midx: split get_midx_checksum() by adding get_midx_hash()

When trying to print out, say, the hexadecimal representation of a
MIDX's hash, our code will do something like:

    hash_to_hex_algop(get_midx_checksum(m),
                      m->source->odb->repo->hash_algo);

, which is both cumbersome and repetitive. In fact, all but a handful of
callers to `get_midx_checksum()` do exactly the above. Reduce the
repetitive nature of calling `get_midx_checksum()` by having it return a
pointer into a static buffer containing the above result.

For the handful of callers that do need to compare the raw bytes and
don't want to deal with an encoded copy (e.g., because they are passing
it to hasheq() or similar), introduce `get_midx_hash()` which returns
the raw bytes.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: ttaylorr

midx-write.c

@@ -955,7 +955,7 @@ static int link_midx_to_chain(struct multi_pack_index *m)
 	}
 
 	for (i = 0; i < ARRAY_SIZE(midx_exts); i++) {
-		const unsigned char *hash = get_midx_checksum(m);
+		const unsigned char *hash = get_midx_hash(m);
 
 		get_midx_filename_ext(m->source, &from,
 				      hash, midx_exts[i].non_split);
@@ -1086,8 +1086,7 @@ static int write_midx_internal(struct odb_source *source,
 		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->source->odb->repo->hash_algo));
+				      get_midx_checksum(m));
 				goto cleanup;
 			}
 			ctx.num_multi_pack_indexes_before++;
@@ -1445,8 +1444,7 @@ static int write_midx_internal(struct odb_source *source,
 		for (uint32_t i = 0; i < ctx.num_multi_pack_indexes_before; i++) {
 			uint32_t j = ctx.num_multi_pack_indexes_before - i - 1;
 
-			keep_hashes[j] = xstrdup(hash_to_hex_algop(get_midx_checksum(m),
-								   r->hash_algo));
+			keep_hashes[j] = xstrdup(get_midx_checksum(m));
 			m = m->base_midx;
 		}
 

midx.c

@@ -24,7 +24,13 @@ void clear_incremental_midx_files_ext(struct odb_source *source, const char *ext
 int cmp_idx_or_pack_name(const char *idx_or_pack_name,
 			 const char *idx_name);
 
-const unsigned char *get_midx_checksum(const struct multi_pack_index *m)
+const char *get_midx_checksum(const struct multi_pack_index *m)
+{
+	return hash_to_hex_algop(get_midx_hash(m),
+				 m->source->odb->repo->hash_algo);
+}
+
+const unsigned char *get_midx_hash(const struct multi_pack_index *m)
 {
 	return m->data + m->data_len - m->source->odb->repo->hash_algo->rawsz;
 }

midx.h

@@ -85,7 +85,8 @@ struct multi_pack_index {
 #define MIDX_EXT_BITMAP "bitmap"
 #define MIDX_EXT_MIDX "midx"
 
-const unsigned char *get_midx_checksum(const struct multi_pack_index *m);
+const char *get_midx_checksum(const struct multi_pack_index *m) /* static buffer */;
+const unsigned char *get_midx_hash(const struct multi_pack_index *m);
 void get_midx_filename(struct odb_source *source, struct strbuf *out);
 void get_midx_filename_ext(struct odb_source *source, struct strbuf *out,
 			   const unsigned char *hash, const char *ext);

pack-bitmap.c

@@ -441,11 +441,11 @@ char *midx_bitmap_filename(struct multi_pack_index *midx)
 	struct strbuf buf = STRBUF_INIT;
 	if (midx->has_chain)
 		get_split_midx_filename_ext(midx->source, &buf,
-					    get_midx_checksum(midx),
+					    get_midx_hash(midx),
 					    MIDX_EXT_BITMAP);
 	else
 		get_midx_filename_ext(midx->source, &buf,
-				      get_midx_checksum(midx),
+				      get_midx_hash(midx),
 				      MIDX_EXT_BITMAP);
 
 	return strbuf_detach(&buf, NULL);
@@ -502,7 +502,7 @@ static int open_midx_bitmap_1(struct bitmap_index *bitmap_git,
 	if (load_bitmap_header(bitmap_git) < 0)
 		goto cleanup;
 
-	if (!hasheq(get_midx_checksum(bitmap_git->midx), bitmap_git->checksum,
+	if (!hasheq(get_midx_hash(bitmap_git->midx), bitmap_git->checksum,
 		    bitmap_repo(bitmap_git)->hash_algo)) {
 		error(_("checksum doesn't match in MIDX and bitmap"));
 		goto cleanup;
@@ -2820,8 +2820,7 @@ void test_bitmap_walk(struct rev_info *revs)
 
 		if (bitmap_is_midx(found))
 			fprintf_ln(stderr, "Located via MIDX '%s'.",
-				   hash_to_hex_algop(get_midx_checksum(found->midx),
-						     revs->repo->hash_algo));
+				   get_midx_checksum(found->midx));
 		else
 			fprintf_ln(stderr, "Located via pack '%s'.",
 				   hash_to_hex_algop(found->pack->hash,

pack-revindex.c

@@ -390,11 +390,11 @@ int load_midx_revindex(struct multi_pack_index *m)
 
 	if (m->has_chain)
 		get_split_midx_filename_ext(m->source, &revindex_name,
-					    get_midx_checksum(m),
+					    get_midx_hash(m),
 					    MIDX_EXT_REV);
 	else
 		get_midx_filename_ext(m->source, &revindex_name,
-				      get_midx_checksum(m),
+				      get_midx_hash(m),
 				      MIDX_EXT_REV);
 
 	ret = load_revindex_from_disk(m->source->odb->repo->hash_algo,

t/helper/test-read-midx.c

@@ -34,7 +34,7 @@ static int read_midx_file(const char *object_dir, const char *checksum,
 		return 1;
 
 	if (checksum) {
-		while (m && strcmp(hash_to_hex(get_midx_checksum(m)), checksum))
+		while (m && strcmp(get_midx_checksum(m), checksum))
 			m = m->base_midx;
 		if (!m)
 			return 1;
@@ -94,7 +94,7 @@ static int read_midx_checksum(const char *object_dir)
 	m = setup_midx(object_dir);
 	if (!m)
 		return 1;
-	printf("%s\n", hash_to_hex(get_midx_checksum(m)));
+	printf("%s\n", get_midx_checksum(m));
 
 	close_midx(m);
 	return 0;