You're presuming you have only a non-rewindable stream as opposed to a file interface, which is why I was explicit about the requirement to be able to rewind the position to avoid a stack. If you only have a non-rewindable stream, then, yes, you need a strack. If you have a file handle, you do not.

(and yes, you did presume something; if you have rewindable file handle, you do not need to keep the characters; you can instead-re-read them)