huffman.rb in protocol-hpack-1.5.0

- old
+ new

@@ -4,10 +4,11 @@
 # Copyright, 2014-2015, by Kaoru Maeda.
 # Copyright, 2015, by Ilya Grigorik.
 # Copyright, 2015, by Tamir Duberstein.
 # Copyright, 2018-2024, by Samuel Williams.
 # Copyright, 2022, by Daniel Morrison.
+# Copyright, 2024, by Nathan Froyd.
 
 require_relative 'huffman/machine'
 require_relative 'error'
 
 module Protocol
@@ -20,29 +21,30 @@
 			# Encodes provided value via huffman encoding.
 			# Length is not encoded in this method.
 			#
 			# @param str [String]
 			# @return [String] binary string
-			def encode(str)
+			def self.encode(str)
 				bitstring = str.each_byte.map {|chr| ENCODE_TABLE[chr]}.join
 				bitstring << '1' * ((8 - bitstring.size) % 8)
 				[bitstring].pack('B*')
 			end
 
 			# Decodes provided Huffman coded string.
 			#
 			# @param buf [Buffer]
 			# @return [String] binary string
 			# @raise [CompressionError] when Huffman coded string is malformed
-			def decode(buffer)
+			def self.decode(buffer)
 				emit = String.new.b
 				state = 0 # start state
 
 				mask = (1 << BITS_AT_ONCE) - 1
 				buffer.each_byte do |c|
-					(8 / BITS_AT_ONCE - 1).downto(0) do |shift|
-						branch = (c >> (shift * BITS_AT_ONCE)) & mask
+					shift = BITS_AT_ONCE
+					while shift >= 0
+						branch = (c >> shift) & mask
 						
 						# MACHINE[state] = [final, [transitions]]
 						#  [final] unfinished bits so far are prefix of the EOS code.
 						# Each transition is [emit, next]
 						#  [emit] character to be emitted on this transition, empty string, or EOS.
@@ -50,9 +52,10 @@
 						value, state = MACHINE[state][branch]
 						
 						raise CompressionError, 'Huffman decode error (EOS found)' if value == EOS
 						
 						emit << value.chr if value
+						shift -= BITS_AT_ONCE
 					end
 				end
 				# Check whether partial input is correctly filled
 				unless state <= MAX_FINAL_STATE
 					raise CompressionError, 'Huffman decode error (EOS invalid)'