// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
/*
 * 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 <arpa/inet.h>
#include "net.h"
#include "IPChecksum.h"

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 uint64_t*>(data);
  while (len >= 8) {
    csum += ntohq(*p64++);
    len -= 8;
  }
  auto p16 = reinterpret_cast<const 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 & 0xffffffffffffffff) + (csum >> 64);
  uint64_t csum = (csum1 & 0xffffffffffffffff) + (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();
}
