Class: Cabriolet::SZDD::Compressor

Inherits:
Object
  • Object
show all
Defined in:
lib/cabriolet/szdd/compressor.rb

Overview

Compressor creates SZDD compressed files

SZDD files wrap LZSS-compressed data with a header containing metadata about the original file. The compressor supports both NORMAL (used by MS-DOS EXPAND.EXE) and QBASIC formats.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(io_system = nil) ⇒ Compressor

Initialize a new SZDD compressor

Parameters:

  • io_system (System::IOSystem, nil) (defaults to: nil) —

    Custom I/O system or nil for default



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# File 'lib/cabriolet/szdd/compressor.rb', line 17

def initialize(io_system = nil)
  @io_system = io_system || System::IOSystem.new
end

Instance Attribute Details

#io_system ⇒ Object (readonly)

Returns the value of attribute io_system.



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# File 'lib/cabriolet/szdd/compressor.rb', line 11

def io_system
  @io_system
end

Instance Method Details

#compress(input_file, output_file, **options) ⇒ Integer

Compress a file to SZDD format

Parameters:

  • input_file (String) —

    Path to input file

  • output_file (String) —

    Path to output SZDD file

  • options (Hash) —

    Compression options

Options Hash (**options):

  • :missing_char (String) —

    Last character of original filename for reconstruction

  • :format (Symbol) —

    Format to use (:normal or :qbasic, default: :normal)

Returns:

  • (Integer) —

    Bytes written to output file

Raises:

  • (Errors::CompressionError) —

    if compression fails



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# File 'lib/cabriolet/szdd/compressor.rb', line 32

def compress(input_file, output_file, **options)
  format = options.fetch(:format, :normal)
  missing_char = options[:missing_char]

  validate_format(format)
  validate_missing_char(missing_char) if missing_char

  input_handle = @io_system.open(input_file, Constants::MODE_READ)
  output_handle = @io_system.open(output_file, Constants::MODE_WRITE)

  begin
    # Get input size
    input_size = @io_system.seek(input_handle, 0, Constants::SEEK_END)
    @io_system.seek(input_handle, 0, Constants::SEEK_START)

    # Write header
    header_bytes = write_header(
      output_handle,
      format,
      input_size,
      missing_char,
    )

    # Compress data using LZSS
    lzss_mode = if format == :normal
                  Compressors::LZSS::MODE_EXPAND
                else
                  Compressors::LZSS::MODE_QBASIC
                end

    compressor = Compressors::LZSS.new(
      @io_system,
      input_handle,
      output_handle,
      2048,
      lzss_mode,
    )

    compressed_bytes = compressor.compress

    header_bytes + compressed_bytes
  ensure
    @io_system.close(input_handle) if input_handle
    @io_system.close(output_handle) if output_handle
  end
end

#compress_data(data, output_file, **options) ⇒ Integer

Compress data from memory to SZDD format

Parameters:

  • data (String) —

    Input data to compress

  • output_file (String) —

    Path to output SZDD file

  • options (Hash) —

    Compression options

Options Hash (**options):

  • :missing_char (String) —

    Last character of original filename

  • :format (Symbol) —

    Format to use (:normal or :qbasic, default: :normal)

Returns:

  • (Integer) —

    Bytes written to output file

Raises:

  • (Errors::CompressionError) —

    if compression fails



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# File 'lib/cabriolet/szdd/compressor.rb', line 90

def compress_data(data, output_file, **options)
  format = options.fetch(:format, :normal)
  missing_char = options[:missing_char]

  validate_format(format)
  validate_missing_char(missing_char) if missing_char

  input_handle = System::MemoryHandle.new(data)
  output_handle = @io_system.open(output_file, Constants::MODE_WRITE)

  begin
    # Write header
    header_bytes = write_header(
      output_handle,
      format,
      data.bytesize,
      missing_char,
    )

    # Compress data using LZSS
    lzss_mode = if format == :normal
                  Compressors::LZSS::MODE_EXPAND
                else
                  Compressors::LZSS::MODE_QBASIC
                end

    compressor = Compressors::LZSS.new(
      @io_system,
      input_handle,
      output_handle,
      2048,
      lzss_mode,
    )

    compressed_bytes = compressor.compress

    header_bytes + compressed_bytes
  ensure
    @io_system.close(output_handle) if output_handle
  end
end