ros的init机制续篇

这篇博客主要探讨init的实现过程

ros::init(argc, argv, "add_two_ints_client")

实现代码在init.cpp文件，这里直接给出来

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#include "ros/init.h"
#include "ros/names.h"
#include "ros/xmlrpc_manager.h"
#include "ros/poll_manager.h"
#include "ros/connection_manager.h"
#include "ros/topic_manager.h"
#include "ros/service_manager.h"
#include "ros/this_node.h"
#include "ros/network.h"
#include "ros/file_log.h"
#include "ros/callback_queue.h"
#include "ros/param.h"
#include "ros/rosout_appender.h"
#include "ros/subscribe_options.h"
#include "ros/transport/transport_tcp.h"
#include "ros/internal_timer_manager.h"
#include "xmlrpcpp/XmlRpcSocket.h"

#include "roscpp/GetLoggers.h"
#include "roscpp/SetLoggerLevel.h"
#include "roscpp/Empty.h"

#include <ros/console.h>
#include <ros/time.h>
#include <rosgraph_msgs/Clock.h>

#include <algorithm>

#include <signal.h>

#include <cstdlib>

namespace ros
{

namespace master
{
void init(const M_string& remappings);
}

namespace this_node
{
void init(const std::string& names, const M_string& remappings, uint32_t options);
}

namespace network
{
void init(const M_string& remappings);
}

namespace param
{
void init(const M_string& remappings);
}

namespace file_log
{
void init(const M_string& remappings);
}

CallbackQueuePtr g_global_queue;
ROSOutAppender* g_rosout_appender;
static CallbackQueuePtr g_internal_callback_queue;

static bool g_initialized = false;
static bool g_started = false;
static bool g_atexit_registered = false;
static boost::mutex g_start_mutex;
static bool g_ok = false;
static uint32_t g_init_options = 0;
static bool g_shutdown_requested = false;
static volatile bool g_shutting_down = false;
static boost::recursive_mutex g_shutting_down_mutex;
static boost::thread g_internal_queue_thread;

bool isInitialized()
{
  return g_initialized;
}

bool isShuttingDown()
{
  return g_shutting_down;
}

void checkForShutdown()
{
  if (g_shutdown_requested)
  {
    // Since this gets run from within a mutex inside PollManager, we need to prevent ourselves from deadlocking with
    // another thread that's already in the middle of shutdown()
    boost::recursive_mutex::scoped_try_lock lock(g_shutting_down_mutex, boost::defer_lock);
    while (!lock.try_lock() && !g_shutting_down)
    {
      ros::WallDuration(0.001).sleep();
    }

    if (!g_shutting_down)
    {
      shutdown();
    }

    g_shutdown_requested = false;
  }
}

void requestShutdown()
{
  g_shutdown_requested = true;
}

void atexitCallback()
{
  if (ok() && !isShuttingDown())
  {
    ROSCPP_LOG_DEBUG("shutting down due to exit() or end of main() without cleanup of all NodeHandles");
    g_started = false; // don't shutdown singletons, because they are already destroyed
    shutdown();
  }
}

void shutdownCallback(XmlRpc::XmlRpcValue& params, XmlRpc::XmlRpcValue& result)
{
  int num_params = 0;
  if (params.getType() == XmlRpc::XmlRpcValue::TypeArray)
    num_params = params.size();
  if (num_params > 1)
  {
    std::string reason = params[1];
    ROS_WARN("Shutdown request received.");
    ROS_WARN("Reason given for shutdown: [%s]", reason.c_str());
    requestShutdown();
  }

  result = xmlrpc::responseInt(1, "", 0);
}

bool getLoggers(roscpp::GetLoggers::Request&, roscpp::GetLoggers::Response& resp)
{
  std::map<std::string, ros::console::levels::Level> loggers;
  bool success = ::ros::console::get_loggers(loggers);
  if (success)
  {
    for (std::map<std::string, ros::console::levels::Level>::const_iterator it = loggers.begin(); it != loggers.end(); it++)
    {
      roscpp::Logger logger;
      logger.name = it->first;
      ros::console::levels::Level level = it->second;
      if (level == ros::console::levels::Debug)
      {
        logger.level = "debug";
      }
      else if (level == ros::console::levels::Info)
      {
        logger.level = "info";
      }
      else if (level == ros::console::levels::Warn)
      {
        logger.level = "warn";
      }
      else if (level == ros::console::levels::Error)
      {
        logger.level = "error";
      }
      else if (level == ros::console::levels::Fatal)
      {
        logger.level = "fatal";
      }
      resp.loggers.push_back(logger);
    }
  }
  return success;
}

bool setLoggerLevel(roscpp::SetLoggerLevel::Request& req, roscpp::SetLoggerLevel::Response&)
{
  std::transform(req.level.begin(), req.level.end(), req.level.begin(), (int(*)(int))std::toupper);

  ros::console::levels::Level level;
  if (req.level == "DEBUG")
  {
    level = ros::console::levels::Debug;
  }
  else if (req.level == "INFO")
  {
    level = ros::console::levels::Info;
  }
  else if (req.level == "WARN")
  {
    level = ros::console::levels::Warn;
  }
  else if (req.level == "ERROR")
  {
    level = ros::console::levels::Error;
  }
  else if (req.level == "FATAL")
  {
    level = ros::console::levels::Fatal;
  }
  else
  {
    return false;
  }

