thodg/libgit2/src/midx.h

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• Hash : f847fa7b
  Author :
  Date : 2020-02-16T02:00:56
  

  midx: Support multi-pack-index files in odb_pack.c This change adds support for reading multi-pack-index files from the packfile odb backend. This also makes git_pack_file objects open their backing failes lazily in more scenarios, since the multi-pack-index can avoid having to open them in some cases (yay!). This change also refreshes the documentation found in src/odb_pack.c to match the updated code. Part of: #5399

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• src/midx.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_midx_h__
  #define INCLUDE_midx_h__
  
  #include "common.h"
  
  #include <ctype.h>
  
  #include "map.h"
  #include "mwindow.h"
  #include "odb.h"
  
  /*
   * A multi-pack-index file.
   *
   * This file contains a merged index for multiple independent .pack files. This
   * can help speed up locating objects without requiring a garbage collection
   * cycle to create a single .pack file.
   *
   * Support for this feature was added in git 2.21, and requires the
   * `core.multiPackIndex` config option to be set.
   */
  typedef struct git_midx_file {
  	git_map index_map;
  
  	/* The table of Packfile Names. */
  	git_vector packfile_names;
  
  	/* The OID Fanout table. */
  	const uint32_t *oid_fanout;
  	/* The total number of objects in the index. */
  	uint32_t num_objects;
  
  	/* The OID Lookup table. */
  	git_oid *oid_lookup;
  
  	/* The Object Offsets table. Each entry has two 4-byte fields with the pack index and the offset. */
  	const unsigned char *object_offsets;
  
  	/* The Object Large Offsets table. */
  	const unsigned char *object_large_offsets;
  	/* The number of entries in the Object Large Offsets table. Each entry has an 8-byte with an offset */
  	size_t num_object_large_offsets;
  
  	/* The trailer of the file. Contains the SHA1-checksum of the whole file. */
  	git_oid checksum;
  
  	/* something like ".git/objects/pack/multi-pack-index". */
  	git_buf filename;
  } git_midx_file;
  
  /*
   * An entry in the multi-pack-index file. Similar in purpose to git_pack_entry.
   */
  typedef struct git_midx_entry {
  	/* The index within idx->packfile_names where the packfile name can be found. */
  	size_t pack_index;
  	/* The offset within the .pack file where the requested object is found. */
  	off64_t offset;
  	/* The SHA-1 hash of the requested object. */
  	git_oid sha1;
  } git_midx_entry;
  
  int git_midx_open(
  		git_midx_file **idx_out,
  		const char *path);
  bool git_midx_needs_refresh(
  		const git_midx_file *idx,
  		const char *path);
  int git_midx_entry_find(
  		git_midx_entry *e,
  		git_midx_file *idx,
  		const git_oid *short_oid,
  		size_t len);
  int git_midx_foreach_entry(
  		git_midx_file *idx,
  		git_odb_foreach_cb cb,
  		void *data);
  int git_midx_close(git_midx_file *idx);
  void git_midx_free(git_midx_file *idx);
  
  /* This is exposed for use in the fuzzers. */
  int git_midx_parse(
  		git_midx_file *idx,
  		const unsigned char *data,
  		size_t size);
  
  #endif
  

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