Function writer_finish_section

reftable/writer.c:504–590

}

static int writer_finish_section(struct reftable_writer *w)
{
	struct reftable_block_stats *bstats = NULL;
	uint8_t typ = block_writer_type(w->block_writer);
	uint64_t index_start = 0;
	int max_level = 0;
	size_t threshold = w->opts.unpadded ? 1 : 3;
	int before_blocks = w->stats.idx_stats.blocks;
	int err;

	err = writer_flush_block(w);
	if (err < 0)
		return err;

	/*
	 * When the section we are about to index has a lot of blocks then the
	 * index itself may span across multiple blocks, as well. This would
	 * require a linear scan over index blocks only to find the desired
	 * indexed block, which is inefficient. Instead, we write a multi-level
	 * index where index records of level N+1 will refer to index blocks of
	 * level N. This isn't constant time, either, but at least logarithmic.
	 *
	 * This loop handles writing this multi-level index. Note that we write
	 * the lowest-level index pointing to the indexed blocks first. We then
	 * continue writing additional index levels until the current level has
	 * less blocks than the threshold so that the highest level will be at
	 * the end of the index section.
	 *
	 * Readers are thus required to start reading the index section from
	 * its end, which is why we set `index_start` to the beginning of the
	 * last index section.
	 */
	while (w->index_len > threshold) {
		struct reftable_index_record *idx = NULL;
		size_t i, idx_len;

		max_level++;
		index_start = w->next;
		err = writer_reinit_block_writer(w, REFTABLE_BLOCK_TYPE_INDEX);
		if (err < 0)
			return err;

		idx = w->index;
		idx_len = w->index_len;

		w->index = NULL;
		w->index_len = 0;
		w->index_cap = 0;
		for (i = 0; i < idx_len; i++) {
			struct reftable_record rec = {
				.type = REFTABLE_BLOCK_TYPE_INDEX,
				.u = {
					.idx = idx[i],
				},
			};

			err = writer_add_record(w, &rec);
			if (err < 0)