C++利用libcurl获取下载文件名称及大小

Content-Disposition: inline;filename=hello.jpg

Content-Disposition: attachment;filename=hello.jpg

static size_t header_callback(char *buffer, size_t size,
                              size_t nitems, void *userdata)
{
  /* received header is nitems * size long in 'buffer' NOT ZERO TERMINATED */
  /* 'userdata' is set with CURLOPT_HEADERDATA */
  return nitems * size;
}
 
CURL *curl = curl_easy_init();
if(curl) 
{
  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
 
  curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, header_callback);
 
  curl_easy_perform(curl);
}

size_t header_callback(void *buffer, size_t size, size_t nitems, void *userdata)
{
	string sHeaderData = (char*)buffer;
	string sKey = "Content-Disposition";
	std::size_t nFound = sHeaderData.find(sKey);
	if (nFound != std::string::npos)
	{
		printf("Header data: %s \n", (char*)buffer);
		stringstream ss(sHeaderData);     
		char cSplit = ';'; // 设定好分隔符号
		sKey = "filename=";
		vector<string> results; // 用来存储结果
		string strResult;
		while (getline(ss, strResult, cSplit))
		{
			nFound = strResult.find(sKey);
			if (nFound != std::string::npos)
			{
				string sFileName = strResult.substr(nFound + sKey.length());
				sKey = '"';
				nFound = sFileName.find(sKey);
				if (nFound != std::string::npos)
				{
					sFileName = sFileName.substr(1, sFileName.length()-2);
				}
				m_sFileName = sFileName;
				printf("sFileName: %s \n", m_sFileName.c_str());
				break;
			}
		}
	}

	return nitems * size;
}

double getDownloadFileInfo(const string url)
{
    CURL *easy_handle = NULL;
	int ret = CURLE_OK;
	double size = -1;

	do
	{
		easy_handle = curl_easy_init();
		if (!easy_handle)
		{
            ZLOG("curl_easy_init error");
			break;
		}

		// Only get the header data
		curl_easy_setopt(easy_handle, CURLOPT_URL, url.c_str());
		curl_easy_setopt(easy_handle, CURLOPT_CUSTOMREQUEST, "GET");    //使用CURLOPT_CUSTOMREQUEST
		//ret |= curl_easy_setopt(easy_handle, CURLOPT_HEADER, 1L);
		curl_easy_setopt(easy_handle, CURLOPT_NOBODY, 1L);
        //ret |= curl_easy_setopt(easy_handle, CURLOPT_WRITEFUNCTION, nousecb);	

		curl_easy_setopt(easy_handle, CURLOPT_HEADERFUNCTION, header_callback);

		ret = curl_easy_perform(easy_handle);
		if (ret != CURLE_OK)
		{
			char s[100] = {0};
			sprintf_s(s, sizeof(s), "error:%d:%s", ret, curl_easy_strerror(static_cast<CURLcode>(ret)));

            ZLOG(s);
			break;
		}

		// size = -1 if no Content-Length return or Content-Length=0
		ret = curl_easy_getinfo(easy_handle, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &size);

		if (ret != CURLE_OK)
		{
            ZLOG("curl_easy_getinfo error");
			break;
		}

	} while (0);

	curl_easy_cleanup(easy_handle);

	if (size > 0.0)
	{
		downloadFileLength = size;
	}

	return size;
}