content: // 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.
  
  part of dart.io;
  
  class _CryptoUtils {
    static String bytesToHex(List<int> bytes) {
      var result = new StringBuffer();
      for (var part in bytes) {
        result.write('${part < 16 ? '0' : ''}${part.toRadixString(16)}');
      }
      return result.toString();
    }
  
    static const int PAD = 61; // '='
    static const int CR = 13;  // '\r'
    static const int LF = 10;  // '\n'
    static const int LINE_LENGTH = 76;
  
    static const String _encodeTable =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  
    static const String _encodeTableUrlSafe =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
  
    // Lookup table used for finding Base 64 alphabet index of a given byte.
    // -2 : Outside Base 64 alphabet.
    // -1 : '\r' or '\n'
    //  0 : = (Padding character).
    // >0 : Base 64 alphabet index of given byte.
    static const List<int> _decodeTable =
        const [ -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -1, -2, -2, -1, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 62, -2, 62, -2, 63,
                52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -2, -2, -2,  0, -2, -2,
                -2,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
                15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -2, -2, -2, -2, 63,
                -2, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
                41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
                -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2 ];
  
    static String bytesToBase64(List<int> bytes,
                                [bool urlSafe = false,
                                 bool addLineSeparator = false]) {
      int len = bytes.length;
      if (len == 0) {
        return "";
      }
      final String lookup = urlSafe ? _encodeTableUrlSafe : _encodeTable;
      // Size of 24 bit chunks.
      final int remainderLength = len.remainder(3);
      final int chunkLength = len - remainderLength;
      // Size of base output.
      int outputLen = ((len ~/ 3) * 4) + ((remainderLength > 0) ? 4 : 0);
      // Add extra for line separators.
      if (addLineSeparator) {
        outputLen += ((outputLen - 1) ~/ LINE_LENGTH) << 1;
      }
      List<int> out = new List<int>(outputLen);
  
      // Encode 24 bit chunks.
      int j = 0, i = 0, c = 0;
      while (i < chunkLength) {
        int x = ((bytes[i++] << 16) & 0xFFFFFF) |
                ((bytes[i++] << 8) & 0xFFFFFF) |
                  bytes[i++];
        out[j++] = lookup.codeUnitAt(x >> 18);
        out[j++] = lookup.codeUnitAt((x >> 12) & 0x3F);
        out[j++] = lookup.codeUnitAt((x >> 6)  & 0x3F);
        out[j++] = lookup.codeUnitAt(x & 0x3f);
        // Add optional line separator for each 76 char output.
        if (addLineSeparator && ++c == 19 && j < outputLen - 2) {
            out[j++] = CR;
            out[j++] = LF;
            c = 0;
        }
      }
  
      // If input length if not a multiple of 3, encode remaining bytes and
      // add padding.
      if (remainderLength == 1) {
        int x = bytes[i];
        out[j++] = lookup.codeUnitAt(x >> 2);
        out[j++] = lookup.codeUnitAt((x << 4) & 0x3F);
        out[j++] = PAD;
        out[j++] = PAD;
      } else if (remainderLength == 2) {
        int x = bytes[i];
        int y = bytes[i + 1];
        out[j++] = lookup.codeUnitAt(x >> 2);
        out[j++] = lookup.codeUnitAt(((x << 4) | (y >> 4)) & 0x3F);
        out[j++] = lookup.codeUnitAt((y << 2) & 0x3F);
        out[j++] = PAD;
      }
  
      return new String.fromCharCodes(out);
    }
  
    static List<int> base64StringToBytes(String input,
                                         [bool ignoreInvalidCharacters = true]) {
      int len = input.length;
      if (len == 0) {
        return new List<int>(0);
      }
  
      // Count '\r', '\n' and illegal characters, For illegal characters,
      // if [ignoreInvalidCharacters] is false, throw an exception.
      int extrasLen = 0;
      for (int i = 0; i < len; i++) {
        int c = _decodeTable[input.codeUnitAt(i)];
        if (c < 0) {
          extrasLen++;
          if(c == -2 && !ignoreInvalidCharacters) {
            throw new FormatException('Invalid character: ${input[i]}');
          }
        }
      }
  
      if ((len - extrasLen) % 4 != 0) {
        throw new FormatException('''Size of Base 64 characters in Input
            must be a multiple of 4. Input: $input''');
      }
  