  bool success = ::ros::console::set_logger_level(req.logger, level);
  if (success)
  {
    console::notifyLoggerLevelsChanged();
  }

  return success;
}

bool closeAllConnections(roscpp::Empty::Request&, roscpp::Empty::Response&)
{
  ROSCPP_LOG_DEBUG("close_all_connections service called, closing connections");
  ConnectionManager::instance()->clear(Connection::TransportDisconnect);
  return true;
}

void clockCallback(const rosgraph_msgs::Clock::ConstPtr& msg)
{
  Time::setNow(msg->clock);
}

CallbackQueuePtr getInternalCallbackQueue()
{
  if (!g_internal_callback_queue)
  {
    g_internal_callback_queue.reset(new CallbackQueue);
  }

  return g_internal_callback_queue;
}

void basicSigintHandler(int sig)
{
  (void)sig;
  ros::requestShutdown();
}

void internalCallbackQueueThreadFunc()
{
  disableAllSignalsInThisThread();

  CallbackQueuePtr queue = getInternalCallbackQueue();

  while (!g_shutting_down)
  {
    queue->callAvailable(WallDuration(0.1));
  }
}

bool isStarted()
{
  return g_started;
}

void start()
{
  boost::mutex::scoped_lock lock(g_start_mutex);
  if (g_started)
  {
    return;
  }

  g_shutdown_requested = false;
  g_shutting_down = false;
  g_started = true;
  g_ok = true;

  bool enable_debug = false;
  std::string enable_debug_env;
  if ( get_environment_variable(enable_debug_env,"ROSCPP_ENABLE_DEBUG") )
  {
    try
    {
      enable_debug = boost::lexical_cast<bool>(enable_debug_env.c_str());
    }
    catch (boost::bad_lexical_cast&)
    {
    }
  }

#ifdef _MSC_VER
  if (env_ipv6)
  {
    free(env_ipv6);
  }
#endif

  param::param("/tcp_keepalive", TransportTCP::s_use_keepalive_, TransportTCP::s_use_keepalive_);

  PollManager::instance()->addPollThreadListener(checkForShutdown);
  XMLRPCManager::instance()->bind("shutdown", shutdownCallback);

  initInternalTimerManager();

  TopicManager::instance()->start();
  ServiceManager::instance()->start();
  ConnectionManager::instance()->start();
  PollManager::instance()->start();
  XMLRPCManager::instance()->start();

  if (!(g_init_options & init_options::NoSigintHandler))
  {
    signal(SIGINT, basicSigintHandler);
  }

  ros::Time::init();

  if (!(g_init_options & init_options::NoRosout))
  {
    g_rosout_appender = new ROSOutAppender;
    ros::console::register_appender(g_rosout_appender);
  }

  if (g_shutting_down) goto end;

  {
    ros::AdvertiseServiceOptions ops;
    ops.init<roscpp::GetLoggers>(names::resolve("~get_loggers"), getLoggers);
    ops.callback_queue = getInternalCallbackQueue().get();
    ServiceManager::instance()->advertiseService(ops);
  }

  if (g_shutting_down) goto end;

  {
    ros::AdvertiseServiceOptions ops;
    ops.init<roscpp::SetLoggerLevel>(names::resolve("~set_logger_level"), setLoggerLevel);
    ops.callback_queue = getInternalCallbackQueue().get();
    ServiceManager::instance()->advertiseService(ops);
  }

  if (g_shutting_down) goto end;

  if (enable_debug)
  {
    ros::AdvertiseServiceOptions ops;
    ops.init<roscpp::Empty>(names::resolve("~debug/close_all_connections"), closeAllConnections);
    ops.callback_queue = getInternalCallbackQueue().get();
    ServiceManager::instance()->advertiseService(ops);
  }

  if (g_shutting_down) goto end;

  {
    bool use_sim_time = false;
    param::param("/use_sim_time", use_sim_time, use_sim_time);

    if (use_sim_time)
    {
      Time::setNow(ros::Time());
    }

    if (g_shutting_down) goto end;

    if (use_sim_time)
    {
      ros::SubscribeOptions ops;
      ops.init<rosgraph_msgs::Clock>(names::resolve("/clock"), 1, clockCallback);
      ops.callback_queue = getInternalCallbackQueue().get();
      TopicManager::instance()->subscribe(ops);
    }
  }

  if (g_shutting_down) goto end;

  g_internal_queue_thread = boost::thread(internalCallbackQueueThreadFunc);
  getGlobalCallbackQueue()->enable();

  ROSCPP_LOG_DEBUG("Started node [%s], pid [%d], bound on [%s], xmlrpc port [%d], tcpros port [%d], using [%s] time", 
		   this_node::getName().c_str(), getpid(), network::getHost().c_str(), 
		   XMLRPCManager::instance()->getServerPort(), ConnectionManager::instance()->getTCPPort(), 
		   Time::useSystemTime() ? "real" : "sim");

