huffman.rb in protocol-hpack-1.4.2

- old
+ new

@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 # Copyright, 2018, by Samuel G. D. Williams. <http://www.codeotaku.com>
 # Copyrigh, 2013, by Ilya Grigorik.
 # 
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -22,13 +24,11 @@
 require_relative 'huffman/machine'
 require_relative 'error'
 
 module Protocol
 	module HPACK
-		# Implementation of huffman encoding for HPACK
-		#
-		# - http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-10
+		# Implementation of huffman encoding for HPACK.
 		class Huffman
 			BITS_AT_ONCE = 4
 			EOS = 256
 
 			# Encodes provided value via huffman encoding.
@@ -45,38 +45,39 @@
 			# Decodes provided Huffman coded string.
 			#
 			# @param buf [Buffer]
 			# @return [String] binary string
 			# @raise [CompressionError] when Huffman coded string is malformed
-			def decode(buf)
-				emit = ''
+			def decode(buffer)
+				emit = String.new.b
 				state = 0 # start state
 
 				mask = (1 << BITS_AT_ONCE) - 1
-				buf.each_byte do |chr|
+				buffer.each_byte do |c|
 					(8 / BITS_AT_ONCE - 1).downto(0) do |shift|
-						branch = (chr >> (shift * BITS_AT_ONCE)) & mask
+						branch = (c >> (shift * BITS_AT_ONCE)) & 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.
 						#  [next] next state number.
-						trans = MACHINE[state][branch]
-						raise CompressionError, 'Huffman decode error (EOS found)' if trans.first == EOS
-						emit << trans.first.chr if trans.first
-						state = trans.last
+						value, state = MACHINE[state][branch]
+						
+						raise CompressionError, 'Huffman decode error (EOS found)' if value == EOS
+						
+						emit << value.chr if value
 					end
 				end
 				# Check whether partial input is correctly filled
 				unless state <= MAX_FINAL_STATE
 					raise CompressionError, 'Huffman decode error (EOS invalid)'
 				end
 				emit.force_encoding(Encoding::BINARY)
 			end
 
-			# Huffman table as specified in
-			# - http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-10#appendix-B
+			# Huffman table as specified in https://tools.ietf.org/html/rfc7541#appendix-B
 			CODES = [
 				[0x1ff8, 13],
 				[0x7fffd8, 23],
 				[0xfffffe2, 28],
 				[0xfffffe3, 28],
@@ -106,100 +107,100 @@
 				[0xffffff7, 28],
 				[0xffffff8, 28],
 				[0xffffff9, 28],
 				[0xffffffa, 28],
 				[0xffffffb, 28],
-				[0x14,  6],
+				[0x14, 6],
 				[0x3f8, 10],
 				[0x3f9, 10],
 				[0xffa, 12],
 				[0x1ff9, 13],
-				[0x15,  6],
-				[0xf8,  8],
+				[0x15, 6],
+				[0xf8, 8],
 				[0x7fa, 11],
 				[0x3fa, 10],
 				[0x3fb, 10],
-				[0xf9,  8],
+				[0xf9, 8],
 				[0x7fb, 11],
-				[0xfa,  8],
-				[0x16,  6],
-				[0x17,  6],
-				[0x18,  6],
-				[0x0,  5],
-				[0x1,  5],
-				[0x2,  5],
-				[0x19,  6],
-				[0x1a,  6],
-				[0x1b,  6],
-				[0x1c,  6],
-				[0x1d,  6],
-				[0x1e,  6],
-				[0x1f,  6],
-				[0x5c,  7],
-				[0xfb,  8],
+				[0xfa, 8],
+				[0x16, 6],
+				[0x17, 6],
+				[0x18, 6],
+				[0x0, 5],
+				[0x1, 5],
+				[0x2, 5],
+				[0x19, 6],
+				[0x1a, 6],
+				[0x1b, 6],
+				[0x1c, 6],
+				[0x1d, 6],
+				[0x1e, 6],
+				[0x1f, 6],
+				[0x5c, 7],
+				[0xfb, 8],
 				[0x7ffc, 15],
-				[0x20,  6],
+				[0x20, 6],
 				[0xffb, 12],
 				[0x3fc, 10],
 				[0x1ffa, 13],
-				[0x21,  6],
-				[0x5d,  7],
-				[0x5e,  7],
-				[0x5f,  7],
-				[0x60,  7],
-				[0x61,  7],
-				[0x62,  7],
-				[0x63,  7],
-				[0x64,  7],
-				[0x65,  7],
-				[0x66,  7],
-				[0x67,  7],
-				[0x68,  7],
-				[0x69,  7],
-				[0x6a,  7],
-				[0x6b,  7],
-				[0x6c,  7],
-				[0x6d,  7],
-				[0x6e,  7],
-				[0x6f,  7],
-				[0x70,  7],
-				[0x71,  7],
-				[0x72,  7],
-				[0xfc,  8],
-				[0x73,  7],
-				[0xfd,  8],
+				[0x21, 6],
+				[0x5d, 7],
+				[0x5e, 7],
+				[0x5f, 7],
+				[0x60, 7],
+				[0x61, 7],
+				[0x62, 7],
+				[0x63, 7],
+				[0x64, 7],
+				[0x65, 7],
+				[0x66, 7],
+				[0x67, 7],
+				[0x68, 7],
+				[0x69, 7],
+				[0x6a, 7],
+				[0x6b, 7],
+				[0x6c, 7],
+				[0x6d, 7],
+				[0x6e, 7],
+				[0x6f, 7],
+				[0x70, 7],
+				[0x71, 7],
+				[0x72, 7],
+				[0xfc, 8],
+				[0x73, 7],
+				[0xfd, 8],
 				[0x1ffb, 13],
 				[0x7fff0, 19],
 				[0x1ffc, 13],
 				[0x3ffc, 14],
-				[0x22,  6],
+				[0x22, 6],
 				[0x7ffd, 15],
-				[0x3,  5],
-				[0x23,  6],
-				[0x4,  5],
-				[0x24,  6],
-				[0x5,  5],
-				[0x25,  6],
-				[0x26,  6],
-				[0x27,  6],
-				[0x6,  5],
-				[0x74,  7],
-				[0x75,  7],
-				[0x28,  6],
-				[0x29,  6],
-				[0x2a,  6],
-				[0x7,  5],
-				[0x2b,  6],
-				[0x76,  7],
-				[0x2c,  6],
-				[0x8,  5],
-				[0x9,  5],
-				[0x2d,  6],
-				[0x77,  7],
-				[0x78,  7],
-				[0x79,  7],
-				[0x7a,  7],
-				[0x7b,  7],
+				[0x3, 5],
+				[0x23, 6],
+				[0x4, 5],
+				[0x24, 6],
+				[0x5, 5],
+				[0x25, 6],
+				[0x26, 6],
+				[0x27, 6],
+				[0x6, 5],
+				[0x74, 7],
+				[0x75, 7],
+				[0x28, 6],
+				[0x29, 6],
+				[0x2a, 6],
+				[0x7, 5],
+				[0x2b, 6],
+				[0x76, 7],
+				[0x2c, 6],
+				[0x8, 5],
+				[0x9, 5],
+				[0x2d, 6],
+				[0x77, 7],
+				[0x78, 7],
+				[0x79, 7],
+				[0x7a, 7],
+				[0x7b, 7],
 				[0x7ffe, 15],
 				[0x7fc, 11],
 				[0x3ffd, 14],
 				[0x1ffd, 13],
 				[0xffffffc, 28],