Implement md5 hash in crypto library.

lib/crypto/sha_utils.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.
-
-// Constants.
-final _MASK_8 = 0xff;
-final _MASK_32 = 0xffffffff;
-final _BITS_PER_BYTE = 8;
-final _BYTES_PER_WORD = 4;
-
-// Base class encapsulating common behavior for SHA cryptographic hash
-// functions.
-class _SHAHashBase implements Hash {
-  _SHAHashBase(int this._chunkSizeInWords, int this._digestSizeInWords)
-      : _pendingData = [] {
-    _currentChunk = new List(_chunkSizeInWords);
-    _h = new List(_digestSizeInWords);
-  }
-
-  // Update the hasher with more data.
-  _SHAHashBase update(List<int> data) {
-    if (_digestCalled) {
-      throw new HashException(
-          'Hash update method called after digest was retrieved');
-    }
-    _lengthInBytes += data.length;
-    _pendingData.addAll(data);
-    _iterate();
-    return this;
-  }
-
-  // Finish the hash computation and return the digest string.
-  List<int> digest() {
-    if (_digestCalled) {
-      return _resultAsBytes();
-    }
-    _digestCalled = true;
-    _finalizeData();
-    _iterate();
-    assert(_pendingData.length == 0);
-    return _resultAsBytes();
-  }
-
-  // Returns the block size of the hash in bytes.
-  int get blockSize() {
-    return _chunkSizeInWords * _BYTES_PER_WORD;
-  }
-
-  // Create a fresh instance of this Hash.
-  abstract newInstance();
-
-  // One round of the hash computation.
-  abstract _updateHash(List<int> m);
-
-  // Helper methods.
-  _add32(x, y) => (x + y) & _MASK_32;
-  _roundUp(val, n) => (val + n - 1) & -n;
-
-  // Compute the final result as a list of bytes from the hash words.
-  _resultAsBytes() {
-    var result = [];
-    for (var i = 0; i < _h.length; i++) {
-      result.addAll(_wordToBytes(_h[i]));
-    }
-    return result;
-  }
-
-  // Converts a list of bytes to a chunk of 32-bit words.
-  _bytesToChunk(List<int> data, int dataIndex) {
-    assert((data.length - dataIndex) >= (_chunkSizeInWords * _BYTES_PER_WORD));
-    for (var wordIndex = 0; wordIndex < _chunkSizeInWords; wordIndex++) {
-      var word = (data[dataIndex++] & 0xff) << 24;
-      word |= (data[dataIndex++] & _MASK_8) << 16;
-      word |= (data[dataIndex++] & _MASK_8) << 8;
-      word |= (data[dataIndex++] & _MASK_8);
-      _currentChunk[wordIndex] = word;
-    }
-  }
-
-  // Convert a 32-bit word to four bytes.
-  _wordToBytes(int word) {
-    List<int> bytes = new List(_BYTES_PER_WORD);
-    bytes[0] = word >> 24;
-    bytes[1] = (word >> 16) & _MASK_8;
-    bytes[2] = (word >> 8) & _MASK_8;
-    bytes[3] = word & _MASK_8;
-    return bytes;
-  }
-
-  // Iterate through data updating the hash computation for each
-  // chunk.
-  _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 remaining = len - index;
-      _pendingData = _pendingData.getRange(index, remaining);
-    }
-  }
-
-  // Finalize the data. Add a 1 bit to the end of the message. Expand with
-  // 0 bits and the length of the message.
-  _finalizeData() {
-    _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++) {
-      _pendingData.add(0);
-    }
-    var lengthInBits = _lengthInBytes * _BITS_PER_BYTE;
-    _pendingData.addAll(_wordToBytes(lengthInBits >> 32));
-    _pendingData.addAll(_wordToBytes(lengthInBits & _MASK_32));
-  }
-
-  // Hasher state.
-  final int _chunkSizeInWords;
-  final int _digestSizeInWords;
-  int _lengthInBytes = 0;
-  List<int> _pendingData;
-  List<int> _currentChunk;
-  List<int> _h;
-  bool _digestCalled = false;
-}