code: public void setMaxHeaderTableSize(ByteBuf out, long maxHeaderTableSize) throws Http2Exception {
          if (maxHeaderTableSize < MIN_HEADER_TABLE_SIZE || maxHeaderTableSize > MAX_HEADER_TABLE_SIZE) {
              throw connectionError(PROTOCOL_ERROR, "Header Table Size must be >= %d and <= %d but was %d",
                      MIN_HEADER_TABLE_SIZE, MAX_HEADER_TABLE_SIZE, maxHeaderTableSize);
          }
          if (this.maxHeaderTableSize == maxHeaderTableSize) {
              return;
          }
          this.maxHeaderTableSize = maxHeaderTableSize;
          ensureCapacity(0);
          // Casting to integer is safe as we verified the maxHeaderTableSize is a valid unsigned int.
          encodeInteger(out, 0x20, 5, maxHeaderTableSize);
      }
docs: Set the maximum table size.