  // Label used to abort if we've started shutting down in the middle of start(), which can happen in
  // threaded code or if Ctrl-C is pressed while we're initializing
end:
  // If we received a shutdown request while initializing, wait until we've shutdown to continue
  if (g_shutting_down)
  {
    boost::recursive_mutex::scoped_lock lock(g_shutting_down_mutex);
  }
}

void check_ipv6_environment() {
  char* env_ipv6 = NULL;
#ifdef _MSC_VER
  _dupenv_s(&env_ipv6, NULL, "ROS_IPV6");
#else
  env_ipv6 = getenv("ROS_IPV6");
#endif

  bool use_ipv6 = (env_ipv6 && strcmp(env_ipv6,"on") == 0);
  TransportTCP::s_use_ipv6_ = use_ipv6;
  XmlRpc::XmlRpcSocket::s_use_ipv6_ = use_ipv6;
}

void init(const M_string& remappings, const std::string& name, uint32_t options)
{
  if (!g_atexit_registered)
  {
    g_atexit_registered = true;
    atexit(atexitCallback);
  }

  if (!g_global_queue)
  {
    g_global_queue.reset(new CallbackQueue);
  }

  if (!g_initialized)
  {
    g_init_options = options;
    g_ok = true;

    ROSCONSOLE_AUTOINIT;
    // Disable SIGPIPE
#ifndef WIN32
    signal(SIGPIPE, SIG_IGN);
#endif
    check_ipv6_environment();
    network::init(remappings);
    master::init(remappings);
    // names:: namespace is initialized by this_node
    this_node::init(name, remappings, options);
    file_log::init(remappings);
    param::init(remappings);

    g_initialized = true;
  }
}

void init(int& argc, char** argv, const std::string& name, uint32_t options)
{
  M_string remappings;

  int full_argc = argc;
  // now, move the remapping argv's to the end, and decrement argc as needed
  for (int i = 0; i < argc; )
  {
    std::string arg = argv[i];
    size_t pos = arg.find(":=");
    if (pos != std::string::npos)
    {
      std::string local_name = arg.substr(0, pos);
      std::string external_name = arg.substr(pos + 2);

      ROSCPP_LOG_DEBUG("remap: %s => %s", local_name.c_str(), external_name.c_str());
      remappings[local_name] = external_name;

      // shuffle everybody down and stuff this guy at the end of argv
      char *tmp = argv[i];
      for (int j = i; j < full_argc - 1; j++)
        argv[j] = argv[j+1];
      argv[argc-1] = tmp;
      argc--;
    }
    else
    {
      i++; // move on, since we didn't shuffle anybody here to replace it
    }
  }

  init(remappings, name, options);
}

void init(const VP_string& remappings, const std::string& name, uint32_t options)
{
  M_string remappings_map;
  VP_string::const_iterator it = remappings.begin();
  VP_string::const_iterator end = remappings.end();
  for (; it != end; ++it)
  {
    remappings_map[it->first] = it->second;
  }

  init(remappings_map, name, options);
}

std::string getROSArg(int argc, const char* const* argv, const std::string& arg)
{
  for (int i = 0; i < argc; ++i)
  {
    std::string str_arg = argv[i];
    size_t pos = str_arg.find(":=");
    if (str_arg.substr(0,pos) == arg)
    {
      return str_arg.substr(pos+2);
    }
  }
  return "";
}

void removeROSArgs(int argc, const char* const* argv, V_string& args_out)
{
  for (int i = 0; i < argc; ++i)
  {
    std::string arg = argv[i];
    size_t pos = arg.find(":=");
    if (pos == std::string::npos)
    {
      args_out.push_back(arg);
    }
  }
}

void spin()
{
  SingleThreadedSpinner s;
  spin(s);
}

void spin(Spinner& s)
{
  s.spin();
}

void spinOnce()
{
  g_global_queue->callAvailable(ros::WallDuration());
}

void waitForShutdown()
{
  while (ok())
  {
    WallDuration(0.05).sleep();
  }
}

CallbackQueue* getGlobalCallbackQueue()
{
  return g_global_queue.get();
}

bool ok()
{
  return g_ok;
}

void shutdown()
{
  boost::recursive_mutex::scoped_lock lock(g_shutting_down_mutex);
  if (g_shutting_down)
    return;
  else
    g_shutting_down = true;

  ros::console::shutdown();

  g_global_queue->disable();
  g_global_queue->clear();

  if (g_internal_queue_thread.get_id() != boost::this_thread::get_id())
  {
    g_internal_queue_thread.join();
  }
  //ros::console::deregister_appender(g_rosout_appender);
  delete g_rosout_appender;
  g_rosout_appender = 0;

  if (g_started)
  {
    TopicManager::instance()->shutdown();
    ServiceManager::instance()->shutdown();
    PollManager::instance()->shutdown();
    ConnectionManager::instance()->shutdown();
    XMLRPCManager::instance()->shutdown();
  }

  g_started = false;
  g_ok = false;
  Time::shutdown();
}

}

---

需要探讨的函数init是：

void init(int& argc, char** argv, const std::string& name, uint32_t options)
{
  M_string remappings;

  int full_argc = argc;
  // now, move the remapping argv's to the end, and decrement argc as needed
  for (int i = 0; i < argc; )
  {
    std::string arg = argv[i];
    size_t pos = arg.find(":=");
    if (pos != std::string::npos)
    {
      std::string local_name = arg.substr(0, pos);
      std::string external_name = arg.substr(pos + 2);

