thodg/libgit2/src/pack.h

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• Hash : 0edc26c8
  Author :
  Date : 2019-12-13T18:54:13
  

  pack: refactor streams to use `git_zstream` While we do have a `git_zstream` abstraction that encapsulates all the calls to zlib as well as its error handling, we do not use it in our pack file code. Refactor it to make the code a lot easier to understand.

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• src/pack.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_pack_h__
  #define INCLUDE_pack_h__
  
  #include "common.h"
  
  #include "git2/oid.h"
  
  #include "array.h"
  #include "map.h"
  #include "mwindow.h"
  #include "odb.h"
  #include "offmap.h"
  #include "oidmap.h"
  #include "zstream.h"
  
  #define GIT_PACK_FILE_MODE 0444
  
  #define PACK_SIGNATURE 0x5041434b	/* "PACK" */
  #define PACK_VERSION 2
  #define pack_version_ok(v) ((v) == htonl(2) || (v) == htonl(3))
  struct git_pack_header {
  	uint32_t hdr_signature;
  	uint32_t hdr_version;
  	uint32_t hdr_entries;
  };
  
  /*
   * The first four bytes of index formats later than version 1 should
   * start with this signature, as all older git binaries would find this
   * value illegal and abort reading the file.
   *
   * This is the case because the number of objects in a packfile
   * cannot exceed 1,431,660,000 as every object would need at least
   * 3 bytes of data and the overall packfile cannot exceed 4 GiB with
   * version 1 of the index file due to the offsets limited to 32 bits.
   * Clearly the signature exceeds this maximum.
   *
   * Very old git binaries will also compare the first 4 bytes to the
   * next 4 bytes in the index and abort with a "non-monotonic index"
   * error if the second 4 byte word is smaller than the first 4
   * byte word. This would be true in the proposed future index
   * format as idx_signature would be greater than idx_version.
   */
  
  #define PACK_IDX_SIGNATURE 0xff744f63	/* "\377tOc" */
  
  struct git_pack_idx_header {
  	uint32_t idx_signature;
  	uint32_t idx_version;
  };
  
  typedef struct git_pack_cache_entry {
  	size_t last_usage; /* enough? */
  	git_atomic refcount;
  	git_rawobj raw;
  } git_pack_cache_entry;
  
  struct pack_chain_elem {
  	off64_t base_key;
  	off64_t offset;
  	size_t size;
  	git_object_t type;
  };
  
  typedef git_array_t(struct pack_chain_elem) git_dependency_chain;
  
  #define GIT_PACK_CACHE_MEMORY_LIMIT 16 * 1024 * 1024
  #define GIT_PACK_CACHE_SIZE_LIMIT 1024 * 1024 /* don't bother caching anything over 1MB */
  
  typedef struct {
  	size_t memory_used;
  	size_t memory_limit;
  	size_t use_ctr;
  	git_mutex lock;
  	git_offmap *entries;
  } git_pack_cache;
  
  struct git_pack_file {
  	git_mwindow_file mwf;
  	git_map index_map;
  	git_mutex lock; /* protect updates to mwf and index_map */
  	git_atomic refcount;
  
  	uint32_t num_objects;
  	uint32_t num_bad_objects;
  	git_oid *bad_object_sha1; /* array of git_oid */
  
  	int index_version;
  	git_time_t mtime;
  	unsigned pack_local:1, pack_keep:1, has_cache:1;
  	git_oidmap *idx_cache;
  	git_oid **oids;
  
  	git_pack_cache bases; /* delta base cache */
  
  	time_t last_freshen; /* last time the packfile was freshened */
  
  	/* something like ".git/objects/pack/xxxxx.pack" */
  	char pack_name[GIT_FLEX_ARRAY]; /* more */
  };
  
  struct git_pack_entry {
  	off64_t offset;
  	git_oid sha1;
  	struct git_pack_file *p;
  };
  
  typedef struct git_packfile_stream {
  	off64_t curpos;
  	int done;
  	git_zstream zstream;
  	struct git_pack_file *p;
  	git_mwindow *mw;
  } git_packfile_stream;
  
  size_t git_packfile__object_header(unsigned char *hdr, size_t size, git_object_t type);
  
  int git_packfile__name(char **out, const char *path);
  
  int git_packfile_unpack_header(
  		size_t *size_p,
  		git_object_t *type_p,
  		git_mwindow_file *mwf,
  		git_mwindow **w_curs,
  		off64_t *curpos);
  
  int git_packfile_resolve_header(
  		size_t *size_p,
  		git_object_t *type_p,
  		struct git_pack_file *p,
  		off64_t offset);
  
  int git_packfile_unpack(git_rawobj *obj, struct git_pack_file *p, off64_t *obj_offset);
  
  int git_packfile_stream_open(git_packfile_stream *obj, struct git_pack_file *p, off64_t curpos);
  ssize_t git_packfile_stream_read(git_packfile_stream *obj, void *buffer, size_t len);
  void git_packfile_stream_dispose(git_packfile_stream *obj);
  
  off64_t get_delta_base(struct git_pack_file *p, git_mwindow **w_curs,
  		off64_t *curpos, git_object_t type,
  		off64_t delta_obj_offset);
  
  void git_packfile_close(struct git_pack_file *p, bool unlink_packfile);
  void git_packfile_free(struct git_pack_file *p);
  int git_packfile_alloc(struct git_pack_file **pack_out, const char *path);
  
  int git_pack_entry_find(
  		struct git_pack_entry *e,
  		struct git_pack_file *p,
  		const git_oid *short_oid,
  		size_t len);
  int git_pack_foreach_entry(
  		struct git_pack_file *p,
  		git_odb_foreach_cb cb,
  		void *data);
  
  #endif
  

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