (void *)NULL;
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}
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void *
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realloc(void *old, size_t size)
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{
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register void *p = old - sizeof(void *), *next, *new;
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register size_t len = ALIGN(size, sizeof(void *)) + sizeof(void *), n;
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next = (void *) (* (vir_bytes *) p & ~BUSY);
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n = next - old; /* old size */
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while ((new = NEXT(next)) != NULL && !((vir_bytes) new & BUSY))
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next = new;
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if (next - p >= len) { /* does it still fit */
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if ((new = p + len) < next) { /* even too big */
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NEXT(new) = next;
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NEXT(p) = (void *) ((vir_bytes) new | BUSY);
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}
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else
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NEXT(p) = (void *) ((vir_bytes) next | BUSY);
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return(old);
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}
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if ((new = malloc(size)) == NULL) /* it didn't fit */
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return((void *)NULL);
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bcopy(old, new, n); /* n < size */
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* (vir_bytes *) p &= ~BUSY;
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return(new);
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}
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void
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free(void *p)
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{
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if (p != (void *)NULL)
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*(vir_bytes *) (p - sizeof(void *)) &= ~BUSY;
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}
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