      ROSCPP_LOG_DEBUG("remap: %s => %s", local_name.c_str(), external_name.c_str());
      remappings[local_name] = external_name;

      // shuffle everybody down and stuff this guy at the end of argv
      char *tmp = argv[i];
      for (int j = i; j < full_argc - 1; j++)
        argv[j] = argv[j+1];
      argv[argc-1] = tmp;
      argc--;
    }
    else
    {
      i++; // move on, since we didn't shuffle anybody here to replace it
    }
  }

  init(remappings, name, options);
}

• 这个函数有四个输入参数，返回值为空。
  参数1：int& argc: 引用类型，由类型的实际值引用（类似于指针）表示的数据类型。如果为某个变量分配一个引用类型，则该变量将引用（或“指向”）原始值。不创建任何副本。引用类型包括类、接口、委托和装箱值类型。这个参数用来表示输入字符串的个数，字符串是在第二个参数中给出。
  参数2：char** argv：指向指针的指针类型。定义一个指向指针的指针时，第一个指针包含了第二个指针的地址，第二个指针指向包含实际值的位置。（详细见博客）一个字符类型的指针是能够用来表示一个字符串的，所以利用字符类型的指向指针的指针是能够用来表示多个字符串。
  参数3：const std::string& name: 节点的名字。const：const是一个C语言（ANSI C）的关键字，具有着举足轻重的地位。它限定一个变量不允许被改变，产生静态作用。使用const在一定程度上可以提高程序的安全性和可靠性。这里的节点名字在函数的实现中是不能改变的，因为这里传入的参数是引用类型，一旦修改后，其他文件中的相应值也被修改，这是不可取的。那这里为什么不是传递单纯的值类型呢？
  参数4：uint32_t options: 枚举类型的节点创建的类型，其值定义如下：
  NoSigintHandler：通过ctrl-c或者ctrl-z关闭节点失效
  AnonymousName：在节点名字后面添加随机数保证节点名字的唯一性（节点的名称有大作用吗？）
  NoRosout：不广播节点的一些运行消息到/rosout话题

enum InitOption
{
  /**
 - Don't install a SIGINT handler.  You should install your own SIGINT handler in this
 - case, to ensure that the node gets shutdown correctly when it exits.
   */
  NoSigintHandler = 1 << 0,
  /** \brief Anonymize the node name.  Adds a random number to the end of your node's name, to make it unique.
   */
  AnonymousName = 1 << 1,
  /**
 - \brief Don't broadcast rosconsole output to the /rosout topic
   */
  NoRosout = 1 << 2,
};

---

• 定义一个map容器

M_string remappings;

其中M_string的定义是：

typedef std::map<std::string, std::string> M_string;

map是C++ STL 的一个关联容器，它提供一对一（其中第一个可以称为关键字，每个关键字只能在map中出现一次，第二个可能称为该关键字的值）的数据处理能力，由于这个特性，它完成有可能在我们处理一对一数据的时候，在编程上提供快速通道。也就是通过第一个关键字，我们就能找到第二个关键字的数据。举个例子，在使用launch文件启动节点是需要指定一些参数，这时所定义的参数名（name）和参数值(value)就是存在这样的一个容器中，之后在代码中通过参数名去获取参数值。

<arg name="fcu_url" value="$(arg fcu_url)" />

---

• 提取从字符串数组（字符类型的指向指针的指针）中提取参数。find、substr时string的常见使用类型。

#find()返回值是字母在母串中的位置（下标记录），如果没有找到，那么会返回一个特别的标记npos。（见博客）

substr()是C++语言函数，主要功能是复制子字符串，要求从指定位置开始，并具有指定的长度。如果没有指定长度_Count或_Count+_Off超出了源字符串的长度，则子字符串将延续到源字符串的结尾。
函数原型：
substr(size_type _Off = 0,size_type _Count = npos)
参数：
_Off——所需的子字符串的起始位置。字符串中第一个字符的索引为 0,默认值为0。
_Count——复制的字符数目
返回值——一个子字符串，从其指定的位置开始
具体见博客

---

ROSCPP_LOG_DEBUG是一个宏定义在文件file_log.h中，打印信息到终端中。

#define ROSCPP_LOG_DEBUG(...) ROS_DEBUG_NAMED("roscpp_internal", __VA_ARGS__)

ROSCPP_LOG_DEBUG

• 将参数和参数值压入map容器中

remappings[local_name] = external_name;

---

调用另一个初始化函数init

void init(const M_string& remappings, const std::string& name, uint32_t options)

init(remappings, name, options);

完整的函数实现：

void init(const M_string& remappings, const std::string& name, uint32_t options)
{
  if (!g_atexit_registered)
  {
    g_atexit_registered = true;
    atexit(atexitCallback);
  }

  if (!g_global_queue)
  {
    g_global_queue.reset(new CallbackQueue);
  }

  if (!g_initialized)
  {
    g_init_options = options;
    g_ok = true;

