Class: GitStore::PackStorage

Inherits:
Object
  • Object
show all
Defined in:
lib/git_store/pack.rb

Constant Summary collapse

OBJ_OFS_DELTA = 
6
OBJ_REF_DELTA = 
7
FanOutCount = 
256
SHA1Size = 
20
IdxOffsetSize = 
4
OffsetSize = 
4
CrcSize = 
4
OffsetStart = 
FanOutCount * IdxOffsetSize
SHA1Start = 
OffsetStart + OffsetSize
EntrySize = 
OffsetSize + SHA1Size
EntrySizeV2 = 
SHA1Size + CrcSize + OffsetSize

Instance Method Summary collapse

Constructor Details

#initialize(file) ⇒ PackStorage

Returns a new instance of PackStorage.



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# File 'lib/git_store/pack.rb', line 84

def initialize(file)
  if file =~ /\.idx$/
    file = file[0...-3] + 'pack'
  end
  @name = file
  @cache = {}
  init_pack
end

Instance Method Details

#[](sha1) ⇒ Object 



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# File 'lib/git_store/pack.rb', line 155

def [](sha1)
  if obj = @cache[sha1]
    return obj
  end

  offset = find_object(sha1)
  return nil if !offset
  @cache[sha1] = obj = parse_object(offset)
  return obj
end

#cache_objects ⇒ Object 



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# File 'lib/git_store/pack.rb', line 128

def cache_objects
  @cache = {}
  with_packfile do |packfile|
    each_entry do |sha, offset|
      data, type = unpack_object(packfile, offset, {:caching => true})
      if data
        @cache[sha] = [type, data]
      end
    end
  end
end

#close ⇒ Object 



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# File 'lib/git_store/pack.rb', line 144

def close
  # shouldnt be anything open now
end

#each_entry ⇒ Object 



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# File 'lib/git_store/pack.rb', line 180

def each_entry
  with_idx do |idx|
    if @version == 2
      data = read_data_v2(idx)
      data.each do |sha1, crc, offset|
        yield sha1, offset
      end
    else
      pos = OffsetStart
      @size.times do
        offset = idx[pos,OffsetSize].unpack('N')[0]
        sha1 = idx[pos+OffsetSize,SHA1Size]
        pos += EntrySize
        yield sha1, offset
      end
    end
  end
end

#each_sha1 ⇒ Object 



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# File 'lib/git_store/pack.rb', line 220

def each_sha1
  with_idx do |idx|
    if @version == 2
      data = read_data_v2(idx)
      data.each do |sha1, crc, offset|
        yield sha1
      end
    else
      pos = SHA1Start
      @size.times do
        sha1 = idx[pos,SHA1Size]
        pos += EntrySize
        yield sha1
      end
    end
  end
end

#find_object_in_index(idx, sha1) ⇒ Object 



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# File 'lib/git_store/pack.rb', line 238

def find_object_in_index(idx, sha1)
  slot = sha1[0]
  return nil if !slot
  first, last = @offsets[slot,2]
  while first < last
    mid = (first + last) / 2
    if @version == 2
      midsha1 = idx[OffsetStart + (mid * SHA1Size), SHA1Size]
      cmp = midsha1 <=> sha1

      if cmp < 0
        first = mid + 1
      elsif cmp > 0
        last = mid
      else
        pos = OffsetStart + (@size * (SHA1Size + CrcSize)) + (mid * OffsetSize)
        offset = idx[pos, OffsetSize].unpack('N')[0]
        return offset
      end
    else
      midsha1 = idx[SHA1Start + mid * EntrySize,SHA1Size]
      cmp = midsha1 <=> sha1

      if cmp < 0
        first = mid + 1
      elsif cmp > 0
        last = mid
      else
        pos = OffsetStart + mid * EntrySize
        offset = idx[pos,OffsetSize].unpack('N')[0]
        return offset
      end
    end
  end
  nil
end

#get_shas ⇒ Object

given an index file, list out the shas that it’s packfile contains



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# File 'lib/git_store/pack.rb', line 149

def get_shas
  shas = []
  each_sha1 { |sha| shas << sha.unpack("H*")[0] }
  shas
end

#init_pack ⇒ Object 



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# File 'lib/git_store/pack.rb', line 166

def init_pack
  with_idx do |idx|
    @offsets = [0]
    FanOutCount.times do |i|
      pos = idx[i * IdxOffsetSize,IdxOffsetSize].unpack('N')[0]
      if pos < @offsets[i]
        raise PackFormatError, "pack #@name has discontinuous index #{i}"
      end
      @offsets << pos
    end
    @size = @offsets[-1]
  end
end

#name ⇒ Object 



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# File 'lib/git_store/pack.rb', line 140

def name
  @name
end

#parse_object(offset) ⇒ Object 



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# File 'lib/git_store/pack.rb', line 284

def parse_object(offset)
  data, type = with_packfile do |packfile|
    unpack_object(packfile, offset)
  end

  return data, OBJ_TYPES[type]
end

#with_idx(index_file = nil) {|idx| ... } ⇒ Object

Yields:

  • (idx) 


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# File 'lib/git_store/pack.rb', line 93

def with_idx(index_file = nil)
  if !index_file
    index_file = @name
    idxfile = File.open(@name[0...-4]+'idx')
  else
    idxfile = File.open(index_file)
  end

  # read header
  sig = idxfile.read(4)
  ver = idxfile.read(4).unpack("N")[0]

  if sig == PACK_IDX_SIGNATURE
    if(ver != 2)
      raise PackFormatError, "pack #@name has unknown pack file version #{ver}"
    end
    @version = 2
  else
    @version = 1
  end

  idx = Mmap.new(idxfile, @version)
  yield idx
  idx.unmap
  idxfile.close
end

#with_packfile ⇒ Object 



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# File 'lib/git_store/pack.rb', line 120

def with_packfile
  packfile = File.open(@name)
  result = yield packfile
  packfile.close

  result
end