void *tmalloc(unsigned nbytes)
{
CHUNK *p;
unsigned size;
if (bot == NULL)
init();
size = sizeof(CHUNK) * ((nbytes+sizeof(CHUNK)-1)/sizeof(CHUNK) + 1);
for (p = bot; p != NULL; p = RIGHT(p))
if (GET_FREEBIT(p) && CHUNKSIZE(p) >= size)
break;
if (p == NULL)
return NULL;
if (CHUNKSIZE(p) > size) /* create a remainder chunk */
{
CHUNK *q, *pr;
CLR_FREEBIT(p); /* required for pointer manipulation */
q = (CHUNK *)((char *)p + CHUNKSIZE(p) - size);
pr = p->s.r;
q->s.l = p; q->s.r = pr;
p->s.r = q; pr->s.l = q;
SET_FREEBIT(p);
p = q; /* return q, not the remainder */
}
CLR_FREEBIT(p); //what's going on here?
return FROMCHUNK(p);
}
void tfree(void *vp)
{
CHUNK *p, *q;
if (vp == NULL)
return;
p = TOCHUNK(vp);
CLR_FREEBIT(p);
q = p->s.l;
if (q != NULL && GET_FREEBIT(q)) /* try to consolidate leftward */
{
CLR_FREEBIT(q);
q->s.r = p->s.r;
p->s.r->s.l = q;
SET_FREEBIT(q);
p = q;
}
q = RIGHT(p);
if (q != NULL && GET_FREEBIT(q)) /* try to consolidate rightward */
{
CLR_FREEBIT(q);
p->s.r = q->s.r;
q->s.r->s.l = p;
SET_FREEBIT(q);
}
SET_FREEBIT(p);
}
static void init(void)
{
bot = &arena[0]; top = &arena[ARENA_CHUNKS-1];
bot->s.l = NULL; bot->s.r = top;
top->s.l = bot; top->s.r = NULL;
SET_FREEBIT(bot); CLR_FREEBIT(top);
}
void *tmalloc(unsigned nbytes)
{
CHUNK *p;
unsigned size;
if (bot == NULL)
init();
size = sizeof(CHUNK) * ((nbytes+sizeof(CHUNK)-1)/sizeof(CHUNK) + 1);
for (p = bot; p != NULL; p = RIGHT(p))
if (GET_FREEBIT(p) && CHUNKSIZE(p) >= size)
break;
if (p == NULL)
return NULL;
CLR_FREEBIT(p);
if (CHUNKSIZE(p) > size) /* create a remainder chunk */
{
CHUNK *q, *pr;
q = (CHUNK *)(size + (char *)p);
pr = p->s.r;
q->s.l = p; q->s.r = pr;
p->s.r = q; pr->s.l = q;
SET_FREEBIT(q);
}
return FROMCHUNK(p);
}
static void init(void)
{
arena = mmap(HEAP_START, ARENA_CHUNKS * sizeof(CHUNK),
PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
assert (arena != MAP_FAILED);
bot = &arena[0]; top = &arena[ARENA_CHUNKS-1];
bot->s.l = NULL; bot->s.r = top;
top->s.l = bot; top->s.r = NULL;
SET_FREEBIT(bot); CLR_FREEBIT(top);
}