thodg/got/lib/got_lib_pack.h

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• Show log

  Commit

• Author : Stefan Sperling
  Date : 2019-06-29 23:26:36
  Hash : dd88155e
  Message : disambiguate abbreviated object IDs based on object type

• lib/got_lib_pack.h

• /*
   * Copyright (c) 2018, 2019 Stefan Sperling <stsp@openbsd.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  /* An open pack file. */
  struct got_pack {
  	char *path_packfile;
  	int fd;
  	uint8_t *map;
  	size_t filesize;
  	struct got_privsep_child *privsep_child;
  };
  
  const struct got_error *got_pack_stop_privsep_child(struct got_pack *);
  const struct got_error *got_pack_close(struct got_pack *);
  
  #define GOT_PACK_PREFIX		"pack-"
  #define GOT_PACKFILE_SUFFIX	".pack"
  #define GOT_PACKIDX_SUFFIX		".idx"
  #define GOT_PACKFILE_NAMELEN	(strlen(GOT_PACK_PREFIX) + \
  				SHA1_DIGEST_STRING_LENGTH - 1 + \
  				strlen(GOT_PACKFILE_SUFFIX))
  #define GOT_PACKIDX_NAMELEN	(strlen(GOT_PACK_PREFIX) + \
  				SHA1_DIGEST_STRING_LENGTH - 1 + \
  				strlen(GOT_PACKIDX_SUFFIX))
  
  /* See Documentation/technical/pack-format.txt in Git. */
  
  struct got_packidx_trailer {
  	u_int8_t	packfile_sha1[SHA1_DIGEST_LENGTH];
  	u_int8_t	packidx_sha1[SHA1_DIGEST_LENGTH];
  } __attribute__((__packed__));
  
  struct got_packidx_object_id {
  	u_int8_t sha1[SHA1_DIGEST_LENGTH];
  } __attribute__((__packed__));
  
  /* Ignore pack index version 1 which is no longer written by Git. */
  #define GOT_PACKIDX_VERSION 2
  
  struct got_packidx_v2_hdr {
  	uint32_t	*magic;		/* big endian */
  #define GOT_PACKIDX_V2_MAGIC 0xff744f63	/* "\377t0c" */
  	uint32_t	*version;
  
  	/* 
  	 * Each entry N in the fanout table contains the number of objects in
  	 * the packfile whose SHA1 begins with a byte less than or equal to N.
  	 * The last entry (index 255) contains the number of objects in the
  	 * pack file whose first SHA1 byte is <= 0xff, and thus records the
  	 * total number of objects in the pack file. All pointer variables
  	 * below point to tables with a corresponding number of entries.
  	 */
  	uint32_t	*fanout_table;	/* values are big endian */
  #define GOT_PACKIDX_V2_FANOUT_TABLE_ITEMS (0xff + 1)
  
  	/* Sorted SHA1 checksums for each object in the pack file. */
  	struct got_packidx_object_id *sorted_ids;
  
  	/* CRC32 of the packed representation of each object. */
  	uint32_t	*crc32;
  
  	/* Offset into the pack file for each object. */
  	uint32_t	*offsets;		/* values are big endian */
  #define GOT_PACKIDX_OFFSET_VAL_MASK		0x7fffffff
  #define GOT_PACKIDX_OFFSET_VAL_IS_LARGE_IDX	0x80000000
  
  	/* Large offsets table is empty for pack files < 2 GB. */
  	uint64_t	*large_offsets;		/* values are big endian */
  
  	struct got_packidx_trailer *trailer;
  };
  
