Class: LZ4::StreamDecoder

Inherits:
Object
  • Object
show all
Includes:
BasicStream
Defined in:
lib/extlz4/oldstream.rb

Overview

LZ4 ストリームを伸張するためのクラスです。

Constant Summary

Constants included from BasicStream

BasicStream::BLOCK_CHECKSUM, BasicStream::BLOCK_INDEPENDENCY, BasicStream::BLOCK_MAXIMUM_SIZES, BasicStream::LITERAL_DATA_BLOCK_FLAG, BasicStream::MAGIC_NUMBER, BasicStream::MAGIC_NUMBER_LEGACY, BasicStream::PRESET_DICTIONARY, BasicStream::STREAM_CHECKSUM, BasicStream::STREAM_SIZE, BasicStream::VERSION_NUMBER, BasicStream::VERSION_NUMBER_MASK

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#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

Instance Attribute Details

#blockchecksum ⇒ Object (readonly)

Returns the value of attribute blockchecksum.



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# File 'lib/extlz4/oldstream.rb', line 353

def blockchecksum
  @blockchecksum
end

#blockindependence ⇒ Object (readonly)

Returns the value of attribute blockindependence.



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# File 'lib/extlz4/oldstream.rb', line 352

def blockindependence
  @blockindependence
end

#blockmaximum ⇒ Object (readonly)

Returns the value of attribute blockmaximum.



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# File 'lib/extlz4/oldstream.rb', line 355

def blockmaximum
  @blockmaximum
end

#presetdict ⇒ Object (readonly)

Returns the value of attribute presetdict.



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# File 'lib/extlz4/oldstream.rb', line 357

def presetdict
  @presetdict
end

#streamchecksum ⇒ Object (readonly)

Returns the value of attribute streamchecksum.



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# File 'lib/extlz4/oldstream.rb', line 354

def streamchecksum
  @streamchecksum
end

#streamsize ⇒ Object (readonly)

Returns the value of attribute streamsize.



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# File 'lib/extlz4/oldstream.rb', line 356

def streamsize
  @streamsize
end

#version ⇒ Object (readonly)

Returns the value of attribute version.



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# File 'lib/extlz4/oldstream.rb', line 351

def version
  @version
end

Instance Method Details

#close ⇒ Object 



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# File 'lib/extlz4/oldstream.rb', line 411

def close
  @io = nil
end

#eof ⇒ Object Also known as: eof? 



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# File 'lib/extlz4/oldstream.rb', line 439

def eof
  !@pos
end

#getbyte ⇒ Object 



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# File 'lib/extlz4/oldstream.rb', line 434

def getbyte
  w = read(1) or return nil
  w.getbyte(0)
end

#pos ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/extlz4/oldstream.rb', line 453

def pos
  raise NotImplementedError
end

#pos=(pos) ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/extlz4/oldstream.rb', line 457

def pos=(pos)
  raise NotImplementedError
end

#read(*args) ⇒ Object

call-seq:

read -> string or nil
read(size) -> string or nil
read(size, dest) -> string or nil



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# File 'lib/extlz4/oldstream.rb', line 421

def read(*args)
  case args.size
  when 0
    read_all
  when 1
    read_part(args[0].to_i, "")
  when 2
    read_part(args[0].to_i, args[1])
  else
    raise ArgumentError, "wrong number of arguments (#{args.size} for 0 .. 2)"
  end
end

#seek(off, cur) ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/extlz4/oldstream.rb', line 449

def seek(off, cur)
  raise NotImplementedError
end

#tell ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/extlz4/oldstream.rb', line 445

def tell
  raise NotImplementedError
end