focal (3) std::basic_istream.3cxx.gz
NAME
std::basic_istream< _CharT, _Traits > - Template class basic_istream.
SYNOPSIS
Inherited by std::basic_ifstream< _CharT, _Traits >.
Classes
class sentry
Performs setup work for input streams.
Public Types
typedef ctype< _CharT > __ctype_type
typedef basic_ios< _CharT, _Traits > __ios_type
typedef basic_istream< _CharT, _Traits > __istream_type
typedef num_get< _CharT, istreambuf_iterator< _CharT, _Traits > > __num_get_type
typedef basic_streambuf< _CharT, _Traits > __streambuf_type
typedef _CharT char_type
typedef _Traits::int_type int_type
typedef _Traits::off_type off_type
typedef _Traits::pos_type pos_type
typedef _Traits traits_type
Public Member Functions
basic_istream (__streambuf_type *__sb)
Base constructor.
virtual ~basic_istream ()
Base destructor.
template<typename _ValueT > basic_istream< _CharT, _Traits > & _M_extract (_ValueT &__v)
basic_istream< char > & getline (char_type *__s, streamsize __n, char_type __delim)
Explicit specialization declarations, defined in src/istream.cc.
basic_istream< wchar_t > & getline (char_type *__s, streamsize __n, char_type __delim)
basic_istream< char > & ignore (streamsize __n)
basic_istream< wchar_t > & ignore (streamsize __n)
basic_istream< char > & ignore (streamsize __n, int_type __delim)
basic_istream< wchar_t > & ignore (streamsize __n, int_type __delim)
__istream_type & operator>> (__ios_type &(*__pf)(__ios_type &))
__istream_type & operator>> (__istream_type &(*__pf)(__istream_type &))
Interface for manipulators.
__istream_type & operator>> (ios_base &(*__pf)(ios_base &))
Protected Attributes
streamsize _M_gcount
Friends
class sentry
Unformatted Input Functions
All the unformatted input functions have some common behavior. Each starts by constructing a temporary
object of type std::basic_istream::sentry with the second argument (noskipws) set to true. This has
several effects, concluding with the setting of a status flag; see the sentry documentation for more.
If the sentry status is good, the function tries to extract whatever data is appropriate for the type of
the argument.
The number of characters extracted is stored for later retrieval by gcount().
If an exception is thrown during extraction, ios_base::badbit will be turned on in the stream's error
state (without causing an ios_base::failure to be thrown) and the original exception will be rethrown if
badbit is set in the exceptions mask.
int_type get ()
Simple extraction.
__istream_type & get (char_type &__c)
Simple extraction.
__istream_type & get (char_type *__s, streamsize __n, char_type __delim)
Simple multiple-character extraction.
__istream_type & get (char_type *__s, streamsize __n)
Simple multiple-character extraction.
__istream_type & get (__streambuf_type &__sb, char_type __delim)
Extraction into another streambuf.
__istream_type & get (__streambuf_type &__sb)
Extraction into another streambuf.
__istream_type & getline (char_type *__s, streamsize __n, char_type __delim)
String extraction.
__istream_type & getline (char_type *__s, streamsize __n)
String extraction.
__istream_type & ignore (streamsize __n, int_type __delim)
Discarding characters.
__istream_type & ignore (streamsize __n)
Simple extraction.
__istream_type & ignore ()
Simple extraction.
int_type peek ()
Looking ahead in the stream.
__istream_type & read (char_type *__s, streamsize __n)
Extraction without delimiters.
streamsize readsome (char_type *__s, streamsize __n)
Extraction until the buffer is exhausted, but no more.
__istream_type & putback (char_type __c)
Unextracting a single character.
__istream_type & unget ()
Unextracting the previous character.
int sync ()
Synchronizing the stream buffer.
pos_type tellg ()
Getting the current read position.
__istream_type & seekg (pos_type)
Changing the current read position.
__istream_type & seekg (off_type, ios_base::seekdir)
Changing the current read position.
basic_istream ()
Simple extraction.
basic_istream (const basic_istream &)=delete
Simple extraction.
basic_istream (basic_istream &&__rhs)
Simple extraction.
basic_istream & operator= (const basic_istream &)=delete
Simple extraction.
basic_istream & operator= (basic_istream &&__rhs)
Simple extraction.
void swap (basic_istream &__rhs)
Simple extraction.
template<typename _ValueT > __istream_type & _M_extract (_ValueT &__v)
Simple extraction.
