libstdc++
std::basic_ifstream< _CharT, _Traits > Class Template Reference
Inheritance diagram for std::basic_ifstream< _CharT, _Traits >:
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Public Types

typedef ctype< _CharT > __ctype_type
 
typedef basic_filebuf< char_type, traits_type > __filebuf_type
 
typedef basic_ios< _CharT, _Traits > __ios_type
 
typedef basic_istream< char_type, traits_type > __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_type::int_type int_type
 
typedef traits_type::off_type off_type
 
typedef traits_type::pos_type pos_type
 
typedef _Traits traits_type
 

Public Member Functions

 basic_ifstream ()
 
 basic_ifstream (basic_ifstream &&__rhs)
 
 basic_ifstream (const basic_ifstream &)=delete
 
 basic_ifstream (const char *__s, ios_base::openmode __mode=ios_base::in)
 
 basic_ifstream (const std::string &__s, ios_base::openmode __mode=ios_base::in)
 
 ~basic_ifstream ()
 
template<typename _ValueT >
basic_istream< _CharT, _Traits > & _M_extract (_ValueT &__v)
 
void close ()
 
basic_istream< char > & getline (char_type *__s, streamsize __n, char_type __delim)
 
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)
 
bool is_open ()
 
bool is_open () const
 
void open (const char *__s, ios_base::openmode __mode=ios_base::in)
 
void open (const std::string &__s, ios_base::openmode __mode=ios_base::in)
 
basic_ifstreamoperator= (basic_ifstream &&__rhs)
 
basic_ifstreamoperator= (const basic_ifstream &)=delete
 
__istream_typeoperator>> (__ios_type &(*__pf)(__ios_type &))
 
__istream_typeoperator>> (__istream_type &(*__pf)(__istream_type &))
 
__istream_typeoperator>> (ios_base &(*__pf)(ios_base &))
 
__filebuf_typerdbuf () const
 
void swap (basic_ifstream &__rhs)
 
Extractors

All the operator>> functions (aka formatted 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 false. 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.

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.

__istream_typeoperator>> (bool &__n)
 
__istream_typeoperator>> (short &__n)
 
__istream_typeoperator>> (unsigned short &__n)
 
__istream_typeoperator>> (int &__n)
 
__istream_typeoperator>> (unsigned int &__n)
 
__istream_typeoperator>> (long &__n)
 
__istream_typeoperator>> (unsigned long &__n)
 
__istream_typeoperator>> (long long &__n)
 
__istream_typeoperator>> (unsigned long long &__n)
 
__istream_typeoperator>> (float &__f)
 
__istream_typeoperator>> (double &__f)
 
__istream_typeoperator>> (long double &__f)
 
__istream_typeoperator>> (void *&__p)
 
__istream_typeoperator>> (__streambuf_type *__sb)
 
streamsize gcount () const
 
Extractors

All the operator>> functions (aka formatted 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 false. 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.

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.

__istream_typeoperator>> (bool &__n)
 
__istream_typeoperator>> (short &__n)
 
__istream_typeoperator>> (unsigned short &__n)
 
__istream_typeoperator>> (int &__n)
 
__istream_typeoperator>> (unsigned int &__n)
 
__istream_typeoperator>> (long &__n)
 
__istream_typeoperator>> (unsigned long &__n)
 
__istream_typeoperator>> (long long &__n)
 
__istream_typeoperator>> (unsigned long long &__n)
 
__istream_typeoperator>> (float &__f)
 
__istream_typeoperator>> (double &__f)
 
__istream_typeoperator>> (long double &__f)
 
__istream_typeoperator>> (void *&__p)
 
__istream_typeoperator>> (__streambuf_type *__sb)
 
streamsize gcount () const
 

Protected Attributes

streamsize _M_gcount
 

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 ()
 
__istream_typeget (char_type &__c)
 
__istream_typeget (char_type *__s, streamsize __n, char_type __delim)
 
__istream_typeget (char_type *__s, streamsize __n)
 
__istream_typeget (__streambuf_type &__sb, char_type __delim)
 
__istream_typeget (__streambuf_type &__sb)
 
__istream_typegetline (char_type *__s, streamsize __n, char_type __delim)
 
__istream_typegetline (char_type *__s, streamsize __n)
 
__istream_typeignore (streamsize __n, int_type __delim)
 
__istream_typeignore (streamsize __n)
 
__istream_typeignore ()
 
int_type peek ()
 
__istream_typeread (char_type *__s, streamsize __n)
 
streamsize readsome (char_type *__s, streamsize __n)
 
__istream_typeputback (char_type __c)
 
__istream_typeunget ()
 
int sync ()
 
pos_type tellg ()
 
__istream_typeseekg (pos_type)
 
__istream_typeseekg (off_type, ios_base::seekdir)
 
void swap (basic_istream &__rhs)
 
template<typename _ValueT >
__istream_type_M_extract (_ValueT &__v)
 

Detailed Description

template<typename _CharT, typename _Traits>
class std::basic_ifstream< _CharT, _Traits >

Controlling input for files.

