code: public static ChunkHeader read(IoBuffer in) {
          int remaining = in.remaining();
          if (remaining > 0) {
              byte headerByte = in.get();
              ChunkHeader h = new ChunkHeader();
              // going to check highest 2 bits
              h.format = (byte) ((0b11000000 & headerByte) >> 6);
              int fmt = headerByte & 0x3f;
              switch (fmt) {
                  case 0:
                      // two byte header
                      h.size = 2;
                      if (remaining < 2) {
                          throw new ProtocolException("Bad chunk header, at least 2 bytes are expected");
                      }
                      h.channelId = 64 + (in.get() & 0xff);
                      break;
                  case 1:
                      // three byte header
                      h.size = 3;
                      if (remaining < 3) {
                          throw new ProtocolException("Bad chunk header, at least 3 bytes are expected");
                      }
                      byte b1 = in.get();
                      byte b2 = in.get();
                      h.channelId = 64 + ((b2 & 0xff) << 8 | (b1 & 0xff));
                      break;
                  default:
                      // single byte header
                      h.size = 1;
                      h.channelId = 0x3f & headerByte;
                      break;
              }
              // check channel id is valid
              if (h.channelId < 0) {
                  throw new ProtocolException("Bad channel id: " + h.channelId);
              }
              log.trace("CHUNK header byte {}, count {}, header {}, channel {}", String.format("%02x", headerByte), h.size, 0, h.channelId);
              return h;
          } else {
              // at least one byte for valid decode
              throw new ProtocolException("Bad chunk header, at least 1 byte is expected");
          }
      }
docs: Read chunk header from the buffer.
  
  @param in
  buffer
  @return ChunkHeader instance