text: /*
   * 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 "git2/types.h"
  #include "git2/sys/commit_graph.h"
  
  #include "map.h"
  #include "vector.h"
  #include "oid.h"
  #include "hash.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. */
  	unsigned char *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. */
  	unsigned char checksum[GIT_HASH_SHA1_SIZE];
  } git_commit_graph_file;
  
  /**
   * An entry in the commit-graph file. Provides a subset of the information that
   * can be obtained from the commit header.
   */
  typedef struct git_commit_graph_entry {
  	/* The generation number of the commit within the graph */
  	size_t generation;
  
  	/* Time in seconds from UNIX epoch. */
  	git_time_t commit_time;
  
  	/* The number of parents of the commit. */
  	size_t parent_count;
  
  	/*
  	 * The indices of the parent commits within the Commit Data table. The value
  	 * of `GIT_COMMIT_GRAPH_MISSING_PARENT` indicates that no parent is in that
  	 * position.
  	 */
  	size_t parent_indices[2];
  
  	/* The index within the Extra Edge List of any parent after the first two. */
  	size_t extra_parents_index;
  
  	/* The SHA-1 hash of the root tree of the commit. */
  	git_oid tree_oid;
  
  	/* The SHA-1 hash of the requested commit. */
  	git_oid sha1;
  } git_commit_graph_entry;
  
  /* A wrapper for git_commit_graph_file to enable lazy loading in the ODB. */
  struct git_commit_graph {
  	/* The path to the commit-graph file. Something like ".git/objects/info/commit-graph". */
  	git_str filename;
  
  	/* The underlying commit-graph file. */
  	git_commit_graph_file *file;
  
  	/* Whether the commit-graph file was already checked for validity. */
  	bool checked;
  };
  
  /** Create a new commit-graph, optionally opening the underlying file. */
  int git_commit_graph_new(git_commit_graph **cgraph_out, const char *objects_dir, bool open_file);
  
  /** Open and validate a commit-graph file. */
  int git_commit_graph_file_open(git_commit_graph_file **file_out, const char *path);
  
  /*
   * Attempt to get the git_commit_graph's commit-graph file. This object is
   * still owned by the git_commit_graph. If the repository does not contain a commit graph,
   * it will return GIT_ENOTFOUND.
   *
   * This function is not thread-safe.
   */
  int git_commit_graph_get_file(git_commit_graph_file **file_out, git_commit_graph *cgraph);
  
  /* Marks the commit-graph file as needing a refresh. */
  void git_commit_graph_refresh(git_commit_graph *cgraph);
  
  /*
   * A writer for `commit-graph` files.
   */
  struct git_commit_graph_writer {
  	/*
  	 * The path of the `objects/info` directory where the `commit-graph` will be
  	 * stored.
  	 */
  	git_str objects_info_dir;
  
  	/* The list of packed commits. */
  	git_vector commits;
  };
  
  int git_commit_graph__writer_dump(
  	git_str *cgraph,
  	git_commit_graph_writer *w,
  	git_commit_graph_writer_options *opts);
  
  /*
   * Returns whether the git_commit_graph_file needs to be reloaded since the
   * contents of the commit-graph file have changed on disk.
   */
  bool git_commit_graph_file_needs_refresh(
  		const git_commit_graph_file *file, const char *path);
  
  int git_commit_graph_entry_find(
  		git_commit_graph_entry *e,
  		const git_commit_graph_file *file,
  		const git_oid *short_oid,
  		size_t len);
  int git_commit_graph_entry_parent(
  		git_commit_graph_entry *parent,
  		const git_commit_graph_file *file,
  		const git_commit_graph_entry *entry,
  		size_t n);
  int git_commit_graph_file_close(git_commit_graph_file *cgraph);
  void git_commit_graph_file_free(git_commit_graph_file *cgraph);
  
  /* This is exposed for use in the fuzzers. */
  int git_commit_graph_file_parse(
  		git_commit_graph_file *file,
  		const unsigned char *data,
  		size_t size);
  
  #endif
  