    ROSCONSOLE_AUTOINIT;
    // Disable SIGPIPE
#ifndef WIN32
    signal(SIGPIPE, SIG_IGN);
#endif
    check_ipv6_environment();
    network::init(remappings);
    master::init(remappings);
    // names:: namespace is initialized by this_node
    this_node::init(name, remappings, options);
    file_log::init(remappings);
    param::init(remappings);

    g_initialized = true;
  }
}

---

一开始g_atexit_registered是false，所以会进入if语句里面，进入之后就赋值为true。

static bool g_atexit_registered = false;

---

组成程序退出的回调函数：
使用atexit函数注册的退出函数是在进程正常退出时，才会被调用。如果是因为收到信号signal而导致程序退出，如kill pid，那么atexit所注册的函数将不会被调用。这个函数是定义关联在signal.h中。signal.h是C标准函数库中的信号处理部分， 定义了程序执行时如何处理不同的信号。信号用作进程间通信， 报告异常行为（如除零）、用户的一些按键组合（如同时按下Ctrl与C键，产生信号SIGINT）。

atexit(atexitCallback);

atexitCallback回调函数打印一些消息到终端和调用shutdown结束节点

void atexitCallback()
{
  if (ok() && !isShuttingDown())
  {
    ROSCPP_LOG_DEBUG("shutting down due to exit() or end of main() without cleanup of all NodeHandles");
    g_started = false; // don't shutdown singletons, because they are already destroyed
    shutdown();
  }
}

shutdown()函数的定义，解释在文件中注明
boost::recursive_mutex::scoped_lock lock(g_shutting_down_mutex);是一个递归锁。
递归锁：同一个线程在不解锁的情况下，可以多次获取锁定同一个递归锁，而且不会产生死锁。非递归锁：在不解锁的情况下，当同一个线程多次获取同一个递归锁时，会产生死锁。具体见博客。

void shutdown()
{
  boost::recursive_mutex::scoped_lock lock(g_shutting_down_mutex);//线程锁---重入锁或者称为递归锁
  if (g_shutting_down)//如果已经关闭则退出
    return;
  else
    g_shutting_down = true;//置关闭节点的标记为true

  ros::console::shutdown();//关闭日记的输出

  g_global_queue->disable();//关闭队列
  g_global_queue->clear();//清空队列

  if (g_internal_queue_thread.get_id() != boost::this_thread::get_id())
  {
    g_internal_queue_thread.join();//关闭线程
  }
  //ros::console::deregister_appender(g_rosout_appender);
  delete g_rosout_appender;//回收内存
  g_rosout_appender = 0;

  if (g_started)
  {
    TopicManager::instance()->shutdown();//关闭话题管理
    ServiceManager::instance()->shutdown();//关闭服务管理
    PollManager::instance()->shutdown();//关闭线程池
    ConnectionManager::instance()->shutdown();//关闭通信连接
    XMLRPCManager::instance()->shutdown();//关闭话题之间通信
  }
  g_started = false;
  g_ok = false;
  Time::shutdown();//关闭时间服务
}

---

接着init的函数继续分析

if (!g_global_queue)//这个指针是否为空
  {
    g_global_queue.reset(new CallbackQueue);//如果为空则创建一个回调队列的指针
  }

g_global_queue的定义为

CallbackQueuePtr g_global_queue;

CallbackQueuePtr的定义为一个回调队列的共享指针

typedef boost::shared_ptr<CallbackQueue> CallbackQueuePtr;

reset()是boost::shared_ptr的一个函数，其中reset() 相当于释放当前所控制的对象
reset(T* p) 相当于释放当前所控制的对象，然后接管p所指的对象。

---

ROSCONSOLE_AUTOINIT是定义在console.h文件中。这个的主要作用是初始化日志输出的库，常并不需要直接调用，具体的内容如下：

#define ROSCONSOLE_AUTOINIT \
  do \
  { \
    if (ROS_UNLIKELY(!::ros::console::g_initialized)) \
    { \
      ::ros::console::initialize(); \
    } \
  } while(false)

ROSCONSOLE_AUTOINIT

---

由于各个节点之间采用TCP通信，为了保证一个节点退出时，其他节点不受影响，所以采用signal函数。这个函数会在Linux系统中运行。这时产生SIGPIPE信号时就不会中止程序,直接把这个信号忽略掉。

#ifndef WIN32
    signal(SIGPIPE, SIG_IGN);
#endif

• SIGPIPE信号产生的规则：当一个进程向某个已收到RST的套接字执行写操作时，内核向该进程发送SIGPIPE信号。
• SIG_IGN是忽略信号。定义如下：

#define SIG_IGN (void (*)())1

---

chek_ipv6_environment的定义如下：

check_ipv6_environment();

void check_ipv6_environment() {
  char* env_ipv6 = NULL;
#ifdef _MSC_VER
  _dupenv_s(&env_ipv6, NULL, "ROS_IPV6");
#else
  env_ipv6 = getenv("ROS_IPV6");
#endif

  bool use_ipv6 = (env_ipv6 && strcmp(env_ipv6,"on") == 0);
  TransportTCP::s_use_ipv6_ = use_ipv6;
  XmlRpc::XmlRpcSocket::s_use_ipv6_ = use_ipv6;
}

