C++ named requirements: FormattedInputFunction

< cpp‎ | named req
C++ named requirements
Type properties
Container Elements

Stream I/O
Random Numbers


[edit] Requirements

A FormattedInputFunction is a stream input function that performs the following:

  • Constructs an object of type basic_istream::sentry with automatic storage duration and with the noskipws argument set to false, which performs the following:
  • if eofbit or badbit are set on the input stream, sets the failbit as well, and if exceptions on failbit are enabled in this input stream's exception mask ((exceptions() & failbit) != 0), throws ios_base::failure.
  • flushes the tie()'d output stream, if applicable.
  • if ios_base::skipws flag is set on this input stream, extracts and discards characters from the input stream until one of the following becomes true:
  • the next available character on the input stream is not a whitespace character, as tested by the std::ctype facet of the locale currently imbued in this input stream. The non-whitespace character is not extracted.
  • the end of the stream is reached, in which case failbit and eofbit are set and if the stream is on for exceptions on one of these bits, ios_base::failure is thrown.
  • Checks the status of the sentry by calling sentry::operator bool(), which is equivalent to basic_ios::good.
  • If the sentry returned false or sentry's constructor threw an exception, no input takes place.
  • If the sentry returned true, performs the input as if by calling rdbuf()->sbumpc() or rdbuf()->sgetc().
  • if the end of the stream is reached (the call to rdbuf()->sbumpc() or rdbuf()->sgetc() returns Traits::eof()), sets eofbit. If exceptions on eofbit are enabled in this stream's exception mask ((exceptions() & eofbit) != 0), throws ios_base::failure.
  • if an exception is thrown during input, sets badbit in the input stream. If exceptions on badbit are enabled in this stream's exception mask ((exceptions() & badbit) != 0), the exception is also rethrown.
  • If no exception was thrown, returns *this.
  • In any event, whether terminating by exception or returning, the sentry's destructor is called before leaving this function.

[edit] Standard library

The following standard library functions are FormattedInputFunctions.

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 160 C++98 the process of determining whether the exception caught
is rethrown mentioned a non-existing function exception()
corrected to exceptions()