muduo源码剖析之InetAddress

InetAddress

InetAddress 类是 muduo 网络库中的一个重要类，用于表示网络中的 IP 地址和端口号。

InetAddress 类在 muduo 网络库中被广泛使用，用于表示网络中的通信实体的地址信息，例如服务器地址、客户端地址等。通过 InetAddress 类，我们可以方便地操作 IP 地址和端口号，实现网络通信的功能。

源码比较简单,已经编写详细注释

源码剖析

InetAddress.h

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)
//
// This is a public header file, it must only include public header files.

#ifndef MUDUO_NET_INETADDRESS_H
#define MUDUO_NET_INETADDRESS_H

#include "muduo/base/copyable.h"
#include "muduo/base/StringPiece.h"

#include 

namespace muduo
{
namespace net
{
namespace sockets
{
const struct sockaddr* sockaddr_cast(const struct sockaddr_in6* addr);
}

///
/// Wrapper of sockaddr_in.
///
/// This is an POD interface class.
class InetAddress : public muduo::copyable
{
 public:
  /// Constructs an endpoint with given port number.
  /// Mostly used in TcpServer listening.
  explicit InetAddress(uint16_t port = 0, bool loopbackOnly = false, bool ipv6 = false);

  /// Constructs an endpoint with given ip and port.
  /// @c ip should be "1.2.3.4"
  InetAddress(StringArg ip, uint16_t port, bool ipv6 = false);

  /// Constructs an endpoint with given struct @c sockaddr_in
  /// Mostly used when accepting new connections
  explicit InetAddress(const struct sockaddr_in& addr)
    : addr_(addr)
  { }

  explicit InetAddress(const struct sockaddr_in6& addr)
    : addr6_(addr)
  { }
  //返回addr_地址成员变量的协议族
  sa_family_t family() const { return addr_.sin_family; }

  //获取ip地址的点十分进制的字符串
  string toIp() const;

  //获取ip地址和port端口的点十分进制的字符串
  string toIpPort() const;

  //获取端口号(本机字节序)
  uint16_t port() const;

  // default copy/assignment are Okay
  //返回sockaddr结构体指针
  const struct sockaddr* getSockAddr() const { return sockets::sockaddr_cast(&addr6_); }

  //设置SockAddr
  void setSockAddrInet6(const struct sockaddr_in6& addr6) { addr6_ = addr6; }

  //获取ip地址(网络字节序)
  uint32_t ipv4NetEndian() const;

  //获取端口号(网络字节序)
  uint16_t portNetEndian() const { return addr_.sin_port; }

  // resolve hostname to IP address, not changing port or sin_family
  // return true on success.
  // thread safe
  //通过主机名解析出ip地址
  static bool resolve(StringArg hostname, InetAddress* result);
  // static std::vector resolveAll(const char* hostname, uint16_t port = 0);

  // set IPv6 ScopeID
  //设置ipv6地址的作用域范围。
  void setScopeId(uint32_t scope_id);

 private:
  union
  {
    //ipv4
    struct sockaddr_in addr_;
    //ipv6
    struct sockaddr_in6 addr6_;
  };
};

}  // namespace net
}  // namespace muduo

#endif  // MUDUO_NET_INETADDRESS_H

InetAddress.cc

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include "muduo/net/InetAddress.h"

#include "muduo/base/Logging.h"
#include "muduo/net/Endian.h"
#include "muduo/net/SocketsOps.h"

#include 
#include 

// INADDR_ANY use (type)value casting.
#pragma GCC diagnostic ignored "-Wold-style-cast"
static const in_addr_t kInaddrAny = INADDR_ANY;
static const in_addr_t kInaddrLoopback = INADDR_LOOPBACK;
#pragma GCC diagnostic error "-Wold-style-cast"

//     /* Structure describing an Internet socket address.  */
//     struct sockaddr_in {
//         sa_family_t    sin_family; /* address family: AF_INET */
//         uint16_t       sin_port;   /* port in network byte order */
//         struct in_addr sin_addr;   /* internet address */
//     };

//     /* Internet address. */
//     typedef uint32_t in_addr_t;
//     struct in_addr {
//         in_addr_t       s_addr;     /* address in network byte order */
//     };

