Question regarding fwrite(), filesize(), binary stream

[lierduh]

I have the stream of the binary data. I need to use some file
associated function with it. For example filesize(), imagesize() etc.
At the moment, I write this data stream into a tmp file
fwrite('/tmp/tempfile', 'x+'), do the file functions, then unlink()
it. It surely is not an elegant way to do, let along a good
portability way.

Is there a way to create a file in the memory from the data stream? or
even use file functions without first write the stream into a file?
Thanks.