Improve the style of code in lib/.

lib/src/hash_base.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library crypto.hash_base;
 
-import 'dart:math' as math;
 import 'dart:typed_data';
 
+import 'package:typed_data/typed_data.dart';
+
 import 'hash.dart';
 import 'utils.dart';
 
 /// A base class for [Hash] implementations.
 ///
-/// Subclasses should override [updateHash], and define it to update [h] with
-/// the results of the hash function.
+/// Subclasses should override [updateHash] and [digest].
 abstract class HashBase implements Hash {
-  /// The size (in 32-bit words) of the chunks of input data that the hash
-  /// function consumes at once.
-  final int _chunkSizeInWords;
-
-  /// The size (in 32-bit words) of the digest that the hash function emits.
-  final int _digestSizeInWords;
-
   /// Whether the hash function operates on big-endian words.
-  final bool _bigEndianWords;
+  final Endianness _endian;
 
   /// The words in the current chunk.
+  ///
+  /// This is an instance variable to avoid re-allocating, but its data isn't
+  /// used across invocations of [_iterate].
   final Uint32List _currentChunk;
 
-  /// The words in the current digest.
-  ///
-  /// The size of this buffer is given by the `digestSizeInWords` constructor
-  /// parameter.
-  final Uint32List h;
-
   /// The length of the input data so far, in bytes.
   int _lengthInBytes = 0;
 
   /// Data that has yet to be processed by the hash function.
-  List<int> _pendingData;
+  final _pendingData = new Uint8Buffer();
 
   /// Whether [close] has been called.
-  bool _digestCalled = false;
+  bool _isClosed = false;
+
+  /// The words in the current digest.
+  ///
+  /// This should be updated each time [updateHash] is called.
+  Uint32List get digest;
+
+  int get blockSize => _currentChunk.lengthInBytes;
 
   /// Creates a new hash.
   ///
   /// [chunkSizeInWords] represents the size of the input chunks processed by
-  /// the algorithm. [digestSizeInWords] represents the size of the algorithm's
-  /// output digest. Both are in terms of 32-bit words.
-  HashBase(
-      int chunkSizeInWords, int digestSizeInWords, bool this._bigEndianWords)
-      : _pendingData = [],
-        _currentChunk = new Uint32List(chunkSizeInWords),
-        h = new Uint32List(digestSizeInWords),
-        _chunkSizeInWords = chunkSizeInWords,
-        _digestSizeInWords = digestSizeInWords;
+  /// the algorithm, in terms of 32-bit words.
+  HashBase(int chunkSizeInWords, {Endianness endian: Endianness.BIG_ENDIAN})
+      : _endian = endian,
+        _currentChunk = new Uint32List(chunkSizeInWords);
+
+  /// Runs a single iteration of the hash computation, updating [digest] with
+  /// the result.
+  ///
+  /// [m] is the current chunk, whose size is given by the `chunkSizeInWords`
+  /// parameter passed to the constructor.
+  void updateHash(Uint32List chunk);
 
   void add(List<int> data) {
-    if (_digestCalled) {
-      throw new StateError(
-          'Hash update method called after digest was retrieved');
-    }
+    if (_isClosed) throw new StateError('Hash.add() called after close().');
     _lengthInBytes += data.length;
     _pendingData.addAll(data);
     _iterate();
   }
 
   List<int> close() {
-    if (_digestCalled) {
-      return _resultAsBytes();
-    }
-    _digestCalled = true;
+    if (_isClosed) return _byteDigest();
+    _isClosed = true;
+
     _finalizeData();
     _iterate();
-    assert(_pendingData.length == 0);
-    return _resultAsBytes();
+    assert(_pendingData.isEmpty);
+    return _byteDigest();
   }
 
-  int get blockSize {
-    return _chunkSizeInWords * BYTES_PER_WORD;
-  }
+  Uint8List _byteDigest() {
+    if (_endian == Endianness.HOST_ENDIAN) return digest.buffer.asUint8List();
 
