Function XLogRecGetBlockTag

src/backend/access/transam/xlogreader.c:1542–1559

* Returns information about the block that a block reference refers to. * * If the WAL record contains a block reference with the given ID, *rnode, * *forknum, and *blknum are filled in (if not NULL), and returns true. * Otherwise returns false. */

 * Otherwise returns false.
 */
bool
XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id,
				   RelFileNode *rnode, ForkNumber *forknum, BlockNumber *blknum)
{
	DecodedBkpBlock *bkpb;

	if (!record->blocks[block_id].in_use)
		return false;

	bkpb = &record->blocks[block_id];
	if (rnode)
		*rnode = bkpb->rnode;
	if (forknum)
		*forknum = bkpb->forknum;
	if (blknum)
		*blknum = bkpb->blkno;
	return true;
}

/*
 * Returns the data associated with a block reference, or NULL if there is