commit: add generation number to struct commit
The generation number of a commit is defined recursively as follows:
* If a commit A has no parents, then the generation number of A is one.
* If a commit A has parents, then the generation number of A is one
more than the maximum generation number among the parents of A.
Add a uint32_t generation field to struct commit so we can pass this
information to revision walks. We use three special values to signal
the generation number is invalid:
GENERATION_NUMBER_INFINITY 0xFFFFFFFF
GENERATION_NUMBER_MAX 0x3FFFFFFF
GENERATION_NUMBER_ZERO 0
The first (_INFINITY) means the generation number has not been loaded or
computed. The second (_MAX) means the generation number is too large to
store in the commit-graph file. The third (_ZERO) means the generation
number was loaded from a commit graph file that was written by a version
of git that did not support generation numbers.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/alloc.c b/alloc.c
index cf4f8b6..e8ab14f 100644
--- a/alloc.c
+++ b/alloc.c
@@ -94,6 +94,7 @@ void *alloc_commit_node(void)
c->object.type = OBJ_COMMIT;
c->index = alloc_commit_index();
c->graph_pos = COMMIT_NOT_FROM_GRAPH;
+ c->generation = GENERATION_NUMBER_INFINITY;
return c;
}
diff --git a/commit-graph.c b/commit-graph.c
index 70fa1b2..9ad21c3 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -262,6 +262,8 @@ static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uin
date_low = get_be32(commit_data + g->hash_len + 12);
item->date = (timestamp_t)((date_high << 32) | date_low);
+ item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
+
pptr = &item->parents;
edge_value = get_be32(commit_data + g->hash_len);
diff --git a/commit.h b/commit.h
index 23a3f36..aac3b8c 100644
--- a/commit.h
+++ b/commit.h
@@ -10,6 +10,9 @@
#include "pretty.h"
#define COMMIT_NOT_FROM_GRAPH 0xFFFFFFFF
+#define GENERATION_NUMBER_INFINITY 0xFFFFFFFF
+#define GENERATION_NUMBER_MAX 0x3FFFFFFF
+#define GENERATION_NUMBER_ZERO 0
struct commit_list {
struct commit *item;
@@ -30,6 +33,7 @@ struct commit {
*/
struct tree *maybe_tree;
uint32_t graph_pos;
+ uint32_t generation;
};
extern int save_commit_buffer;
