diff options
Diffstat (limited to 'commit-graph.c')
| -rw-r--r-- | commit-graph.c | 37 |
1 files changed, 34 insertions, 3 deletions
diff --git a/commit-graph.c b/commit-graph.c index 6b1f02e179..ad3582451d 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -1319,6 +1319,37 @@ static int write_graph_chunk_data(struct hashfile *f, return 0; } +/* + * Compute the generation offset between the commit date and its generation. + * This is what's ultimately stored as generation number in the commit graph. + * + * Note that the computation of the commit date is more involved than you might + * think. Instead of using the full commit date, we're in fact masking bits so + * that only the 34 lowest bits are considered. This results from the fact that + * commit graphs themselves only ever store 34 bits of the commit date + * themselves. + * + * This means that if we have a commit date that exceeds 34 bits we'll end up + * in situations where depending on whether the commit has been parsed from the + * object database or the commit graph we'll have different dates, where the + * ones parsed from the object database would have full 64 bit precision. + * + * But ultimately, we only ever want the offset to be relative to what we + * actually end up storing on disk, and hence we have to mask all the other + * bits. + */ +static timestamp_t compute_generation_offset(struct commit *c) +{ + timestamp_t masked_date; + + if (sizeof(timestamp_t) > 4) + masked_date = c->date & (((timestamp_t) 1 << 34) - 1); + else + masked_date = c->date; + + return commit_graph_data_at(c)->generation - masked_date; +} + static int write_graph_chunk_generation_data(struct hashfile *f, void *data) { @@ -1329,7 +1360,7 @@ static int write_graph_chunk_generation_data(struct hashfile *f, struct commit *c = ctx->commits.items[i]; timestamp_t offset; repo_parse_commit(ctx->r, c); - offset = commit_graph_data_at(c)->generation - c->date; + offset = compute_generation_offset(c); display_progress(ctx->progress, ++ctx->progress_cnt); if (offset > GENERATION_NUMBER_V2_OFFSET_MAX) { @@ -1350,7 +1381,7 @@ static int write_graph_chunk_generation_data_overflow(struct hashfile *f, int i; for (i = 0; i < ctx->commits.nr; i++) { struct commit *c = ctx->commits.items[i]; - timestamp_t offset = commit_graph_data_at(c)->generation - c->date; + timestamp_t offset = compute_generation_offset(c); display_progress(ctx->progress, ++ctx->progress_cnt); if (offset > GENERATION_NUMBER_V2_OFFSET_MAX) { @@ -1733,7 +1764,7 @@ static void compute_generation_numbers(struct write_commit_graph_context *ctx) for (i = 0; i < ctx->commits.nr; i++) { struct commit *c = ctx->commits.items[i]; - timestamp_t offset = commit_graph_data_at(c)->generation - c->date; + timestamp_t offset = compute_generation_offset(c); if (offset > GENERATION_NUMBER_V2_OFFSET_MAX) ctx->num_generation_data_overflows++; } |