curl 库的使用

一个简单的调用 Face++ 人脸识别 API 示例

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

using namespace std;

size_t writeData(char *ptr, size_t size, size_t nmemb, void *content)
{
    string data(ptr, size * nmemb);
    *((stringstream*) content) << data << endl;
    return size * nmemb;
}

int main(void)
{
    // 初始化
    CURL *curl = curl_easy_init();
    // 设置 URL
    curl_easy_setopt(curl, CURLOPT_URL, "https://api-cn.faceplusplus.com/facepp/v3/detect");

    // 添加配置表单
    curl_mime *multipart = curl_mime_init(curl);
    curl_mimepart *part = curl_mime_addpart(multipart);
    curl_mime_name(part, "api_key");
    curl_mime_data(part, "tDgu41ZgpJkD9FZCZMiXdeyF2qqZEnY7", CURL_ZERO_TERMINATED);
    part = curl_mime_addpart(multipart);
    curl_mime_name(part, "api_secret");
    curl_mime_data(part, "wgRRh1aNW40nVzkllj8qtz22BgKHLeKf", CURL_ZERO_TERMINATED);
    part = curl_mime_addpart(multipart);
    curl_mime_name(part, "image_file");
    curl_mime_filedata(part, "face.jpg");

    curl_easy_setopt(curl, CURLOPT_MIMEPOST, multipart);

    //添加回调函数
    stringstream response; 
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writeData);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);

    // 执行 post 请求
    CURLcode rescode = curl_easy_perform(curl);
    if (CURLE_OK != rescode)
        fprintf(stderr, "\n\n-------post error-------\n %s \n\n", curl_easy_strerror(rescode));
    
    // 打印请求结果
    cout << response.str() << endl;

    curl_mime_free(multipart);
    curl_easy_cleanup(curl);

    return 0;
}

运行结果

image.png

进行简单的封装

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

class Curl
{
    
private:
    const char *url;
    CURL *curl;
    curl_mime *multipart;
    static size_t writeData(char *ptr, size_t size, size_t nmemb, void *curl);

public:
    Curl(const char *url);
    void addPartData(const char *name, const char *data, size_t size = -1);
    void addPartFile(const char *name, const char *filename);
    std::string post();
    ~Curl();
};


using namespace std;

size_t Curl::writeData(char *ptr, size_t size, size_t nmemb, void *content)
{
    string data(ptr, size * nmemb);
    *((stringstream*) content) << data << endl;
    return size * nmemb;
}


string Curl::post()
{

    curl_easy_setopt(curl, CURLOPT_URL, url);
    curl_easy_setopt(curl, CURLOPT_MIMEPOST, multipart);

    stringstream response; 
    // Set call back
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, this->writeData);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);

    CURLcode rescode = curl_easy_perform(curl);
    if (CURLE_OK != rescode)
        fprintf(stderr, "\n\n-------post error-------\n %s \n\n", curl_easy_strerror(rescode));

    return response.str();
}


Curl::Curl(const char *url)
{
    this->url = url;
    curl = curl_easy_init();
    multipart = curl_mime_init(curl);
}


void Curl::addPartData(const char *name, const char *data, size_t size)
{
    curl_mimepart *part = part = curl_mime_addpart(multipart);
    curl_mime_name(part, name);
    curl_mime_data(part, data, size);
}

void Curl::addPartFile(const char *name, const char *filename)
{
    curl_mimepart *part = part = curl_mime_addpart(multipart);
    curl_mime_name(part, name);
    curl_mime_filedata(part, filename);
}

Curl::~Curl()
{
    curl_mime_free(multipart);
    curl_easy_cleanup(curl);
}

// -------- main -------
#include <iostream>

int main()
{
    const char * key = "tDgu41ZgpJkD9FZCZMiXdeyF2qqZEnY7";
    const char * secret = "wgRRh1aNW40nVzkllj8qtz22BgKHLeKf";
    
    Curl curl = "https://api-cn.faceplusplus.com/facepp/v3/detect";

    curl.addPartData("api_key", key);
    curl.addPartData("api_secret", secret);
    curl.addPartFile("image_file", "face.jpg");

    cout << curl.post() << endl;

    return 0;
}