WebExtension with Native messaging C++ App side

Add-ons Development
#1

Hope this will we helpful :slight_smile:

App side C++ porting

#include <iostream>
#include <string>
#include <json.hpp>

using namespace std;
using namespace nlohmann;


struct message_t {
    string content;
    uint32_t length;
};

// Read a message from stdin and decode it.
json get_message() {
    char raw_length[4];
    fread(raw_length, 4, sizeof(char), stdin);
    uint32_t message_length = *reinterpret_cast<uint32_t*>(raw_length);
    if(!message_length)
        exit(EXIT_SUCCESS);

    char message[message_length];
    fread(message, message_length, sizeof(char), stdin);
    string m( message, message + sizeof message / sizeof message[0] );
    return json::parse(m);
}

// Encode a message for transmission, given its content.
message_t encode_message(json content) {
    string encoded_content = content.dump();
    message_t m;  
    m.content = encoded_content;
    m.length = (uint32_t) encoded_content.length();    
    return m;
}

// Send an encoded message to stdout.
void send_message(message_t encoded_message) {
    char* raw_length = reinterpret_cast<char*>(&encoded_message.length);
    fwrite (raw_length , 4, sizeof(char), stdout);
    fwrite (encoded_message.content.c_str(), encoded_message.length, sizeof(char), stdout);
    fflush(stdout);
}

int main(int argc, char *argv[])
{
    while(true) {
        json message = get_message();
        if(message == "ping")
            send_message(encode_message("pong"));
    }
}
#2

You can use ``` to start and end code blocks, and if you do ```cpp or similar you start a code block with c++ syntax highlighting.

2 Likes
#4

Thx for you suggestion freaktechnik

#5

Very useful! Thanks very much.

#6

Can you please explain what exactly is going on here? As I understand it, the first fread() gets the length, i.e. number of bytes, of the JSON that is present on stdin?

#7

NVM I should have read the docs:

Each message is serialized using JSON, UTF-8 encoded and is preceded with a 32-bit value containing the message length in native byte order.

1 Like