tests/standalone/io/hash_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.

/// Hash routines copied from private helpers in dart:io.
library hashes;

// Constants.
const _MASK_8 = 0xff;
const _MASK_32 = 0xffffffff;
const _BITS_PER_BYTE = 8;
const _BYTES_PER_WORD = 4;
const _pow2_32 = 0x100000000;

// Base class encapsulating common behavior for cryptographic hash
// functions.
abstract class _HashBase {
  // Hasher state.
  final int _chunkSizeInWords;
  final int _digestSizeInWords;
  final bool _bigEndianWords;
  int _lengthInBytes = 0;
  List<int> _pendingData;
  List<int> _currentChunk;
  List<int> _h;
  bool _digestCalled = false;

  _HashBase(
      this._chunkSizeInWords, this._digestSizeInWords, this._bigEndianWords)
      : _pendingData = [] {
    _currentChunk = new List(_chunkSizeInWords);
    _h = new List(_digestSizeInWords);
  }

  // Update the hasher with more data.
  add(List<int> data) {
    if (_digestCalled) {
      throw new StateError(
          'Hash update method called after digest was retrieved');
    }
    _lengthInBytes += data.length;
    _pendingData.addAll(data);
    _iterate();
  }

  // Finish the hash computation and return the digest string.
  List<int> close() {
    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.
  newInstance();

  // One round of the hash computation.
  _updateHash(List<int> m);

  // Helper methods.
  _add32(x, y) => (x + y) & _MASK_32;
  _roundUp(val, n) => (val + n - 1) & -n;

  // Rotate left limiting to unsigned 32-bit values.
  int _rotl32(int val, int shift) {
    var mod_shift = shift & 31;
    return ((val << mod_shift) & _MASK_32) |
        ((val & _MASK_32) >> (32 - mod_shift));
  }

  // Compute the final result as a list of bytes from the hash words.
  List<int> _resultAsBytes() {
    var result = <int>[];
    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 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;
    }
  }

  // Convert a 32-bit word to four bytes.
  List<int> _wordToBytes(int word) {
    List<int> bytes = new List(_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;
  }

  // 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);
      }
      _pendingData = _pendingData.sublist(index, len);
    }
  }

  // Finalize the data. Add a 1 bit to the end of the message. Expand with
  // 0 bits and add 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;
    assert(lengthInBits < _pow2_32);
    if (_bigEndianWords) {
      _pendingData.addAll(_wordToBytes(0));
      _pendingData.addAll(_wordToBytes(lengthInBits & _MASK_32));
    } else {
      _pendingData.addAll(_wordToBytes(lengthInBits & _MASK_32));
      _pendingData.addAll(_wordToBytes(0));
    }
  }
}

// The SHA1 hasher is used to compute an SHA1 message digest.
class SHA1 extends _HashBase {
  // Construct a SHA1 hasher object.
  SHA1()
      : _w = new List(80),
        super(16, 5, true) {
    _h[0] = 0x67452301;
    _h[1] = 0xEFCDAB89;
    _h[2] = 0x98BADCFE;
    _h[3] = 0x10325476;
    _h[4] = 0xC3D2E1F0;
  }

  // Returns a new instance of this Hash.
  SHA1 newInstance() {
    return new SHA1();
  }

  // Compute one iteration of the SHA1 algorithm with a chunk of
  // 16 32-bit pieces.
  void _updateHash(List<int> m) {
    assert(m.length == 16);

    var a = _h[0];
    var b = _h[1];
    var c = _h[2];
    var d = _h[3];
    var e = _h[4];

    for (var i = 0; i < 80; i++) {
      if (i < 16) {
        _w[i] = m[i];
      } else {
        var n = _w[i - 3] ^ _w[i - 8] ^ _w[i - 14] ^ _w[i - 16];
        _w[i] = _rotl32(n, 1);
      }
      var t = _add32(_add32(_rotl32(a, 5), e), _w[i]);
      if (i < 20) {
        t = _add32(_add32(t, (b & c) | (~b & d)), 0x5A827999);
      } else if (i < 40) {
        t = _add32(_add32(t, (b ^ c ^ d)), 0x6ED9EBA1);
      } else if (i < 60) {
        t = _add32(_add32(t, (b & c) | (b & d) | (c & d)), 0x8F1BBCDC);
      } else {
        t = _add32(_add32(t, b ^ c ^ d), 0xCA62C1D6);
      }

      e = d;
      d = c;
      c = _rotl32(b, 30);
      b = a;
      a = t & _MASK_32;
    }

    _h[0] = _add32(a, _h[0]);
    _h[1] = _add32(b, _h[1]);
    _h[2] = _add32(c, _h[2]);
    _h[3] = _add32(d, _h[3]);
    _h[4] = _add32(e, _h[4]);
  }

  List<int> _w;
}