pack-bitmap.c: read pseudo-merge extension

Now that the scaffolding for reading the pseudo-merge extension has been
laid, teach the pack-bitmap machinery to read the pseudo-merge extension
when present.

Note that pseudo-merges themselves are not yet used during traversal,
this step will be taken by a future commit.

In the meantime, read the table and initialize the pseudo_merge_map
structure introduced by a previous commit. When the pseudo-merge
extension is present, `load_bitmap_header()` performs basic sanity
checks to make sure that the table is well-formed.

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

diff --git a/pack-bitmap.c b/pack-bitmap.c
index 3519edb896b06c6632422a92ed5ac7b8fd4fce91..fc9c3e2fc434892d08fde092fb5ae27f2e0e3edf 100644 (file)
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -20,6 +20,7 @@
 #include "list-objects-filter-options.h"
 #include "midx.h"
 #include "config.h"
+#include "pseudo-merge.h"
 
 /*
  * An entry on the bitmap index, representing the bitmap for a given
@@ -86,6 +87,9 @@ struct bitmap_index {
         */
        unsigned char *table_lookup;
 
+       /* This contains the pseudo-merge cache within 'map' (if found). */
+       struct pseudo_merge_map pseudo_merges;
+
        /*
         * Extended index.
         *
@@ -205,6 +209,41 @@ static int load_bitmap_header(struct bitmap_index *index)
                                index->table_lookup = (void *)(index_end - table_size);
                        index_end -= table_size;
                }
+
+               if (flags & BITMAP_OPT_PSEUDO_MERGES) {
+                       unsigned char *pseudo_merge_ofs;
+                       size_t table_size;
+                       uint32_t i;
+
+                       if (sizeof(table_size) > index_end - index->map - header_size)
+                               return error(_("corrupted bitmap index file (too short to fit pseudo-merge table header)"));
+
+                       table_size = get_be64(index_end - 8);
+                       if (table_size > index_end - index->map - header_size)
+                               return error(_("corrupted bitmap index file (too short to fit pseudo-merge table)"));
+
+                       if (git_env_bool("GIT_TEST_USE_PSEUDO_MERGES", 1)) {
+                               const unsigned char *ext = (index_end - table_size);
+
+                               index->pseudo_merges.map = index->map;
+                               index->pseudo_merges.map_size = index->map_size;
+                               index->pseudo_merges.commits = ext + get_be64(index_end - 16);
+                               index->pseudo_merges.commits_nr = get_be32(index_end - 20);
+                               index->pseudo_merges.nr = get_be32(index_end - 24);
+
+                               CALLOC_ARRAY(index->pseudo_merges.v,
+                                            index->pseudo_merges.nr);
+
+                               pseudo_merge_ofs = index_end - 24 -
+                                       (index->pseudo_merges.nr * sizeof(uint64_t));
+                               for (i = 0; i < index->pseudo_merges.nr; i++) {
+                                       index->pseudo_merges.v[i].at = get_be64(pseudo_merge_ofs);
+                                       pseudo_merge_ofs += sizeof(uint64_t);
+                               }
+                       }
+
+                       index_end -= table_size;
+               }
        }
 
        index->entry_count = ntohl(header->entry_count);