Function hash_get_lock

src/jrd/lck.cpp:1020–1080

static Lock* hash_get_lock(Lock* lock, USHORT* hash_slot, Lock*** prior)
{
/**************************************
 *
 *	h a s h _ g e t _ l o c k
 *
 **************************************
 *
 * Functional description
 *	Return the first matching identical
 *	lock to the passed lock.  To minimize
 *	code for searching through the hash
 *	table, return hash_slot or prior lock
 *	if requested.
 *
 **************************************/
	fb_assert(LCK_CHECK_LOCK(lock));

	Jrd::Attachment* const att = lock->getLockAttachment();
	if (!att)
		return NULL;

	if (!att->att_compatibility_table)
		hash_allocate(lock);

	const USHORT hash_value =
		(USHORT) InternalHash::hash(lock->lck_length, lock->getKeyPtr(), LOCK_HASH_SIZE);

	if (hash_slot)
		*hash_slot = hash_value;

	// if no collisions found, we're done

	Lock* match = (*att->att_compatibility_table)[hash_value];
	if (!match)
		return NULL;

	if (prior)
		*prior = & (*att->att_compatibility_table)[hash_value];

	// look for an identical lock

	fb_assert(LCK_CHECK_LOCK(match));
	for (Lock* collision = match; collision; collision = collision->lck_collision)
	{
		fb_assert(LCK_CHECK_LOCK(collision));
		if (collision->lck_type == lock->lck_type &&
			collision->lck_length == lock->lck_length)
		{
			// check that the keys are the same

			if (!memcmp(lock->getKeyPtr(), collision->getKeyPtr(), lock->lck_length))
				return collision;
		}

		if (prior)
			*prior = &collision->lck_collision;
	}