C++ protobuf示例

朱雀 2021-05-13 15:39 1197阅读 0赞

1、linux上安装protobuf3：

1）下载：

[https://download.csdn.net/download/liuxiao723846/11584862][https_download.csdn.net_download_liuxiao723846_11584862]

2）编译安装：

function check_install_status() {
        if [ $? -ne 0 ]; then
            echo "--!!ERROR"
            exit 1
        fi
    }
    
    #install protobuf3
    if [ ! -d protobuf-3.6.0 ]; then
        tar -zxf protobuf-3.6.0.tar.gz
        cd protobuf-3.6.0
        ./autogen.sh
        ./autogen.sh && ./configure
            check_install_status
        make -j8
            check_install_status
        make install
            check_install_status
        cd python
        python setup.py install
            check_install_status
        ldconfig
        cd ../../
    fi

2、简单示例：

1）person.proto:

package test;
    
    message Person {
      required string name = 1;
      required int32 id = 2;
      optional string email = 3;
    }

编译，生成C++代码：

$ protoc ./person.proto --cpp_out=./
    $ ll
    -rw-rw-r--. 1 roo roo  17237 Aug 20 21:19 person.pb.cc
    -rw-rw-r--. 1 roo roo  12965 Aug 20 21:19 person.pb.h

2）编写C++业务代码：

#include <iostream>
    #include <fstream>
    #include "person.pb.h"
    #include "google/protobuf/io/zero_copy_stream_impl.h"
    #include "google/protobuf/text_format.h"
    
    
    using namespace test;
    int main(){
      Person p;
      p.set_name("test");
      p.set_id(1);
      p.set_email("a.iabc.com");
    
      //------------------将pb二进制信息保存到字符串
      std::string str;
      p.SerializeToString(&str);
      std::cout<<str<<std::endl;  
     
      //------------------将pb文本信息写入文件
      std::ofstream fw; 
      fw.open("./Person.txt", std::ios::out | std::ios::binary);
      google::protobuf::io::OstreamOutputStream *output = new google::protobuf::io::OstreamOutputStream(&fw);
      google::protobuf::TextFormat::Print(p, output);
    
      delete output;
      fw.close();
    
      //---------------------将pb文本信息保存到字符串
      std::string str1;
      google::protobuf::TextFormat::PrintToString(p, &str1);
      std::cout<<str1<<std::endl;
    
      //---------------------反序列化
      Person p1;
      p1.ParseFromString(str);
      std::cout<<"name:"<<p1.name()<<",email:"<<p1.email()<<std::endl;
    
      return 0;
    }

3）编译、运行：

g++ -g -o run person_test.cpp ./person.pb.cc -I. -lprotobuf -pthread -std=c++11
    或者
    g++ -g -o run person_test.cpp ./person.pb.cc -I. -I/usr/local/protobuf/include -L/usr/local/protobuf/lib -lprotobuf -pthread -std=c++11

4）api说明：

*  p.SerializeToString(&str)：将对象p序列化成二进制数据，保存到字符串中；
 *  二进制虽然小，但是可读性差，所以通过google::protobuf::TextFormat::print()方法生成文本数据写入文件；为此需要引入google/protobuf/text\_format.h(否则会报‘google::protobuf::TextFormat’ has not been declared错误)、zero\_copy\_stream\_impl.h(否则会报OstreamOutputStream找不到)
 *  除了将pb信息序列化成文本写入文件外，还可以调用google::protobuf::TextFormat::PrintToString(mrlist, &str1); 方法将pb文本信息保存到字符串中；（别忘了加text\_format.h头文件）
 *  p1.ParseFromString(str);：将字符串中的二进制信息反序列成Person对象；
 *  C++版pb的api一般为：pb对象.set\_消息属性(value)；设置属性值；pb对象.消息属性()；获取属性值；

3、复杂示例：

1）pb消息结构test.proto：

syntax = "proto2";
    package video_stream;
    
    message Item{
    	optional string id = 1;
        optional float score = 2;
    }
    message ModelItems{
        optional string modelName = 1;
        repeated Item itemList = 2;
    }
    message ModelRecallInfoList{
        repeated ModelItems modelItemsList = 1;
    }
    
    message InnerUserPrefResponse {
    	optional map<string, ModelItems> user_feed_map = 1;
    }

编译：

$ protoc ./test.proto --cpp_out=./
    $ ll
    -rw-rw-r--. 1 roo roo  55676 Aug 20 23:28 test.pb.cc
    -rw-rw-r--. 1 roo roo  32236 Aug 20 23:28 test.pb.h

2）c++业务代码：

#include <iostream>
    #include <fstream>
    #include "test.pb.h"
    #include "google/protobuf/io/zero_copy_stream_impl.h"
    #include "google/protobuf/text_format.h"
    
    using namespace video_stream;
    
    int main(){
    
      ModelRecallInfoList mrlist;
      ModelItems* items;
      Item* item;
      
      //model_item1
      items = mrlist.add_modelitemslist();
      items->set_modelname("model_items1");
      //item1
      item = items->add_itemlist(); 
      item->set_id("item1");
      item->set_score(0.9);
      //item2
      item = items->add_itemlist();
      item->set_id("item2");
      item->set_score(1.2);
      
