Function get_buffer

src/jrd/cch.cpp:3778–3988

static BufferDesc* get_buffer(thread_db* tdbb, const PageNumber page, SyncType syncType, int wait)
{
/**************************************
 *
 *	g e t _ b u f f e r
 *
 **************************************
 *
 * Functional description
 *	Get a buffer.  If possible, get a buffer already assigned
 *	to the page.  Otherwise get one from the free list or pick
 *	the least recently used buffer to be reused.
 *
 * input
 *	page:		page to get
 *	syncType:	type of lock to acquire on the page.
 *	wait:	1 => Wait as long as necessary to get the lock.
 *				This can cause deadlocks of course.
 *			0 => If the lock can't be acquired immediately,
 *				give up and return 0;
 *			<negative number> => Latch timeout interval in seconds.
 *
 * return
 *	BufferDesc pointer if successful.
 *	NULL pointer if timeout occurred (only possible is wait <> 1).
 *		if cache manager doesn't have any pages to write anymore.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->getDatabase();
	BufferControl* bcb = dbb->dbb_bcb;
	Attachment* att = tdbb->getAttachment();

	if (att && att->att_bdb_cache)
	{
		if (BufferDesc* bdb = att->att_bdb_cache->get(page))
		{
			if (bdb->addRef(tdbb, syncType, wait))
			{
				if (bdb->bdb_page == page)
				{
					recentlyUsed(bdb);
					tdbb->bumpStats(RuntimeStatistics::PAGE_FETCHES);
					return bdb;
				}

				bdb->release(tdbb, true);
				att->att_bdb_cache->remove(page);
			}
			else
			{
				fb_assert(wait <= 0);
				if (bdb->bdb_page == page)
					return nullptr;
			}
		}
	}