//     struct sockaddr_in6 {
//         sa_family_t     sin6_family;   /* address family: AF_INET6 */
//         uint16_t        sin6_port;     /* port in network byte order */
//         uint32_t        sin6_flowinfo; /* IPv6 flow information */
//         struct in6_addr sin6_addr;     /* IPv6 address */
//         uint32_t        sin6_scope_id; /* IPv6 scope-id */
//     };

using namespace muduo;
using namespace muduo::net;

static_assert(sizeof(InetAddress) == sizeof(struct sockaddr_in6),
              "InetAddress is same size as sockaddr_in6");
static_assert(offsetof(sockaddr_in, sin_family) == 0, "sin_family offset 0");
static_assert(offsetof(sockaddr_in6, sin6_family) == 0, "sin6_family offset 0");
static_assert(offsetof(sockaddr_in, sin_port) == 2, "sin_port offset 2");
static_assert(offsetof(sockaddr_in6, sin6_port) == 2, "sin6_port offset 2");

InetAddress::InetAddress(uint16_t portArg, bool loopbackOnly, bool ipv6)
{
  static_assert(offsetof(InetAddress, addr6_) == 0, "addr6_ offset 0");
  static_assert(offsetof(InetAddress, addr_) == 0, "addr_ offset 0");
  if (ipv6)
  {
    memZero(&addr6_, sizeof addr6_);
    addr6_.sin6_family = AF_INET6;
    in6_addr ip = loopbackOnly ? in6addr_loopback : in6addr_any;
    addr6_.sin6_addr = ip;
    addr6_.sin6_port = sockets::hostToNetwork16(portArg);
  }
  else
  {
    memZero(&addr_, sizeof addr_);
    addr_.sin_family = AF_INET;
    in_addr_t ip = loopbackOnly ? kInaddrLoopback : kInaddrAny;
    addr_.sin_addr.s_addr = sockets::hostToNetwork32(ip);
    addr_.sin_port = sockets::hostToNetwork16(portArg);
  }
}

InetAddress::InetAddress(StringArg ip, uint16_t portArg, bool ipv6)
{
  if (ipv6 || strchr(ip.c_str(), ':'))
  {
    memZero(&addr6_, sizeof addr6_);
    sockets::fromIpPort(ip.c_str(), portArg, &addr6_);
  }
  else
  {
    memZero(&addr_, sizeof addr_);
    sockets::fromIpPort(ip.c_str(), portArg, &addr_);
  }
}

string InetAddress::toIpPort() const
{
  char buf[64] = "";
  sockets::toIpPort(buf, sizeof buf, getSockAddr());
  return buf;
}

string InetAddress::toIp() const
{
  char buf[64] = "";
  sockets::toIp(buf, sizeof buf, getSockAddr());
  return buf;
}

uint32_t InetAddress::ipv4NetEndian() const
{
  assert(family() == AF_INET);
  return addr_.sin_addr.s_addr;
}

uint16_t InetAddress::port() const
{
  return sockets::networkToHost16(portNetEndian());
}

static __thread char t_resolveBuffer[64 * 1024];

bool InetAddress::resolve(StringArg hostname, InetAddress* out)
{
  assert(out != NULL);
  struct hostent hent;
  struct hostent* he = NULL;
  int herrno = 0;
  memZero(&hent, sizeof(hent));

  //通过主机名解析出ip地址
  int ret = gethostbyname_r(hostname.c_str(), &hent, t_resolveBuffer, sizeof t_resolveBuffer, &he, &herrno);
  if (ret == 0 && he != NULL)
  {
    assert(he->h_addrtype == AF_INET && he->h_length == sizeof(uint32_t));
    out->addr_.sin_addr = *reinterpret_cast<struct in_addr*>(he->h_addr);
    return true;
  }
  else
  {
    if (ret)
    {
      LOG_SYSERR << "InetAddress::resolve";
    }
    return false;
  }
}

void InetAddress::setScopeId(uint32_t scope_id)
{
  if (family() == AF_INET6)
  {
    addr6_.sin6_scope_id = scope_id;
  }
}