ACE_INET_Addr类 API

ACE_INET_Addr类，在这个ACE_网络框架中，应该是比较重要的辅助类，该类主要封装了C SOCKET 的地址对象，通过外观封装的模式，把struct sockaddr_in封装在内。方便用户的操作。 

因此个人认为掌握此类的常用构造方法和常用的成员函数，并深刻的理解，对于后续的学习ACE或者开发ACE网络应用程序应该会起到很大的帮助。工欲用其器、必先利其器。就先让我们把ACE_INET_Addr对象深刻的牢记在心中吧。

/* -*- C++ -*- */

//=============================================================================
/**
 *  @file    INET_Addr.h
 *
 *  $Id: INET_Addr.h 78617 2007-06-27 20:40:19Z mesnier_p $
 *
 *  @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
 */
//=============================================================================

#ifndef ACE_INET_ADDR_H
#define ACE_INET_ADDR_H
#include /**/ "ace/pre.h"

#include "ace/Sock_Connect.h"

#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

#include "ace/Addr.h"

#if defined(ACE_VXWORKS)
   // Needed to get INET_ADDR_LEN
#  include /**/ "inetLib.h"
#endif /* ACE_VXWORKS */

ACE_BEGIN_VERSIONED_NAMESPACE_DECL

/**
 * @class ACE_INET_Addr
 *
 * @brief Defines a C++ wrapper facade for the Internet domain address
 * family format.
 */
class ACE_Export ACE_INET_Addr : public ACE_Addr
{
public:
  // = Initialization methods.

  /// Default constructor.
  /// 默认构造函数
  ACE_INET_Addr (void);

  /// Copy constructor.
  /// 拷贝构造函数
  ACE_INET_Addr (const ACE_INET_Addr &);

  /// Creates an ACE_INET_Addr from a sockaddr_in structure.
  /// 使用参数@addr 地址初始化ACE_INET_Addr对象。
  /// 参数@len 为 @addr结构地址对象的长度，使用 sizeof(strcut sockaddr_in)
  ACE_INET_Addr (const sockaddr_in *addr, int len);

  /// Creates an ACE_INET_Addr from a <port_number> and the remote
  /// <host_name>. The port number is assumed to be in host byte order.
  /// To set a port already in network byte order, please @see set().
  /// Use address_family to select IPv6 (PF_INET6) vs. IPv4 (PF_INET).
  /// 使用参数 @port_number 和 host_name 构造一个ACE_INET_Addr对象。
  /// @port_number应该为主机字节序，构造函数需要把它转换了网络字节序。
  /// 如果port_number为网络字节序，请使用 set成员函数或者set_port_number成员函数。
  /// @address_family 用于指定ACE_INET_Addr的地址类型PF_INET(IPv4)或者PF_INET6(IPv6)
  ACE_INET_Addr (u_short port_number,
                 const char host_name[],
                 int address_family = AF_UNSPEC);

  /**
   * Initializes an ACE_INET_Addr from the <address>, which can be
   * "ip-number:port-number" (e.g., "tango.cs.wustl.edu:1234" or
   * "128.252.166.57:1234").  If there is no ':' in the <address> it
   * is assumed to be a port number, with the IP address being
   * INADDR_ANY.
   * 使用参数@address初始化一个ACE_INET_Addr对象。
   * address的格式为 ip-number:port-number 或者 port-number.
   * ip-number 可以为点分号的IP地址，也可是是域名地址。
   * 如果参数@address没有提供 ip-number，只提供port-number时，地址被初始化为INADDR_ANY
   * port-number 为主机字节序。
   */
  explicit ACE_INET_Addr (const char address[],
                          int address_family = AF_UNSPEC);

  /**
   * Creates an ACE_INET_Addr from a <port_number> and an Internet
   * <ip_addr>.  This method assumes that <port_number> and <ip_addr>
   * are in host byte order. If you have addressing information in
   * network byte order, @see set().
   * 使用主机字节序的@port_number 和 @ip_addr初始化一个ACE_INET_Addr对象。
   * 如port_number或者 ip_addr为网络字节序时，请使用 set成员函数。
   */
  explicit ACE_INET_Addr (u_short port_number,
                          ACE_UINT32 ip_addr = INADDR_ANY);

