midx: implement writing incremental MIDX bitmaps

Now that the pack-bitmap machinery has learned how to read and interact
with an incremental MIDX bitmap, teach the pack-bitmap-write.c machinery
(and relevant callers from within the MIDX machinery) to write such
bitmaps.

The details for doing so are mostly straightforward. The main changes
are as follows:

  - find_object_pos() now makes use of an extra MIDX parameter which is
    used to locate the bit positions of objects which are from previous
    layers (and thus do not exist in the current layer's pack_order
    field).

    (Note also that the pack_order field is moved into struct
    write_midx_context to further simplify the callers for
    write_midx_bitmap()).

  - bitmap_writer_build_type_index() first determines how many objects
    precede the current bitmap layer and offsets the bits it sets in
    each respective type-level bitmap by that amount so they can be OR'd
    together.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Acked-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 38 insertions, 19 deletions

diff --git a/midx-write.c b/midx-write.c
index 48d6558253..0897cbd829 100644
--- a/midx-write.c
+++ b/midx-write.c
@@ -647,16 +647,22 @@ static uint32_t *midx_pack_order(struct write_midx_context *ctx)
 	return pack_order;
 }
 
-static void write_midx_reverse_index(char *midx_name, unsigned char *midx_hash,
-				     struct write_midx_context *ctx)
+static void write_midx_reverse_index(struct write_midx_context *ctx,
+				     const char *object_dir,
+				     unsigned char *midx_hash)
 {
 	struct strbuf buf = STRBUF_INIT;
 	char *tmp_file;
 
 	trace2_region_enter("midx", "write_midx_reverse_index", ctx->repo);
 
-	strbuf_addf(&buf, "%s-%s.rev", midx_name, hash_to_hex_algop(midx_hash,
-								    ctx->repo->hash_algo));
+	if (ctx->incremental)
+		get_split_midx_filename_ext(ctx->repo->hash_algo, &buf,
+					    object_dir, midx_hash,
+					    MIDX_EXT_REV);
+	else
+		get_midx_filename_ext(ctx->repo->hash_algo, &buf, object_dir,
+				      midx_hash, MIDX_EXT_REV);
 
 	tmp_file = write_rev_file_order(ctx->repo->hash_algo, NULL, ctx->pack_order,
 					ctx->entries_nr, midx_hash, WRITE_REV);
@@ -829,22 +835,29 @@ static struct commit **find_commits_for_midx_bitmap(uint32_t *indexed_commits_nr
 	return cb.commits;
 }
 
-static int write_midx_bitmap(struct repository *r, const char *midx_name,
+static int write_midx_bitmap(struct write_midx_context *ctx,
+			     const char *object_dir,
 			     const unsigned char *midx_hash,
 			     struct packing_data *pdata,
 			     struct commit **commits,
 			     uint32_t commits_nr,
-			     uint32_t *pack_order,
 			     unsigned flags)
 {
 	int ret, i;
 	uint16_t options = 0;
 	struct bitmap_writer writer;
 	struct pack_idx_entry **index;
-	char *bitmap_name = xstrfmt("%s-%s.bitmap", midx_name,
-				    hash_to_hex_algop(midx_hash, r->hash_algo));
+	struct strbuf bitmap_name = STRBUF_INIT;
+
+	trace2_region_enter("midx", "write_midx_bitmap", ctx->repo);
 
-	trace2_region_enter("midx", "write_midx_bitmap", r);
+	if (ctx->incremental)
+		get_split_midx_filename_ext(ctx->repo->hash_algo, &bitmap_name,
+					    object_dir, midx_hash,
+					    MIDX_EXT_BITMAP);
+	else
+		get_midx_filename_ext(ctx->repo->hash_algo, &bitmap_name,
+				      object_dir, midx_hash, MIDX_EXT_BITMAP);
 
 	if (flags & MIDX_WRITE_BITMAP_HASH_CACHE)
 		options |= BITMAP_OPT_HASH_CACHE;
@@ -861,7 +874,8 @@ static int write_midx_bitmap(struct repository *r, const char *midx_name,
 	for (i = 0; i < pdata->nr_objects; i++)
 		index[i] = &pdata->objects[i].idx;
 