Detailed Description
template<typename _CharT, typename _Traits>
class std::basic_istream< _CharT, _Traits >" Template class basic_istream.
Template Parameters
_CharT Type of character stream.
_Traits Traits for character type, defaults to char_traits<_CharT>.
This is the base class for all input streams. It provides text formatting of all builtin types, and
communicates with any class derived from basic_streambuf to do the actual input.
Definition at line 83 of file iosfwd.
Constructor & Destructor Documentation
template<typename _CharT , typename _Traits > std::basic_istream< _CharT, _Traits >::basic_istream
(__streambuf_type * __sb) [inline], [explicit]
Base constructor. This ctor is almost never called by the user directly, rather from derived classes'
initialization lists, which pass a pointer to their own stream buffer.
Definition at line 93 of file istream.
template<typename _CharT , typename _Traits > virtual std::basic_istream< _CharT, _Traits >::~basic_istream
() [inline], [virtual]
Base destructor. This does very little apart from providing a virtual base dtor.
Definition at line 103 of file istream.
template<typename _CharT , typename _Traits > std::basic_istream< _CharT, _Traits >::basic_istream ()
[inline], [protected]
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
Definition at line 606 of file istream.
template<typename _CharT , typename _Traits > std::basic_istream< _CharT, _Traits >::basic_istream (const
basic_istream< _CharT, _Traits > &) [protected], [delete]
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
template<typename _CharT , typename _Traits > std::basic_istream< _CharT, _Traits >::basic_istream
(basic_istream< _CharT, _Traits > && __rhs) [inline], [protected]
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
Definition at line 613 of file istream.
Member Function Documentation
template<typename _CharT , typename _Traits > template<typename _ValueT > __istream_type& std::basic_istream<
_CharT, _Traits >::_M_extract (_ValueT & __v) [protected]
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
template<typename _CharT , typename _Traits > streamsize std::basic_istream< _CharT, _Traits >::gcount ()
const [inline]
Character counting.
Returns
The number of characters extracted by the previous unformatted input function dispatched for this
stream.
Definition at line 269 of file istream.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits >::int_type std::basic_istream<
_CharT, _Traits >::get
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
Definition at line 244 of file istream.tcc.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits >::get
(__streambuf_type & __sb) [inline]
Extraction into another streambuf.
Parameters
__sb A streambuf in which to store data.
Returns
*this
Returns get(__sb,widen('\n')).
Definition at line 387 of file istream.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::get (__streambuf_type & __sb, char_type __delim)
Extraction into another streambuf.
Parameters
__sb A streambuf in which to store data.
__delim A 'stop' character.
Returns
*this
Characters are extracted and inserted into __sb until one of the following happens:
• the input sequence reaches EOF
• insertion into the output buffer fails (in this case, the character that would have been inserted is
not extracted)
• the next character equals __delim (in this case, the character is not extracted)
• an exception occurs (and in this case is caught)
If no characters are stored, failbit is set in the stream's error state.
Definition at line 364 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::get (char_type & __c)
Simple extraction.
Parameters
__c The character in which to store data.
Returns
*this
Tries to extract a character and store it in __c. If none are available, sets failbit and returns
traits::eof().
Note
This function is not overloaded on signed char and unsigned char.
Definition at line 280 of file istream.tcc.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits >::get
(char_type * __s, streamsize __n) [inline]
Simple multiple-character extraction.
Parameters
__s Pointer to an array.
__n Maximum number of characters to store in s.
Returns
*this
Returns get(__s,__n,widen('\n')).
Definition at line 354 of file istream.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::get (char_type * __s, streamsize __n, char_type __delim)
Simple multiple-character extraction.
Parameters
__s Pointer to an array.
__n Maximum number of characters to store in __s.
__delim A 'stop' character.
Returns
*this
Characters are extracted and stored into __s until one of the following happens:
• __n-1 characters are stored
• the input sequence reaches EOF
• the next character equals __delim, in which case the character is not extracted
If no characters are stored, failbit is set in the stream's error state.
In any case, a null character is stored into the next location in the array.
Note
This function is not overloaded on signed char and unsigned char.
Definition at line 317 of file istream.tcc.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits >::getline
(char_type * __s, streamsize __n) [inline]
String extraction.
Parameters
__s A character array in which to store the data.
__n Maximum number of characters to extract.
Returns
*this
Returns getline(__s,__n,widen('\n')).
Definition at line 427 of file istream.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::getline (char_type * __s, streamsize __n, char_type __delim)
String extraction.
