pack-objects: learn about pack index version 2

This is the reading part only.  No creation of index v2 is provided.

(extracted from commit c553ca25bd60dc9fd50b8bc7bd329601b81cee66)

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index b9c3da2cd11d1852285bf4718bdc3b451d2b361d..5198563afcade83818e9c5fe4c01ec27e4b0e36b 100644 (file)
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -172,13 +172,33 @@ static void prepare_pack_revindex(struct pack_revindex *rix)
        int i;
        const char *index = p->index_data;
 
-       index += 4 * 256;
        rix->revindex = xmalloc(sizeof(*rix->revindex) * (num_ent + 1));
-       for (i = 0; i < num_ent; i++) {
-               uint32_t hl = *((uint32_t *)(index + 24 * i));
-               rix->revindex[i].offset = ntohl(hl);
-               rix->revindex[i].nr = i;
+       index += 4 * 256;
+
+       if (p->index_version > 1) {
+               const uint32_t *off_32 =
+                       (uint32_t *)(index + 8 + p->num_objects * (20 + 4));
+               const uint32_t *off_64 = off_32 + p->num_objects;
+               for (i = 0; i < num_ent; i++) {
+                       uint32_t off = ntohl(*off_32++);
+                       if (!(off & 0x80000000)) {
+                               rix->revindex[i].offset = off;
+                       } else {
+                               rix->revindex[i].offset =
+                                       ((uint64_t)ntohl(*off_64++)) << 32;
+                               rix->revindex[i].offset |=
+                                       ntohl(*off_64++);
+                       }
+                       rix->revindex[i].nr = i;
+               }
+       } else {
+               for (i = 0; i < num_ent; i++) {
+                       uint32_t hl = *((uint32_t *)(index + 24 * i));
+                       rix->revindex[i].offset = ntohl(hl);
+                       rix->revindex[i].nr = i;
+               }
        }
+
        /* This knows the pack format -- the 20-byte trailer
         * follows immediately after the last object data.
         */