  /* An open pack index file. */
  struct got_packidx {
  	char *path_packidx; /* actual on-disk path */
  	int fd;
  	uint8_t *map;
  	size_t len;
  	struct got_packidx_v2_hdr hdr; /* convenient pointers into map */
  };
  
  struct got_packfile_hdr {
  	uint32_t	signature;
  #define GOT_PACKFILE_SIGNATURE	0x5041434b	/* 'P' 'A' 'C' 'K' */
  	uint32_t	version;	/* big endian */
  #define GOT_PACKFILE_VERSION 2
  	uint32_t	nobjects;	/* big endian */
  };
  
  struct got_packfile_obj_hdr {
  	/* 
  	 * The object size field uses a variable length encoding:
  	 * size0...sizeN form a 4+7+7+...+7 bit integer, where size0 is the
  	 * least significant part and sizeN is the most significant part.
  	 * If the MSB of a size byte is set, an additional size byte follows.
  	 * Of the 7 remaining bits of size0, the first 3 bits indicate the
  	 * object's type, and the remaining 4 bits contribute to the size.
  	 */
  	uint8_t *size;		/* variable length */
  #define GOT_PACK_OBJ_SIZE_MORE		0x80
  #define GOT_PACK_OBJ_SIZE0_TYPE_MASK	0x70 /* See struct got_object->type */
  #define GOT_PACK_OBJ_SIZE0_TYPE_MASK_SHIFT	4
  #define GOT_PACK_OBJ_SIZE0_VAL_MASK	0x0f
  #define GOT_PACK_OBJ_SIZE_VAL_MASK	0x7f
  };
  
  /* If object is not a DELTA type. */
  struct got_packfile_object_data {
  	uint8_t *data;	/* compressed */
  };
  
  /* If object is of type	GOT_OBJ_TYPE_REF_DELTA. */
  struct got_packfile_object_data_ref_delta {
  	uint8_t sha1[SHA1_DIGEST_LENGTH];
  	uint8_t *delta_data;		/* compressed */
  };
  
  /* If object is of type GOT_OBJ_TYPE_OFFSET_DELTA. */
  struct got_packfile_object_data_offset_delta {
  	/* 
  	 * This offset is interpreted as a negative offset from
  	 * the got_packfile_obj_hdr corresponding to this object.
  	 * The size provided in the header specifies the amount
  	 * of compressed delta data that follows.
  	 *
  	 * This field uses a variable length encoding of N bytes,
  	 * where the MSB is always set except for the last byte.
  	 * The value is encoded as a series of N 7 bit integers,
  	 * which are concatenated, and if N > 1 the value 2^7 +
  	 * 2^14 + ... + 2^(7 * (n-1)) is added to the result.
  	 */
  	uint8_t *offset;	/* variable length */
  #define GOT_PACK_OBJ_DELTA_OFF_MORE		0x80
  #define GOT_PACK_OBJ_DELTA_OFF_VAL_MASK		0x7f
  	uint8_t *delta_data;		/* compressed */
  };
  
  struct got_packfile_obj_data {
  	union {
  		struct got_packfile_object_data data;
  		struct got_packfile_object_data_ref_delta ref_delta;
  		struct got_packfile_object_data_offset_delta offset_delta;
  	} __attribute__((__packed__));
  } __attribute__((__packed__));
  
  const struct got_error *got_packidx_init_hdr(struct got_packidx *, int);
  const struct got_error *got_packidx_open(struct got_packidx **,
      const char *, int);
  const struct got_error *got_packidx_close(struct got_packidx *);
  int got_packidx_get_object_idx(struct got_packidx *, struct got_object_id *);
  const struct got_error *got_packidx_match_id_str_prefix(
      struct got_object_id_queue *, struct got_packidx *, const char *);
  
  const struct got_error *got_packfile_open_object(struct got_object **,
      struct got_pack *, struct got_packidx *, int, struct got_object_id *);
  const struct got_error *got_pack_get_max_delta_object_size(uint64_t *,
      struct got_object *);
  const struct got_error *got_packfile_extract_object(struct got_pack *,
      struct got_object *, FILE *, FILE *, FILE *);
  const struct got_error *got_packfile_extract_object_to_mem(uint8_t **, size_t *,
      struct got_object *, struct got_pack *);
  struct got_pack *got_repo_get_cached_pack(struct got_repository *, const char *);