/*
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;
}
/*
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
deletes a node as identified by hashnr/keey/keylen from the list
that starts from 'head'
RETURN
0 - ok
1 - not found
NOTE
it uses pins[0..2], on return all pins are removed.
*/
static int ldelete(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr,
const uchar *key, uint keylen, LF_PINS *pins)
{
CURSOR cursor;
int res;
for (;;)
{
if (!lfind(head, cs, hashnr, key, keylen, &cursor, pins))
{
res= 1; /* not found */
break;
}
else
{
/* mark the node deleted */
if (my_atomic_casptr((void **) (char*) &(cursor.curr->link),
(void **) (char*) &cursor.next,
(void *)(((intptr)cursor.next) | 1)))
{
/* and remove it from the list */
if (my_atomic_casptr((void **)cursor.prev,
(void **)(char*)&cursor.curr, cursor.next))
_lf_alloc_free(pins, cursor.curr);
else
{
/*
somebody already "helped" us and removed the node ?
Let's check if we need to help that someone too!
(to ensure the number of "set DELETED flag" actions
is equal to the number of "remove from the list" actions)
*/
lfind(head, cs, hashnr, key, keylen, &cursor, pins);
}
res= 0;
break;
}
}
}
_lf_unpin(pins, 0);
_lf_unpin(pins, 1);
_lf_unpin(pins, 2);
return res;
}
/*
DESCRIPTION
insert a 'node' in the list that starts from 'head' in the correct
position (as found by lfind)
RETURN
0 - inserted
not 0 - a pointer to a duplicate (not pinned and thus unusable)
NOTE
it uses pins[0..2], on return all pins are removed.
if there're nodes with the same key value, a new node is added before them.
*/
static LF_SLIST *linsert(LF_SLIST * volatile *head, CHARSET_INFO *cs,
LF_SLIST *node, LF_PINS *pins, uint flags)
{
CURSOR cursor;
int res;
for (;;)
{
if (lfind(head, cs, node->hashnr, node->key, node->keylen,
&cursor, pins) &&
(flags & LF_HASH_UNIQUE))
{
res= 0; /* duplicate found */
break;
}
else
{
node->link= (intptr)cursor.curr;
DBUG_ASSERT(node->link != (intptr)node); /* no circular references */
DBUG_ASSERT(cursor.prev != &node->link); /* no circular references */
if (my_atomic_casptr((void **) cursor.prev,
(void **)(char*) &cursor.curr, node))
{
res= 1; /* inserted ok */
break;
}
}
}
_lf_unpin(pins, 0);
_lf_unpin(pins, 1);
_lf_unpin(pins, 2);
/*
Note that cursor.curr is not pinned here and the pointer is unreliable,
the object may dissapear anytime. But if it points to a dummy node, the
pointer is safe, because dummy nodes are never freed - initialize_bucket()
uses this fact.
*/
return res ? 0 : cursor.curr;
}
