The callback function will be passed as much data as possible in all invokes,
but you cannot possibly make any assumptions. It may be one byte, it may be
-thousands. The maximum amount of data that can be passed to the write callback
-is defined in the curl.h header file: CURL_MAX_WRITE_SIZE.
+thousands. The maximum amount of body data that can be passed to the write
+callback is defined in the curl.h header file: CURL_MAX_WRITE_SIZE (the usual
+default is 16K). If you however have \fICURLOPT_HEADER\fP set, which sends
+header data to the write callback, you can get up to
+\fICURL_MAX_HTTP_HEADER\fP bytes of header data passed into it. This usually
+means 100K.
.IP CURLOPT_WRITEDATA
Data pointer to pass to the file write function. If you use the
\fICURLOPT_WRITEFUNCTION\fP option, this is the pointer you'll get as
to your function, it'll signal an error to the library. This will abort the
transfer and return \fICURL_WRITE_ERROR\fP.
+A complete header that is passed to this function can be up to
+\fICURL_MAX_HTTP_HEADER\fP (100K) bytes.
+
If this option is not set, or if it is set to NULL, but
\fICURLOPT_HEADERDATA\fP (\fICURLOPT_WRITEHEADER\fP) is set to anything but
NULL, the function used to accept response data will be used instead. That is,