103 lines
2.3 KiB
C
103 lines
2.3 KiB
C
/* $Header$ */
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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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extern bcopy();
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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) (* (char **) (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 char *sbrk(), *brk();
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static char *bottom, *top;
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static grow(len)
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unsigned len;
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{
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register char *p;
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register int click = CLICK_SIZE;
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while (click >= 4) {
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p = (char *) ALIGN((vir_bytes) top + sizeof(char *) + len, click)
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+ BUGFIX;
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if (p > top && brk(p - BUGFIX) >= 0) break;
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click >>= 1;
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}
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if (click < 4) return(0);
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top = p - (BUGFIX + sizeof(char *));
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for (p = bottom; NEXT(p) != 0; p = (char *) (* (vir_bytes *) p & ~BUSY))
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;
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NEXT(p) = top;
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NEXT(top) = 0;
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return(1);
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}
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char *malloc(size)
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unsigned size;
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{
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register char *p, *next, *new;
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register unsigned len = ALIGN(size, sizeof(char *)) + sizeof(char *);
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if ((p = bottom) == 0) {
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top = bottom = p = sbrk(sizeof(char *));
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NEXT(p) = 0;
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}
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while ((next = NEXT(p)) != 0)
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if ((vir_bytes) next & BUSY) /* already in use */
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p = (char *) ((vir_bytes) next & ~BUSY);
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else {
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while ((new = NEXT(next)) != 0 && !((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) = (char *) ((vir_bytes) new | BUSY);
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return(p + sizeof(char *));
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}
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p = next;
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}
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return grow(len) ? malloc(size) : 0;
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}
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char *realloc(old, size)
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char *old;
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unsigned size;
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{
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register char *p = old - sizeof(char *), *next, *new;
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register unsigned len = ALIGN(size, sizeof(char *)) + sizeof(char *), n;
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next = (char *) (* (vir_bytes *) p & ~BUSY);
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n = next - old; /* old size */
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while ((new = NEXT(next)) != 0 && !((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) = (char *) ((vir_bytes) new | BUSY);
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}
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else
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NEXT(p) = (char *) ((vir_bytes) next | BUSY);
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return(old);
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}
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if ((new = malloc(size)) == 0) /* it didn't fit */
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return(0);
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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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free(p)
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char *p;
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{
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* (vir_bytes *) (p - sizeof(char *)) &= ~BUSY;
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}
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