How to Validate an Excel XLSX File using C/C++

If we’re designing applications to process and store Excel XLSX files, we want to be completely sure our spreadsheets are valid and secure before we commit them to a database.

Thankfully, using the below code, we can easily incorporate an XSLX document validation step which detects errors within the file structure and identifies if the file is password-protected. Equipped with this information, we can root our invalid spreadsheets and potential security concerns before storing such files in a sensitive location.

To structure our API call in C/C++, let’s start by installing libcurl:

libcurl/7.75.0

Then let’s include the below ready-to-run code examples in our file & supply a free-tier Cloudmersive API key to authorize our request:

CURL *curl;
CURLcode res;
curl = curl_easy_init();
if(curl) {
     curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
     curl_easy_setopt(curl, CURLOPT_URL, "https://api.cloudmersive.com/convert/validate/xlsx");
     curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
     curl_easy_setopt(curl, CURLOPT_DEFAULT_PROTOCOL, "https");
     struct curl_slist *headers = NULL;
     headers = curl_slist_append(headers, "Content-Type: multipart/form-data");
     headers = curl_slist_append(headers, "Apikey: YOUR-API-KEY-HERE");
     curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
     curl_mime *mime;
     curl_mimepart *part;
     mime = curl_mime_init(curl);
     part = curl_mime_addpart(mime);
     curl_mime_name(part, "inputFile");
     curl_mime_filedata(part, "/path/to/file");
     curl_easy_setopt(curl, CURLOPT_MIMEPOST, mime);
     res = curl_easy_perform(curl);
     curl_mime_free(mime);
}
curl_easy_cleanup(curl);

We can now validate up to 800 files per month for free with no commitment. Quick and easy!