From 9e88447bb64c67f80f1a373bc97ea52f4e335d8c Mon Sep 17 00:00:00 2001
From: Timofey Solomko <tsolomko@gmail.com>
Date: Tue, 1 Nov 2016 23:49:26 +0300
Subject: [PATCH] ExtraLength and extraDistance calculations are now done
 inside decompress function.

---
 Sources/Deflate.swift      | 11 +++++------
 Sources/HuffmanTable.swift | 22 +---------------------
 2 files changed, 6 insertions(+), 27 deletions(-)

diff --git a/Sources/Deflate.swift b/Sources/Deflate.swift
index 5e0a82c5..d5e9668e 100644
--- a/Sources/Deflate.swift
+++ b/Sources/Deflate.swift
@@ -169,10 +169,10 @@ public class Deflate: DecompressionAlgorithm {
                         break
                     } else if symbol >= 257 && symbol <= 285 {
                         let start = (index, shift)
-                        let addBits = HuffmanTable.Constants.extraLengthBits(n: symbol)
-                        guard addBits != -1 else { throw DeflateError.HuffmanTableError }
-                        index += shift + addBits >= 8 ? 1 : 0
-                        shift = shift + addBits >= 8 ? shift - (8 - addBits) : shift + addBits
+                        let extraLength = (257 <= symbol && symbol <= 260) || symbol == 285 ?
+                            0 : ((symbol - 257) >> 2) - 1
+                        index += shift + extraLength >= 8 ? 1 : 0
+                        shift = shift + extraLength >= 8 ? shift - (8 - extraLength) : shift + extraLength
                         let end = (index, shift)
                         var length = HuffmanTable.Constants.lengthBase[symbol - 257] +
                             convertToInt(reversedUint8Array: data.bits(from: start, to: end))
@@ -186,8 +186,7 @@ public class Deflate: DecompressionAlgorithm {
 
                         if newSymbol >= 0 && newSymbol <= 29 {
                             let start = (index, shift)
-                            let extraDistance = HuffmanTable.Constants.extraDistanceBits(n: newSymbol)
-                            guard extraDistance != -1 else { throw DeflateError.HuffmanTableError }
+                            let extraDistance = newSymbol == 0 || newSymbol == 1 ? 0 : (newSymbol >> 1) - 1
                             if shift + extraDistance >= 16 {
                                 index += 2
                                 shift = shift - (16 - extraDistance)
diff --git a/Sources/HuffmanTable.swift b/Sources/HuffmanTable.swift
index b91997b9..52fdd179 100644
--- a/Sources/HuffmanTable.swift
+++ b/Sources/HuffmanTable.swift
@@ -14,7 +14,7 @@ class HuffmanTable: CustomStringConvertible {
         static let codeLengthOrders: [Int] =
             [16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15]
 
-        // Substract 257 from index!
+        /// - Warning: Substract 257 from index!
         static let lengthBase: [Int] =
             [3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 35,
              43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258]
@@ -24,26 +24,6 @@ class HuffmanTable: CustomStringConvertible {
              257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
              8193, 12289, 16385, 24577]
 
-        static func extraLengthBits(n: Int) -> Int {
-            if (n >= 257 && n <= 260) || n == 285 {
-                return 0
-            } else if n >= 261 && n <= 284 {
-                return ((n - 257) >> 2) - 1
-            } else {
-                return -1
-            }
-        }
-
-        static func extraDistanceBits(n: Int) -> Int {
-            if n >= 0 && n <= 1 {
-                return 0
-            } else if n >= 2 && n <= 29 {
-                return (n >> 1) - 1
-            } else {
-                return -1
-            }
-        }
-
     }
 
     var lengths: [HuffmanLength]