Signed-off-by: Derrick Stolee <dsto...@microsoft.com>
---
 midx.c | 107 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
 midx.h |   1 +
 2 files changed, 96 insertions(+), 12 deletions(-)

diff --git a/midx.c b/midx.c
index c258e3ebdf..02cbfc5bd5 100644
--- a/midx.c
+++ b/midx.c
@@ -47,7 +47,6 @@ struct multi_pack_index *load_multi_pack_index(const char 
*object_dir)
        fd = git_open(midx_name);
 
        if (fd < 0) {
-               error_errno(_("failed to read %s"), midx_name);
                FREE_AND_NULL(midx_name);
                return NULL;
        }
@@ -276,6 +275,29 @@ int fill_midx_entry(const struct object_id *oid, struct 
pack_entry *e, struct mu
        return nth_midxed_pack_entry(m, e, pos);
 }
 
+int midx_contains_pack(struct multi_pack_index *m, const char *idx_name)
+{
+       uint32_t first = 0, last = m->num_packs;
+
+       while (first < last) {
+               uint32_t mid = first + (last - first) / 2;
+               const char *current;
+               int cmp;
+
+               current = m->pack_names[mid];
+               cmp = strcmp(idx_name, current);
+               if (!cmp)
+                       return 1;
+               if (cmp > 0) {
+                       first = mid + 1;
+                       continue;
+               }
+               last = mid;
+       }
+
+       return 0;
+}
+
 int prepare_multi_pack_index_one(struct repository *r, const char *object_dir)
 {
        struct multi_pack_index *m = r->objects->multi_pack_index;
@@ -322,6 +344,7 @@ struct pack_list
        uint32_t alloc_list;
        uint32_t alloc_names;
        size_t pack_name_concat_len;
+       struct multi_pack_index *m;
 };
 
 static void add_pack_to_midx(const char *full_path, size_t full_path_len,
@@ -330,6 +353,9 @@ static void add_pack_to_midx(const char *full_path, size_t 
full_path_len,
        struct pack_list *packs = (struct pack_list *)data;
 
        if (ends_with(file_name, ".idx")) {
+               if (packs->m && midx_contains_pack(packs->m, file_name))
+                       return;
+
                ALLOC_GROW(packs->list, packs->nr + 1, packs->alloc_list);
                ALLOC_GROW(packs->names, packs->nr + 1, packs->alloc_names);
 
@@ -413,6 +439,23 @@ static int midx_oid_compare(const void *_a, const void *_b)
        return a->pack_int_id - b->pack_int_id;
 }
 
+static int nth_midxed_pack_midx_entry(struct multi_pack_index *m,
+                                     uint32_t *pack_perm,
+                                     struct pack_midx_entry *e,
+                                     uint32_t pos)
+{
+       if (pos >= m->num_objects)
+               return 1;
+
+       nth_midxed_object_oid(&e->oid, m, pos);
+       e->pack_int_id = pack_perm[nth_midxed_pack_int_id(m, pos)];
+       e->offset = nth_midxed_offset(m, pos);
+
+       /* consider objects in midx to be from "old" packs */
+       e->pack_mtime = 0;
+       return 0;
+}
+
 static void fill_pack_entry(uint32_t pack_int_id,
                            struct packed_git *p,
                            uint32_t cur_object,
@@ -438,7 +481,8 @@ static void fill_pack_entry(uint32_t pack_int_id,
  * Copy only the de-duplicated entries (selected by most-recent modified time
  * of a packfile containing the object).
  */
-static struct pack_midx_entry *get_sorted_entries(struct packed_git **p,
+static struct pack_midx_entry *get_sorted_entries(struct multi_pack_index *m,
+                                                 struct packed_git **p,
                                                  uint32_t *perm,
                                                  uint32_t nr_packs,
                                                  uint32_t *nr_objects)
@@ -447,8 +491,9 @@ static struct pack_midx_entry *get_sorted_entries(struct 
packed_git **p,
        uint32_t alloc_fanout, alloc_objects, total_objects = 0;
        struct pack_midx_entry *entries_by_fanout = NULL;
        struct pack_midx_entry *deduplicated_entries = NULL;
+       uint32_t start_pack = m ? m->num_packs : 0;
 
-       for (cur_pack = 0; cur_pack < nr_packs; cur_pack++) {
+       for (cur_pack = start_pack; cur_pack < nr_packs; cur_pack++) {
                total_objects += p[cur_pack]->num_objects;
        }
 
@@ -466,7 +511,23 @@ static struct pack_midx_entry *get_sorted_entries(struct 
packed_git **p,
        for (cur_fanout = 0; cur_fanout < 256; cur_fanout++) {
                uint32_t nr_fanout = 0;
 
