C++异常处理与错误码返回结合使用

errno

HRESULT

errno

std::exception

std::runtime_error

std::logic_error

#include <stdexcept>
#include <string>
#include <system_error> // For std::system_error and std::error_code
#include <iostream>
#include <fstream> // For file operations
#include <vector>

// 1. 定义自定义异常类
class FileOperationException : public std::runtime_error {
public:
    // 可以存储原始错误码，方便调试
    explicit FileOperationException(const std::string& message, int errorCode = 0)
        : std::runtime_error(message), originalErrorCode_(errorCode) {}

    int getOriginalErrorCode() const { return originalErrorCode_; }

private:
    int originalErrorCode_;
};

class FileNotFoundError : public FileOperationException {
public:
    explicit FileNotFoundError(const std::string& message, int errorCode = 0)
        : FileOperationException(message, errorCode) {}
};

class PermissionDeniedError : public FileOperationException {
public:
    explicit PermissionDeniedError(const std::string& message, int errorCode = 0)
        : FileOperationException(message, errorCode) {}
};

// 2. 封装底层C风格文件操作，将errno转换为C++异常
void openAndReadFile(const std::string& filename) {
    std::ifstream file(filename);
    if (!file.is_open()) {
        // 在这里，我们通常无法直接获取errno，因为std::ifstream封装了它
        // 但如果是一个C风格的open()，我们可以这样做：
        // int fd = open(filename.c_str(), O_RDONLY);
        // if (fd == -1) {
        //     int err = errno; // 捕获原始errno
        //     if (err == ENOENT) {
        //         throw FileNotFoundError("Failed to open file: " + filename + ". File does not exist.", err);
        //     } else if (err == EACCES) {
        //         throw PermissionDeniedError("Failed to open file: " + filename + ". Permission denied.", err);
        //     } else {
        //         throw FileOperationException("Failed to open file: " + filename + ". System error code: " + std::to_string(err), err);
        //     }
        // }
        // For std::ifstream, we might infer or provide a more generic message
        throw FileOperationException("Failed to open file: " + filename + ". Check path and permissions.");
    }

    std::string line;
    while (std::getline(file, line)) {
        std::cout << line << std::endl;
    }
    // std::ifstream 在析构时会自动关闭文件，符合RAII
}

// 另一个例子：处理一个假想的返回错误码的API
enum class NetworkErrorCode {
    Success = 0,
    ConnectionRefused,
    Timeout,
    InvalidHost,
    UnknownError
};

NetworkErrorCode connectToServer(const std::string& host, int port) {
    if (host == "bad.host") return NetworkErrorCode::InvalidHost;
    if (port == 8080) return NetworkErrorCode::ConnectionRefused; // Simulate connection refused
    if (port == 9000) return NetworkErrorCode::Timeout; // Simulate timeout
    return NetworkErrorCode::Success;
}

// 封装并转换网络错误码
void establishNetworkConnection(const std::string& host, int port) {
    NetworkErrorCode ec = connectToServer(host, port);
    if (ec != NetworkErrorCode::Success) {
        std::string message = "Network connection failed to " + host + ":" + std::to_string(port) + ". ";
        switch (ec) {
            case NetworkErrorCode::ConnectionRefused:
                throw std::runtime_error(message + "Connection refused.");
            case NetworkErrorCode::Timeout:
                throw std::runtime_error(message + "Timeout occurred.");
            case NetworkErrorCode::InvalidHost:
                throw std::invalid_argument(message + "Invalid host specified.");
            case NetworkErrorCode::UnknownError:
            default:
                throw std::runtime_error(message + "Unknown network error.");
        }
    }
    std::cout << "Successfully connected to " << host << ":" << port << std::endl;
}

// 示例使用
int main() {
    std::cout << "--- File Operations ---" << std::endl;
    try {
        openAndReadFile("non_existent_file.txt");
    } catch (const FileNotFoundError& e) {
        std::cerr << "Caught FileNotFoundError: " << e.what() << " (Error code: " << e.getOriginalErrorCode() << ")" << std::endl;
    } catch (const FileOperationException& e) {
        std::cerr << "Caught FileOperationException: " << e.what() << " (Error code: " << e.getOriginalErrorCode() << ")" << std::endl;
    } catch (const std::exception& e) {
        std::cerr << "Caught general exception: " << e.what() << std::endl;
    }

    std::cout << "\n--- Network Operations ---" << std::endl;
    try {
        establishNetworkConnection("good.host", 8080); // Will simulate connection refused
    } catch (const std::invalid_argument& e) {
        std::cerr << "Caught invalid argument: " << e.what() << std::endl;
    } catch (const std::runtime_error& e) {
        std::cerr << "Caught runtime error: " << e.what() << std::endl;
    } catch (const std::exception& e) {
        std::cerr << "Caught general exception: " << e.what() << std::endl;
    }

    try {
        establishNetworkConnection("bad.host", 1234); // Will simulate invalid host
    } catch (const std::invalid_argument& e) {
        std::cerr << "Caught invalid argument: " << e.what() << std::endl;
    }

    try {
        establishNetworkConnection("good.host", 1234); // Success
    } catch (const std::exception& e) {
        std::cerr << "Caught unexpected exception: " << e.what() << std::endl;
    }

    return 0;
}