//----------------------------------------------------------------
fifocell * fifoget (fifo * ff)
{
fifocell * volatile head;
fifocell * next;
short done = 0;
do {
LWARX (&ff->head);
head = ff->head; /* read the head cell */
next = head->link; /* read the next cell */
/*
WARNING: the next pointer still needs to be checked before reading its value
*/
if (head == ff->tail) { /* is queue empty or tail falling behind? */
if (head->link == fifo_end(ff) && STWCX (&ff->head, (void *)head, (void *)head)) /* is queue really empty? */
return 0; /* queue is empty; return NULL */
/* tail is pointing to head in a non empty queue, */
/* try to set tail to the next cell */
CASLNE (&ff->tail, (void *)head, fifo_end(ff));
}
else if (next != fifo_end(ff)) { /* if we are not competing on the dummy cell */
/* and we try to set head to the next cell */
done = STWCX (&ff->head, (void *)head, next);
}
} while (!done);
msAtomicDec (&ff->count);
if (head == &ff->dummy) {
fifoput(ff,head);
head = fifoget(ff);
}
return (fifocell *)head;
}
//----------------------------------------------------------------
fifocell * fifoget(fifo * ff)
{
fifocell * volatile head;
fifocell * next;
unsigned long ic, oc;
short done = 0;
do {
oc = ff->oc; /* read the head modification count */
ic = ff->ic; /* read the tail modification count */
head = ff->head; /* read the head cell */
next = head->link; /* read the next cell */
if (oc == ff->oc) { /* ensures that next is a valid pointer */
/* to avoid failure when reading next value */
if (head == ff->tail) { /* is queue empty or tail falling behind? */
if (next == fifo_end(ff)) /* is queue empty? */
return 0; /* queue is empty; return NULL */
/* tail is pointing to head in a non empty queue, */
/* try to set tail to the next cell */
CAS2 (&ff->tail, head, ic, next, ic+1);
}
else if (next != fifo_end(ff)) { /* if we are not competing on the dummy cell */
/* and we try to set head to the next cell */
done = CAS2 (&ff->head, head, oc, next, oc+1);
}
}
} while (!done);
msAtomicDec (&ff->count);
if (head == &ff->dummy) {
fifoput(ff,head);
head = fifoget(ff);
}
return (fifocell *)head;
}
//----------------------------------------------------------------
void fifoinit (fifo* ff)
{
ff->count.value = 0;
ff->oc = ff->ic = 0;
ff->dummy.link = fifo_end(ff);
ff->head = ff->tail = &ff->dummy;
}
//----------------------------------------------------------------
void fifoput (fifo * ff, fifocell * cl)
{
fifocell * volatile tail;
cl->link = fifo_end(ff); /* set the cell next pointer to the end marker */
while (1) {
tail = ff->tail; /* read the tail cell */
/* try to link the cell to the tail cell */
if (CAS (&tail->link, fifo_end(ff), cl)) {
break;
}
else {
/* tail was not pointing to the last cell, try to set tail to the next cell */
CASLNE (&ff->tail, (void *)tail, fifo_end(ff));
}
}
CASLNE (&ff->tail, (void *)tail, fifo_end(ff));
msAtomicInc (&ff->count);
}
//----------------------------------------------------------------
void fifoput (fifo * ff, fifocell * cl)
{
long ic;
fifocell * volatile tail;
cl->link = fifo_end(ff); /* set the cell next pointer to the end marker */
while (1) {
ic = ff->ic; /* read the tail modification count */
tail = ff->tail; /* read the tail cell */
/* try to link the cell to the tail cell */
if (CAS (&tail->link, fifo_end(ff), cl))
break;
else
/* tail was not pointing to the last cell, try to set tail to the next cell */
CAS2 (&ff->tail, tail, ic, tail->link, ic+1);
}
/* enqeue is done, try to set tail to the enqueued cell */
CAS2 (&ff->tail, tail, ic, cl, ic+1);
msAtomicInc (&ff->count);
}
static void test2() {
fifo_t *f1 = fifo_new(1024 * 4);
int i;
void *p;
for (i = 0; i < 1023; i++) {
p = fifo_alloc(f1, 13);
assert(p);
*(int *)p = i;
fifo_put(f1, p, 13);
p = fifo_get(f1, 13);
assert(p);
assert(*(int *)p == i);
fifo_end(f1, p, 13);
}
assert(fifo_empty(f1));
}
static void test3() {
fifo_t *f1 = fifo_new(1024 * 4);
int i;
void *p;
for (i = 0; i < 1023; i++) {
p = fifo_alloc(f1, 13);
assert(p);
*(int *)p = i;
fifo_put(f1, p, 13);
p = fifo_extend(f1, p, 13, 13 * 2);
assert(p);
fifo_put(f1, p, 26);
printf("%u %u\n", f1->pt, f1->gt);
p = fifo_get(f1, 26);
assert(p);
assert(*(int *)p == i);
fifo_end(f1, p, 26);
}
assert(fifo_empty(f1));
}
