C++ named requirements: FormattedInputFunction
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FormattedInputFunction
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[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
noskipwsargument set to false, which performs the following:
- if eofbit or badbit are set on the input stream, sets the
failbitas well, and if exceptions onfailbitare 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::skipwsflag 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
failbitandeofbitare set and if the stream is on for exceptions on one of these bits, ios_base::failure is thrown.
- if eofbit or badbit are set on the input stream, sets the
- 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 oneofbitare enabled in this stream's exception mask ((exceptions() & eofbit) != 0), throws ios_base::failure. - if an exception is thrown during input, sets
badbitin the input stream. If exceptions onbadbitare enabled in this stream's exception mask ((exceptions() & badbit) != 0), the exception is also rethrown. - If no exception was thrown, returns *this.
- if the end of the stream is reached (the call to rdbuf()->sbumpc() or rdbuf()->sgetc() returns Traits::eof()), sets
- 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.
- basic_istream::operator>>(int, long, double, void*, bool)
- operator>>(std::basic_istream, char&)
- operator>>(std::basic_istream, char*)
- operator>>(std::basic_istream, std::bitset)
- operator>>(std::basic_istream, std::string)
-
operator>>, when called on the return value of std::get_money
[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() |