serialization and deserialization

In the process of network communication , We may want to pass more than just a string , We may need to pass on more complex structures , For example, structure type , In this case, we need to use serialization and deserialization .

Suppose Zhang San and Li Si are using QQ Chat , Zhang San sent a message to Li Si “ Hello , I am Zhang San. ”, This is the time , It looks like only one string was sent , actually , Zhang San's nickname 、 The time to send messages should be sent to Li Si's host .

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Catalog

One 、 What is serialization and deserialization

Two 、 Why do I need serialization and deserialization （ Advantages of serialization and deserialization ）

1、 Convenient transmission

2、 Realize the decoupling of application layer display and network transmission

3、 ... and 、 How to serialize and deserialize ？

1、 install jsoncpp-devel

2、 serialize （ Structure Turn it into json character string ）

(1) preparation ： Declared structure

(2) Start serializing

3、 Deserialization （json character string Turn it into Structure ）

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One 、 What is serialization and deserialization

Because the structure is not convenient for transmission , Generally, you need to convert the structure into a “ Long string ”, Then send it to the network , This process is called serialization .

Corresponding , When Li Si was receiving , You need to convert this long string into a form that the other party can recognize , Like a structure , This process is called deserialization .

Two 、 Why do I need serialization and deserialization （ Advantages of serialization and deserialization ）

1、 Convenient transmission

Between the principles of structure alignment , Structured data is not convenient for network transmission

Maybe you think , Since the whole structure cannot be transmitted , Then pass each member of the structure in the form of string one by one , This is theoretically feasible , But one host may receive data from multiple hosts , This is the time , It is difficult to distinguish which host sent the data .

2、 Realize the decoupling of application layer display and network transmission

Suppose Zhang San sends a string "10 + 20", Let Li Si calculate , If not serialized , But if it is sent directly , Delivery is really convenient , But from the perspective of Li Si , The cost of parsing is too high .

If we convert a structure into a string （ Namely serialization ）, When Li Si received it , Then convert back to the structure , In this case , Li Si doesn't need to know how this string is parsed . Because the things in Li Si's and Zhang San's hands are the same , Below as long as Make an agreement , Let Li Si know how to use the passed thing . This realizes the decoupling of network transmission and upper display ！！

3、 ... and 、 How to serialize and deserialize ？

To achieve serialization and deserialization , Predecessors have already had corresponding solutions , such as xml、json、protocbuff etc. , Here we mainly introduce how to convert the structure type into json Format , as well as json Transfer structure type .

1、 install jsoncpp-devel

According to different user types , Choose the corresponding installation method by yourself

sudo yum install -y jsoncpp-devel        // Ordinary users 
yum install -y jsoncpp-devel             // The super user 

After successful installation, enter the following instructions to check whether there is a corresponding header file

2、 serialize （ Structure Turn it into json character string ）

(1) preparation ： Declared structure

Suppose you want to transfer a structure to the opposite , Let's declare a simple structure first

// Sent to the network , As a request 
typedef struct Request{
    int x;
    char op;
    char* msg;
} request_t;

(2) Start serializing

To understand the process , I take the animation we are familiar with as an example . SpongeBob has the raw materials ready root, Fry on an iron plate , After some operation , I got a hamburger .

#include <jsoncpp/json/json.h>
#include <iostream>
using namespace std;

int main(){
    request_t req = {10,'+',"Hello,world"};        // Initialize structure 

    Json::Value root;               // raw material root             
    root["datax"] = req.x;          // Put it in the designated position on the iron plate 
    root["dataop"] = req.op;
    root["datamsg"] = req.msg;

    Json::FastWriter writer;
    //Json::StyledWriter writer;     // Both of them can be written , As for the difference , You can see the printed results 
    std::string json_str = writer.write(root);    // The hamburger is finished 
    return 0;
}

The test results are as follows ：

======================= StyledWriter =======================

======================= FastWriter =======================

3、 Deserialization （json character string Turn it into Structure ）

Now the boss stole it Crab boss's exclusive hamburger , Boss ruffian used a high-tech machine to decompose this hamburger , Will be decomposed into the state of raw materials , Put it on a tray , In order to observe what materials are used to make hamburgers .

// The middle quotation mark needs to be used '\' escape 
std::string json_str = "{\"datamsg\":\"Hello,world\",\"dataop\":43,\"datax\":10}";
Json::Reader reader;
Json::Value root;

reader.parse(json_str,root);    // If converted to root It is not convenient to pass parameters in the future , Fill in req in 
request_t req;
req.x = root["datax"].asInt();    //root Each of them key Corresponding value All are Json::Value type 
req.op = root["dataop"].asInt();
req.msg = root["datamsg"].asString().c_str();

cout<<req.x<<" "<<req.op<<" "<<req.msg<<endl;

The test results are as follows ：