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commit-graph: compute generation numbers 

While preparing commits to be written into a commit-graph file, compute
the generation numbers using a depth-first strategy.

The only commits that are walked in this depth-first search are those
without a precomputed generation number. Thus, computation time will be
relative to the number of new commits to the commit-graph file.

If a computed generation number would exceed GENERATION_NUMBER_MAX, then
use GENERATION_NUMBER_MAX instead.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Derrick Stolee 2018-05-01 12:47:09 +00:00 committed by Junio C Hamano
parent 83073cc994
commit 3258c66332
1 changed files with 43 additions and 0 deletions
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43
commit-graph.c
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@ -439,6 +439,8 @@ static void write_graph_chunk_data(struct hashfile *f, int hash_len,
else
packedDate[0] = 0;
packedDate[0] |= htonl((*list)->generation << 2);
packedDate[1] = htonl((*list)->date);
hashwrite(f, packedDate, 8);
@ -571,6 +573,45 @@ static void close_reachable(struct packed_oid_list *oids)
}
}
static void compute_generation_numbers(struct packed_commit_list* commits)
{
int i;
struct commit_list *list = NULL;
for (i = 0; i < commits->nr; i++) {
if (commits->list[i]->generation != GENERATION_NUMBER_INFINITY &&
commits->list[i]->generation != GENERATION_NUMBER_ZERO)
continue;
commit_list_insert(commits->list[i], &list);
while (list) {
struct commit *current = list->item;
struct commit_list *parent;
int all_parents_computed = 1;
uint32_t max_generation = 0;
for (parent = current->parents; parent; parent = parent->next) {
if (parent->item->generation == GENERATION_NUMBER_INFINITY ||
parent->item->generation == GENERATION_NUMBER_ZERO) {
all_parents_computed = 0;
commit_list_insert(parent->item, &list);
break;
} else if (parent->item->generation > max_generation) {
max_generation = parent->item->generation;
}
}
if (all_parents_computed) {
current->generation = max_generation + 1;
pop_commit(&list);
if (current->generation > GENERATION_NUMBER_MAX)
current->generation = GENERATION_NUMBER_MAX;
}
}
}
}
void write_commit_graph(const char *obj_dir,
const char **pack_indexes,
int nr_packs,
@ -694,6 +735,8 @@ void write_commit_graph(const char *obj_dir,
if (commits.nr >= GRAPH_PARENT_MISSING)
die(_("too many commits to write graph"));
compute_generation_numbers(&commits);
graph_name = get_commit_graph_filename(obj_dir);
fd = hold_lock_file_for_update(&lk, graph_name, 0);