hash.dart 5 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:typed_data';

/// Data from a non-linear mathematical function that functions as
/// reproducible noise.
final Uint32List _noise = Uint32List.fromList(<int>[
  0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, 0xf57c0faf, 0x4787c62a,
  0xa8304613, 0xfd469501, 0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
  0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, 0xf61e2562, 0xc040b340,
  0x265e5a51, 0xe9b6c7aa, 0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
  0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, 0xa9e3e905, 0xfcefa3f8,
  0x676f02d9, 0x8d2a4c8a, 0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
  0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, 0x289b7ec6, 0xeaa127fa,
  0xd4ef3085, 0x04881d05, 0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
  0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, 0x655b59c3, 0x8f0ccc92,
  0xffeff47d, 0x85845dd1, 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
20
  0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391,
21 22 23 24 25 26 27
]);

/// Per-round shift amounts.
const List<int> _shiftAmounts = <int>[
  07, 12, 17, 22, 07, 12, 17, 22, 07, 12, 17, 22, 07, 12, 17, 22, 05, 09, 14,
  20, 05, 09, 14, 20, 05, 09, 14, 20, 05, 09, 14, 20, 04, 11, 16, 23, 04, 11,
  16, 23, 04, 11, 16, 23, 04, 11, 16, 23, 06, 10, 15, 21, 06, 10, 15, 21, 06,
28
  10, 15, 21, 06, 10, 15, 21,
29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
];

/// A bitmask that limits an integer to 32 bits.
const int _mask32 = 0xFFFFFFFF;

/// An incremental hash computation of md5.
class Md5Hash {
  Md5Hash() {
    _digest[0] = 0x67452301;
    _digest[1] = 0xefcdab89;
    _digest[2] = 0x98badcfe;
    _digest[3] = 0x10325476;
  }

  // 64 bytes is 512 bits.
  static const int _kChunkSize = 64;

  /// The current hash digest.
  final Uint32List _digest = Uint32List(4);
  final Uint8List _scratchSpace = Uint8List(_kChunkSize);
  int _remainingLength = 0;
  int _contentLength = 0;

52
  void addChunk(Uint8List data, [int? stop]) {
53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169
    assert(_remainingLength == 0);
    stop ??= data.length;
    int i = 0;
    for (; i <= stop - _kChunkSize; i += _kChunkSize) {
      final Uint32List view = Uint32List.view(data.buffer, i, 16);
      _writeChunk(view);
    }
    if (i != stop) {
      // The data must be copied so that the provided buffer can be reused.
      int j = 0;
      for (; i < stop; i += 1) {
        _scratchSpace[j] = data[i];
        j += 1;
      }
      _remainingLength = j;
    }
    _contentLength += stop;
  }

  void _writeChunk(Uint32List chunk) {
    // help dart remove bounds checks
    // ignore: unnecessary_statements
    chunk[15];
    // ignore: unnecessary_statements
    _shiftAmounts[63];
    // ignore: unnecessary_statements
    _noise[63];

    int d = _digest[3];
    int c = _digest[2];
    int b = _digest[1];
    int a = _digest[0];
    int e = 0;
    int f = 0;
    int i = 0;
    for (; i < 16; i += 1) {
      e = (b & c) | ((~b & _mask32) & d);
      f = i;
      final int temp = d;
      d = c;
      c = b;
      b = _add32(
          b,
          _rotl32(_add32(_add32(a, e), _add32(_noise[i], chunk[f])),
              _shiftAmounts[i]));
      a = temp;
    }
    for (; i < 32; i += 1) {
      e = (d & b) | ((~d & _mask32) & c);
      f = ((5 * i) + 1) % 16;
      final int temp = d;
      d = c;
      c = b;
      b = _add32(
          b,
          _rotl32(_add32(_add32(a, e), _add32(_noise[i], chunk[f])),
              _shiftAmounts[i]));
      a = temp;
    }
    for (; i < 48; i += 1) {
      e = b ^ c ^ d;
      f = ((3 * i) + 5) % 16;
      final int temp = d;
      d = c;
      c = b;
      b = _add32(
          b,
          _rotl32(_add32(_add32(a, e), _add32(_noise[i], chunk[f])),
              _shiftAmounts[i]));
      a = temp;
    }
    for (; i < 64; i+= 1) {
      e = c ^ (b | (~d & _mask32));
      f = (7 * i) % 16;
      final int temp = d;
      d = c;
      c = b;
      b = _add32(
          b,
          _rotl32(_add32(_add32(a, e), _add32(_noise[i], chunk[f])),
              _shiftAmounts[i]));
      a = temp;
    }

    _digest[0] += a;
    _digest[1] += b;
    _digest[2] += c;
    _digest[3] += d;
  }

  Uint32List finalize() {
    // help dart remove bounds checks
    // ignore: unnecessary_statements
    _scratchSpace[63];
    _scratchSpace[_remainingLength] = 0x80;
    _remainingLength += 1;

    final int zeroes = 56 - _remainingLength;
    for (int i = _remainingLength; i < zeroes; i += 1) {
      _scratchSpace[i] = 0;
    }
    final int bitLength = _contentLength * 8;
    _scratchSpace.buffer.asByteData().setUint64(56, bitLength, Endian.little);
    _writeChunk(Uint32List.view(_scratchSpace.buffer, 0, 16));
    return _digest;
  }

  /// Adds [x] and [y] with 32-bit overflow semantics.
  int _add32(int x, int y) => (x + y) & _mask32;

  /// Bitwise rotates [val] to the left by [shift], obeying 32-bit overflow
  /// semantics.
  int _rotl32(int val, int shift) {
    final int modShift = shift & 31;
    return ((val << modShift) & _mask32) | ((val & _mask32) >> (32 - modShift));
  }
}