[PATCH v5 05/16] commit-graph: add base graphs chunk

From

Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>

Date

Jun 7, 2019, 18:38 UTC

Message-ID

<d14c79f9d508067137baa0b8a8a038b681f5c450.1559932699.git.gitgitgadget@gmail.com>

In-Reply-To

<pull.184.v5.git.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 .../technical/commit-graph-format.txt         | 11 ++++++++--
 commit-graph.c                                | 22 +++++++++++++++++++
 commit-graph.h                                |  1 +
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/Documentation/technical/commit-graph-format.txt b/Documentation/technical/commit-graph-format.txt
index 16452a0504..a4f17441ae 100644
--- a/Documentation/technical/commit-graph-format.txt
+++ b/Documentation/technical/commit-graph-format.txt
@@ -44,8 +44,9 @@ HEADER:
 
   1-byte number (C) of "chunks"
 
-  1-byte (reserved for later use)
-     Current clients should ignore this value.
+  1-byte number (B) of base commit-graphs
+      We infer the length (H*B) of the Base Graphs chunk
+      from this value.
 
 CHUNK LOOKUP:
 
@@ -92,6 +93,12 @@ CHUNK DATA:
       positions for the parents until reaching a value with the most-significant
       bit on. The other bits correspond to the position of the last parent.
 
+  Base Graphs List (ID: {'B', 'A', 'S', 'E'}) [Optional]
+      This list of H-byte hashes describe a set of B commit-graph files that
+      form a commit-graph chain. The graph position for the ith commit in this
+      file's OID Lookup chunk is equal to i plus the number of commits in all
+      base graphs.  If B is non-zero, this chunk must exist.
+
 TRAILER:
 
 	H-byte HASH-checksum of all of the above.
diff --git a/commit-graph.c b/commit-graph.c
index 263c73282e..0ff1a4f379 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -22,6 +22,7 @@
 #define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
 #define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
 #define GRAPH_CHUNKID_EXTRAEDGES 0x45444745 /* "EDGE" */
+#define GRAPH_CHUNKID_BASE 0x42415345 /* "BASE" */
 
 #define GRAPH_DATA_WIDTH (the_hash_algo->rawsz + 16)
 
@@ -262,6 +263,12 @@ struct commit_graph *parse_commit_graph(void *graph_map, int fd,
 			else
 				graph->chunk_extra_edges = data + chunk_offset;
 			break;
+
+		case GRAPH_CHUNKID_BASE:
+			if (graph->chunk_base_graphs)
+				chunk_repeated = 1;
+			else
+				graph->chunk_base_graphs = data + chunk_offset;
 		}
 
 		if (chunk_repeated) {
@@ -280,6 +287,8 @@ struct commit_graph *parse_commit_graph(void *graph_map, int fd,
 		last_chunk_offset = chunk_offset;
 	}
 
+	hashcpy(graph->oid.hash, graph->data + graph->data_len - graph->hash_len);
+
 	if (verify_commit_graph_lite(graph))
 		return NULL;
 
@@ -315,8 +324,21 @@ static int add_graph_to_chain(struct commit_graph *g,
 {
 	struct commit_graph *cur_g = chain;
 
+	if (n && !g->chunk_base_graphs) {
+		warning(_("commit-graph has no base graphs chunk"));
+		return 0;
+	}
+
 	while (n) {
 		n--;
+
+		if (!cur_g ||
+		    !oideq(&oids[n], &cur_g->oid) ||
+		    !hasheq(oids[n].hash, g->chunk_base_graphs + g->hash_len * n)) {
+			warning(_("commit-graph chain does not match"));
+			return 0;
+		}
+
 		cur_g = cur_g->base_graph;
 	}
 
diff --git a/commit-graph.h b/commit-graph.h
index f9fe32ebe3..80f4917ddb 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -55,6 +55,7 @@ struct commit_graph {
 	const unsigned char *chunk_oid_lookup;
 	const unsigned char *chunk_commit_data;
 	const unsigned char *chunk_extra_edges;
+	const unsigned char *chunk_base_graphs;
 };
 
 struct commit_graph *load_commit_graph_one_fd_st(int fd, struct stat *st);

-- 
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