_MSC_VER定义编译器的版本
MS VC++ 16.0 _MSC_VER = 1928 (Visual Studio 2019)
MS VC++ 15.0 _MSC_VER = 1910 (Visual Studio 2017)
MS VC++ 14.0 _MSC_VER = 1900 (Visual Studio 2015)
MS VC++ 12.0 _MSC_VER = 1800 (VisualStudio 2013)
MS VC++ 11.0 _MSC_VER = 1700 (VisualStudio 2012)
MS VC++ 10.0 _MSC_VER = 1600(VisualStudio 2010)
MS VC++ 9.0 _MSC_VER = 1500(VisualStudio 2008)
MS VC++ 8.0 _MSC_VER = 1400(VisualStudio 2005)
MS VC++ 7.1 _MSC_VER = 1310(VisualStudio 2003)
MS VC++ 7.0 _MSC_VER = 1300(VisualStudio .NET)
MS VC++ 6.0 _MSC_VER = 1200(VisualStudio 98)
MS VC++ 5.0 _MSC_VER = 1100(VisualStudio 97)

---

_dupenv_s和getenv的功能是一样的，返回一给定的环境变量值，环境变量名可大写或小写。如果指定的变量在环境中未定义，则返回一空串。只不过在不同编译环境中调用。getenv在vs编译环境会出现警告。

---

是否使用ipv6网络环境。

bool use_ipv6 = (env_ipv6 && strcmp(env_ipv6,"on") == 0);

设置通信网络环境

TransportTCP::s_use_ipv6_ = use_ipv6;
  XmlRpc::XmlRpcSocket::s_use_ipv6_ = use_ipv6;

小结：check_ipv6_environment()函数的作用是获取系统中ipv6网络的环境变量并且根据配置进行修改通信网络的配置。

---

五个初始化函数，通信网络初始、主节点初始化、当前节点初始化、日志文件保存初始化、参数器初始化。

network::init(remappings);
master::init(remappings);
this_node::init(name, remappings, options);
file_log::init(remappings);
param::init(remappings);

定义如下：

namespace master
{
void init(const M_string& remappings);
}

namespace this_node
{
void init(const std::string& names, const M_string& remappings, uint32_t options);
}

namespace network
{
void init(const M_string& remappings);
}

namespace param
{
void init(const M_string& remappings);
}

namespace file_log
{
void init(const M_string& remappings);
}

---

网络初始化：

void init(const M_string& remappings)
{
  M_string::const_iterator it = remappings.find("__hostname");//从map容器中找到网络的ip，可以将ip定义为__hostname
  if (it != remappings.end())//判断是否找到
  {
    g_host = it->second;//如果找到就取ip保存到参数变量中
  }
  else
  {
    it = remappings.find("__ip");//如果找__hostname，找不到，则直接找字段“__ip”
    if (it != remappings.end())//是否找到
    {
      g_host = it->second;//取值
    }
  }

  it = remappings.find("__tcpros_server_port");//服务器的端口
  if (it != remappings.end())
  {
    try
    {
      g_tcpros_server_port = boost::lexical_cast<uint16_t>(it->second);//检查端口是否有效
    }
    catch (boost::bad_lexical_cast&)
    {
      throw ros::InvalidPortException("__tcpros_server_port [" + it->second + "] was not specified as a number within the 0-65535 range");
    }
  }

  if (g_host.empty())//如果找不到相应的网络参数，使用确定的参数。
  {
    g_host = determineHost();
  }
}

determineHost()的定义如下：

std::string determineHost()
{
  std::string ip_env;
  // First, did the user set ROS_HOSTNAME?
  if ( get_environment_variable(ip_env, "ROS_HOSTNAME")) {
    ROSCPP_LOG_DEBUG( "determineIP: using value of ROS_HOSTNAME:%s:", ip_env.c_str());
    if (ip_env.size() == 0)
    {
      ROS_WARN("invalid ROS_HOSTNAME (an empty string)");
    }
    return ip_env;
  }

  // Second, did the user set ROS_IP?
  if ( get_environment_variable(ip_env, "ROS_IP")) {
    ROSCPP_LOG_DEBUG( "determineIP: using value of ROS_IP:%s:", ip_env.c_str());
    if (ip_env.size() == 0)
    {
      ROS_WARN("invalid ROS_IP (an empty string)");
    }
    return ip_env;
  }

  // Third, try the hostname
  char host[1024];
  memset(host,0,sizeof(host));
  if(gethostname(host,sizeof(host)-1) != 0)
  {
    ROS_ERROR("determineIP: gethostname failed");
  }
  // We don't want localhost to be our ip
  else if(strlen(host) && strcmp("localhost", host))
  {
    return std::string(host);
  }