      // Count pad characters, ignore illegal characters at the end.
      int padLength = 0;
      for (int i = len - 1; i >= 0; i--) {
        int currentCodeUnit = input.codeUnitAt(i);
        if (_decodeTable[currentCodeUnit] > 0) break;
        if (currentCodeUnit == PAD) padLength++;
      }
      int outputLen = (((len - extrasLen) * 6) >> 3) - padLength;
      List<int> out = new List<int>(outputLen);
  
      for (int i = 0, o = 0; o < outputLen;) {
        // Accumulate 4 valid 6 bit Base 64 characters into an int.
        int x = 0;
        for (int j = 4; j > 0;) {
          int c = _decodeTable[input.codeUnitAt(i++)];
          if (c >= 0) {
            x = ((x << 6) & 0xFFFFFF) | c;
            j--;
          }
        }
        out[o++] = x >> 16;
        if (o < outputLen) {
          out[o++] = (x >> 8) & 0xFF;
          if (o < outputLen) out[o++] = x & 0xFF;
        }
      }
      return out;
    }
  
  }
  
  // Constants.
  const _MASK_8 = 0xff;
  const _MASK_32 = 0xffffffff;
  const _BITS_PER_BYTE = 8;
  const _BYTES_PER_WORD = 4;
  
  // Base class encapsulating common behavior for cryptographic hash
  // functions.
  abstract class _HashBase {
    _HashBase(int this._chunkSizeInWords,
              int this._digestSizeInWords,
              bool 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.
    _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 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.
    _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 < pow(2, 32));
      if (_bigEndianWords) {
        _pendingData.addAll(_wordToBytes(0));
        _pendingData.addAll(_wordToBytes(lengthInBits & _MASK_32));
      } else {
        _pendingData.addAll(_wordToBytes(lengthInBits & _MASK_32));
        _pendingData.addAll(_wordToBytes(0));
      }
    }
  
    // 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;
  }
  
  // The MD5 hasher is used to compute an MD5 message digest.
  class _MD5 extends _HashBase {
    _MD5() : super(16, 4, false) {
      _h[0] = 0x67452301;
      _h[1] = 0xefcdab89;
      _h[2] = 0x98badcfe;
      _h[3] = 0x10325476;
    }
  
    // Returns a new instance of this Hash.
    _MD5 newInstance() {
      return new _MD5();
    }
  
    static const _k = const [
      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,
      0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391 ];
  
    static const _r = const [
      7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 5,  9, 14,
      20, 5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20, 4, 11, 16, 23, 4, 11,
      16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 6, 10, 15, 21, 6, 10, 15, 21, 6,
      10, 15, 21, 6, 10, 15, 21 ];
  
    // Compute one iteration of the MD5 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 t0;
      var t1;
  
      for (var i = 0; i < 64; i++) {
        if (i < 16) {
          t0 = (b & c) | ((~b & _MASK_32) & d);
          t1 = i;
        } else if (i < 32) {
          t0 = (d & b) | ((~d & _MASK_32) & c);
          t1 = ((5 * i) + 1) % 16;
        } else if (i < 48) {
          t0 = b ^ c ^ d;
          t1 = ((3 * i) + 5) % 16;
        } else {
          t0 = c ^ (b | (~d & _MASK_32));
          t1 = (7 * i) % 16;
        }
  
        var temp = d;
        d = c;
        c = b;
        b = _add32(b, _rotl32(_add32(_add32(a, t0),
                                     _add32(_k[i], m[t1])),
                              _r[i]));
        a = temp;
      }
  
      _h[0] = _add32(a, _h[0]);
      _h[1] = _add32(b, _h[1]);
      _h[2] = _add32(c, _h[2]);
      _h[3] = _add32(d, _h[3]);
    }
  }
  
  // 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;
  }
  