@matheusbsbs / matheus-bagliano / commits / 4805125710

pack-objects: prepare `write_reused_pack()` for multi-pack reuse

The function `write_reused_pack()` within `builtin/pack-objects.c` is responsible for performing pack-reuse on a single pack, and has two main functions: - it dispatches a call to `write_reused_pack_verbatim()` to see if we can reuse portions of the packfile in whole-word chunks - for any remaining objects (that is, any objects that appear after the first "gap" in the bitmap), call write_reused_pack_one() on that object to record it for reuse. Prepare this function for multi-pack reuse by removing the assumption that the bit position corresponding to the first object being reused from a given pack must be at bit position zero. The changes in this function are mostly straightforward. Initialize `i` to the position of the first word to contain bits corresponding to that reuse pack. In most situations, we throw the initialized value away, since we end up replacing it with the return value from write_reused_pack_verbatim(), moving us past the section of whole words that we reused. Likewise, modify the per-object loop to ignore any bits at the beginning of the first word that do not belong to the pack currently being reused, as well as skip to the "done" section once we have processed the last bit corresponding to this pack. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Taylor Blau committed Dec 14, 2023 at 17:24 UTC 48051257101bc4689f91b4ea2eec9606d71686dc

1 file changed +8 -2

builtin/pack-objects.c

+8 -2

@@ -1127,7 +1127,7 @@ static size_t write_reused_pack_verbatim(struct bitmapped_pack *reuse_packfile,

1127 static void write_reused_pack(struct bitmapped_pack *reuse_packfile,

1128 struct hashfile *f)

1129 {

1130 - size_t i = 0;

1130 + size_t i = reuse_packfile->bitmap_pos / BITS_IN_EWORD;

1131 uint32_t offset;

1132 off_t pack_start = hashfile_total(f) - sizeof(struct pack_header);

1133 struct pack_window *w_curs = NULL;

@@ -1145,17 +1145,23 @@ static void write_reused_pack(struct bitmapped_pack *reuse_packfile,

1145 break;

1146

1147 offset += ewah_bit_ctz64(word >> offset);

1148 + if (pos + offset < reuse_packfile->bitmap_pos)

1149 + continue;

1150 + if (pos + offset >= reuse_packfile->bitmap_pos + reuse_packfile->bitmap_nr)

1151 + goto done;

1152 /*

1153 * Can use bit positions directly, even for MIDX

1154 * bitmaps. See comment in try_partial_reuse()

1155 * for why.

1156 */

1153 - write_reused_pack_one(reuse_packfile->p, pos + offset,

1157 + write_reused_pack_one(reuse_packfile->p,

1158 + pos + offset - reuse_packfile->bitmap_pos,

1159 f, pack_start, &w_curs);

1160 display_progress(progress_state, ++written);

1161 }

1162 }

1163

1164 +done:

1165 unuse_pack(&w_curs);

1166 }

1167