  /// Uses <getservbyname> to create an ACE_INET_Addr from a
  /// <port_name>, the remote <host_name>, and the <protocol>.
  /// 通过 getservbyname API获得port_name的端口，eg port_name="ftp"时，得到的端口是21.
  ACE_INET_Addr (const char port_name[],
                 const char host_name[],
                 const char protocol[] = "tcp");

  /**
   * Uses <getservbyname> to create an ACE_INET_Addr from a
   * <port_name>, an Internet <ip_addr>, and the <protocol>.  This
   * method assumes that <ip_addr> is in host byte order.
   */
  ACE_INET_Addr (const char port_name[],
                 ACE_UINT32 ip_addr,
                 const char protocol[] = "tcp");

#if defined (ACE_HAS_WCHAR)
  ACE_INET_Addr (u_short port_number,
                 const wchar_t host_name[],
                 int address_family = AF_UNSPEC);

  explicit ACE_INET_Addr (const wchar_t address[],
                          int address_family = AF_UNSPEC);

  ACE_INET_Addr (const wchar_t port_name[],
                 const wchar_t host_name[],
                 const wchar_t protocol[] = ACE_TEXT_WIDE ("tcp"));

  ACE_INET_Addr (const wchar_t port_name[],
                 ACE_UINT32 ip_addr,
                 const wchar_t protocol[] = ACE_TEXT_WIDE ("tcp"));
#endif /* ACE_HAS_WCHAR */

  /// Default dtor.
  ~ACE_INET_Addr (void);

  // = Direct initialization methods.
  // = 直接初始化方法。当使用默认构造函数创建一个ACE_INET_Addr对象时，可以使用
  // 下面的来设置一个ACE_INET_Addr对象的地址和端口。

  // These methods are useful after the object has been constructed.

  /// Initializes from another ACE_INET_Addr.
  /// 使用一个已经存在的ACE_INET_Addr对象来初始化本对象。
  int set (const ACE_INET_Addr &);

  /**
   * Initializes an ACE_INET_Addr from a <port_number> and the
   * remote <host_name>.
   * 使用参数@port_number 和@host_name初始化 ACE_INET_Addr 对象。
   * If <encode> is non-zero then <port_number> is
   * converted into network byte order, otherwise it is assumed to be
   * in network byte order already and are passed straight through.
   * 如果参数@encode 为TRUE(非零),表示需要set函数内部进行网络字节序的转换,
   * 也就是此时 port_number属于主机字节序的值。否则port_number就是已经是网络
   * 字节序了，无需进行转换，直接赋值即可。
   * address_family can be used to select IPv4/IPv6 if the OS has
   * IPv6 capability (ACE_HAS_IPV6 is defined). To specify IPv6, use
   * the value AF_INET6. To specify IPv4, use AF_INET.
   * 参数@address_family 用于选定IPv4/IPv6的地址格式。使用AF_INET指定IPv4地址,
   * AF_INET6指定IPv4地址格式。
   */
  int set (u_short port_number,
           const char host_name[],
           int encode = 1,
           int address_family = AF_UNSPEC);

  /**
   * Initializes an ACE_INET_Addr from a @a port_number and an Internet
   * @a ip_addr.
   * 使用参数@port_number 和参数 @ip_addr初始化 ACE_INET_Addr对象。
   * If @a encode is non-zero then the port number and IP address
   * are converted into network byte order, otherwise they are assumed to be
   * in network byte order already and are passed straight through.
   * 如果参数@encode 为TRUE(非零)时，表面 @port_number、@ip_addr 为主机字节序，
   * set 函数内部需要把它们转换为网络字节序。否则它们为网络字节序，无需而外的转换
   * 直接赋值。
   * If <map> is non-zero and IPv6 support has been compiled in,
   * then this address will be set to the IPv4-mapped IPv6 address of it.
   */
  int set (u_short port_number,
           ACE_UINT32 ip_addr = INADDR_ANY,
           int encode = 1,
           int map = 0);

