uDDS源程序subscriber

#include <stdio.h>
#include <stdlib.h>
#include <cstring>

#include "IDL_TypeSupport.h"

class UserDataTypeListener : public DataReaderListener {
public:
virtual void on_data_available(DataReader* reader);
};

void UserDataTypeListener::on_data_available(DataReader* reader)
{
   UserDataTypeDataReader *UserDataType_reader = NULL;
   UserDataTypeSeq data_seq;
   SampleInfoSeq info_seq;
   ReturnCode_t retcode;
   int i;

   UserDataType_reader = UserDataTypeDataReader::narrow(reader);
   if (UserDataType_reader == NULL) {
       fprintf(stderr, "DataReader narrow error\n");
       return;
   }

retcode = UserDataType_reader->read(
data_seq, info_seq, 10, 0, 0, 0);

   if (retcode == RETCODE_NO_DATA) {
       return;
   }
   else if (retcode != RETCODE_OK) {
       fprintf(stderr, "take error %d\n", retcode);
       return;
   }

   for (i = 0; i < data_seq.length(); ++i) {
       printf("receive: x=%hd,y=%hd,color=%s\n",
           data_seq[i].x,data_seq[i].y, data_seq[i].color);
delete data_seq[i].color;
data_seq[i].color = NULL;
   }
}

static int subscriber_shutdown(
   DomainParticipant *participant)
{
   ReturnCode_t retcode;
   int status = 0;

   if (participant != NULL) {
       retcode = participant->delete_contained_entities();
       if (retcode != RETCODE_OK) {
           fprintf(stderr, "delete_contained_entities error %d\n", retcode);
           status = -1;
       }

       retcode = DomainParticipantFactory::get_instance()->delete_participant(participant);
       if (retcode != RETCODE_OK) {
           fprintf(stderr, "delete_participant error %d\n", retcode);
           status = -1;
       }
   }
   return status;
}

extern "C" int subscriber_main(int domainId, int sample_count)
{
   DomainParticipant *participant = NULL;
   Subscriber *subscriber = NULL;
   Topic *topic = NULL;
   UserDataTypeListener *reader_listener = NULL;
   DataReader *reader = NULL;
   ReturnCode_t retcode;
   const char *type_name = NULL;
   int count = 0;
   int status = 0;

   participant = DomainParticipantFactory::get_instance()->create_participant(
       domainId, PARTICIPANT_QOS_DEFAULT/* participant榛樿QoS */,
       NULL /* listener */, STATUS_MASK_NONE);
   if (participant == NULL) {
       fprintf(stderr, "create_participant error\n");
       subscriber_shutdown(participant);
       return -1;
   }

   subscriber = participant->create_subscriber(
       SUBSCRIBER_QOS_DEFAULT/* 榛樿QoS */,
       NULL /* listener */, STATUS_MASK_NONE);
   if (subscriber == NULL) {
       fprintf(stderr, "create_subscriber error\n");
       subscriber_shutdown(participant);
       return -1;
   }

   type_name = UserDataTypeTypeSupport::get_type_name();
   retcode = UserDataTypeTypeSupport::register_type(
       participant, type_name);
   if (retcode != RETCODE_OK) {
       fprintf(stderr, "register_type error %d\n", retcode);
       subscriber_shutdown(participant);
       return -1;
   }

   topic = participant->create_topic(
       "Example UserDataType"/* 涓婚鍚嶏紝搴斾笌鍙戝竷鑰呬富棰樺悕涓€鑷?*/,
       type_name, TOPIC_QOS_DEFAULT/* 榛樿QoS */,
       NULL /* listener */, STATUS_MASK_NONE);
   if (topic == NULL) {
       fprintf(stderr, "create_topic error\n");
       subscriber_shutdown(participant);
       return -1;
   }

reader_listener = new UserDataTypeListener();

   reader = subscriber->create_datareader(
       topic, DATAREADER_QOS_DEFAULT/* 榛樿QoS */,
       reader_listener/* listener */, STATUS_MASK_ALL);
   if (reader == NULL) {
       fprintf(stderr, "create_datareader error\n");
       subscriber_shutdown(participant);
       delete reader_listener;
       return -1;
   }

for (count = 0; (sample_count == 0) || (count < sample_count); ++count) {

}

status = subscriber_shutdown(participant);
delete reader_listener;

return status;
}

int main(int argc, char *argv[])
{
int domain_id = 0;
int sample_count = 0;

   if (argc >= 2) {
       domain_id = atoi(argv[1]);
   }
   if (argc >= 3) {
       sample_count = atoi(argv[2]);
   }
   return subscriber_main(domain_id, sample_count);
}

这是一个C++程序，它涉及到RabbitMQ（通常用于消息传递）和ROS（Robot Operating System，一种机器人操作系统）。`subscriber_main`函数创建了一个订阅者(subscriber)，主要用于从指定主题(topic)接收用户自定义数据(UserDataType)的消息：

1. 创建DomainParticipant（领域参与者），这是ROS中的一个核心组件，代表了整个通信上下文。
2. 创建Subscriber（订阅者），用于订阅特定主题的数据流。
3. 注册UserDataType类型，并创建Topic。
4. 实例化UserDataTypeListener，这是数据读取事件的回调函数。
5. 使用DataReader创建一个读者，它会按照指定的质量级(DATAREADER_QOS_DEFAULT)接收消息。
6. 当有样本(sample_count)需要获取时，进入循环等待并处理接收到的消息。

`main`函数作为程序入口，解析命令行参数domain_id和sample_count，然后调用`subscriber_main`函数进行实际操作。

uDDS源程序subscriber

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