thodg/libgit2/src/commit_graph.h

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• Hash : 3fd57a75
  Author :
  Date : 2021-01-04T18:22:43
  

  commit-graph: Introduce a parser for commit-graph files This change is the first in a series to add support for git's commit-graph. This should speed up commit graph traversals by avoiding object parsing and allowing some operations to terminate earlier. Part of: #5757

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• src/commit_graph.h

• /*
   * 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
  

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