/*
Allocate and return an new object.
DESCRIPTION
Pop an unused object from the stack or malloc it is the stack is empty.
pin[0] is used, it's removed on return.
*/
void *_lf_alloc_new(LF_PINS *pins)
{
LF_ALLOCATOR *allocator= (LF_ALLOCATOR *)(pins->pinbox->free_func_arg);
uchar *node;
for (;;)
{
do
{
node= allocator->top;
_lf_pin(pins, 0, node);
} while (node != allocator->top && LF_BACKOFF);
if (!node)
{
node= (void *)my_malloc(allocator->element_size, MYF(MY_WME));
if (allocator->constructor)
allocator->constructor(node);
#ifdef MY_LF_EXTRA_DEBUG
if (likely(node != 0))
my_atomic_add32(&allocator->mallocs, 1);
#endif
break;
}
if (my_atomic_casptr((void **)(char *)&allocator->top,
(void *)&node, anext_node(node)))
break;
}
_lf_unpin(pins, 0);
return node;
}
/*
DESCRIPTION
searches for a node as identified by hashnr/keey/keylen in the list
that starts from 'head'
RETURN
0 - not found
node - found
NOTE
it uses pins[0..2], on return the pin[2] keeps the node found
all other pins are removed.
*/
static LF_SLIST *lsearch(LF_SLIST * volatile *head, CHARSET_INFO *cs,
uint32 hashnr, const uchar *key, uint keylen,
LF_PINS *pins)
{
CURSOR cursor;
int res= lfind(head, cs, hashnr, key, keylen, &cursor, pins);
if (res)
_lf_pin(pins, 2, cursor.curr);
_lf_unpin(pins, 0);
_lf_unpin(pins, 1);
return res ? cursor.curr : 0;
}
/*
DESCRIPTION
Search for hashnr/key/keylen in the list starting from 'head' and
position the cursor. The list is ORDER BY hashnr, key
RETURN
0 - not found
1 - found
NOTE
cursor is positioned in either case
pins[0..2] are used, they are NOT removed on return
*/
static int lfind(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr,
const uchar *key, uint keylen, CURSOR *cursor, LF_PINS *pins)
{
uint32 cur_hashnr;
const uchar *cur_key;
uint cur_keylen;
intptr link;
retry:
cursor->prev= (intptr *)head;
do { /* PTR() isn't necessary below, head is a dummy node */
cursor->curr= (LF_SLIST *)(*cursor->prev);
_lf_pin(pins, 1, cursor->curr);
} while (*cursor->prev != (intptr)cursor->curr && LF_BACKOFF);
for (;;)
{
if (unlikely(!cursor->curr))
return 0; /* end of the list */
do {
/* QQ: XXX or goto retry ? */
link= cursor->curr->link;
cursor->next= PTR(link);
_lf_pin(pins, 0, cursor->next);
} while (link != cursor->curr->link && LF_BACKOFF);
cur_hashnr= cursor->curr->hashnr;
cur_key= cursor->curr->key;
cur_keylen= cursor->curr->keylen;
if (*cursor->prev != (intptr)cursor->curr)
{
(void)LF_BACKOFF;
goto retry;
}
if (!DELETED(link))
{
if (cur_hashnr >= hashnr)
{
int r= 1;
if (cur_hashnr > hashnr ||
(r= my_strnncoll(cs, (uchar*) cur_key, cur_keylen, (uchar*) key,
keylen)) >= 0)
return !r;
}
cursor->prev= &(cursor->curr->link);
_lf_pin(pins, 2, cursor->curr);
}
else
{
/*
we found a deleted node - be nice, help the other thread
and remove this deleted node
*/
if (my_atomic_casptr((void **) cursor->prev,
(void **)(char*) &cursor->curr, cursor->next))
_lf_alloc_free(pins, cursor->curr);
else
{
(void)LF_BACKOFF;
goto retry;
}
}
cursor->curr= cursor->next;
_lf_pin(pins, 1, cursor->curr);
}
}
