text: /*
   * Copyright 2014-present Facebook, Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * 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.
   */
  
  #pragma once
  
  #include <cstring>
  
  #include <array>
  #include <functional>
  #include <iosfwd>
  
  #include <folly/Expected.h>
  #include <folly/FBString.h>
  #include <folly/IPAddressException.h>
  #include <folly/Range.h>
  #include <folly/detail/IPAddress.h>
  #include <folly/hash/Hash.h>
  
  namespace folly {
  
  class IPAddress;
  class IPAddressV4;
  class IPAddressV6;
  
  /**
   * Pair of IPAddressV4, netmask
   */
  typedef std::pair<IPAddressV4, uint8_t> CIDRNetworkV4;
  
  /**
   * Specialization for IPv4 addresses
   */
  typedef std::array<uint8_t, 4> ByteArray4;
  
  /**
   * IPv4 variation of IPAddress.
   *
   * Added methods: toLong, toLongHBO and createIPv6
   *
   * @note toLong/fromLong deal in network byte order, use toLongHBO/fromLongHBO
   * if working in host byte order.
   *
   * @see IPAddress
   */
  class IPAddressV4 {
   public:
    // Max size of std::string returned by toFullyQualified.
    static constexpr size_t kMaxToFullyQualifiedSize =
        4 /*words*/ * 3 /*max chars per word*/ + 3 /*separators*/;
  
    // returns true iff the input string can be parsed as an ipv4-address
    static bool validate(StringPiece ip) noexcept;
  
    // create an IPAddressV4 instance from a uint32_t (network byte order)
    static IPAddressV4 fromLong(uint32_t src);
    // same as above but host byte order
    static IPAddressV4 fromLongHBO(uint32_t src);
  
    /**
     * Create a new IPAddress instance from the provided binary data.
     * @throws IPAddressFormatException if the input length is not 4 bytes.
     */
    static IPAddressV4 fromBinary(ByteRange bytes);
  
    /**
     * Non-throwing version of fromBinary().
     * On failure returns IPAddressFormatError.
     */
    static Expected<IPAddressV4, IPAddressFormatError> tryFromBinary(
        ByteRange bytes) noexcept;
  
    /**
     * Tries to create a new IPAddressV4 instance from provided string and
     * returns it on success. Returns IPAddressFormatError on failure.
     */
    static Expected<IPAddressV4, IPAddressFormatError> tryFromString(
        StringPiece str) noexcept;
  
    /**
     * Returns the address as a Range.
     */
    ByteRange toBinary() const {
      return ByteRange((const unsigned char*)&addr_.inAddr_.s_addr, 4);
    }
  
    /**
     * Create a new IPAddress instance from the in-addr.arpa representation.
     * @throws IPAddressFormatException if the input is not a valid in-addr.arpa
     * representation
     */
    static IPAddressV4 fromInverseArpaName(const std::string& arpaname);
  
    /**
     * Convert a IPv4 address string to a long in network byte order.
     * @param [in] ip the address to convert
     * @return the long representation of the address
     */
    static uint32_t toLong(StringPiece ip);
    // Same as above, but in host byte order.
    // This is slightly slower than toLong.
    static uint32_t toLongHBO(StringPiece ip);
  
    /**
     * Default constructor for IPAddressV4.
     *
     * The address value will be 0.0.0.0
     */
    IPAddressV4();
  
    // Create an IPAddressV4 from a string
    // @throws IPAddressFormatException
    explicit IPAddressV4(StringPiece ip);
  
    // ByteArray4 constructor
    explicit IPAddressV4(const ByteArray4& src) noexcept;
  
    // in_addr constructor
    explicit IPAddressV4(const in_addr src) noexcept;
  
    // Return the V6 mapped representation of the address.
    IPAddressV6 createIPv6() const;
  
    /**
     * Return a V6 address in the format of an 6To4 address.
     */
    IPAddressV6 getIPv6For6To4() const;
  
    // Return the long (network byte order) representation of the address.
    uint32_t toLong() const {
      return toAddr().s_addr;
    }
  
    // Return the long (host byte order) representation of the address.
    // This is slightly slower than toLong.
    uint32_t toLongHBO() const {
      return ntohl(toLong());
    }
  
    /**
     * @see IPAddress#bitCount
     * @returns 32
     */
    static constexpr size_t bitCount() {
      return 32;
    }
  
    /**
     * @See IPAddress#toJson
     */
    std::string toJson() const;
  
    size_t hash() const {
      static const uint32_t seed = AF_INET;
      uint32_t hashed = hash::fnv32_buf(&addr_, 4);
      return hash::hash_combine(seed, hashed);
    }
  
    // @see IPAddress#inSubnet
    // @throws IPAddressFormatException if string doesn't contain a V4 address
    bool inSubnet(StringPiece cidrNetwork) const;
  
    // return true if address is in subnet
    bool inSubnet(const IPAddressV4& subnet, uint8_t cidr) const {
      return inSubnetWithMask(subnet, fetchMask(cidr));
    }
    bool inSubnetWithMask(const IPAddressV4& subnet, const ByteArray4 mask) const;
  
    // @see IPAddress#isLoopback
    bool isLoopback() const;
  
    // @see IPAddress#isLinkLocal
    bool isLinkLocal() const;
  
    // @see IPAddress#isNonroutable
    bool isNonroutable() const;
  
