详细写出基于c++的can dbc解析代码

以下是一个基于C++的CAN DBC解析代码示例：

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <sstream>

struct Signal {
    std::string name;
    int start_bit;
    int bit_length;
    bool is_little_endian;
    double factor;
    double offset;
    double min_value;
    double max_value;
    std::string unit;
};

struct Message {
    int id;
    std::string name;
    std::vector<Signal> signals;
};

std::vector<Message> parse_dbc_file(const std::string& file_path) {
    std::vector<Message> messages;
    std::ifstream file(file_path);
    if (!file.is_open()) {
        std::cerr << "Failed to open DBC file" << std::endl;
        return messages;
    }

    std::string line;
    std::vector<std::string> words;
    Message message;
    Signal signal;
    while (std::getline(file, line)) {
        if (line.empty()) {
            continue;
        }

        std::stringstream ss(line);
        std::string word;
        words.clear();
        while (std::getline(ss, word, ' ')) {
            if (!word.empty()) {
                words.push_back(word);
            }
        }

        if (words[0] == "BO_") {
            if (!message.signals.empty()) {
                messages.push_back(message);
                message.signals.clear();
            }
            message.id = std::stoi(words[1]);
            message.name = words[2];
        } else if (words[0] == "SG_") {
            signal.name = words[1];
            signal.start_bit = std::stoi(words[2]);
            signal.bit_length = std::stoi(words[3]);
            signal.is_little_endian = (words[4] == "0");
            signal.factor = std::stod(words[5]);
            signal.offset = std::stod(words[6]);
            signal.min_value = std::stod(words[7]);
            signal.max_value = std::stod(words[8]);
            signal.unit = words[9];
            message.signals.push_back(signal);
        }
    }
    if (!message.signals.empty()) {
        messages.push_back(message);
    }

    file.close();
    return messages;
}

int main(int argc, char** argv) {
    std::vector<Message> messages = parse_dbc_file("example.dbc");
    for (const auto& message : messages) {
        std::cout << "ID: " << message.id << std::endl;
        std::cout << "Name: " << message.name << std::endl;
        for (const auto& signal : message.signals) {
            std::cout << "  Signal: " << signal.name << std::endl;
            std::cout << "  Start bit: " << signal.start_bit << std::endl;
            std::cout << "  Bit length: " << signal.bit_length << std::endl;
            std::cout << "  Is little endian: " << (signal.is_little_endian ? "true" : "false") << std::endl;
            std::cout << "  Factor: " << signal.factor << std::endl;
            std::cout << "  Offset: " << signal.offset << std::endl;
            std::cout << "  Minimum value: " << signal.min_value << std::endl;
            std::cout << "  Maximum value: " << signal.max_value << std::endl;
            std::cout << "  Unit: " << signal.unit << std::endl;
        }
    }
    return 0;
}

该示例代码首先定义了两个结构体Signal和Message，分别表示CAN信号和CAN消息。然后，该代码定义了一个parse_dbc_file()函数，用于解析DBC文件并返回一个包含所有CAN消息的vector。该函数使用std::ifstream读取DBC文件，并逐行解析文件内容。对于每个BO_行，该函数创建一个新的Message对象并设置其ID和名称，对于每个SG_行，该函数创建一个新的Signal对象并设置其名称、起始位、长度、大小端、因子、偏移、最小值、最大值和单位，并将Signal对象添加到Message对象的signals vector中。最后，该函数返回所有Message对象的vector。

在主函数中，该代码调用parse_dbc_file()函数解析DBC文件，并遍历所有Message对象和Signal对象，并打印它们的属性。