Rename Encoding/DecodingHuffmanTree to just Encoding/DecodingTree

Sources/Common/CodingTree/EncodingTree.swift

@@ -0,0 +1,56 @@
+// Copyright (c) 2019 Timofey Solomko
+// Licensed under MIT License
+//
+// See LICENSE for license information
+
+import Foundation
+import BitByteData
+
+final class EncodingTree {
+
+    private let bitWriter: BitWriter
+
+    private let codingIndices: [[Int]]
+
+    init(codes: [Code], _ bitWriter: BitWriter, reverseCodes: Bool = false) {
+        self.bitWriter = bitWriter
+
+        var codingIndices = Array(repeating: [-1, -1], count: codes.count)
+
+        for code in codes {
+            // Codes have already been reversed.
+            // TODO: This assumption may be only correct for Huffman codes.
+            let treeCode = reverseCodes ? code.code : code.code.reversed(bits: code.bits)
+            codingIndices[code.symbol] = [treeCode, code.bits]
+        }
+        self.codingIndices = codingIndices
+
+    }
+
+    func code(symbol: Int) {
+        guard symbol < self.codingIndices.count
+            else { fatalError("Symbol is not found.") }
+
+        let codingIndex = self.codingIndices[symbol]
+
+        guard codingIndex[0] > -1
+            else { fatalError("Symbol is not found.") }
+
+        self.bitWriter.write(number: codingIndex[0], bitsCount: codingIndex[1])
+    }
+
+    func bitSize(for stats: [Int]) -> Int {
+        var totalSize = 0
+        for (symbol, count) in stats.enumerated() where count > 0 {
+            guard symbol < self.codingIndices.count
+                else { fatalError("Symbol is not found.") }
+            let codingIndex = self.codingIndices[symbol]
+            guard codingIndex[0] > -1
+                else { fatalError("Symbol is not found.") }
+
+            totalSize += count * codingIndex[1]
+        }
+        return totalSize
+    }
+
+}