Method: LZ4::StreamDecoder#initialize

Defined in:
lib/extlz4/oldstream.rb

#initialize(io) ⇒ StreamDecoder

Returns a new instance of StreamDecoder.



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# File 'lib/extlz4/oldstream.rb', line 359

def initialize(io)
  magic = io.read(4).unpack("V")[0]
  case magic
  when MAGIC_NUMBER
    sf = io.getbyte
    @version = (sf >> 6) & 0x03
    raise "stream header error - wrong version number" unless @version == 0x01
    @blockindependence = ((sf >> 5) & 0x01) == 0 ? false : true
    @blockchecksum = ((sf >> 4) & 0x01) == 0 ? false : true
    streamsize = ((sf >> 3) & 0x01) == 0 ? false : true
    @streamchecksum = ((sf >> 2) & 0x01) == 0 ? false : true
    # reserved = (sf >> 1) & 0x01
    presetdict = ((sf >> 0) & 0x01) == 0 ? false : true

    bd = io.getbyte
    # reserved = (bd >> 7) & 0x01
    blockmax = (bd >> 4) & 0x07
    # reserved = (bd >> 0) & 0x0f

    @blockmaximum = BLOCK_MAXIMUM_SIZES[blockmax]
    raise Error, "stream header error - wrong block maximum size (#{blockmax} for 4 .. 7)" unless @blockmaximum

    @streamsize = io.read(8).unpack("Q<")[0] if streamsize
    @presetdict = io.read(4).unpack("V")[0] if presetdict

    headerchecksum = io.getbyte

    if @blockindependence
      @decoder = LZ4.method(:block_decode)
    else
      @decoder = LZ4::BlockDecoder.new.method(:update)
    end
  when MAGIC_NUMBER_LEGACY
    @version = -1
    @blockindependence = true
    @blockchecksum = false
    @streamchecksum = false
    @blockmaximum = 1 << 23 # 8 MiB
    @streamsize = nil
    @presetdict = nil
    @decoder = LZ4.method(:block_decode)
  else
    raise Error, "stream header error - wrong magic number"
  end

  @io = io
  @pos = 0

  @readbuf = "".b
  @decodebuf = "".b
end