code: protected boolean checkBuffer() throws IOException {
          if (!enableMultiReadofPostData) {
              if (null != this.buffer) {
                  if (this.buffer.hasRemaining()) {
                      return true;
                  }
                  this.buffer.release();
                  this.buffer = null;
              }
              try {
                  this.buffer = this.isc.getRequestBodyBuffer();
                  if (null != this.buffer) {
                      // record the new amount of data read from the channel
                      this.bytesRead += this.buffer.remaining();
                      // Tr.debug(tc, "Buffer=" + WsByteBufferUtils.asString(this.buffer));
                      return true;
                  }
                  return false;
              } catch (IOException e) {
                  this.error = e;
                  throw e;
              }
          } else {
              return checkMultiReadBuffer();
          }
      }
docs: Check the input buffer for data. If necessary, attempt a read for a new
  buffer.
  
  @return boolean - true means data is ready
  @throws IOException