Class: Cabriolet::LIT::Decompressor

Inherits:
Object
  • Object
show all
Defined in:
lib/cabriolet/lit/decompressor.rb

Overview

Decompressor is the main interface for LIT file operations

LIT files are Microsoft Reader eBook files that use LZX compression.

NOTE: This implementation handles non-encrypted LIT files only. DES-encrypted (DRM-protected) LIT files are not supported. For encrypted files, use Microsoft Reader or convert to another format first.

Constant Summary collapse

DEFAULT_BUFFER_SIZE =

Input buffer size for decompression

32_768

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(io_system = nil) ⇒ Decompressor

Initialize a new LIT decompressor

Parameters:

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

    Custom I/O system or nil for default



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# File 'lib/cabriolet/lit/decompressor.rb', line 24

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

Instance Attribute Details

#buffer_size ⇒ Object

Returns the value of attribute buffer_size.



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# File 'lib/cabriolet/lit/decompressor.rb', line 15

def buffer_size
  @buffer_size
end

#io_system ⇒ Object (readonly)

Returns the value of attribute io_system.



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# File 'lib/cabriolet/lit/decompressor.rb', line 14

def io_system
  @io_system
end

Instance Method Details

#close(_header) ⇒ void

This method returns an undefined value.

Close a LIT file (no-op for compatibility)

Parameters:



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# File 'lib/cabriolet/lit/decompressor.rb', line 53

def close(_header)
  # No resources to free in the header itself
  # File handles are managed separately during extraction
  nil
end

#extract(header, file, output_path) ⇒ Integer

Extract a file from LIT archive

Parameters:

  • header (Models::LITHeader) —

    LIT header from open()

  • file (Models::LITFile) —

    File entry to extract

  • output_path (String) —

    Where to write the decompressed file

Returns:

  • (Integer) —

    Number of bytes written

Raises:

  • (Errors::DecompressionError) —

    if decompression fails

  • (NotImplementedError) —

    if the file is encrypted



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# File 'lib/cabriolet/lit/decompressor.rb', line 67

def extract(header, file, output_path)
  raise ArgumentError, "Header must not be nil" unless header
  raise ArgumentError, "File must not be nil" unless file
  raise ArgumentError, "Output path must not be nil" unless output_path

  if file.encrypted?
    raise NotImplementedError,
          "DES-encrypted files not yet supported. " \
          "Use Microsoft Reader or another tool to decrypt first."
  end

  input_handle = @io_system.open(header.filename, Constants::MODE_READ)
  output_handle = @io_system.open(output_path, Constants::MODE_WRITE)

  begin
    # Seek to file data
    @io_system.seek(input_handle, file.offset, Constants::SEEK_START)

    bytes_written = if file.compressed?
                      # Decompress using LZX
                      decompress_lzx(
                        input_handle, output_handle, file.length
                      )
                    else
                      # Direct copy
                      copy_data(
                        input_handle, output_handle, file.length
                      )
                    end

    bytes_written
  ensure
    @io_system.close(input_handle) if input_handle
    @io_system.close(output_handle) if output_handle
  end
end

#extract_all(header, output_dir) ⇒ Integer

Extract all files from LIT archive

Parameters:

  • header (Models::LITHeader) —

    LIT header from open()

  • output_dir (String) —

    Directory to extract files to

Returns:

  • (Integer) —

    Number of files extracted

Raises:

  • (Errors::DecompressionError) —

    if extraction fails



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# File 'lib/cabriolet/lit/decompressor.rb', line 110

def extract_all(header, output_dir)
  raise ArgumentError, "Header must not be nil" unless header
  raise ArgumentError, "Output dir must not be nil" unless output_dir

  # Create output directory if it doesn't exist
  ::FileUtils.mkdir_p(output_dir)

  extracted = 0
  header.files.each do |file|
    output_path = ::File.join(output_dir, file.filename)

    # Create subdirectories if needed
    file_dir = ::File.dirname(output_path)
    ::FileUtils.mkdir_p(file_dir) unless ::File.directory?(file_dir)

    extract(header, file, output_path)
    extracted += 1
  end

  extracted
end

#open(filename) ⇒ Models::LITHeader

Open and parse a LIT file

Parameters:

  • filename (String) —

    Path to the LIT file

Returns:

Raises:

  • (Errors::ParseError) —

    if the file is not a valid LIT

  • (NotImplementedError) —

    if the file is DES-encrypted



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# File 'lib/cabriolet/lit/decompressor.rb', line 35

def open(filename)
  header = parse_header(filename)
  header.filename = filename

  # Check for encryption
  if header.encrypted?
    raise NotImplementedError,
          "DES-encrypted LIT files not yet supported. " \
          "Use Microsoft Reader or another tool to decrypt first."
  end

  header
end