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pack-bitmap: use object_id when loading on-disk bitmaps

A pack bitmap file contains the index position of the commit for each bitmap, which we then translate into an object id via nth_packed_object_sha1(). In preparation for that function going away, we can switch to the more type-safe nth_packed_object_id(). Note that even though the result ends up in an object_id this does incur an extra copy of the hash (into our temporary object_id, and then into the final malloc'd stored_bitmap struct). This shouldn't make any measurable difference. If it did, we could avoid this copy _and_ the copy of the rest of the items by allocating the stored_bitmap struct beforehand and reading directly into it from the bitmap file. Or better still, if this is a bottleneck, we could introduce an on-disk index to the bitmap file so we don't have to read every single entry to use just one of them. So it's not worth worrying about micro-optimizing out this one hash copy. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed Feb 23, 2020 at 23:32 UTC 500e4f236606684467b0b34b86e319dfa40747c4

1 file changed +6 -6

pack-bitmap.c

+6 -6

@@ -169,7 +169,7 @@ static int load_bitmap_header(struct bitmap_index *index)

169

170 static struct stored_bitmap *store_bitmap(struct bitmap_index *index,

171 struct ewah_bitmap *root,

172 - const unsigned char *hash,

172 + const struct object_id *oid,

173 struct stored_bitmap *xor_with,

174 int flags)

175 {

@@ -181,7 +181,7 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index,

181 stored->root = root;

182 stored->xor = xor_with;

183 stored->flags = flags;

184 - oidread(&stored->oid, hash);

184 + oidcpy(&stored->oid, oid);

185

186 hash_pos = kh_put_oid_map(index->bitmaps, stored->oid, &ret);

187

@@ -189,7 +189,7 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index,

189 * because the SHA1 already existed on the map. this is bad, there

190 * shouldn't be duplicated commits in the index */

191 if (ret == 0) {

192 - error("Duplicate entry in bitmap index: %s", hash_to_hex(hash));

192 + error("Duplicate entry in bitmap index: %s", oid_to_hex(oid));

193 return NULL;

194 }

195

@@ -221,13 +221,13 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)

221 struct ewah_bitmap *bitmap = NULL;

222 struct stored_bitmap *xor_bitmap = NULL;

223 uint32_t commit_idx_pos;

224 - const unsigned char *sha1;

224 + struct object_id oid;

225

226 commit_idx_pos = read_be32(index->map, &index->map_pos);

227 xor_offset = read_u8(index->map, &index->map_pos);

228 flags = read_u8(index->map, &index->map_pos);

229

230 - sha1 = nth_packed_object_sha1(index->pack, commit_idx_pos);

230 + nth_packed_object_id(&oid, index->pack, commit_idx_pos);

231

232 bitmap = read_bitmap_1(index);

233 if (!bitmap)

@@ -244,7 +244,7 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)

244 }

245

246 recent_bitmaps[i % MAX_XOR_OFFSET] = store_bitmap(

247 - index, bitmap, sha1, xor_bitmap, flags);

247 + index, bitmap, &oid, xor_bitmap, flags);

248 }

249

250 return 0;