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commit-graph: refactor compute_topological_levels()

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This patch extracts the common code used to compute topological levels
and corrected committer dates into a common routine,
compute_reachable_generation_numbers(). For ease of reading, it only
modifies compute_topological_levels() to use this new routine, leaving
compute_generation_numbers() to be modified in the next change.

This new routine dispatches to call the necessary functions to get and
set the generation number for a given commit through a vtable (the
compute_generation_info struct).

Computing the generation number itself is done in
compute_generation_from_max(), which dispatches its implementation based
on the generation version requested, or issuing a BUG() for unrecognized
generation versions. This does not use a vtable because the logic
depends only on the generation number version, not where the data is
being loaded from or being stored to. This is a subtle point that will
make more sense in a future change that modifies the in-memory
generation values instead of just preparing values for writing to a
commit-graph file.

This change looks like it adds a lot of new code. However, two upcoming
changes will be quite small due to the work being done in this change.

Co-authored-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Derrick Stolee 2023-03-20 11:26:49 +00:00 committed by Junio C Hamano
parent b2c51b7590
commit 368d19b0b7
1 changed files with 83 additions and 23 deletions
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106
commit-graph.c
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@ -1446,24 +1446,52 @@ static void close_reachable(struct write_commit_graph_context *ctx)
stop_progress(&ctx->progress);
}
static void compute_topological_levels(struct write_commit_graph_context *ctx)
struct compute_generation_info {
struct repository *r;
struct packed_commit_list *commits;
struct progress *progress;
int progress_cnt;
timestamp_t (*get_generation)(struct commit *c, void *data);
void (*set_generation)(struct commit *c, timestamp_t gen, void *data);
void *data;
};
static timestamp_t compute_generation_from_max(struct commit *c,
timestamp_t max_gen,
int generation_version)
{
switch (generation_version) {
case 1: /* topological levels */
if (max_gen > GENERATION_NUMBER_V1_MAX - 1)
max_gen = GENERATION_NUMBER_V1_MAX - 1;
return max_gen + 1;
case 2: /* corrected commit date */
if (c->date && c->date > max_gen)
max_gen = c->date - 1;
return max_gen + 1;
default:
BUG("attempting unimplemented version");
}
}
static void compute_reachable_generation_numbers(
struct compute_generation_info *info,
int generation_version)
{
int i;
struct commit_list *list = NULL;
if (ctx->report_progress)
ctx->progress = start_delayed_progress(
_("Computing commit graph topological levels"),
ctx->commits.nr);
for (i = 0; i < ctx->commits.nr; i++) {
struct commit *c = ctx->commits.list[i];
uint32_t level;
for (i = 0; i < info->commits->nr; i++) {
struct commit *c = info->commits->list[i];
timestamp_t gen;
repo_parse_commit(info->r, c);
gen = info->get_generation(c, info->data);
display_progress(info->progress, info->progress_cnt + 1);
repo_parse_commit(ctx->r, c);
level = *topo_level_slab_at(ctx->topo_levels, c);
display_progress(ctx->progress, i + 1);
if (level != GENERATION_NUMBER_ZERO)
if (gen != GENERATION_NUMBER_ZERO && gen != GENERATION_NUMBER_INFINITY)
continue;
commit_list_insert(c, &list);
@ -1471,31 +1499,63 @@ static void compute_topological_levels(struct write_commit_graph_context *ctx)
struct commit *current = list->item;
struct commit_list *parent;
int all_parents_computed = 1;
uint32_t max_level = 0;
uint32_t max_gen = 0;
for (parent = current->parents; parent; parent = parent->next) {
repo_parse_commit(ctx->r, parent->item);
level = *topo_level_slab_at(ctx->topo_levels, parent->item);
repo_parse_commit(info->r, parent->item);
gen = info->get_generation(parent->item, info->data);
if (level == GENERATION_NUMBER_ZERO) {
if (gen == GENERATION_NUMBER_ZERO) {
all_parents_computed = 0;
commit_list_insert(parent->item, &list);
break;
}
if (level > max_level)
max_level = level;
if (gen > max_gen)
max_gen = gen;
}
if (all_parents_computed) {
pop_commit(&list);
gen = compute_generation_from_max(
current, max_gen,
generation_version);
info->set_generation(current, gen, info->data);
}
}
}
}
if (max_level > GENERATION_NUMBER_V1_MAX - 1)
max_level = GENERATION_NUMBER_V1_MAX - 1;
*topo_level_slab_at(ctx->topo_levels, current) = max_level + 1;
}
static timestamp_t get_topo_level(struct commit *c, void *data)
{
struct write_commit_graph_context *ctx = data;
return *topo_level_slab_at(ctx->topo_levels, c);
}
static void set_topo_level(struct commit *c, timestamp_t t, void *data)
{
struct write_commit_graph_context *ctx = data;
*topo_level_slab_at(ctx->topo_levels, c) = (uint32_t)t;
}
static void compute_topological_levels(struct write_commit_graph_context *ctx)
{
struct compute_generation_info info = {
.r = ctx->r,
.commits = &ctx->commits,
.get_generation = get_topo_level,
.set_generation = set_topo_level,
.data = ctx,
};
if (ctx->report_progress)
info.progress = ctx->progress
= start_delayed_progress(
_("Computing commit graph topological levels"),
ctx->commits.nr);
compute_reachable_generation_numbers(&info, 1);
stop_progress(&ctx->progress);
}