1 files changed, 67 insertions, 0 deletions
diff --git a/src/commit_graph.h b/src/commit_graph.h
new file mode 100644
index 000000000..01512d76f
--- /dev/null
+++ b/src/commit_graph.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_commit_graph_h__
+#define INCLUDE_commit_graph_h__
+
+#include "common.h"
+
+#include "map.h"
+
+/**
+ * A commit-graph file.
+ *
+ * This file contains metadata about commits, particularly the generation
+ * number for each one. This can help speed up graph operations without
+ * requiring a full graph traversal.
+ *
+ * Support for this feature was added in git 2.19.
+ */
+typedef struct git_commit_graph_file {
+	git_map graph_map;
+
+	/* The OID Fanout table. */
+	const uint32_t *oid_fanout;
+	/* The total number of commits in the graph. */
+	uint32_t num_commits;
+
+	/* The OID Lookup table. */
+	git_oid *oid_lookup;
+
+	/*
+	 * The Commit Data table. Each entry contains the OID of the commit followed
+	 * by two 8-byte fields in network byte order:
+	 * - The indices of the first two parents (32 bits each).
+	 * - The generation number (first 30 bits) and commit time in seconds since
+	 *   UNIX epoch (34 bits).
+	 */
+	const unsigned char *commit_data;
+
+	/*
+	 * The Extra Edge List table. Each 4-byte entry is a network byte order index
+	 * of one of the i-th (i > 0) parents of commits in the `commit_data` table,
+	 * when the commit has more than 2 parents.
+	 */
+	const unsigned char *extra_edge_list;
+	/* The number of entries in the Extra Edge List table. Each entry is 4 bytes wide. */
+	size_t num_extra_edge_list;
+
+	/* The trailer of the file. Contains the SHA1-checksum of the whole file. */
+	git_oid checksum;
+
+	/* something like ".git/objects/info/commit-graph". */
+	git_buf filename;
+} git_commit_graph_file;
+
+int git_commit_graph_open(git_commit_graph_file **cgraph_out, const char *path);
+int git_commit_graph_close(git_commit_graph_file *cgraph);
+void git_commit_graph_free(git_commit_graph_file *cgraph);
+
+/* This is exposed for use in the fuzzers. */
+int git_commit_graph_parse(git_commit_graph_file *cgraph, const unsigned char *data, size_t size);
+
+#endif