Class: GitDB::Pack

Inherits:
Object
  • Object
show all
Defined in:
lib/git-db/pack.rb

Defined Under Namespace

Classes: PackObject

Instance Attribute Summary (collapse)

Instance Method Summary (collapse)

Constructor Details

- (Pack) initialize(io)

A new instance of Pack



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# File 'lib/git-db/pack.rb', line 11

def initialize(io)
  @io = GitDB::Utility::CountingIO.new(io)
end

Instance Attribute Details

- (Object) io (readonly)

Returns the value of attribute io



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# File 'lib/git-db/pack.rb', line 9

def io
  @io
end

Instance Method Details

- (Object) read 



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# File 'lib/git-db/pack.rb', line 15

def read
  header = io.read(12)
  return nil unless header

  signature, version, entries = header.unpack("a4NN")
  raise 'invalid pack signature' unless signature == 'PACK'
  raise 'invalid version'        unless version   == 2

  objects = {}

  1.upto(entries) do
    object_offset = io.offset
    type, size    = unpack_pack_header(io)

    object = case type
      when 1 then GitDB::Objects::Commit.new(read_compressed(io))
      when 2 then GitDB::Objects::Tree.new(read_compressed(io))
      when 3 then GitDB::Objects::Blob.new(read_compressed(io))
      when 4 then GitDB::Objects::Tag.new(read_compressed(io))
      when 5 then raise 'Invalid Type: 5'
      when 6 then
        # offset delta, find the referred-to pack and apply as a patch
        offset = object_offset - unpack_delta_size(io)
        patch  = read_compressed(io)
        base   = objects[offset]
        data   = apply_patch(base.data, patch)
        base.class.new(data)
      when 7 then
        # TODO: patch against sha
        raise "Type 7 unimplemented, please report"
    end

    objects[object_offset] = object
  end

  # read the checksum, TODO: check the checksum
  checksum = io.read(20)

  objects.values.compact
end

- (Object) write(entries) 



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# File 'lib/git-db/pack.rb', line 56

def write(entries)
  # build the pack header
  buffer = ["PACK", 2, entries.length].pack("a4NN")

  # deflate the entries
  entries.each do |entry|
    buffer << pack_pack_header(entry.type, entry.data.length)
    buffer << Zlib::Deflate.deflate(entry.data)
  end

  # calculate a checksum
  checksum = GitDB::hex_to_sha1(Digest::SHA1.hexdigest(buffer))

  # write and flush the buffer
  io.write(buffer)
  io.write(checksum)
  io.flush
end