NetBSD/bin/ksh/alloc.c

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1997-01-12 22:11:37 +03:00
/* $NetBSD: alloc.c,v 1.2 1997/01/12 19:11:38 tls Exp $
1996-09-22 03:35:13 +04:00
/*
* area-based allocation built on malloc/free
*/
#include "sh.h"
#ifdef MEM_DEBUG
# undef alloc
# undef aresize
# undef afree
#endif /* MEM_DEBUG */
#define ICELLS 100 /* number of Cells in small Block */
typedef union Cell Cell;
typedef struct Block Block;
/*
* The Cells in a Block are organized as a set of objects.
* Each object (pointed to by dp) begins with a size in (dp-1)->size,
* followed with "size" data Cells. Free objects are
* linked together via dp->next.
*/
union Cell {
size_t size;
Cell *next;
struct {int _;} junk; /* alignment */
};
struct Block {
Block *next; /* list of Blocks in Area */
Cell *freelist; /* object free list */
Cell *last; /* &b.cell[size] */
Cell cell [1]; /* [size] Cells for allocation */
};
static Block aempty = {&aempty, aempty.cell, aempty.cell};
/* create empty Area */
Area *
ainit(ap)
register Area *ap;
{
ap->freelist = &aempty;
return ap;
}
/* free all object in Area */
void
afreeall(ap)
register Area *ap;
{
register Block *bp;
register Block *tmp;
bp = ap->freelist;
if (bp != NULL && bp != &aempty) {
do {
tmp = bp->next;
free((void*)bp);
bp = tmp;
} while (bp != ap->freelist);
ap->freelist = &aempty;
}
}
/* allocate object from Area */
void *
alloc(size, ap)
size_t size;
register Area *ap;
{
int cells, split;
register Block *bp;
register Cell *dp, *fp, *fpp;
if (size <= 0) {
aerror(ap, "allocate bad size");
return NULL;
}
cells = (unsigned)(size - 1) / sizeof(Cell) + 1;
/* find Cell large enough */
for (bp = ap->freelist; ; bp = bp->next) {
for (fpp = NULL, fp = bp->freelist;
fp != bp->last; fpp = fp, fp = fpp->next)
if ((fp-1)->size >= cells)
goto Found;
/* wrapped around Block list, create new Block */
if (bp->next == ap->freelist) {
bp = (Block*) malloc(offsetof(Block, cell[ICELLS])
+ sizeof(bp->cell[0]) * cells);
if (bp == NULL) {
aerror(ap, "cannot allocate");
return NULL;
}
if (ap->freelist == &aempty)
bp->next = bp;
else {
bp->next = ap->freelist->next;
ap->freelist->next = bp;
}
bp->last = bp->cell + ICELLS + cells;
fp = bp->freelist = bp->cell + 1; /* initial free list */
(fp-1)->size = ICELLS + cells - 1;
fp->next = bp->last;
fpp = NULL;
break;
}
}
Found:
ap->freelist = bp;
dp = fp; /* allocated object */
split = (dp-1)->size - cells;
if (split < 0)
aerror(ap, "allocated object too small");
if (--split <= 0) { /* allocate all */
fp = fp->next;
} else { /* allocate head, free tail */
(fp-1)->size = cells;
fp += cells + 1;
(fp-1)->size = split;
fp->next = dp->next;
}
if (fpp == NULL)
bp->freelist = fp;
else
fpp->next = fp;
return (void*) dp;
}
/* change size of object -- like realloc */
void *
aresize(ptr, size, ap)
register void *ptr;
size_t size;
Area *ap;
{
int cells;
register Cell *dp = (Cell*) ptr;
if (size <= 0) {
aerror(ap, "allocate bad size");
return NULL;
}
cells = (unsigned)(size - 1) / sizeof(Cell) + 1;
if (dp == NULL || (dp-1)->size < cells) { /* enlarge object */
/* XXX check for available adjacent free block */
ptr = alloc(size, ap);
if (dp != NULL) {
memcpy(ptr, dp, (dp-1)->size * sizeof(Cell));
afree((void *) dp, ap);
}
} else { /* shrink object */
int split;
split = (dp-1)->size - cells;
if (--split <= 0) /* cannot split */
;
else { /* shrink head, free tail */
(dp-1)->size = cells;
dp += cells + 1;
(dp-1)->size = split;
afree((void*)dp, ap);
}
}
return (void*) ptr;
}
void
afree(ptr, ap)
void *ptr;
register Area *ap;
{
register Block *bp;
register Cell *fp, *fpp;
register Cell *dp = (Cell*)ptr;
/* find Block containing Cell */
for (bp = ap->freelist; ; bp = bp->next) {
if (bp->cell <= dp && dp < bp->last)
break;
if (bp->next == ap->freelist) {
aerror(ap, "freeing with invalid area");
return;
}
}
/* find position in free list */
for (fpp = NULL, fp = bp->freelist; fp < dp; fpp = fp, fp = fpp->next)
;
if (fp == dp) {
aerror(ap, "freeing free object");
return;
}
/* join object with next */
if (dp + (dp-1)->size == fp-1) { /* adjacent */
(dp-1)->size += (fp-1)->size + 1;
dp->next = fp->next;
} else /* non-adjacent */
dp->next = fp;
/* join previous with object */
if (fpp == NULL)
bp->freelist = dp;
else if (fpp + (fpp-1)->size == dp-1) { /* adjacent */
(fpp-1)->size += (dp-1)->size + 1;
fpp->next = dp->next;
} else /* non-adjacent */
fpp->next = dp;
}
#if DEBUG_ALLOC
void
aprint(ap, ptr, size)
register Area *ap;
void *ptr;
size_t size;
{
Block *bp;
if (!ap)
shellf("aprint: null area pointer\n");
else if (!(bp = ap->freelist))
shellf("aprint: null area freelist\n");
else if (bp == &aempty)
shellf("aprint: area is empty\n");
else {
int i;
Cell *fp;
for (i = 0; !i || bp != ap->freelist; bp = bp->next, i++) {
if (ptr) {
void *eptr = (void *) (((char *) ptr) + size);
/* print block only if it overlaps ptr/size */
if (!((ptr >= (void *) bp
&& ptr <= (void *) bp->last)
|| (eptr >= (void *) bp
&& eptr <= (void *) bp->last)))
continue;
shellf("aprint: overlap of 0x%p .. 0x%p\n",
ptr, eptr);
}
shellf("aprint: block %2d: 0x%p .. 0x%p (%d)\n", i,
bp->cell, bp->last,
(char *) bp->last - (char *) bp->cell);
for (fp = bp->freelist; fp != bp->last; fp = fp->next)
shellf(
"aprint: 0x%p .. 0x%p (%d) free\n",
(fp-1), (fp-1) + (fp-1)->size,
(fp-1)->size * sizeof(Cell));
}
}
}
#endif /* DEBUG_ALLOC */
#ifdef TEST_ALLOC
Area a;
main(int argc, char **argv) {
int i;
char *p [9];
ainit(&a);
for (i = 0; i < 9; i++) {
p[i] = alloc(124, &a);
printf("alloc: %x\n", p[i]);
}
for (i = 1; i < argc; i++)
afree(p[atoi(argv[i])], &a);
afreeall(&a);
return 0;
}
void aerror(Area *ap, const char *msg) {
abort();
}
#endif