[PATCH 13/17] commit-graph: lay groundwork for incremental files

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <dsto...@microsoft.com>

Signed-off-by: Derrick Stolee <dsto...@microsoft.com>
---
 commit-graph.c | 66 ++++++++++++++++++++++++++++++++++++++++++++------
 commit-graph.h |  4 +++
 2 files changed, 62 insertions(+), 8 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index 7723156964..f790f44a9c 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -371,6 +371,25 @@ static int bsearch_graph(struct commit_graph *g, struct 
object_id *oid, uint32_t
                            g->chunk_oid_lookup, g->hash_len, pos);
 }
 
+static void load_oid_from_graph(struct commit_graph *g, int pos, struct 
object_id *oid)
+{
+       if (!g)
+               BUG("NULL commit-graph");
+
+       if (pos < g->num_commits_in_base) {
+               load_oid_from_graph(g->base_graph, pos, oid);
+               return;
+       }
+
+       if (pos >= g->num_commits + g->num_commits_in_base)
+               BUG("position %d is beyond the scope of this commit-graph (%d 
local + %d base commits)",
+                   pos, g->num_commits, g->num_commits_in_base);
+
+       pos -= g->num_commits_in_base;
+
+       hashcpy(oid->hash, g->chunk_oid_lookup + g->hash_len * pos);
+}
+
 static struct commit_list **insert_parent_or_die(struct repository *r,
                                                 struct commit_graph *g,
                                                 uint64_t pos,
@@ -379,10 +398,10 @@ static struct commit_list **insert_parent_or_die(struct 
repository *r,
        struct commit *c;
        struct object_id oid;
 
-       if (pos >= g->num_commits)
+       if (pos >= g->num_commits + g->num_commits_in_base)
                die("invalid parent position %"PRIu64, pos);
 
-       hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
+       load_oid_from_graph(g, pos, &oid);
        c = lookup_commit(r, &oid);
        if (!c)
                die(_("could not find commit %s"), oid_to_hex(&oid));
@@ -393,7 +412,7 @@ static struct commit_list **insert_parent_or_die(struct 
repository *r,
 static void fill_commit_graph_info(struct commit *item, struct commit_graph 
*g, uint32_t pos)
 {
        const unsigned char *commit_data = g->chunk_commit_data + 
GRAPH_DATA_WIDTH * pos;
-       item->graph_pos = pos;
+       item->graph_pos = pos + g->num_commits_in_base;
        item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 }
 
@@ -405,10 +424,25 @@ static int fill_commit_in_graph(struct repository *r,
        uint32_t *parent_data_ptr;
        uint64_t date_low, date_high;
        struct commit_list **pptr;
-       const unsigned char *commit_data = g->chunk_commit_data + (g->hash_len 
+ 16) * pos;
+       const unsigned char *commit_data;
 
-       item->object.parsed = 1;
+       if (pos < g->num_commits_in_base)
+               return fill_commit_in_graph(r, item, g->base_graph, pos);
+
+       if (pos >= g->num_commits + g->num_commits_in_base)
+               BUG("position %d is beyond the scope of this commit-graph (%d 
local + %d base commits)",
+                   pos, g->num_commits, g->num_commits_in_base);
+
+       /*
+        * Store the "full" position, but then use the
+        * "local" position for the rest of the calculation.
+        */
        item->graph_pos = pos;
+       pos -= g->num_commits_in_base;
+
+       commit_data = g->chunk_commit_data + (g->hash_len + 16) * pos;
+
+       item->object.parsed = 1;
 
        item->maybe_tree = NULL;
 
@@ -452,7 +486,18 @@ static int find_commit_in_graph(struct commit *item, 
struct commit_graph *g, uin
                *pos = item->graph_pos;
                return 1;
        } else {
-               return bsearch_graph(g, &(item->object.oid), pos);
+               struct commit_graph *cur_g = g;
+               uint32_t pos_in_g;
+
+               while (cur_g && !bsearch_graph(cur_g, &(item->object.oid), 
&pos_in_g))
+                       cur_g = cur_g->base_graph;
+
+               if (cur_g) {
+                       *pos = pos_in_g + cur_g->num_commits_in_base;
+                       return 1;
+               }
+
+               return 0;
        }
 }
 
@@ -492,8 +537,13 @@ static struct tree *load_tree_for_commit(struct repository 
*r,
                                         struct commit *c)
 {
        struct object_id oid;
-       const unsigned char *commit_data = g->chunk_commit_data +
-                                          GRAPH_DATA_WIDTH * (c->graph_pos);
+       const unsigned char *commit_data;
+
+       if (c->graph_pos < g->num_commits_in_base)
+               return load_tree_for_commit(r, g->base_graph, c);
+
+       commit_data = g->chunk_commit_data +
+                       GRAPH_DATA_WIDTH * (c->graph_pos - 
g->num_commits_in_base);
 
        hashcpy(oid.hash, commit_data);
        c->maybe_tree = lookup_tree(r, &oid);
diff --git a/commit-graph.h b/commit-graph.h
index 70f4caf0c7..170920720d 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -48,10 +48,14 @@ struct commit_graph {
        uint32_t num_commits;
        struct object_id oid;
 
+       uint32_t num_commits_in_base;
+       struct commit_graph *base_graph;
+
        const uint32_t *chunk_oid_fanout;
        const unsigned char *chunk_oid_lookup;
        const unsigned char *chunk_commit_data;
        const unsigned char *chunk_extra_edges;
+       const unsigned char *chunk_base_graph;
 };
 
 struct commit_graph *load_commit_graph_one_fd_st(int fd, struct stat *st);
-- 
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