HMac.withDigest constructor
      
      HMac.withDigest(
    
    
- Digest _digest
 
Implementation
HMac.withDigest(this._digest) {
  _blockLength = _digest.byteLength;
  _digestSize = _digest.digestSize;
  _inputPad = Uint8List(_blockLength);
  _outputBuf = Uint8List(_blockLength + _digestSize);
}