istream utilities
Use these methods for housekeeping on istream objects:
Method: int istream::gcount ()
Report how many characters were read from this istream in the
last unformatted input operation.
Method: int istream::ipfx (int keepwhite)
Ensure that the istream object is ready for reading; check for
errors and end of file and flush any tied stream. ipfx skips
whitespace if you specify 0 as the keepwhite
argument, and ios::skipws is set for this stream.
To avoid skipping whitespace (regardless of the skipws setting on
the stream), use 1 as the argument.
Call istream::ipfx to simplify writing your own methods for reading
istream objects.
A placeholder for compliance with the draft ANSI standard; this method does nothing whatever.
If you wish to write portable standard-conforming code on istream
objects, call isfx after any operation that reads from an
istream; if istream::ipfx has any special effects that
must be cancelled when done, istream::isfx will cancel them.
Method: istream& istream::ignore ([int n] [, int delim])
Discard some number of characters pending input. The first optional
argument n specifies how many characters to skip. The second
optional argument delim specifies a "boundary" character:
ignore returns immediately if this character appears in the
input.
By default, delim is EOF; that is, if you do not specify a
second argument, only the count n restricts how much to ignore
(while input is still available).
If you do not specify how many characters to ignore, ignore
returns after discarding only one character.
Method: istream& istream::putback (char ch)
Attempts to back up one character, replacing the character backed-up
over by ch. Returns EOF if this is not allowed. Putting
back the most recently read character is always allowed. (This method
corresponds to the C function ungetc.)
Method: istream& istream::unget ()
Attempt to back up one character.