Parameters
__s A character array in which to store the data.
__n Maximum number of characters to extract.
__delim A 'stop' character.
Returns
*this
Extracts and stores characters into __s until one of the following happens. Note that these criteria are
required to be tested in the order listed here, to allow an input line to exactly fill the __s array
without setting failbit.
1. the input sequence reaches end-of-file, in which case eofbit is set in the stream error state
2. the next character equals __delim, in which case the character is extracted (and therefore counted in
gcount()) but not stored
3. __n-1 characters are stored, in which case failbit is set in the stream error state
If no characters are extracted, failbit is set. (An empty line of input should therefore not cause
failbit to be set.)
In any case, a null character is stored in the next location in the array.
Definition at line 408 of file istream.tcc.
basic_istream< char > & std::basic_istream< char >::getline (char_type * __s, streamsize __n, char_type
__delim)
Explicit specialization declarations, defined in src/istream.cc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::ignore
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
Definition at line 468 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::ignore (streamsize __n)
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
Definition at line 501 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::ignore (streamsize __n, int_type __delim)
Discarding characters.
Parameters
__n Number of characters to discard.
__delim A 'stop' character.
Returns
*this
Extracts characters and throws them away until one of the following happens:
• if __n != std::numeric_limits<int>::max(), __n characters are extracted
• the input sequence reaches end-of-file
• the next character equals __delim (in this case, the character is extracted); note that this condition
will never occur if __delim equals traits::eof().
NB: Provide three overloads, instead of the single function (with defaults) mandated by the Standard:
this leads to a better performing implementation, while still conforming to the Standard.
Definition at line 563 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream& std::basic_istream< _CharT, _Traits >::operator=
(basic_istream< _CharT, _Traits > && __rhs) [inline], [protected]
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
Definition at line 625 of file istream.
template<typename _CharT , typename _Traits > basic_istream& std::basic_istream< _CharT, _Traits >::operator=
(const basic_istream< _CharT, _Traits > &) [protected], [delete]
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (__istream_type &(*)(__istream_type &) __pf) [inline]
Interface for manipulators. Manipulators such as std::ws and std::dec use these functions in constructs
like std::cin >> std::ws. For more information, see the iomanip header.
Definition at line 120 of file istream.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::operator>> (__streambuf_type * __sb)
Extracting into another streambuf.
Parameters
__sb A pointer to a streambuf
This function behaves like one of the basic arithmetic extractors, in that it also constructs a sentry
object and has the same error handling behavior.
If __sb is NULL, the stream will set failbit in its error state.
Characters are extracted from this stream and inserted into the __sb streambuf until one of the following
occurs:
• the input stream reaches end-of-file,
• insertion into the output buffer fails (in this case, the character that would have been inserted is
not extracted), or
• an exception occurs (and in this case is caught)
If the function inserts no characters, failbit is set.
Definition at line 212 of file istream.tcc.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (bool & __n) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 168 of file istream.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (double & __f) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 218 of file istream.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (float & __f) [inline]
Floating point arithmetic extractors.
Parameters
__f A variable of builtin floating point type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 214 of file istream.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::operator>> (int & __n)
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 167 of file istream.tcc.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (long & __n) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 186 of file istream.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (long double & __f) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 222 of file istream.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (long long & __n) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 195 of file istream.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::operator>> (short & __n)
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 122 of file istream.tcc.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (unsigned int & __n) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 182 of file istream.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (unsigned long & __n) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 190 of file istream.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (unsigned long long & __n) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 199 of file istream.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (unsigned short & __n) [inline]
Integer arithmetic extractors.
Parameters
__n A variable of builtin integral type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 175 of file istream.
template<typename _CharT , typename _Traits > __istream_type& std::basic_istream< _CharT, _Traits
>::operator>> (void *& __p) [inline]
Basic arithmetic extractors.
Parameters
__p A variable of pointer type.
Returns
*this if successful
These functions use the stream's current locale (specifically, the num_get facet) to parse the input
data.
Definition at line 235 of file istream.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits >::int_type std::basic_istream<
_CharT, _Traits >::peek
Looking ahead in the stream.
Returns
The next character, or eof().
If, after constructing the sentry object, good() is false, returns traits::eof(). Otherwise reads but
does not extract the next input character.
Definition at line 628 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::putback (char_type __c)
Unextracting a single character.
Parameters
__c The character to push back into the input stream.
Returns
*this
If rdbuf() is not null, calls rdbuf()->sputbackc(c).
If rdbuf() is null or if sputbackc() fails, sets badbit in the error state.
