anchor.diff:    bool matchesHeader(List<int> header, {int offset = magicOffset}) {
       for (var i = 0; i < header.length; i++) {
         if (this[offset + i] != header[i]) return false;
  +    }
  +
  +    return true;
  +  }
  +
  +  bool get isAllZeroes {
  +    for (var i = 0; i < length; i++) {
  +      if (this[i] != 0) return false;
       }
   
       return true;
  
positive.code:     final $this = this;
      return $this is Uint8List ? $this : Uint8List.fromList(this);
    }
  
    bool get isAllZeroes {
      for (var i = 0; i < length; i++) {
        if (this[i] != 0) return false;
      }
  
      return true;
    }
  }
  
  /// Generates a chunked stream of [length] zeroes.
  
negative.code:   }
  
    int computeUnsignedHeaderChecksum() {
      // Accessing the last element first helps the VM eliminate bounds checks in
      // the loops below.
      this[blockSize - 1];
      var result = checksumLength * _checksumPlaceholder;
  
      for (var i = 0; i < checksumOffset; i++) {
        result += this[i];
      }
      for (var i = _checksumEnd; i < blockSize; i++) {
        result += this[i];
      }
  
      return result;
    }
  
    int computeSignedHeaderChecksum() {
      this[blockSize - 1];
      // Note that _checksumPlaceholder.toSigned(8) == _checksumPlaceholder
      var result = checksumLength * _checksumPlaceholder;
  
      for (var i = 0; i < checksumOffset; i++) {
        result += this[i].toSigned(8);
      }
      for (var i = _checksumEnd; i < blockSize; i++) {
        result += this[i].toSigned(8);
      }
  
      return result;
  