-               for (cur_pack = 0; cur_pack < nr_packs; cur_pack++) {
+               if (m) {
+                       uint32_t start = 0, end;
+
+                       if (cur_fanout)
+                               start = ntohl(m->chunk_oid_fanout[cur_fanout - 
1]);
+                       end = ntohl(m->chunk_oid_fanout[cur_fanout]);
+
+                       for (cur_object = start; cur_object < end; 
cur_object++) {
+                               ALLOC_GROW(entries_by_fanout, nr_fanout + 1, 
alloc_fanout);
+                               nth_midxed_pack_midx_entry(m, perm,
+                                                          
&entries_by_fanout[nr_fanout],
+                                                          cur_object);
+                               nr_fanout++;
+                       }
+               }
+
+               for (cur_pack = start_pack; cur_pack < nr_packs; cur_pack++) {
                        uint32_t start = 0, end;
 
                        if (cur_fanout)
@@ -661,7 +722,7 @@ int write_midx_file(const char *object_dir)
        struct hashfile *f;
        struct lock_file lk;
        struct pack_list packs;
-       uint32_t *pack_perm;
+       uint32_t *pack_perm = NULL;
        uint64_t written = 0;
        uint32_t chunk_ids[MIDX_MAX_CHUNKS + 1];
        uint64_t chunk_offsets[MIDX_MAX_CHUNKS + 1];
@@ -676,24 +737,42 @@ int write_midx_file(const char *object_dir)
                          midx_name);
        }
 
+       packs.m = load_multi_pack_index(object_dir);
+
        packs.nr = 0;
-       packs.alloc_list = 16;
-       packs.alloc_names = 16;
+       packs.alloc_list = packs.m ? packs.m->num_packs : 16;
+       packs.alloc_names = packs.alloc_list;
        packs.list = NULL;
        packs.pack_name_concat_len = 0;
        ALLOC_ARRAY(packs.list, packs.alloc_list);
        ALLOC_ARRAY(packs.names, packs.alloc_names);
 
+       if (packs.m) {
+               for (i = 0; i < packs.m->num_packs; i++) {
+                       ALLOC_GROW(packs.list, packs.nr + 1, packs.alloc_list);
+                       ALLOC_GROW(packs.names, packs.nr + 1, 
packs.alloc_names);
+
+                       packs.list[packs.nr] = NULL;
+                       packs.names[packs.nr] = xstrdup(packs.m->pack_names[i]);
+                       packs.pack_name_concat_len += 
strlen(packs.names[packs.nr]) + 1;
+                       packs.nr++;
+               }
+       }
+
        for_each_file_in_pack_dir(object_dir, add_pack_to_midx, &packs);
 
+       if (packs.m && packs.nr == packs.m->num_packs)
+               goto cleanup;
+
        if (packs.pack_name_concat_len % MIDX_CHUNK_ALIGNMENT)
                packs.pack_name_concat_len += MIDX_CHUNK_ALIGNMENT -
-                                       (packs.pack_name_concat_len % 
MIDX_CHUNK_ALIGNMENT);
+                                             (packs.pack_name_concat_len % 
MIDX_CHUNK_ALIGNMENT);
 
-       ALLOC_ARRAY(pack_perm, packs.nr);
+       ALLOC_ARRAY(pack_perm, packs.alloc_list);
        sort_packs_by_name(packs.names, packs.nr, pack_perm);
 
-       entries = get_sorted_entries(packs.list, pack_perm, packs.nr, 
&nr_entries);
+       entries = get_sorted_entries(packs.m, packs.list, pack_perm, packs.nr, 
&nr_entries);
+
        for (i = 0; i < nr_entries; i++) {
                if (entries[i].offset > 0x7fffffff)
                        num_large_offsets++;
@@ -796,14 +875,18 @@ int write_midx_file(const char *object_dir)
        finalize_hashfile(f, NULL, CSUM_FSYNC | CSUM_HASH_IN_STREAM);
        commit_lock_file(&lk);
 
+cleanup:
        for (i = 0; i < packs.nr; i++) {
-               close_pack(packs.list[i]);
-               FREE_AND_NULL(packs.list[i]);
+               if (packs.list[i]) {
+                       close_pack(packs.list[i]);
+                       FREE_AND_NULL(packs.list[i]);
+               }
                FREE_AND_NULL(packs.names[i]);
        }
 
        FREE_AND_NULL(packs.list);
        FREE_AND_NULL(packs.names);
        FREE_AND_NULL(entries);
+       FREE_AND_NULL(pack_perm);
        return 0;
 }
diff --git a/midx.h b/midx.h
index f7c2ec7893..5faffb7bc6 100644
--- a/midx.h
+++ b/midx.h
@@ -11,6 +11,7 @@ struct object_id *nth_midxed_object_oid(struct object_id *oid,
                                        struct multi_pack_index *m,
                                        uint32_t n);
 int fill_midx_entry(const struct object_id *oid, struct pack_entry *e, struct 
multi_pack_index *m);
+int midx_contains_pack(struct multi_pack_index *m, const char *idx_name);
 int prepare_multi_pack_index_one(struct repository *r, const char *object_dir);
 
 int write_midx_file(const char *object_dir);
-- 
2.18.0.24.g1b579a2ee9

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