C++ concepts: UnformattedInputFunction


An UnformattedInputFunction 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 true, 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, throws ios_base::failure.
    • flushes the tie()'d output stream, if applicable
  • 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:
    • sets the number of extracted characters (gcount) in the input stream to zero
    • if the function was called to write to an array of CharT, writes CharT() (the null character) to the first location of the array
  • 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, 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, the exception is also rethrown.
    • If no exception was thrown during input, sets the number of extracted characters (gcount) in the input stream.
  • In any event, whether terminating by exception or returning, the sentry's destructor is called before leaving this function.

Standard library

The following standard library functions are UnformattedInputFunctions.

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