text: /*
   * This file is open source software, licensed to you under the terms
   * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
   * distributed with this work for additional information regarding copyright
   * ownership.  You may not use this file except in compliance with the License.
   *
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  /*
   * Copyright (C) 2014 Cloudius Systems, Ltd.
   */
  
  #include <seastar/net/ip_checksum.hh>
  #include <seastar/net/net.hh>
  #include <arpa/inet.h>
  
  namespace seastar {
  
  namespace net {
  
  void checksummer::sum(const char* data, size_t len) {
      auto orig_len = len;
      if (odd) {
          csum += uint8_t(*data++);
          --len;
      }
      auto p64 = reinterpret_cast<const packed<uint64_t>*>(data);
      while (len >= 8) {
          csum += ntohq(*p64++);
          len -= 8;
      }
      auto p16 = reinterpret_cast<const packed<uint16_t>*>(p64);
      while (len >= 2) {
          csum += ntohs(*p16++);
          len -= 2;
      }
      auto p8 = reinterpret_cast<const uint8_t*>(p16);
      if (len) {
          csum += *p8++ << 8;
          len -= 1;
      }
      odd ^= orig_len & 1;
  }
  
  uint16_t checksummer::get() const {
      __int128 csum1 = (csum & 0xffff'ffff'ffff'ffff) + (csum >> 64);
      uint64_t csum = (csum1 & 0xffff'ffff'ffff'ffff) + (csum1 >> 64);
      csum = (csum & 0xffff) + ((csum >> 16) & 0xffff) + ((csum >> 32) & 0xffff) + (csum >> 48);
      csum = (csum & 0xffff) + (csum >> 16);
      csum = (csum & 0xffff) + (csum >> 16);
      return htons(~csum);
  }
  
  void checksummer::sum(const packet& p) {
      for (auto&& f : p.fragments()) {
          sum(f.base, f.size);
      }
  }
  
  uint16_t ip_checksum(const void* data, size_t len) {
      checksummer cksum;
      cksum.sum(reinterpret_cast<const char*>(data), len);
      return cksum.get();
  }
  
  
  }
  
  }
  