midx: introduce midx_get_checksum_hex()

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

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

, which is both cumbersome and repetitive. In fact, all but a handful of
callers to `midx_get_checksum_hash()` do exactly the above. Reduce the
repetitive nature of calling `midx_get_checksum_hash()` 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), they may still rely on
`midx_get_checksum_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

@@ -1151,8 +1151,7 @@ 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(midx_get_checksum_hash(m),
-							m->source->odb->repo->hash_algo));
+				      midx_get_checksum_hex(m));
 				goto cleanup;
 			}
 			ctx.num_multi_pack_indexes_before++;
@@ -1520,8 +1519,7 @@ 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(midx_get_checksum_hash(m),
-								   r->hash_algo));
+			keep_hashes[j] = xstrdup(midx_get_checksum_hex(m));
 			m = m->base_midx;
 		}
 

midx.c

@@ -24,6 +24,12 @@ 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 char *midx_get_checksum_hex(const struct multi_pack_index *m)
+{
+	return hash_to_hex_algop(midx_get_checksum_hash(m),
+				 m->source->odb->repo->hash_algo);
+}
+
 const unsigned char *midx_get_checksum_hash(const struct multi_pack_index *m)
 {
 	return m->data + m->data_len - m->source->odb->repo->hash_algo->rawsz;

midx.h

@@ -85,6 +85,7 @@ struct multi_pack_index {
 #define MIDX_EXT_BITMAP "bitmap"
 #define MIDX_EXT_MIDX "midx"
 
+const char *midx_get_checksum_hex(const struct multi_pack_index *m) /* static buffer */;
 const unsigned char *midx_get_checksum_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,

pack-bitmap.c

@@ -2819,8 +2819,7 @@ void test_bitmap_walk(struct rev_info *revs)
 
 		if (bitmap_is_midx(found))
 			fprintf_ln(stderr, "Located via MIDX '%s'.",
-				   hash_to_hex_algop(midx_get_checksum_hash(found->midx),
-						     revs->repo->hash_algo));
+				   midx_get_checksum_hex(found->midx));
 		else
 			fprintf_ln(stderr, "Located via pack '%s'.",
 				   hash_to_hex_algop(found->pack->hash,

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(midx_get_checksum_hash(m)), checksum))
+		while (m && strcmp(midx_get_checksum_hex(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(midx_get_checksum_hash(m)));
+	printf("%s\n", midx_get_checksum_hex(m));
 
 	close_midx(m);
 	return 0;