      //model_items2
      items = mrlist.add_modelitemslist();
      items->set_modelname("model_items2");
      //item1
      item = items->add_itemlist();
      item->set_id("model_item2_item1");
      item->set_score(99.9);
      
      std::string str;
      mrlist.SerializeToString(&str);
      //std::cout<<str<<std::endl;
    
      std::string str1;
      google::protobuf::TextFormat::PrintToString(mrlist, &str1);
      std::cout<<str1<<std::endl;
    
      //---------------------------------------反序列化
      ModelRecallInfoList m;
      m.ParseFromString(str);
      int size = m.modelitemslist_size();
      for(int i=0;i<size;i++){
        ModelItems model_item  = m.modelitemslist(i);
        std::string model_name = model_item.modelname();
        int s1 = model_item.itemlist_size();
        std::string s;
    
        for(int j = 0;j<s1;j++){
          s+=model_item.itemlist(j).id()+",";
        }
        std::cout<<"modelName:"<<model_name<<",itemId:"<<s<<std::endl;
        
        //std::cout<<"modelName:"<<m.modelitemslist(i).modelname()<<std::endl;
      }
      
      //---------------------------------------放到map里
      InnerUserPrefResponse resp;
      auto* map = resp.mutable_user_feed_map(); 
      for (int i=0;i<size;i++){
        ModelItems model_item  = m.modelitemslist(i);
        std::string mn = model_item.modelname();
        (*map)[mn] = model_item; 
      }
    
      std::string str2;
      google::protobuf::TextFormat::PrintToString(resp, &str2);
      std::cout<<"=========================="<<std::endl;
      std::cout<<str2<<std::endl;
      return 0;
    }

编译、运行：

g++ -g -o run test_main.cpp ./test.pb.cc -I. -lprotobuf -pthread -std=c++11

3）api说明：

pb对象中，子对象需要使用指针；

对于repeated类型：

pb对象.add\_属性名() 添加**一个**子对象的**指针**；

pb对象.属性名\_size()返回repeated大小；

pb对象.属性名(i)遍历其中一个子对象；

4、复杂消息示例2：

1）student.proto

package test;
    
    message Address {
      optional string name = 1;
      optional string code = 2;
    }
    message Student {
      required string name = 1;
      required int32 id = 2;
      repeated string email = 3;
      optional Address ads = 4;
      map<string,string> other = 5;
    }

编译

$ protoc ./student.proto --cpp_out=./
    $ ll
    -rw-rw-r--. 1 roo roo  55676 Aug 20 23:28 student.pb.cc
    -rw-rw-r--. 1 roo roo  32236 Aug 20 23:28 student.pb.h

2）C++业务代码student\_test.cpp：

#include <iostream>
    #include "student.pb.h"
    #include "google/protobuf/text_format.h"
    
    using namespace test;
    
    int main(){
      Student p;
      p.set_name("test");
      p.set_id(1);
      p.add_email("a.yxz.com");
      p.add_email("b.abc.com");
      std::string* e = p.add_email();
      *e = "c.iop.com";
      
      Address* ads = p.mutable_ads();
      ads->set_name("taiyuan");
      ads->set_code("0351");
    
      auto* map = p.mutable_other();  
      (*map)["biye"] = "nuc";
      (*map)["job"] = "abc";
    
      //============序列化成二进制
      std::string str;
      p.SerializeToString(&str);
      //std::cout<<str<<std::endl;  
     
      //============序列化成文本，打印
      std::string str1;
      google::protobuf::TextFormat::PrintToString(p, &str1);
      std::cout<<str1<<std::endl;
      
      //===========反序列化
      Student p1;
      p1.ParseFromString(str);
      int es = p1.email_size();
      std::string emails;
      for (int i=0;i<es;i++){
        emails += p1.email(i)+",";
      }
    
      Address adss= p1.ads();
    
      google::protobuf::Map<std::string,std::string> o = p1.other();
      google::protobuf::Map<std::string,std::string>::iterator ite;
      
      std::string others;
      for(ite=o.begin();ite!=o.end();ite++){
        others+=ite->first+":"+ite->second;
      }
      std::cout<<"name:"<<p1.name()<<";id:"<<p1.id()<<";emails:"<<emails<<";addreds:"<<adss.name()<<";other:"<<others<<std::endl;
      return 0;
    }

3）说明：

*  可以看出来，对于子对象、map：设置值得时候一般需要用mutable\_属性()；获取值一般用属性()
 *  对于pb提供的api，可以在生成的.h文件中查看相应的方法；

补充：对于map的操作：

::google::protobuf::Map< ::std::string, ::std::string >* map = test.mutable_values();
    cout << "size: " << f.values_size() << endl;   // size = 0
    // add to map
    (*map)["a"] = "a1";
    (*map)["c"] = "a1";
    (*map)["a"] = "a1";
    cout << "size: " << f.values_size() << endl;   // size = 3
    
    也可以使用下面：
    auto& map = *test.mutable_values();
    map["a"] = "a1";

[https_download.csdn.net_download_liuxiao723846_11584862]: https://download.csdn.net/download/liuxiao723846/11584862