使用curl下载文件并控制流量断点续传和效验文件

typedef struct _tagDownTask
{
    char url[1024];
    char filePath[1024];
    unsigned long totalSize;
    unsigned long currentFileSize;
    unsigned long limitSize; //0为不限制
    FILE* pfile;        //文件句柄
    unsigned long fileSize;
    char checkSum[64];  //md5效验码
}DownTask;

// 获取当前文件大小
size_t curl_get_filesize(const char* filepath)
{
    FILE* fi;
    size_t sz;
    fi = fopen(filepath, "r");
    if (!fi) return 0;

    fseek(fi, 0L, SEEK_END);
    sz = ftell(fi);
    fseek(fi, 0L, SEEK_SET);

    fclose(fi);

    return sz;
}

//功能：效验文件
int curl_checkSum(char* filepath, char* checkSum)
{
    K_INT32 lRet = 0;
    K_CHAR md5[64] = { 0 };
    //生成文件md5码并比较
    //to do 这里的代码就不实现了
    
    return lRet;
}

// 回调函数，用于处理Curl库接收到的数据
size_t curl_write_callback(void *buffer, size_t size, size_t nmemb, void *userdata) {
    DownTask* pTask = (DownTask*)userdata;
    size_t written = fwrite(buffer, size, nmemb, pTask->pfile);
    //分别增加统计
    pTask->totalSize += written;
    pTask->currentFileSize += written;

    // 检查已下载的字节数是否超过限制，如果超过则返回 0，停止下载
    if (pTask->limitSize > 0 && pTask->totalSize >= pTask->limitSize) {
        return 0;
    }
    return written;
}

// 添加一个curl下载任务
int curl_download(DownTask *in_pDownTask)
{
    CURL *curl;
    CURLcode res;
    int lRet = 0;
    char range_header[64];

    //获取已下载文件的大小
    in_pDownTask->currentFileSize = curl_get_filesize(in_pDownTask->filePath);

    // 以追加二进制模式打开文件，实现断点续传
    in_pDownTask->pfile = fopen(in_pDownTask->filePath, "ab");
    if (!in_pDownTask->pfile) {
        fprintf(stderr, "Error opening file.\n");
        return -1;
    }
    
    // 初始化Curl库
    curl_global_init(CURL_GLOBAL_DEFAULT);

    // 创建Curl句柄
    curl = curl_easy_init();
    if (curl) {
        // 设置要下载的URL
        curl_easy_setopt(curl, CURLOPT_URL, in_pDownTask->url);

        // 设置回调函数，处理接收到的数据
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curl_write_callback);

        // 将文件句柄传递给回调函数
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)in_pDownTask);

        // 设置断点续传的起始位置
        if (in_pDownTask->currentFileSize > 0) {
            snprintf(range_header, sizeof(range_header), "Range: bytes=%d-", in_pDownTask->currentFileSize);
            curl_easy_setopt(curl, CURLOPT_RESUME_FROM, (long)in_pDownTask->currentFileSize);
        }
        else {
            curl_easy_setopt(curl, CURLOPT_RESUME_FROM, 0);
        }

        curl_easy_setopt(curl, CURLOPT_HEADERDATA, NULL);

        // 禁用SSL证书验证
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);

        // 执行Curl请求
        res = curl_easy_perform(curl);
        if (res != CURLE_OK) {
            fprintf(stderr, "Curl failed: %s\n", curl_easy_strerror(res));
        }
        // 清理Curl句柄
        curl_easy_cleanup(curl);
    }

    // 关闭文件
    fclose(in_pDownTask->pfile);
    // 清理Curl全局资源
    curl_global_cleanup();
    //下载完成
    if (in_pDownTask->fileSize == in_pDownTask->currentFileSize) {
        //效验检查
        lRet = curl_checkSum(in_pDownTask->filePath, in_pDownTask->checkSum);
        if (lRet == 0) {
            return 0;
        }
        //不通过则删除已下数据
        remove(in_pDownTask->filePath);
        return -1;
    }
	//未完成，下次断点续传
    else if (in_pDownTask->fileSize > in_pDownTask->currentFileSize) {
        return 1;
    }
    else {
        //不通过则删除已下数据
        remove(in_pDownTask->filePath);
        return -1;
    }
}

DownTask task = {0};
sprintf(task.url, "%s", "https://yoururl.com/file.zip");
task.limitSize = 0;
task.fileSize = 123; //你的文件大小
sprintf(task.checkSum, "%s", "your file md5");
sprintf(task.filePath, "%s", "your save path");

curl_download(&task);