How can i add file size to request?

[W7orld]

I want do diaply the file size to the user before starting download, I found this way to get file size for download fetch.getContentLengthForRequest(...) but this way not added the file size to fetch database!! So how can i adding the size to request with the result of fetch.getContentLengthForRequest(...) ?

Or there another way to do that?