Template Parameters
_CharTType of character stream.
_TraitsTraits for character type, defaults to char_traits<_CharT>.

This class supports reading from named files, using the inherited functions from std::basic_istream. To control the associated sequence, an instance of std::basic_filebuf is used, which this page refers to as sb.

Definition at line 492 of file fstream.

Constructor & Destructor Documentation

◆ basic_ifstream() [1/3]

template<typename _CharT , typename _Traits >
std::basic_ifstream< _CharT, _Traits >::basic_ifstream ( )
inline

Default constructor.

Initializes sb using its default constructor, and passes &sb to the base class initializer. Does not open any files (you haven't given it a filename to open).

Definition at line 518 of file fstream.

◆ basic_ifstream() [2/3]

template<typename _CharT , typename _Traits >
std::basic_ifstream< _CharT, _Traits >::basic_ifstream ( const char *  __s,
ios_base::openmode  __mode = ios_base::in 
)
inlineexplicit

Create an input file stream.

Parameters
__sNull terminated string specifying the filename.
__modeOpen file in specified mode (see std::ios_base).

ios_base::in is automatically included in __mode.

Definition at line 529 of file fstream.

◆ basic_ifstream() [3/3]

template<typename _CharT , typename _Traits >
std::basic_ifstream< _CharT, _Traits >::basic_ifstream ( const std::string __s,
ios_base::openmode  __mode = ios_base::in 
)
inlineexplicit

Create an input file stream.

Parameters
__sstd::string specifying the filename.
__modeOpen file in specified mode (see std::ios_base).

ios_base::in is automatically included in __mode.

Definition at line 562 of file fstream.

◆ ~basic_ifstream()

template<typename _CharT , typename _Traits >
std::basic_ifstream< _CharT, _Traits >::~basic_ifstream ( )
inline

The destructor does nothing.

The file is closed by the filebuf object, not the formatting stream.

Definition at line 599 of file fstream.

Member Function Documentation

◆ _M_extract()

template<typename _CharT , typename _Traits >
template<typename _ValueT >
__istream_type& std::basic_istream< _CharT, _Traits >::_M_extract ( _ValueT &  __v)
protectedinherited

Simple extraction.

Returns
A character, or eof().

Tries to extract a character. If none are available, sets failbit and returns traits::eof().

◆ close()

template<typename _CharT , typename _Traits >
void std::basic_ifstream< _CharT, _Traits >::close ( )
inline

Close the file.

Calls std::basic_filebuf::close(). If that function fails, failbit is set in the stream's error state.

Definition at line 730 of file fstream.

◆ gcount()

template<typename _CharT , typename _Traits >
streamsize std::basic_istream< _CharT, _Traits >::gcount ( ) const
inlineinherited

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.

◆ get() [1/6]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits >::int_type std::basic_istream< _CharT, _Traits >::get
inherited

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.

◆ get() [2/6]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::get ( __streambuf_type __sb)
inlineinherited

Extraction into another streambuf.

Parameters
__sbA streambuf in which to store data.
Returns
*this

Returns get(__sb,widen('\n')).

Definition at line 387 of file istream.

◆ get() [3/6]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::get ( __streambuf_type __sb,
char_type  __delim 
)
inherited

Extraction into another streambuf.

Parameters
__sbA streambuf in which to store data.
__delimA "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.

◆ get() [4/6]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::get ( char_type &  __c)
inherited

Simple extraction.

Parameters
__cThe 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.

◆ get() [5/6]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::get ( char_type *  __s,
streamsize  __n 
)
inlineinherited

Simple multiple-character extraction.

Parameters
__sPointer to an array.
__nMaximum number of characters to store in s.
Returns
*this

Returns get(__s,__n,widen('\n')).

Definition at line 354 of file istream.

◆ get() [6/6]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::get ( char_type *  __s,
streamsize  __n,
char_type  __delim 
)
inherited

Simple multiple-character extraction.

Parameters
__sPointer to an array.
__nMaximum number of characters to store in __s.
__delimA "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.

◆ getline() [1/3]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::getline ( char_type *  __s,
streamsize  __n 
)
inlineinherited

String extraction.

Parameters
__sA character array in which to store the data.
__nMaximum number of characters to extract.
Returns
*this

Returns getline(__s,__n,widen('\n')).

Definition at line 427 of file istream.

◆ getline() [2/3]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::getline ( char_type *  __s,
streamsize  __n,
char_type  __delim 
)
inherited

String extraction.

Parameters
__sA character array in which to store the data.
__nMaximum number of characters to extract.
__delimA "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.

◆ getline() [3/3]

basic_istream< char > & std::basic_istream< char >::getline ( char_type *  __s,
streamsize  __n,
char_type  __delim 
)
inherited

Explicit specialization declarations, defined in src/istream.cc.