  /// Uses <getservbyname> to initialize an ACE_INET_Addr from a
  /// <port_name>, the remote <host_name>, and the <protocol>.
  int set (const char port_name[],
           const char host_name[],
           const char protocol[] = "tcp");

  /**
   * Uses <getservbyname> to initialize an ACE_INET_Addr from a
   * <port_name>, an <ip_addr>, and the <protocol>.  This assumes that
   * <ip_addr> is already in network byte order.
   */
  int set (const char port_name[],
           ACE_UINT32 ip_addr,
           const char protocol[] = "tcp");

  /**
   * Initializes an ACE_INET_Addr from the @a addr, which can be
   * "ip-number:port-number" (e.g., "tango.cs.wustl.edu:1234" or
   * "128.252.166.57:1234").  If there is no ':' in the <address> it
   * is assumed to be a port number, with the IP address being
   * INADDR_ANY.
   * 参数@addr格式为 %s:%d 或者 %d。
   * %s为 IP地址或者域名， %d 为服务端口号。
   * 也就是如果addr 数组中没有 冒号':' 时，此时地址被设置为 INADD_ANY，端口为@addr指定。
   */
  int set (const char addr[], int address_family = AF_UNSPEC);

  /// Creates an ACE_INET_Addr from a sockaddr_in structure.
  /// 使用 sockaddr_in 结构设置ACE_INET_Addr对象。
  int set (const sockaddr_in *,
           int len);

#if defined (ACE_HAS_WCHAR)
 /**
 * 定义宽字符支持的接口。
 */
  int set (u_short port_number,
           const wchar_t host_name[],
           int encode = 1,
           int address_family = AF_UNSPEC);

  int set (const wchar_t port_name[],
           const wchar_t host_name[],
           const wchar_t protocol[] = ACE_TEXT_WIDE ("tcp"));

  int set (const wchar_t port_name[],
           ACE_UINT32 ip_addr,
           const wchar_t protocol[] = ACE_TEXT_WIDE ("tcp"));

  int set (const wchar_t addr[], int address_family = AF_UNSPEC);
#endif /* ACE_HAS_WCHAR */

  /// Return a pointer to the underlying network address.
  /// 获得原始的网络地址指针，根据IPv4或者IPv6,可以得到一个 struct sockaddr地址的指针。
  virtual void *get_addr (void) const;
  int get_addr_size(void) const;

  /// Set a pointer to the address.
  virtual void set_addr (void *, int len);

  /// Set a pointer to the address.
  virtual void set_addr (void *, int len, int map);

  /**
   * Transform the current ACE_INET_Addr address into string format.
   * If <ipaddr_format> is non-0 this produces "ip-number:port-number"
   * (e.g., "128.252.166.57:1234"), whereas if <ipaddr_format> is 0
   * this produces "ip-name:port-number" (e.g.,
   * "tango.cs.wustl.edu:1234").  Returns -1 if the @a size of the
   * <buffer> is too small, else 0.
   * 把地址转换为字符串， 参数@ipaddr_format指定转换的格式，如果
   * @ipaddr_format为 TRUE(非零)时，转换为点分十进制的IP地址格式。否则
   * 可能转换为域名的地址格式。
   * @return 成功时返回 0，否则返回 -1，此时参数@buffer的长度太短。
   *
   */
  virtual int addr_to_string (ACE_TCHAR buffer[],
                              size_t size,
                              int ipaddr_format = 1) const;

  /**
   * Initializes an ACE_INET_Addr from the @a address, which can be
   * "ip-addr:port-number" (e.g., "tango.cs.wustl.edu:1234"),
   * "ip-addr:port-name" (e.g., "tango.cs.wustl.edu:telnet"),
   * "ip-number:port-number" (e.g., "128.252.166.57:1234"), or
   * "ip-number:port-name" (e.g., "128.252.166.57:telnet").  If there
   * is no ':' in the <address> it is assumed to be a port number,
   * with the IP address being INADDR_ANY.
   * 把字符串表示的地址格式转换为 ACE_INET_Addr对象的地址。
   * 地址格式可以为 [{ip-addr|ip-number}:]{port-number|port-name}
   * 如果地址格式没有包括冒号':'时，函数内部认为只是设置 port-number|port-name,
   * 地址被设置为 INADDR_ANY
   */
  virtual int string_to_addr (const char address[],
                              int address_family = AF_UNSPEC);

