c++ - 使用 libcurl 和 C++ 将从 IMAP 服务器下载的电子邮件保存到文件中

Question

我可以从 IMAP 服务器获取电子邮件，但无法将它们保存到计算机上的文件中以供以后处理。有没有办法使用 libcurl 在 C++ 中执行此操作？

    #include <stdio.h>
#include <curl/curl.h>
int main(void)
{
  CURL *curl;
  CURLcode res = CURLE_OK;

  curl = curl_easy_init();
  if(curl) {
    /* Set username and password */
    curl_easy_setopt(curl, CURLOPT_USERNAME, "username");
    curl_easy_setopt(curl, CURLOPT_PASSWORD, "password");

    curl_easy_setopt(curl, CURLOPT_URL, "imaps://imap.gmail.com/INBOX/;UID=1");
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);

    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0);
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

    /* Perform the fetch */
    res = curl_easy_perform(curl);

    /* Check for errors */
    if(res != CURLE_OK)
      fprintf(stderr, "curl_easy_perform() failed: %s\n",
              curl_easy_strerror(res));

    /* Always cleanup */
    curl_easy_cleanup(curl);
  }

  return (int)res;
}

Answer 1

您正在执行数据传输:

res = curl_easy_perform(curl);

但是您没有对这些数据做任何事情。您必须设置一个回调函数，只要 curl_easy_perform(curl) 返回 CURLE_OK 就会被调用。

这是libcurl tutorial说:

Let's assume for a while that you want to receive data as the URL identifies a remote resource you want to get here. Since you write a sort of application that needs this transfer, I assume that you would like to get the data passed to you directly instead of simply getting it passed to stdout. So, you write your own function that matches this prototype:

size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp);

You tell libcurl to pass all data to this function by issuing a function similar to this:

curl_easy_setopt(easyhandle, CURLOPT_WRITEFUNCTION, write_data);