Question

我有以下代码：

#define FROM    "<example@gmail.com>"
#define TO      "<example2@gmail.com>"

const char *payload_text[] = {
    "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n",
    "To: " TO "\r\n",
    "From: " FROM "(Example User)\r\n",
    "Subject: SMTP TLS example message\r\n",
    "MIME-Version: 1.0\r\n",
    "Content-Type: multipart/mixed; boundary=\"KkK170891tpbkKk__FV_KKKkkkjjwq\"\r\n",
    "\r\n",
    "This is a multipart message in MIME format.",
    "\r\n",
    "--KkK170891tpbkKk__FV_KKKkkkjjwq\r\n",
    "Content-Type: text/plain",
    "\r\n",
    "here goes the text message\r\n",
    "\r\n",
    "--KkK170891tpbkKk__FV_KKKkkkjjwq\r\n",
    "Content-Type: image/jpeg; name=\"test.jpg\"\r\n",
    "Content-Transfer-Encoding: base64\r\n",
    "Content-Disposition: attachment; filename=\"test.jpg\"\r\n",
    "\r\n",
    NULL, /*19*/
    "\r\n",
    "--KkK170891tpbkKk__FV_KKKkkkjjwq--\r\n",
    NULL
};

struct upload_status {
    int lines_read;
};

static size_t payload_source(void *ptr, size_t size, size_t nmemb, void *userp) {
  struct upload_status *upload_ctx = (struct upload_status *)userp;
  const char *data;

  if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
    return 0;
  }

  data = payload_text[upload_ctx->lines_read];

  if(data) {
    size_t len = strlen(data);
    memcpy(ptr, data, len);
    upload_ctx->lines_read++;

    return len;
  }

  return 0;
}

std::string readFileToBase64(const char* filename) {
    /* converts binary file to base64 */
}

std::string split76(std::string in) {
    int lines = in.length() / 76;

    for(int i=0;i<lines;i++) {
        in.insert((i+1)*76+i*2, "\r\n");
    }

    return in;
}

int main(void) {
    payload_text[19] = split76(readFileToBase64("C:\\Users\\thrymgjol\\code\\emailtest\\bin\\Release\\test.jpg")).c_str();

  CURL *curl;
  CURLcode res = CURLE_OK;
  struct curl_slist *recipients = NULL;
  struct upload_status upload_ctx;

  upload_ctx.lines_read = 0;

  curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_USERNAME, "example2@gmail.com");
    curl_easy_setopt(curl, CURLOPT_PASSWORD, "legitpassword");
    curl_easy_setopt(curl, CURLOPT_URL, "smtp://smtp.gmail.com:587");
    curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
    curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM);
    recipients = curl_slist_append(recipients, TO);
    curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
    curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
    res = curl_easy_perform(curl);
    if(res != CURLE_OK)
      fprintf(stderr, "curl_easy_perform() failed: %s\n",
              curl_easy_strerror(res));

    curl_slist_free_all(recipients);
    curl_easy_cleanup(curl);
  }

  return (int)res;
}

但是，当我编译并运行时，payload_source()在第18次指示后停止读取payload_text。这完全切断了我的附件，我分配给payload_text [19]。关于它为什么这样做的任何想法？

Answer 1

问题是从split76返回的值是临时的，并在分配完成后销毁。之后任何尝试访问它都会导致未定义的行为。如果你需要存储一个指向字符串缓冲区的指针，你可以创建一个本地std::string来保持它，确保它足够长，可以使用。

std::string encodedFile(split76(readFileToBase64("C:\\Users\\thrymgjol\\code\\emailtest\\bin\\Release\\test.jpg")));
payload_text[19] = encodedFile.c_str();

Const char *没有正确分配？

1 个答案: