Better way to determine length of a std::istream?

The "best" way is to avoid needing the length :)

• Not all streams are seekable (For example, imagine an istream on a network socket)
• The return type from tellg() is not necessarily numeric (the only requirement is that it can be passed back to seekg() to return to the same position)
• Even if it is numeric, it is not necessarily a number of bytes. For example, it could be a "magic" value meaning "at the end"
• For fstreams, issues like case and linefeed conversion can screw things up