#if defined (ACE_HAS_WCHAR)
  /*
  virtual int string_to_addr (const char address[]);
  */
#endif /* ACE_HAS_WCHAR */

  /**
   * Sets the port number without affecting the host name.  If
   * <encode> is enabled then <port_number> is converted into network
   * byte order, otherwise it is assumed to be in network byte order
   * already and are passed straight through.
   * 设置ACE_INET_Addr对象的端口部分，不影响地址域。
   * 参数@encode 的意思等同 set函数的@encode参数。
   */
  void set_port_number (u_short,
                        int encode = 1);

  /**
   * Sets the address without affecting the port number.  If
   * <encode> is enabled then <ip_addr> is converted into network
   * byte order, otherwise it is assumed to be in network byte order
   * already and are passed straight through.  The size of the address
   * is specified in the @a len parameter.
   * If <map> is non-zero, IPv6 support has been compiled in, and
   * <ip_addr> is an IPv4 address, then this address is set to the IPv4-mapped
   * IPv6 address of it.
   * 设置ACE_INET_Addr对象的地址部分，不改变地址对象的端口。
   * 参数@enable与set函数的@encode一致。
   * 参数@len指定 参数@ip_addr的长度。
   * 参数@map 为 TRUE(非零)是，表示支持IPv6地址格式，否则为IPv4的地址。
   */
  int set_address (const char *ip_addr,
                   int len,
                   int encode = 1,
                   int map = 0);

#if (defined (__linux__) || defined (ACE_WIN32)) && defined (ACE_HAS_IPV6)
  /**
   * Sets the interface that should be used for this address. This only has
   * an effect when the address is link local, otherwise it does nothing.
   */
  int set_interface (const char *intf_name);
#endif /* (__linux__ || ACE_WIN32) && ACE_HAS_IPV6 */

  /// Return the port number, converting it into host byte-order.
  u_short get_port_number (void) const;

  /**
   * Return the character representation of the name of the host,
   * storing it in the <hostname> (which is assumed to be
   * <hostnamelen> bytes long).  This version is reentrant.  If
   * <hostnamelen> is greater than 0 then <hostname> will be
   * NUL-terminated even if -1 is returned.
   */
  int get_host_name (char hostname[],
                     size_t hostnamelen) const;

#if defined (ACE_HAS_WCHAR)
  int get_host_name (wchar_t hostname[],
                     size_t hostnamelen) const;
#endif /* ACE_HAS_WCHAR */

  /**
   * Return the character representation of the hostname.  This
   * version is non-reentrant since it returns a pointer to a static
   * data area.  You should therefore either (1) do a "deep copy" of
   * the address returned by get_host_name(), e.g., using strdup() or
   * (2) use the "reentrant" version of get_host_name() described
   * above.
   */
  const char *get_host_name (void) const;

  /**
   * Return the "dotted decimal" Internet address representation of
   * the hostname storing it in the @a addr (which is assumed to be
   * <addr_size> bytes long).  This version is reentrant.
   */
  const char *get_host_addr (char *addr, int addr_size) const;

  /**
   * Return the "dotted decimal" Internet address representation of
   * the hostname.  This version is non-reentrant since it returns a
   * pointer to a static data area.  You should therefore either
   * (1) do a "deep copy" of the address returned by get_host_addr(), e.g.,
   * using strdup() or (2) use the "reentrant" version of
   * get_host_addr() described above.
   */
  const char *get_host_addr (void) const;

  /// Return the 4-byte IP address, converting it into host byte
  /// order.
  ACE_UINT32 get_ip_address (void) const;

  /// Return @c true if the IP address is INADDR_ANY or IN6ADDR_ANY.
  bool is_any (void) const;

