使用c++编写一个基于libcurl的http传输的类

以下是一个简单的基于libcurl的HTTP传输类的示例代码：

#include <string>
#include <curl/curl.h>

class HttpTransfer {
public:
    HttpTransfer() {
        curl_global_init(CURL_GLOBAL_ALL);
        curl_ = curl_easy_init();
    }

    ~HttpTransfer() {
        if (curl_ != nullptr) {
            curl_easy_cleanup(curl_);
            curl_ = nullptr;
        }
        curl_global_cleanup();
    }

    void SetUrl(const std::string& url) {
        url_ = url;
    }

    void SetTimeout(long timeout) {
        timeout_ = timeout;
    }

    void SetHeaders(const std::vector<std::string>& headers) {
        headers_ = headers;
    }

    void SetBody(const std::string& body) {
        body_ = body;
    }

    CURLcode Get(std::string& response) {
        return transfer("GET", response);
    }

    CURLcode Post(std::string& response) {
        return transfer("POST", response);
    }

private:
    CURL* curl_;
    std::string url_;
    long timeout_ = 10;
    std::vector<std::string> headers_;
    std::string body_;

    static size_t write_callback(char* ptr, size_t size, size_t nmemb, void* userdata) {
        std::string* response = static_cast<std::string*>(userdata);
        response->append(ptr, size * nmemb);
        return size * nmemb;
    }

    CURLcode transfer(const std::string& method, std::string& response) {
        if (curl_ == nullptr) {
            return CURLE_FAILED_INIT;
        }

        curl_easy_setopt(curl_, CURLOPT_URL, url_.c_str());
        curl_easy_setopt(curl_, CURLOPT_TIMEOUT, timeout_);
        curl_easy_setopt(curl_, CURLOPT_CUSTOMREQUEST, method.c_str());
        curl_easy_setopt(curl_, CURLOPT_HTTPHEADER, headers_.data());
        curl_easy_setopt(curl_, CURLOPT_POSTFIELDS, body_.c_str());
        curl_easy_setopt(curl_, CURLOPT_WRITEFUNCTION, write_callback);
        curl_easy_setopt(curl_, CURLOPT_WRITEDATA, &response);

        CURLcode res = curl_easy_perform(curl_);
        return res;
    }
};

这个类提供了设置URL、超时、HTTP头、HTTP主体和发送GET或POST请求的函数。使用方法如下：

HttpTransfer transfer;
transfer.SetUrl("https://www.example.com/");
transfer.SetTimeout(30);

std::vector<std::string> headers = {"Content-Type: application/json"};
transfer.SetHeaders(headers);

std::string body = "{\"key\": \"value\"}";
transfer.SetBody(body);

std::string response;
CURLcode res = transfer.Post(response);
if (res == CURLE_OK) {
    // 处理响应
} else {
    // 处理错误
}

注意在使用curl_easy_cleanup函数清理curl句柄之前，应该先判断curl句柄是否为nullptr，以避免野指针的问题。