How do I check if a StringStream variable is empty/null?

Question

Just a quick question here guys. I\'ve been searching to no avail so far.

A bit more info here:

stringstream report_string;

report_string << \         


        

Answer 1

It's normally reasonable and readable to use...

report_string.str().empty()

...but that may involve dynamic allocation and copying the entire string to a temporary, only to be thrown away.

If performance is important, another option is...

report_string.peek() == decltype(report_string)::traits_type::eof()

• this looks for a character not yet extracted from the stream, ignoring input that's already been successfully parsed/extracted

  • that's different from testing report_string.str().empty(), which still "sees" already-extracted input

• if earlier parsing left the stream in a fail state you haven't clear()ed, this will return eof() regardless of whether there are more unextracted characters