    // @see IPAddress#isPrivate
    bool isPrivate() const;
  
    // @see IPAddress#isMulticast
    bool isMulticast() const;
  
    // @see IPAddress#isZero
    bool isZero() const {
      constexpr auto zero = ByteArray4{{}};
      return 0 == std::memcmp(bytes(), zero.data(), zero.size());
    }
  
    bool isLinkLocalBroadcast() const {
      return (INADDR_BROADCAST == toLongHBO());
    }
  
    // @see IPAddress#mask
    IPAddressV4 mask(size_t numBits) const;
  
    // @see IPAddress#str
    std::string str() const;
  
    std::string toInverseArpaName() const;
  
    // return underlying in_addr structure
    in_addr toAddr() const {
      return addr_.inAddr_;
    }
  
    sockaddr_in toSockAddr() const {
      sockaddr_in addr;
      memset(&addr, 0, sizeof(sockaddr_in));
      addr.sin_family = AF_INET;
      memcpy(&addr.sin_addr, &addr_.inAddr_, sizeof(in_addr));
      return addr;
    }
  
    ByteArray4 toByteArray() const {
      ByteArray4 ba{{0}};
      std::memcpy(ba.data(), bytes(), 4);
      return ba;
    }
  
    // @see IPAddress#toFullyQualified
    std::string toFullyQualified() const {
      return str();
    }
  
    // @see IPAddress#toFullyQualifiedAppend
    void toFullyQualifiedAppend(std::string& out) const;
  
    // @see IPAddress#version
    uint8_t version() const {
      return 4;
    }
  
    /**
     * Return the mask associated with the given number of bits.
     * If for instance numBits was 24 (e.g. /24) then the V4 mask returned should
     * be {0xff, 0xff, 0xff, 0x00}.
     * @param [in] numBits bitmask to retrieve
     * @throws abort if numBits == 0 or numBits > bitCount()
     * @return mask associated with numBits
     */
    static const ByteArray4 fetchMask(size_t numBits);
  
    // Given 2 IPAddressV4, mask pairs extract the longest common IPAddress,
    // mask pair
    static CIDRNetworkV4 longestCommonPrefix(
        const CIDRNetworkV4& one,
        const CIDRNetworkV4& two);
    // Number of bytes in the address representation.
    static size_t byteCount() {
      return 4;
    }
    // get nth most significant bit - 0 indexed
    bool getNthMSBit(size_t bitIndex) const {
      return detail::getNthMSBitImpl(*this, bitIndex, AF_INET);
    }
    // get nth most significant byte - 0 indexed
    uint8_t getNthMSByte(size_t byteIndex) const;
    // get nth bit - 0 indexed
    bool getNthLSBit(size_t bitIndex) const {
      return getNthMSBit(bitCount() - bitIndex - 1);
    }
    // get nth byte - 0 indexed
    uint8_t getNthLSByte(size_t byteIndex) const {
      return getNthMSByte(byteCount() - byteIndex - 1);
    }
  
    const unsigned char* bytes() const {
      return addr_.bytes_.data();
    }
  
   private:
    union AddressStorage {
      static_assert(
          sizeof(in_addr) == sizeof(ByteArray4),
          "size of in_addr and ByteArray4 are different");
      in_addr inAddr_;
      ByteArray4 bytes_;
      AddressStorage() {
        std::memset(this, 0, sizeof(AddressStorage));
      }
      explicit AddressStorage(const ByteArray4 bytes) : bytes_(bytes) {}
      explicit AddressStorage(const in_addr addr) : inAddr_(addr) {}
    } addr_;
  
    /**
     * Set the current IPAddressV4 object to have the address specified by bytes.
     * Returns IPAddressFormatError if bytes.size() is not 4.
     */
    Expected<Unit, IPAddressFormatError> trySetFromBinary(
        ByteRange bytes) noexcept;
  };
  
  // boost::hash uses hash_value() so this allows boost::hash to work
  // automatically for IPAddressV4
  size_t hash_value(const IPAddressV4& addr);
  std::ostream& operator<<(std::ostream& os, const IPAddressV4& addr);
  // Define toAppend() to allow IPAddressV4 to be used with to<string>
  void toAppend(IPAddressV4 addr, std::string* result);
  void toAppend(IPAddressV4 addr, fbstring* result);
  
  /**
   * Return true if two addresses are equal.
   */
  inline bool operator==(const IPAddressV4& addr1, const IPAddressV4& addr2) {
    return (addr1.toLong() == addr2.toLong());
  }
  // Return true if addr1 < addr2
  inline bool operator<(const IPAddressV4& addr1, const IPAddressV4& addr2) {
    return (addr1.toLongHBO() < addr2.toLongHBO());
  }
  // Derived operators
  inline bool operator!=(const IPAddressV4& a, const IPAddressV4& b) {
    return !(a == b);
  }
  inline bool operator>(const IPAddressV4& a, const IPAddressV4& b) {
    return b < a;
  }
  inline bool operator<=(const IPAddressV4& a, const IPAddressV4& b) {
    return !(a > b);
  }
  inline bool operator>=(const IPAddressV4& a, const IPAddressV4& b) {
    return !(a < b);
  }
  
  } // namespace folly
  
  namespace std {
  template <>
  struct hash<folly::IPAddressV4> {
    size_t operator()(const folly::IPAddressV4 addr) const {
      return addr.hash();
    }
  };
  } // namespace std
  