Class: LZ4::BasicStream::Header

Inherits:
Struct
  • Object
show all
Defined in:
lib/extlz4/oldstream.rb,
lib/extlz4/oldstream.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#blockchecksum ⇒ Object

Returns the value of attribute blockchecksum

Returns:

  • (Object) —

    the current value of blockchecksum



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# File 'lib/extlz4/oldstream.rb', line 121

def blockchecksum
  @blockchecksum
end

#blockindependence ⇒ Object

Returns the value of attribute blockindependence

Returns:

  • (Object) —

    the current value of blockindependence



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# File 'lib/extlz4/oldstream.rb', line 121

def blockindependence
  @blockindependence
end

#blocksize ⇒ Object

Returns the value of attribute blocksize

Returns:

  • (Object) —

    the current value of blocksize



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# File 'lib/extlz4/oldstream.rb', line 121

def blocksize
  @blocksize
end

#magic ⇒ Object

Returns the value of attribute magic

Returns:

  • (Object) —

    the current value of magic



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# File 'lib/extlz4/oldstream.rb', line 121

def magic
  @magic
end

#predictid ⇒ Object

Returns the value of attribute predictid

Returns:

  • (Object) —

    the current value of predictid



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# File 'lib/extlz4/oldstream.rb', line 121

def predictid
  @predictid
end

#streamchecksum ⇒ Object

Returns the value of attribute streamchecksum

Returns:

  • (Object) —

    the current value of streamchecksum



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# File 'lib/extlz4/oldstream.rb', line 121

def streamchecksum
  @streamchecksum
end

#streamsize ⇒ Object

Returns the value of attribute streamsize

Returns:

  • (Object) —

    the current value of streamsize



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# File 'lib/extlz4/oldstream.rb', line 121

def streamsize
  @streamsize
end

#version ⇒ Object

Returns the value of attribute version

Returns:

  • (Object) —

    the current value of version



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# File 'lib/extlz4/oldstream.rb', line 121

def version
  @version
end

Class Method Details

.load(io) ⇒ Object 



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# File 'lib/extlz4/oldstream.rb', line 131

def self.load(io)
  case magic = io.read(4).unpack("V")
  when MAGIC_NUMBER_LEGACY
    new(magic, -1, true, false, false, 8 * 1024 * 1024, nil, nil)
  when MAGIC_NUMBER
    (sf, bd) = io.read(2).unpack("CC")
    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
    predictid = ((sf >> 0) & 0x01) == 0 ? false : true

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

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

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

    headerchecksum = io.getbyte

    new(magic, version, blockindependence, blockchecksum, streamchecksum, blocksize, streamsize, predictid)
  else
    raise "could not recognized magic number (0x%08x)" % (magic || nil)
  end
end

.pack(*args) ⇒ Object 



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# File 'lib/extlz4/oldstream.rb', line 164

def self.pack(*args)
  new(*args).pack
end

Instance Method Details

#pack ⇒ Object 



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# File 'lib/extlz4/oldstream.rb', line 168

def pack
  raise "wrong magic number" unless magic == MAGIC_NUMBER
  raise "wrong version number" unless version == VERSION_NUMBER

  header = [magic].pack("V")
  sd = version |
       (blockindependence ? BLOCK_INDEPENDENCY : 0) |
       (blockchecksum ? BLOCK_CHECKSUM : 0) |
       (streamsize ? STREAM_SIZE : 0) |
       (streamchecksum ? STREAM_CHECKSUM : 0) |
       (predictid ? PRESET_DICTIONARY : 0)
  bd = (BLOCK_MAXIMUM_SIZES.rassoc(blocksize)[0] << 4)
  desc = [sd, bd].pack("CC")
  header << desc
  header << [streamsize].pack("Q<") if streamsize
  header << [predictid].pack("V") if predictid
  header << [XXhash.xxh32(desc) >> 8].pack("C")
end