  // Fourth, fall back on interface search, which will yield an IP address

#ifdef HAVE_IFADDRS_H
  struct ifaddrs *ifa = NULL, *ifp = NULL;
  int rc;
  if ((rc = getifaddrs(&ifp)) < 0)
  {
    ROS_FATAL("error in getifaddrs: [%s]", strerror(rc));
    ROS_BREAK();
  }
  char preferred_ip[200] = {0};
  for (ifa = ifp; ifa; ifa = ifa->ifa_next)
  {
    char ip_[200];
    socklen_t salen;
    if (!ifa->ifa_addr)
      continue; // evidently this interface has no ip address
    if (ifa->ifa_addr->sa_family == AF_INET)
      salen = sizeof(struct sockaddr_in);
    else if (ifa->ifa_addr->sa_family == AF_INET6)
      salen = sizeof(struct sockaddr_in6);
    else
      continue;
    if (getnameinfo(ifa->ifa_addr, salen, ip_, sizeof(ip_), NULL, 0,
                    NI_NUMERICHOST) < 0)
    {
      ROSCPP_LOG_DEBUG( "getnameinfo couldn't get the ip of interface [%s]", ifa->ifa_name);
      continue;
    }
    //ROS_INFO( "ip of interface [%s] is [%s]", ifa->ifa_name, ip);
    // prefer non-private IPs over private IPs
    if (!strcmp("127.0.0.1", ip_) || strchr(ip_,':'))
      continue; // ignore loopback unless we have no other choice
    if (ifa->ifa_addr->sa_family == AF_INET6 && !preferred_ip[0])
      strcpy(preferred_ip, ip_);
    else if (isPrivateIP(ip_) && !preferred_ip[0])
      strcpy(preferred_ip, ip_);
    else if (!isPrivateIP(ip_) &&
             (isPrivateIP(preferred_ip) || !preferred_ip[0]))
      strcpy(preferred_ip, ip_);
  }
  freeifaddrs(ifp);
  if (!preferred_ip[0])
  {
    ROS_ERROR( "Couldn't find a preferred IP via the getifaddrs() call; I'm assuming that your IP "
        "address is 127.0.0.1.  This should work for local processes, "
        "but will almost certainly not work if you have remote processes."
        "Report to the ROS development team to seek a fix.");
    return std::string("127.0.0.1");
  }
  ROSCPP_LOG_DEBUG( "preferred IP is guessed to be %s", preferred_ip);
  return std::string(preferred_ip);
#else
  // @todo Fix IP determination in the case where getifaddrs() isn't
  // available.
  ROS_ERROR( "You don't have the getifaddrs() call; I'm assuming that your IP "
             "address is 127.0.0.1.  This should work for local processes, "
             "but will almost certainly not work if you have remote processes."
             "Report to the ROS development team to seek a fix.");
  return std::string("127.0.0.1");
#endif
}

---

master的初始化代码如下：

void init(const M_string& remappings)
{
  M_string::const_iterator it = remappings.find("__master");//找master的ip配置参数
  if (it != remappings.end())
  {
    g_uri = it->second;
  }

  if (g_uri.empty())
  {
    char *master_uri_env = NULL;
    #ifdef _MSC_VER
      _dupenv_s(&master_uri_env, NULL, "ROS_MASTER_URI");
    #else
      master_uri_env = getenv("ROS_MASTER_URI");
    #endif
    if (!master_uri_env)
    {
      ROS_FATAL( "ROS_MASTER_URI is not defined in the environment. Either " \
                 "type the following or (preferrably) add this to your " \
                 "~/.bashrc file in order set up your " \
                 "local machine as a ROS master:\n\n" \
                 "export ROS_MASTER_URI=http://localhost:11311\n\n" \
                 "then, type 'roscore' in another shell to actually launch " \
                 "the master program.");
      ROS_BREAK();
    }

    g_uri = master_uri_env;

#ifdef _MSC_VER
    // http://msdn.microsoft.com/en-us/library/ms175774(v=vs.80).aspx
    free(master_uri_env);
#endif
  }

  // Split URI into
  if (!network::splitURI(g_uri, g_host, g_port))
  {
    ROS_FATAL( "Couldn't parse the master URI [%s] into a host:port pair.", g_uri.c_str());
    ROS_BREAK();
  }
}

network::splitURI的定义如下：

bool splitURI(const std::string& uri, std::string& host, uint32_t& port)
{
  // skip over the protocol if it's there
  if (uri.substr(0, 7) == std::string("http://"))
    host = uri.substr(7);
  else if (uri.substr(0, 9) == std::string("rosrpc://"))
    host = uri.substr(9);
  // split out the port
  std::string::size_type colon_pos = host.find_first_of(":");
  if (colon_pos == std::string::npos)
    return false;
  std::string port_str = host.substr(colon_pos+1);
  std::string::size_type slash_pos = port_str.find_first_of("/");
  if (slash_pos != std::string::npos)
    port_str = port_str.erase(slash_pos);
  port = atoi(port_str.c_str());
  host = host.erase(colon_pos);
  return true;
}