-	bitmap_writer_init(&writer, r, pdata);
+	bitmap_writer_init(&writer, ctx->repo, pdata,
+			   ctx->incremental ? ctx->base_midx : NULL);
 	bitmap_writer_show_progress(&writer, flags & MIDX_PROGRESS);
 	bitmap_writer_build_type_index(&writer, index);
 
@@ -879,7 +893,7 @@ static int write_midx_bitmap(struct repository *r, const char *midx_name,
 	 * bitmap_writer_finish().
 	 */
 	for (i = 0; i < pdata->nr_objects; i++)
-		index[pack_order[i]] = &pdata->objects[i].idx;
+		index[ctx->pack_order[i]] = &pdata->objects[i].idx;
 
 	bitmap_writer_select_commits(&writer, commits, commits_nr);
 	ret = bitmap_writer_build(&writer);
@@ -887,14 +901,14 @@ static int write_midx_bitmap(struct repository *r, const char *midx_name,
 		goto cleanup;
 
 	bitmap_writer_set_checksum(&writer, midx_hash);
-	bitmap_writer_finish(&writer, index, bitmap_name, options);
+	bitmap_writer_finish(&writer, index, bitmap_name.buf, options);
 
 cleanup:
 	free(index);
-	free(bitmap_name);
+	strbuf_release(&bitmap_name);
 	bitmap_writer_free(&writer);
 
-	trace2_region_leave("midx", "write_midx_bitmap", r);
+	trace2_region_leave("midx", "write_midx_bitmap", ctx->repo);
 
 	return ret;
 }
@@ -1077,8 +1091,6 @@ static int write_midx_internal(struct repository *r, const char *object_dir,
 	ctx.repo = r;
 
 	ctx.incremental = !!(flags & MIDX_WRITE_INCREMENTAL);
-	if (ctx.incremental && (flags & MIDX_WRITE_BITMAP))
-		die(_("cannot write incremental MIDX with bitmap"));
 
 	if (ctx.incremental)
 		strbuf_addf(&midx_name,
@@ -1119,6 +1131,13 @@ static int write_midx_internal(struct repository *r, const char *object_dir,
 	if (ctx.incremental) {
 		struct multi_pack_index *m = ctx.base_midx;
 		while (m) {
+			if (flags & MIDX_WRITE_BITMAP && load_midx_revindex(m)) {
+				error(_("could not load reverse index for MIDX %s"),
+				      hash_to_hex_algop(get_midx_checksum(m),
+							m->repo->hash_algo));
+				result = 1;
+				goto cleanup;
+			}
 			ctx.num_multi_pack_indexes_before++;
 			m = m->base_midx;
 		}
@@ -1387,7 +1406,7 @@ static int write_midx_internal(struct repository *r, const char *object_dir,
 
 	if (flags & MIDX_WRITE_REV_INDEX &&
 	    git_env_bool("GIT_TEST_MIDX_WRITE_REV", 0))
-		write_midx_reverse_index(midx_name.buf, midx_hash, &ctx);
+		write_midx_reverse_index(&ctx, object_dir, midx_hash);
 
 	if (flags & MIDX_WRITE_BITMAP) {
 		struct packing_data pdata;
@@ -1410,8 +1429,8 @@ static int write_midx_internal(struct repository *r, const char *object_dir,
 		FREE_AND_NULL(ctx.entries);
 		ctx.entries_nr = 0;
 
-		if (write_midx_bitmap(r, midx_name.buf, midx_hash, &pdata,
-				      commits, commits_nr, ctx.pack_order,
+		if (write_midx_bitmap(&ctx, object_dir,
+				      midx_hash, &pdata, commits, commits_nr,
 				      flags) < 0) {
 			error(_("could not write multi-pack bitmap"));
 			result = 1;