AppendWithLen append i in the QUIC varint format with the desired length.

Len determines the number of bytes that will be needed to write the number i.

NewReader returns a Reader for r.

NewWriter returns a Writer for w.

Read reads a number in the QUIC varint format from r.

Write writes i in the QUIC varint format to w.

Max is the maximum allowed value for a QUIC varint (2^62-1).

Min is the minimum value allowed for a QUIC varint.

Reader implements both the io.ByteReader and io.Reader interfaces.

Writer implements both the io.ByteWriter and io.Writer interfaces.