data points to the data bytes: those are copied to the part and their storage may safely be reused after call. datasize is the number of data bytes: it can be set to CURL_ZERO_TERMINATED to indicate data is a nul-terminated character string. part is the part's to assign contents to.
Setting a part's contents twice is valid: only the value set by the last call is retained. It is possible to unassign part's contents by setting data to NULL.
Setting very large data is memory consuming: one might consider using curl_mime_data_cb(3) in such a case.
curl_mime *mime; curl_mimepart *part; /* create a mime handle */ mime = curl_mime_init(easy); /* add a part */ part = curl_mime_addpart(mime); /* add data to the part */ curl_mime_data(part, "raw contents to send", CURL_ZERO_TERMINATED);