public string BuildString()
{
End();
var result = NS2Bridge.CreateString(_jwtLength, _jwt, (destination, state) => {
NS2Bridge.Latin1ToUtf16(state.AsSpan(0, _jwtLength), destination);
});
return(result);
}
public bool TryBuildTo(Span <char> destination, out int charsWritten)
{
End();
if (destination.Length < _jwtLength)
{
charsWritten = 0;
return(false);
}
NS2Bridge.Latin1ToUtf16(_jwt.AsSpan(0, _jwtLength), destination);
charsWritten = _jwtLength;
return(true);
}
/// <summary>
/// Returns number of ASCII characters of the JTW. The actual token can be retrieved using Build or WriteTo
/// </summary>
/// <returns></returns>
public int End()
{
if (_writer == null)
{
return(_jwtLength); // writer is set to null after token is formatted.
}
if (_isDisposed)
{
throw new ObjectDisposedException(nameof(JwtBuilder));
}
_writer.WriteEndObject();
_writer.Flush();
Debug.Assert(_memoryStream.GetType() == typeof(MemoryStream));
int payloadLength = (int)_writer.BytesCommitted; // writer is wrrapping MemoryStream, and so the length will never overflow int.
int payloadIndex = headerSha256.Length;
int maxBufferLength;
checked {
maxBufferLength =
Base64.GetMaxEncodedToUtf8Length(headerSha256.Length + payloadLength)
+ 1 // dot
+ Base64.GetMaxEncodedToUtf8Length(32); // signature SHA256 hash size
}
_memoryStream.Capacity = maxBufferLength; // make room for in-place Base64 conversion
_jwt = _memoryStream.GetBuffer();
_writer = null; // this will prevent subsequent additions of claims.
Span <byte> toEncode = _jwt.AsSpan(payloadIndex);
OperationStatus status = NS2Bridge.Base64UrlEncodeInPlace(toEncode, payloadLength, out int payloadWritten);
Debug.Assert(status == OperationStatus.Done); // Buffer is adjusted above, and so encoding should always fit
// Add signature
int headerAndPayloadLength = payloadWritten + headerSha256.Length;
_jwt[headerAndPayloadLength] = (byte)'.';
int headerAndPayloadAndSeparatorLength = headerAndPayloadLength + 1;
using (HMACSHA256 hash = new HMACSHA256(_key))
{
var hashed = hash.ComputeHash(_jwt, 0, headerAndPayloadLength);
status = NS2Bridge.Base64UrlEncode(hashed, _jwt.AsSpan(headerAndPayloadAndSeparatorLength), out int consumend, out int signatureLength);
Debug.Assert(status == OperationStatus.Done); // Buffer is adjusted above, and so encoding should always fit
_jwtLength = headerAndPayloadAndSeparatorLength + signatureLength;
}
return(_jwtLength);
}