docs: protected WsByteBuffer[] flushCache(WsByteBuffer[] buffers) {
          // PK13351 - use the offset/length version to write only what we need
          // to and avoid the extra memory allocation
          int pos = this.bytePosition;
          if (0 == pos) {
              // nothing to write
              return buffers;
          }
          this.bytePosition = 0;
          return GenericUtils.putByteArray(buffers, this.byteCache, 0, pos, this);
      }