Class: Cabriolet::HLP::QuickHelp::TopicCompressor

Inherits:
Object
  • Object
show all
Defined in:
lib/cabriolet/hlp/quickhelp/topic_compressor.rb

Overview

Compresses topic text using QuickHelp keyword compression

Class Method Summary collapse

Class Method Details

.compress_topic(text) ⇒ Hash

Compress topic text using QuickHelp keyword compression

QuickHelp format uses:

  • 0x00-0x0F: Literal bytes

  • 0x10-0x17: Dictionary entry references

  • 0x18: Run of spaces

  • 0x19: Run of bytes (repeat)

  • 0x1A: Escape byte (next byte is literal)

  • 0x1B-0xFF: Literal bytes

Without a dictionary, we encode literals directly and escape control characters (0x10-0x1A) with 0x1A prefix.

Topic text format:

  • Each line: [len][newline][attrs]

  • len includes itself, text, newline, attr_len

  • attr_len includes itself and attrs, minimum 1 (just 0xFF terminator)



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# File 'lib/cabriolet/hlp/quickhelp/topic_compressor.rb', line 28

def self.compress_topic(text)
  topic_data = TopicBuilder.build_topic_data(text)
  encoded = encode_keyword_compression(topic_data)

  # Prepend decompressed length (2 bytes)
  length_header = [topic_data.bytesize].pack("v")

  {
    text: text,
    compressed: length_header + encoded,
    decompressed_length: topic_data.bytesize,
    compressed_length: (length_header + encoded).bytesize,
  }
end

.encode_keyword_compression(data) ⇒ String

Encode data using QuickHelp keyword compression format



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# File 'lib/cabriolet/hlp/quickhelp/topic_compressor.rb', line 62

def self.encode_keyword_compression(data)
  result = +""

  data.bytes.each do |byte|
    if byte < 0x10 || byte == 0x1B || byte > 0x1A
      # Literal byte (except control range 0x10-0x1A)
      result << byte.chr
    elsif byte.between?(0x10, 0x1A)
      # Control byte - escape it
      result << 0x1A.chr << byte.chr
    else
      # 0x1B is also literal (above control range)
      result << byte.chr
    end
  end

  result
end

.store_uncompressed(text) ⇒ Hash

Store topic without compression



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# File 'lib/cabriolet/hlp/quickhelp/topic_compressor.rb', line 47

def self.store_uncompressed(text)
  topic_data = TopicBuilder.build_topic_data(text)

  {
    text: text,
    compressed: topic_data,
    decompressed_length: topic_data.bytesize,
    compressed_length: topic_data.bytesize,
  }
end