midx: read pack names into array

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

midx.c

@@ -37,6 +37,7 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir)
 	uint32_t hash_version;
 	char *midx_name = get_midx_filename(object_dir);
 	uint32_t i;
+	const char *cur_pack_name;
 
 	fd = git_open(midx_name);
 
@@ -115,6 +116,22 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir)
 	if (!m->chunk_pack_names)
 		die(_("multi-pack-index missing required pack-name chunk"));
 
+	m->pack_names = xcalloc(m->num_packs, sizeof(*m->pack_names));
+
+	cur_pack_name = (const char *)m->chunk_pack_names;
+	for (i = 0; i < m->num_packs; i++) {
+		m->pack_names[i] = cur_pack_name;
+
+		cur_pack_name += strlen(cur_pack_name) + 1;
+
+		if (i && strcmp(m->pack_names[i], m->pack_names[i - 1]) <= 0) {
+			error(_("multi-pack-index pack names out of order: '%s' before '%s'"),
+			      m->pack_names[i - 1],
+			      m->pack_names[i]);
+			goto cleanup_fail;
+		}
+	}
+
 	return m;
 
 cleanup_fail:

midx.h

@@ -16,6 +16,7 @@ struct multi_pack_index {
 
 	const unsigned char *chunk_pack_names;
 
+	const char **pack_names;
 	char object_dir[FLEX_ARRAY];
 };
 

t/helper/test-read-midx.c

@@ -6,6 +6,7 @@
 
 static int read_midx_file(const char *object_dir)
 {
+	uint32_t i;
 	struct multi_pack_index *m = load_multi_pack_index(object_dir);
 
 	if (!m)
@@ -24,6 +25,10 @@ static int read_midx_file(const char *object_dir)
 
 	printf("\n");
 
+	printf("packs:\n");
+	for (i = 0; i < m->num_packs; i++)
+		printf("%s\n", m->pack_names[i]);
+
 	printf("object-dir: %s\n", m->object_dir);
 
 	return 0;

t/t5319-multi-pack-index.sh

@@ -5,11 +5,18 @@ test_description='multi-pack-indexes'
 
 midx_read_expect () {
 	NUM_PACKS=$1
-	cat >expect <<-EOF
-	header: 4d494458 1 1 $NUM_PACKS
-	chunks: pack-names
-	object-dir: .
-	EOF
+	{
+		cat <<-EOF &&
+		header: 4d494458 1 1 $NUM_PACKS
+		chunks: pack-names
+		packs:
+		EOF
+		if test $NUM_PACKS -ge 1
+		then
+			ls pack/ | grep idx | sort
+		fi &&
+		printf "object-dir: .\n"
+	} >expect &&
 	test-tool read-midx . >actual &&
 	test_cmp expect actual
 }