Function buf_ensure_head_space

src/backend/access/bitmap/bitmapinsert.c:1961–1974

* buf_ensure_head_space() -- If there is no space in the header words, * move words in the given buffer to disk and free the existing space, * and then allocate new space for future new words. * * The number of bytes freed are returned. */

 * The number of bytes freed are returned.
 */
static uint16
buf_ensure_head_space(Relation rel, BMTIDBuffer *buf, 
					  Buffer lovBuffer, OffsetNumber off, bool use_wal)
{
	uint16 bytes_freed = 0;

	if (buf->curword >= (BM_NUM_OF_HEADER_WORDS * BM_HRL_WORD_SIZE))
	{
		bytes_freed = buf_free_mem_block(rel, buf, lovBuffer, off, use_wal);
		bytes_freed -= buf_extend(buf);
	}

	return bytes_freed;
}

/*
 * buf_extend() -- Enlarge the memory allocated to a buffer.