-  /// Runs a single iteration of the hash computation, updating [h] with the
-  /// result.
-  ///
-  /// [m] is the current chunk, whose size is given by the `chunkSizeInWords`
-  /// parameter passed to the constructor.
-  void updateHash(Uint32List m);
-
-  /// Computes the final result of the hash as a list of bytes from the hash
-  /// words.
-  List<int> _resultAsBytes() {
-    var result = [];
-    for (var i = 0; i < h.length; i++) {
-      result.addAll(_wordToBytes(h[i]));
+    var byteDigest = new Uint8List(digest.lengthInBytes);
+    var byteData = byteDigest.buffer.asByteData();
+    for (var i = 0; i < digest.length; i++) {
+      byteData.setUint32(i * bytesPerWord, digest[i]);
     }
-    return result;
-  }
-
-  /// Converts a list of bytes to a chunk of 32-bit words.
-  ///
-  /// Stores the result in [_currentChunk].
-  void _bytesToChunk(List<int> data, int dataIndex) {
-    assert((data.length - dataIndex) >= (_chunkSizeInWords * BYTES_PER_WORD));
-
-    for (var wordIndex = 0; wordIndex < _chunkSizeInWords; wordIndex++) {
-      var w3 = _bigEndianWords ? data[dataIndex] : data[dataIndex + 3];
-      var w2 = _bigEndianWords ? data[dataIndex + 1] : data[dataIndex + 2];
-      var w1 = _bigEndianWords ? data[dataIndex + 2] : data[dataIndex + 1];
-      var w0 = _bigEndianWords ? data[dataIndex + 3] : data[dataIndex];
-      dataIndex += 4;
-      var word = (w3 & 0xff) << 24;
-      word |= (w2 & MASK_8) << 16;
-      word |= (w1 & MASK_8) << 8;
-      word |= (w0 & MASK_8);
-      _currentChunk[wordIndex] = word;
-    }
-  }
-
-  /// Converts a 32-bit word to four bytes.
-  List<int> _wordToBytes(int word) {
-    List bytes = new List<int>(BYTES_PER_WORD);
-    bytes[0] = (word >> (_bigEndianWords ? 24 : 0)) & MASK_8;
-    bytes[1] = (word >> (_bigEndianWords ? 16 : 8)) & MASK_8;
-    bytes[2] = (word >> (_bigEndianWords ? 8 : 16)) & MASK_8;
-    bytes[3] = (word >> (_bigEndianWords ? 0 : 24)) & MASK_8;
-    return bytes;
+    return byteDigest;
   }
 
   /// Iterates through [_pendingData], updating the hash computation for each
   /// chunk.
   void _iterate() {
-    var len = _pendingData.length;
-    var chunkSizeInBytes = _chunkSizeInWords * BYTES_PER_WORD;
-    if (len >= chunkSizeInBytes) {
-      var index = 0;
-      for (; (len - index) >= chunkSizeInBytes; index += chunkSizeInBytes) {
-        _bytesToChunk(_pendingData, index);
-        updateHash(_currentChunk);
+    var pendingDataBytes = _pendingData.buffer.asByteData();
+    var pendingDataChunks = _pendingData.length ~/ _currentChunk.lengthInBytes;
+    for (var i = 0; i < pendingDataChunks; i++) {
+      // Copy words from the pending data buffer into the current chunk buffer.
+      for (var j = 0; j < _currentChunk.length; j++) {
+        _currentChunk[j] = pendingDataBytes.getUint32(
+            i * _currentChunk.lengthInBytes + j * bytesPerWord, _endian);
       }
-      _pendingData = _pendingData.sublist(index, len);
+
+      // Run the hash function on the current chunk.
+      updateHash(_currentChunk);
     }
+
+    // Remove all pending data up to the last clean chunk break.
+    _pendingData.removeRange(
+        0, pendingDataChunks * _currentChunk.lengthInBytes);
   }
 
   /// Finalizes [_pendingData].
   ///
   /// This adds a 1 bit to the end of the message, and expands it with 0 bits to
   /// pad it out.
   void _finalizeData() {
+    // Pad out the data with 0x80, eight 0s, and as many more 0s as we need to
+    // land cleanly on a chunk boundary.
     _pendingData.add(0x80);
     var contentsLength = _lengthInBytes + 9;
-    var chunkSizeInBytes = _chunkSizeInWords * BYTES_PER_WORD;
-    var finalizedLength = _roundUp(contentsLength, chunkSizeInBytes);
-    var zeroPadding = finalizedLength - contentsLength;
-    for (var i = 0; i < zeroPadding; i++) {
+    var finalizedLength = _roundUp(contentsLength, _currentChunk.lengthInBytes);
+    for (var i = 0; i < finalizedLength - contentsLength; i++) {
       _pendingData.add(0);
     }
-    var lengthInBits = _lengthInBytes * BITS_PER_BYTE;
-    const MAX_UINT64 = 0xFFFFFFFFFFFFFFFF;
-    if (lengthInBits > MAX_UINT64) {
+
+    var lengthInBits = _lengthInBytes * bitsPerByte;
+    if (lengthInBits > maxUint64) {
       throw new UnsupportedError(
-          "Hash undefined for message bit lengths larger than 64 bits");
+          "Hashing is unsupported for messages with more than 2^64 bits.");
     }
-    if (_bigEndianWords) {
-      _pendingData.addAll(_wordToBytes((lengthInBits >> 32) & MASK_32));
-      _pendingData.addAll(_wordToBytes(lengthInBits & MASK_32));
-    } else {
-      _pendingData.addAll(_wordToBytes(lengthInBits & MASK_32));
-      _pendingData.addAll(_wordToBytes((lengthInBits >> 32) & MASK_32));
-    }
+
+    // Add the full length of the input data as a 64-bit value at the end of the
+    // hash.
+    var offset = _pendingData.length;
+    _pendingData.addAll(new Uint8List(8));
+    _pendingData.buffer.asByteData().setUint64(offset, lengthInBits, _endian);
   }
 
-  /// Rounds [val] to the nearest multiple of [n].
-  int _roundUp(val, n) => (val + n - 1) & -n;
+  /// Rounds [val] up to the next multiple of [n], as long as [n] is a power of
+  /// two.
+  int _roundUp(int val, int n) => (val + n - 1) & -n;
 }