  /// Return @c true if the IP address is IPv4/IPv6 loopback address.
  bool is_loopback (void) const;

  /// Return @c true if the IP address is IPv4/IPv6 multicast address.
  bool is_multicast (void) const;

#if defined (ACE_HAS_IPV6)
  /// Return @c true if the IP address is IPv6 linklocal address.
  bool is_linklocal (void) const;

  /// Return @c true if the IP address is IPv4-mapped IPv6 address.
  bool is_ipv4_mapped_ipv6 (void) const;

  /// Return @c true if the IP address is IPv4-compatible IPv6 address.
  bool is_ipv4_compat_ipv6 (void) const;
#endif /* ACE_HAS_IPV6 */

  /**
   * Returns @c true if @c this is less than @a rhs.  In this context,
   * "less than" is defined in terms of IP address and TCP port
   * number.  This operator makes it possible to use @c ACE_INET_Addrs
   * in STL maps.
   * 定义次函数，有何实际的应用吗？比较2个地址的大小有何实际意义?
   *
   */
  bool operator < (const ACE_INET_Addr &rhs) const;

  /// Compare two addresses for equality.  The addresses are considered
  /// equal if they contain the same IP address and port number.
  /// 比较2个地址是否相等，包括地址部分和端口部分。
  bool operator == (const ACE_INET_Addr &SAP) const;

  /// Compare two addresses for inequality.
  /// 比较2个地址是否不相等
  bool operator != (const ACE_INET_Addr &SAP) const;

  /// A variation of the equality operator, this method only compares the
  /// IP address and ignores the port number.
  /// 比较2个地址是否相等，只比较地址部分，忽略端口部分。
  bool is_ip_equal (const ACE_INET_Addr &SAP) const;

  /// Computes and returns hash value.
  virtual u_long hash (void) const;

  /// Dump the state of an object.
  void dump (void) const;

  /// Declare the dynamic allocation hooks.
  ACE_ALLOC_HOOK_DECLARE;

private:
  /// Insure that @a hostname is properly null-terminated.
  int get_host_name_i (char hostname[], size_t hostnamelen) const;

  // Methods to gain access to the actual address of
  // the underlying internet address structure.
  void *ip_addr_pointer (void) const;
  int ip_addr_size (void) const;
  int determine_type (void) const;

  /// Initialize underlying inet_addr_ to default values
  void reset (void);

  /// Underlying representation.
  /// This union uses the knowledge that the two structures share the
  /// first member, sa_family (as all sockaddr structures do).
  union
  {
    sockaddr_in  in4_;
#if defined (ACE_HAS_IPV6)
    sockaddr_in6 in6_;
#endif /* ACE_HAS_IPV6 */
  } inet_addr_;

#if defined (ACE_VXWORKS)
  char buf_[INET_ADDR_LEN];
#endif
};

ACE_END_VERSIONED_NAMESPACE_DECL

#if defined (__ACE_INLINE__)
#include "ace/INET_Addr.inl"
#endif /* __ACE_INLINE__ */

#include /**/ "ace/post.h"
#endif /* ACE_INET_ADDR_H */

总结：

1.在set、set_port_number、set_address中都提供了一个参数@encode,此参数在构造函数的参数中并没有提供。因为也意味着，使用任何一个构造函数来创建一个ACE_INET_Addr对象时，其地址和端口必须是主机字节序的。如果地址或者端口为网络字节序时，必须转换为主机字节序才可以使用构造函数。或者使用默认的构造函数，在通过set、set_port_number、set_address等成员函数，指定encode参数为FALSE(0)时，也可以直接把网络字节序的地址和端口设置给ACE_INET_Addr对象。如果地址和端口是2中不同的字节序，需要分别使用set_address和set_port_number进行设置，否则就可以使用set函数一次性设置地址和端口。

2.比较2个ACE_INET_Addr对象的相等性。 根据情况使用不同的成员函数。

  地址和端口都要相等时，使用 ==进行比较。

  只比较地址时，忽略端口时。使用 is_ip_equal 成员函数。