Module: LZString::Custom

Included in:
LZString
Defined in:
lib/lzstring/custom.rb

Overview

Module for custom encoding/decoding

Class Method Summary collapse

Class Method Details

.compress_to_custom(input, key_str) ⇒ String

Compress a string to custom encoding

Parameters:

  • input (String) —

    String to compress

  • key_str (String) —

    Custom key string for compression

Returns:

  • (String) —

    Compressed string with custom encoding



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# File 'lib/lzstring/custom.rb', line 8

def self.compress_to_custom(input, key_str)
  return "" if input.nil? || input.empty? || key_str.nil? || key_str.empty?

  begin
    # Force input to UTF-8 encoding
    input = input.to_s.dup.force_encoding(Encoding::UTF_8)
    key_str = key_str.to_s.dup.force_encoding(Encoding::UTF_8)

    # Validate key string length
    raise ArgumentError, "Custom key string must have at least 2 characters" if key_str.length < 2

    res_str = ""
    val = 0
    c = 0

    # Use the _compress function with custom parameters
    LZString._compress(input, 6) do |a|
      val = (val << 6) | a
      c += 6

      while c >= 6
        c -= 6
        index = (val >> c) & 63
        res_str += begin
          key_str[index].chr
        rescue
          "?"
        end
      end

      a
    end

    # Handle remaining bits
    if c.positive?
      res_str += begin
        key_str[((val << 6) >> c) & 63].chr
      rescue
        "?"
      end
    end

    res_str
  rescue
    # Log error and return empty string on failure
    # STDERR.puts "Custom compression error: #{e.message}"
    ""
  end
end

.decompress_from_custom(input, key_str) ⇒ String?

Decompress a string from custom encoding

Parameters:

  • input (String) —

    Compressed string with custom encoding

  • key_str (String) —

    Custom key string used for compression

Returns:

  • (String, nil) —

    Decompressed string or nil if decompression fails



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# File 'lib/lzstring/custom.rb', line 62

def self.decompress_from_custom(input, key_str)
  return "" if input.nil? || input.empty? || key_str.nil? || key_str.empty?

  begin
    # Force input to UTF-8 encoding
    input = input.to_s.dup.force_encoding(Encoding::UTF_8)
    key_str = key_str.to_s.dup.force_encoding(Encoding::UTF_8)

    # Validate key string length
    raise ArgumentError, "Custom key string must have at least 2 characters" if key_str.length < 2

    # Create a reverse mapping for the key string
    reverse_dict = {}
    key_str.chars.each_with_index do |char, index|
      reverse_dict[char] = index
    end

    # Use the _decompress function with custom parameters
    result = LZString._decompress(input.length, 32) do |index|
      if index >= input.length
        0
      else
        char = input[index]
        if reverse_dict.key?(char)
          reverse_dict[char]
        else
          0 # Use 0 for characters not in the key string
        end
      end
    end

    # Ensure proper UTF-8 encoding of the result
    if result.is_a?(String)
      # Force UTF-8 encoding and replace invalid bytes
      result.force_encoding(Encoding::UTF_8)

      # Check if the result is valid UTF-8, if not try to repair
      unless result.valid_encoding?
        # Replace invalid sequences with a replacement character
        result = result.encode(Encoding::UTF_8,
                               Encoding::UTF_8,
                               invalid: :replace,
                               undef: :replace,
                               replace: "?")
      end

    end
    result
  rescue
    # Log error and return nil on failure
    # STDERR.puts "Custom decompression error: #{e.message}"
    nil
  end
end