这个节点初始化代码：

void ThisNode::init(const std::string& name, const M_string& remappings, uint32_t options)
{
  char *ns_env = NULL;
#ifdef _MSC_VER
  _dupenv_s(&ns_env, NULL, "ROS_NAMESPACE");
#else
  ns_env = getenv("ROS_NAMESPACE");
#endif

  if (ns_env)
  {
    namespace_ = ns_env;
#ifdef _MSC_VER
    free(ns_env);
#endif
  }

  if (name.empty()) {
    throw InvalidNameException("The node name must not be empty");
  }

  name_ = name;

  bool disable_anon = false;
  M_string::const_iterator it = remappings.find("__name");
  if (it != remappings.end())
  {
    name_ = it->second;
    disable_anon = true;
  }

  it = remappings.find("__ns");
  if (it != remappings.end())
  {
    namespace_ = it->second;
  }

  if (namespace_.empty())
  {
    namespace_ = "/";
  }

  namespace_ = (namespace_ == "/")
    ? std::string("/") 
    : ("/" + namespace_)
    ;


  std::string error;
  if (!names::validate(namespace_, error))
  {
    std::stringstream ss;
    ss << "Namespace [" << namespace_ << "] is invalid: " << error;
    throw InvalidNameException(ss.str());
  }

  // names must be initialized here, because it requires the namespace to already be known so that it can properly resolve names.
  // It must be done before we resolve g_name, because otherwise the name will not get remapped.
  names::init(remappings);

  if (name_.find("/") != std::string::npos)
  {
    throw InvalidNodeNameException(name_, "node names cannot contain /");
  }
  if (name_.find("~") != std::string::npos)
  {
    throw InvalidNodeNameException(name_, "node names cannot contain ~");
  }

  name_ = names::resolve(namespace_, name_);

  if (options & init_options::AnonymousName && !disable_anon)
  {
    char buf[200];
    snprintf(buf, sizeof(buf), "_%llu", (unsigned long long)WallTime::now().toNSec());
    name_ += buf;
  }

  ros::console::setFixedFilterToken("node", name_);
}

日记输出的初始化代码：

void init(const M_string& remappings)
{
  std::string log_file_name;
  M_string::const_iterator it = remappings.find("__log");
  if (it != remappings.end())
  {
    log_file_name = it->second;
  }

  {
    // Log filename can be specified on the command line through __log
    // If it's been set, don't create our own name
    if (log_file_name.empty())
    {
      // Setup the logfile appender
      // Can't do this in rosconsole because the node name is not known
      pid_t pid = getpid();
      std::string ros_log_env;
      if ( get_environment_variable(ros_log_env, "ROS_LOG_DIR"))
      {
        log_file_name = ros_log_env + std::string("/");
      }
      else
      {
        if ( get_environment_variable(ros_log_env, "ROS_HOME"))
        {
          log_file_name = ros_log_env + std::string("/log/");
        }
        else
        {
          // Not cross-platform?
          if( get_environment_variable(ros_log_env, "HOME") )
          {
            std::string dotros = ros_log_env + std::string("/.ros/");
            fs::create_directory(dotros);
            log_file_name = dotros + "log/";
            fs::create_directory(log_file_name);
          }
        }
      }

      // sanitize the node name and tack it to the filename
      for (size_t i = 1; i < this_node::getName().length(); i++)
      {
        if (!isalnum(this_node::getName()[i]))
        {
          log_file_name += '_';
        }
        else
        {
          log_file_name += this_node::getName()[i];
        }
      }

      char pid_str[100];
      snprintf(pid_str, sizeof(pid_str), "%d", pid);
      log_file_name += std::string("_") + std::string(pid_str) + std::string(".log");
    }

    log_file_name = fs::system_complete(log_file_name).string();
    g_log_directory = fs::path(log_file_name).parent_path().string();
  }
}

参数器初始化代码：

void init(const M_string& remappings)
{
  M_string::const_iterator it = remappings.begin();
  M_string::const_iterator end = remappings.end();
  for (; it != end; ++it)
  {
    const std::string& name = it->first;
    const std::string& param = it->second;

    if (name.size() < 2)
    {
      continue;
    }

    if (name[0] == '_' && name[1] != '_')
    {
      std::string local_name = "~" + name.substr(1);

      bool success = false;

      try
      {
        int32_t i = boost::lexical_cast<int32_t>(param);
        ros::param::set(names::resolve(local_name), i);
        success = true;
      }
      catch (boost::bad_lexical_cast&)
      {

      }

      if (success)
      {
        continue;
      }

      try
      {
        double d = boost::lexical_cast<double>(param);
        ros::param::set(names::resolve(local_name), d);
        success = true;
      }
      catch (boost::bad_lexical_cast&)
      {

      }

      if (success)
      {
        continue;
      }

      if (param == "true" || param == "True" || param == "TRUE")
      {
        ros::param::set(names::resolve(local_name), true);
      }
      else if (param == "false" || param == "False" || param == "FALSE")
      {
        ros::param::set(names::resolve(local_name), false);
      }
      else
      {
        ros::param::set(names::resolve(local_name), param);
      }
    }
  }

  XMLRPCManager::instance()->bind("paramUpdate", paramUpdateCallback);
}

到此一个节点基础的初始化就完成，网络、主节点等模块将下篇博客详细分析。