pack-bitmap-write.c: move commit_positions into commit_pos fields

In 7cc8f971085 (pack-objects: implement bitmap writing, 2013-12-21), the
bitmapped_commit struct was introduced, including the 'commit_pos'
field, which has been unused ever since its introduction more than a
decade ago.

Instead, we have used the nearby `commit_positions` array leaving the
bitmapped_commit struct with an unused 4-byte field.

We could drop the `commit_pos` field as unused, and continue to store
the values in the auxiliary array. But we could also drop the array and
store the data for each bitmapped_commit struct inside of the structure
itself, which is what this patch does.

In any spot that we previously read `commit_positions[i]`, we can now
instead read `writer.selected[i].commit_pos`. There are a few spots that
need changing as a result:

  - write_selected_commits_v1() is a simple transformation, since we're
    just reading the field. As a result, the function no longer needs an
    explicit argument to pass the commit_positions array.

  - write_lookup_table() also no longer needs the explicit
    commit_positions array passed in as an argument. But it still needs
    to sort an array of indices into the writer.selected array to read
    them in commit_pos order, so table_cmp() is adjusted accordingly.

  - bitmap_writer_finish() no longer needs to allocate, populate, and
    free the commit_positions table. Instead, we can just write the data
    directly into each struct bitmapped_commit.

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

diff --git a/pack-bitmap-write.c b/pack-bitmap-write.c
index c6c8f94cc514476a5a6f543cbb86a260020e9753..2ae82b86966d4d61e67b6cd15c67404ab9e9115c 100644 (file)
--- a/pack-bitmap-write.c
+++ b/pack-bitmap-write.c
@@ -670,9 +670,7 @@ static const struct object_id *oid_access(size_t pos, const void *table)
        return &index[pos]->oid;
 }
 
-static void write_selected_commits_v1(struct hashfile *f,
-                                     uint32_t *commit_positions,
-                                     off_t *offsets)
+static void write_selected_commits_v1(struct hashfile *f, off_t *offsets)
 {
        int i;
 
@@ -682,7 +680,7 @@ static void write_selected_commits_v1(struct hashfile *f,
                if (offsets)
                        offsets[i] = hashfile_total(f);
 
-               hashwrite_be32(f, commit_positions[i]);
+               hashwrite_be32(f, stored->commit_pos);
                hashwrite_u8(f, stored->xor_offset);
                hashwrite_u8(f, stored->flags);
 
@@ -690,23 +688,20 @@ static void write_selected_commits_v1(struct hashfile *f,
        }
 }
 
-static int table_cmp(const void *_va, const void *_vb, void *_data)
+static int table_cmp(const void *_va, const void *_vb)
 {
-       uint32_t *commit_positions = _data;
-       uint32_t a = commit_positions[*(uint32_t *)_va];
-       uint32_t b = commit_positions[*(uint32_t *)_vb];
+       struct bitmapped_commit *a = &writer.selected[*(uint32_t *)_va];
+       struct bitmapped_commit *b = &writer.selected[*(uint32_t *)_vb];
 
-       if (a > b)
-               return 1;
-       else if (a < b)
+       if (a->commit_pos < b->commit_pos)
                return -1;
+       else if (a->commit_pos > b->commit_pos)
+               return 1;
 
        return 0;
 }
 
-static void write_lookup_table(struct hashfile *f,
-                              uint32_t *commit_positions,
-                              off_t *offsets)
+static void write_lookup_table(struct hashfile *f, off_t *offsets)
 {
        uint32_t i;
        uint32_t *table, *table_inv;
@@ -722,7 +717,7 @@ static void write_lookup_table(struct hashfile *f,
         * bitmap corresponds to j'th bitmapped commit (among the selected
         * commits) in lex order of OIDs.
         */
-       QSORT_S(table, writer.selected_nr, table_cmp, commit_positions);
+       QSORT(table, writer.selected_nr, table_cmp);
 
        /* table_inv helps us discover that relationship (i'th bitmap
         * to j'th commit by j = table_inv[i])
@@ -753,7 +748,7 @@ static void write_lookup_table(struct hashfile *f,
                        xor_row = 0xffffffff;
                }
 
-               hashwrite_be32(f, commit_positions[table[i]]);
+               hashwrite_be32(f, writer.selected[table[i]].commit_pos);
                hashwrite_be64(f, (uint64_t)offsets[table[i]]);
                hashwrite_be32(f, xor_row);
        }
@@ -789,7 +784,6 @@ void bitmap_writer_finish(struct pack_idx_entry **index,
        static uint16_t flags = BITMAP_OPT_FULL_DAG;
        struct strbuf tmp_file = STRBUF_INIT;
        struct hashfile *f;
-       uint32_t *commit_positions = NULL;
        off_t *offsets = NULL;
        uint32_t i;
 
@@ -814,22 +808,20 @@ void bitmap_writer_finish(struct pack_idx_entry **index,
        if (options & BITMAP_OPT_LOOKUP_TABLE)
                CALLOC_ARRAY(offsets, index_nr);
 
-       ALLOC_ARRAY(commit_positions, writer.selected_nr);
-
        for (i = 0; i < writer.selected_nr; i++) {
                struct bitmapped_commit *stored = &writer.selected[i];
-               int commit_pos = oid_pos(&stored->commit->object.oid, index, index_nr, oid_access);
+               int commit_pos = oid_pos(&stored->commit->object.oid, index,
+                                        index_nr, oid_access);
 
                if (commit_pos < 0)
                        BUG(_("trying to write commit not in index"));
-
-               commit_positions[i] = commit_pos;
+               stored->commit_pos = commit_pos;
        }
 
-       write_selected_commits_v1(f, commit_positions, offsets);
+       write_selected_commits_v1(f, offsets);
 
        if (options & BITMAP_OPT_LOOKUP_TABLE)
-               write_lookup_table(f, commit_positions, offsets);
+               write_lookup_table(f, offsets);
 
        if (options & BITMAP_OPT_HASH_CACHE)
                write_hash_cache(f, index, index_nr);
@@ -844,6 +836,5 @@ void bitmap_writer_finish(struct pack_idx_entry **index,
                die_errno("unable to rename temporary bitmap file to '%s'", filename);
 
        strbuf_release(&tmp_file);
-       free(commit_positions);
        free(offsets);
 }