Class: Omnizip::Implementations::SevenZip::LZMA2::Encoder

Inherits:
Base::LZMA2EncoderBase show all
Includes:
Algorithms::LZMA2Const
Defined in:
lib/omnizip/implementations/seven_zip/lzma2/encoder.rb

Overview

7-Zip SDK LZMA2 encoder implementation.

This encoder produces LZMA2 compressed data compatible with 7-Zip format. It uses the same LZMA encoding logic as XZ Utils, but with 7-Zip format requirements (no EOS marker, no padding).

Key differences from XZ Utils implementation:

  • No EOS marker (raw LZMA2 data ends with 0x00 control byte)
  • No chunk padding (XZ pads to 4-byte boundary)
  • No LZMA2 property byte in data stream (method ID only in container)

Based on LZMA SDK by Igor Pavlov Reference: https://www.7-zip.org/sdk.html

LZMA2 format (as used by 7-Zip):

  • Control byte specifies chunk type and dictionary reset
  • Dictionary size follows in some chunk types
  • Uncompressed size follows in some chunk types
  • Compressed data follows

Defined Under Namespace

Modules: StringCompat

Constant Summary collapse

MAX_UNCOMPRESSED_CHUNK =

Maximum chunk sizes (from LZMA2 specification)

2 * 1024 * 1024
MAX_COMPRESSED_CHUNK =

2MB

64 * 1024
UINT32_MAX =

Encoding constants

0xFFFFFFFF
REPS = 
4
MATCH_LEN_MIN = 
2

Constants included from Algorithms::LZMA2Const

Algorithms::LZMA2Const::CHUNK_MAX, Algorithms::LZMA2Const::CONTROL_END, Algorithms::LZMA2Const::CONTROL_LZMA_MIN, Algorithms::LZMA2Const::CONTROL_UNCOMPRESSED, Algorithms::LZMA2Const::CONTROL_UNCOMPRESSED_RESET, Algorithms::LZMA2Const::DICT_SIZE_MAX, Algorithms::LZMA2Const::DICT_SIZE_MIN, Algorithms::LZMA2Const::FLAG_RESET_DICT, Algorithms::LZMA2Const::FLAG_RESET_PROPERTIES, Algorithms::LZMA2Const::FLAG_RESET_STATE, Algorithms::LZMA2Const::FLAG_UNCOMPRESSED_SIZE, Algorithms::LZMA2Const::HEADER_MAX, Algorithms::LZMA2Const::HEADER_UNCOMPRESSED, Algorithms::LZMA2Const::UNCOMPRESSED_MAX

Constants inherited from Base::LZMA2EncoderBase

Base::LZMA2EncoderBase::COMPRESSED_MAX, Base::LZMA2EncoderBase::UNCOMPRESSED_MAX

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Base::LZMA2EncoderBase

#standalone?

Constructor Details

#initialize(dict_size:, lc: 3, lp: 0, pb: 2, standalone: false) ⇒ Encoder

Initialize 7-Zip SDK LZMA2 encoder

Parameters:

  • dict_size (Integer) —

    Dictionary size (must be power of 2)

  • lc (Integer) (defaults to: 3) —

    Literal context bits (0-8)

  • lp (Integer) (defaults to: 0) —

    Literal position bits (0-4)

  • pb (Integer) (defaults to: 2) —

    Position bits (0-4)

  • standalone (Boolean) (defaults to: false) —

    Include property byte (false for 7-Zip)



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# File 'lib/omnizip/implementations/seven_zip/lzma2/encoder.rb', line 69

def initialize(dict_size:, lc: 3, lp: 0, pb: 2, standalone: false)
  super

  # Initialize shared state across all chunks
  # Using XZ Utils components (tested and working)

  @dictionary = Omnizip::Algorithms::LZMA::Dictionary.new(dict_size)
  @state = Omnizip::Algorithms::LZMA::LZMAState.new(0)
  @models = Omnizip::Algorithms::LZMA::XzProbabilityModels.new(lc,
                                                               lp, pb)
  @match_finder = Omnizip::Algorithms::LZMA::MatchFinder.new(@dictionary)
  @optimal = Omnizip::Algorithms::LZMA::OptimalEncoder.new(mode: :fast)

  # Track previous byte for literal context
  @prev_byte = 0

  # First chunk always resets dictionary (7-Zip compatibility)
  @need_dictionary_reset = true
  @need_state_reset = false
  @need_properties = true
end

Instance Attribute Details

#dict_size ⇒ Object (readonly)

Returns the value of attribute dict_size.



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# File 'lib/omnizip/implementations/seven_zip/lzma2/encoder.rb', line 60

def dict_size
  @dict_size
end

#lc ⇒ Object (readonly)

Returns the value of attribute lc.



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# File 'lib/omnizip/implementations/seven_zip/lzma2/encoder.rb', line 60

def lc
  @lc
end

#lp ⇒ Object (readonly)

Returns the value of attribute lp.



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# File 'lib/omnizip/implementations/seven_zip/lzma2/encoder.rb', line 60

def lp
  @lp
end

#pb ⇒ Object (readonly)

Returns the value of attribute pb.



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# File 'lib/omnizip/implementations/seven_zip/lzma2/encoder.rb', line 60

def pb
  @pb
end

#standalone ⇒ Object (readonly)

Returns the value of attribute standalone.



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# File 'lib/omnizip/implementations/seven_zip/lzma2/encoder.rb', line 60

def standalone
  @standalone
end

Instance Method Details

#encode(data) ⇒ String

Encode data with LZMA2 compression

Parameters:

  • data (String) —

    Input data to compress

Returns:

  • (String) —

    LZMA2 compressed data (7-Zip format)



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# File 'lib/omnizip/implementations/seven_zip/lzma2/encoder.rb', line 95

def encode(data)
  return "" if data.empty?

  output = StringIO.new
  output.set_encoding(Encoding::BINARY)

  # Write property byte if standalone mode
  if @standalone
    prop_byte = encode_dict_size(@dict_size)
    output.putc(prop_byte)
  end

  # Reset match finder state for each encoding session
  @match_finder.reset

  # Process in chunks
  input = StringIO.new(data)
  input.set_encoding(Encoding::BINARY)

  while !input.eof?
    chunk_data = input.read(MAX_UNCOMPRESSED_CHUNK)
    break if chunk_data.nil? || chunk_data.empty?

    chunk = encode_chunk(chunk_data)
    output.write(chunk)

    # Update reset flags for next chunk
    @need_dictionary_reset = false
    @need_state_reset = false
    @need_properties = false
  end

  # End of stream marker (0x00)
  output.write(Omnizip::Algorithms::LZMA2::LZMA2Chunk.end_chunk.to_bytes)

  output.string
end

#implementation_name ⇒ Symbol

Get implementation identifier

Returns:

  • (Symbol) —

    :seven_zip_sdk



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# File 'lib/omnizip/implementations/seven_zip/lzma2/encoder.rb', line 136

def implementation_name
  :seven_zip_sdk
end