Function XLogRecGetBlockData

src/backend/access/transam/xlogreader.c:1566–1588

* Returns the data associated with a block reference, or NULL if there is * no data (e.g. because a full-page image was taken instead). The returned * pointer points to a MAXALIGNed buffer. */

 * pointer points to a MAXALIGNed buffer.
 */
char *
XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
{
	DecodedBkpBlock *bkpb;

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

	bkpb = &record->blocks[block_id];

	if (!bkpb->has_data)
	{
		if (len)
			*len = 0;
		return NULL;
	}
	else
	{
		if (len)
			*len = bkpb->data_len;
		return bkpb->data;
	}
}

/*
 * Restore a full-page image from a backup block attached to an XLOG record.