class HuffmanCoding
Constants
- VERSION
Attributes
binary[R]
code_table[R]
last_byte_bits[R]
Public Class Methods
decode(coding)
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# File lib/huffman_coding.rb, line 36 def decode(coding) text = String.new code_table = coding.code_table.invert previous = String.new add_binary_char = proc do |binary_char| previous << binary_char if (char = code_table[previous]) text << char previous = String.new end end bytes = coding.binary.bytes.map{|s| s.to_s(2) } # bytes = ['101000', '11', '10101111', ...] last_byte = bytes.pop bytes.each do |byte| (8 - byte.size).times{ add_binary_char['0'] } byte.each_char{|s| add_binary_char[s] } end (coding.last_byte_bits - last_byte.size).times{ add_binary_char['0'] } last_byte.each_char{|s| add_binary_char[s] } return text end
encode(input_array, frequencies = HuffmanCoding::Utils.tally(input_array))
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# File lib/huffman_coding.rb, line 21 def encode(input_array, frequencies = HuffmanCoding::Utils.tally(input_array)) if frequencies.size == 1 code_table = { frequencies.keys[0] => '0' } else code_table = {} build_tree(frequencies).traverse('', code_table) end result_binary_string = input_array.map{|char| code_table[char] }.join last_byte_bits = result_binary_string.size % 8 last_byte_bits = 8 if last_byte_bits == 0 binary = result_binary_string.scan(/.{1,8}/).map{|s| s.to_i(2) }.pack('C*') return new(binary, last_byte_bits, code_table) end
new(binary, last_byte_bits, code_table)
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# File lib/huffman_coding.rb, line 13 def initialize(binary, last_byte_bits, code_table) @binary = binary @last_byte_bits = last_byte_bits @code_table = code_table.freeze end
Private Class Methods
build_tree(frequencies)
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# File lib/huffman_coding.rb, line 65 def build_tree(frequencies) level_nodes = LevelNodes.new(frequencies.map{|letter, frequency| Node.new(letter, frequency) }) while level_nodes.size > 1 left_level, left_node = level_nodes.pop_min_node right_level, right_node = level_nodes.pop_min_node next_level = (left_level > right_level ? left_level : right_level) + 1 new_node = Node.new(nil, left_node.weight + right_node.weight, left_node, right_node) level_nodes.push_node(next_level, new_node) end return new_node end