Note
This function first clears eofbit. Since no characters are extracted, the next call to gcount() will
return 0, as required by DR 60.
Definition at line 719 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::read (char_type * __s, streamsize __n)
Extraction without delimiters.
Parameters
__s A character array.
__n Maximum number of characters to store.
Returns
*this
If the stream state is good(), extracts characters and stores them into __s until one of the following
happens:
• __n characters are stored
• the input sequence reaches end-of-file, in which case the error state is set to failbit|eofbit.
Note
This function is not overloaded on signed char and unsigned char.
Definition at line 658 of file istream.tcc.
template<typename _CharT , typename _Traits > streamsize std::basic_istream< _CharT, _Traits >::readsome
(char_type * __s, streamsize __n)
Extraction until the buffer is exhausted, but no more.
Parameters
__s A character array.
__n Maximum number of characters to store.
Returns
The number of characters extracted.
Extracts characters and stores them into __s depending on the number of characters remaining in the
streambuf's buffer, rdbuf()->in_avail(), called A here:
• if A == -1, sets eofbit and extracts no characters
• if A == 0, extracts no characters
• if A > 0, extracts min(A,n)
The goal is to empty the current buffer, and to not request any more from the external input sequence
controlled by the streambuf.
Definition at line 687 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::seekg (off_type __off, ios_base::seekdir __dir)
Changing the current read position.
Parameters
__off A file offset object.
__dir The direction in which to seek.
Returns
*this
If fail() is not true, calls rdbuf()->pubseekoff(__off,__dir). If that function fails, sets failbit.
Note
This function first clears eofbit. It does not count the number of characters extracted, if any, and
therefore does not affect the next call to gcount().
Definition at line 892 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::seekg (pos_type __pos)
Changing the current read position.
Parameters
__pos A file position object.
Returns
*this
If fail() is not true, calls rdbuf()->pubseekpos(__pos). If that function fails, sets failbit.
Note
This function first clears eofbit. It does not count the number of characters extracted, if any, and
therefore does not affect the next call to gcount().
Definition at line 853 of file istream.tcc.
template<typename _CharT , typename _Traits > void std::basic_istream< _CharT, _Traits >::swap
(basic_istream< _CharT, _Traits > & __rhs) [inline], [protected]
Simple extraction.
Returns
A character, or eof().
Tries to extract a character. If none are available, sets failbit and returns traits::eof().
Definition at line 632 of file istream.
template<typename _CharT , typename _Traits > int std::basic_istream< _CharT, _Traits >::sync
Synchronizing the stream buffer.
Returns
0 on success, -1 on failure
If rdbuf() is a null pointer, returns -1.
Otherwise, calls rdbuf()->pubsync(), and if that returns -1, sets badbit and returns -1.
Otherwise, returns 0.
Note
This function does not count the number of characters extracted, if any, and therefore does not
affect the next call to gcount().
Definition at line 789 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits >::pos_type std::basic_istream<
_CharT, _Traits >::tellg
Getting the current read position.
Returns
A file position object.
If fail() is not false, returns pos_type(-1) to indicate failure. Otherwise returns
rdbuf()->pubseekoff(0,cur,in).
Note
This function does not count the number of characters extracted, if any, and therefore does not
affect the next call to gcount(). At variance with putback, unget and seekg, eofbit is not cleared
first.
Definition at line 825 of file istream.tcc.
template<typename _CharT , typename _Traits > basic_istream< _CharT, _Traits > & std::basic_istream< _CharT,
_Traits >::unget
Unextracting the previous character.
Returns
*this
If rdbuf() is not null, calls rdbuf()->sungetc(c).
If rdbuf() is null or if sungetc() fails, sets badbit in the error state.
Note
This function first clears eofbit. Since no characters are extracted, the next call to gcount() will
return 0, as required by DR 60.
Definition at line 754 of file istream.tcc.
Referenced by std::__detail::operator>>().
Member Data Documentation
template<typename _CharT , typename _Traits > streamsize std::basic_istream< _CharT, _Traits >::_M_gcount
[protected]
The number of characters extracted in the previous unformatted function; see gcount().
Definition at line 82 of file istream.
Referenced by std::basic_istream< char >::get(), std::basic_istream< char >::getline(),
std::basic_istream< char >::ignore(), std::basic_istream< char >::peek(), std::basic_istream< char
>::putback(), std::basic_istream< char >::read(), std::basic_istream< char >::readsome(), and
std::basic_istream< char >::unget().
Author
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