◆ ignore() [1/3]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::ignore
inherited

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.

◆ ignore() [2/3]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::ignore ( streamsize  __n)
inherited

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.

◆ ignore() [3/3]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::ignore ( streamsize  __n,
int_type  __delim 
)
inherited

Discarding characters.

Parameters
__nNumber of characters to discard.
__delimA "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.

◆ is_open()

template<typename _CharT , typename _Traits >
bool std::basic_ifstream< _CharT, _Traits >::is_open ( )
inline

Wrapper to test for an open file.

Returns
rdbuf()->is_open()

Definition at line 640 of file fstream.

◆ open() [1/2]

template<typename _CharT , typename _Traits >
void std::basic_ifstream< _CharT, _Traits >::open ( const char *  __s,
ios_base::openmode  __mode = ios_base::in 
)
inline

Opens an external file.

Parameters
__sThe name of the file.
__modeThe open mode flags.

Calls std::basic_filebuf::open(s,__mode|in). If that function fails, failbit is set in the stream's error state.

Definition at line 658 of file fstream.

◆ open() [2/2]

template<typename _CharT , typename _Traits >
void std::basic_ifstream< _CharT, _Traits >::open ( const std::string __s,
ios_base::openmode  __mode = ios_base::in 
)
inline

Opens an external file.

Parameters
__sThe name of the file.
__modeThe open mode flags.

Calls std::basic_filebuf::open(__s,__mode|in). If that function fails, failbit is set in the stream's error state.

Definition at line 697 of file fstream.

◆ operator>>() [1/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( __istream_type &(*)(__istream_type &)  __pf)
inlineinherited

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.

◆ operator>>() [2/15]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::operator>> ( __streambuf_type __sb)
inherited

Extracting into another streambuf.

Parameters
__sbA 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.

◆ operator>>() [3/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( bool &  __n)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [4/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( double &  __f)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [5/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( float &  __f)
inlineinherited

Floating point arithmetic extractors.

Parameters
__fA 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.

◆ operator>>() [6/15]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::operator>> ( int &  __n)
inherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [7/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( long &  __n)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [8/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( long double &  __f)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [9/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( long long &  __n)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [10/15]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::operator>> ( short &  __n)
inherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [11/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( unsigned int &  __n)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [12/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( unsigned long &  __n)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [13/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( unsigned long long &  __n)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [14/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( unsigned short &  __n)
inlineinherited

Integer arithmetic extractors.

Parameters
__nA 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.

◆ operator>>() [15/15]

template<typename _CharT , typename _Traits >
__istream_type& std::basic_istream< _CharT, _Traits >::operator>> ( void *&  __p)
inlineinherited

Basic arithmetic extractors.

Parameters
__pA 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.

◆ peek()

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits >::int_type std::basic_istream< _CharT, _Traits >::peek
inherited

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.

◆ putback()

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::putback ( char_type  __c)
inherited

Unextracting a single character.

Parameters
__cThe 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.

◆ rdbuf()

template<typename _CharT , typename _Traits >
__filebuf_type* std::basic_ifstream< _CharT, _Traits >::rdbuf ( ) const
inline

Accessing the underlying buffer.

Returns
The current basic_filebuf buffer.

This hides both signatures of std::basic_ios::rdbuf().

Definition at line 632 of file fstream.

◆ read()

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::read ( char_type *  __s,
streamsize  __n 
)
inherited

Extraction without delimiters.

Parameters
__sA character array.
__nMaximum 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.

◆ readsome()

template<typename _CharT , typename _Traits >
streamsize std::basic_istream< _CharT, _Traits >::readsome ( char_type *  __s,
streamsize  __n 
)
inherited

Extraction until the buffer is exhausted, but no more.

Parameters
__sA character array.
__nMaximum 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.

◆ seekg() [1/2]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::seekg ( off_type  __off,
ios_base::seekdir  __dir 
)
inherited

Changing the current read position.

Parameters
__offA file offset object.
__dirThe 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.

◆ seekg() [2/2]

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::seekg ( pos_type  __pos)
inherited

Changing the current read position.

Parameters
__posA 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.

◆ swap()

template<typename _CharT , typename _Traits >
void std::basic_istream< _CharT, _Traits >::swap ( basic_istream< _CharT, _Traits > &  __rhs)
inlineprotectedinherited

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.

◆ sync()

template<typename _CharT , typename _Traits >
int std::basic_istream< _CharT, _Traits >::sync
inherited

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.

◆ tellg()

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits >::pos_type std::basic_istream< _CharT, _Traits >::tellg
inherited

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.

◆ unget()

template<typename _CharT , typename _Traits >
basic_istream< _CharT, _Traits > & std::basic_istream< _CharT, _Traits >::unget
inherited

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

◆ _M_gcount

template<typename _CharT , typename _Traits >
streamsize std::basic_istream< _CharT, _Traits >::_M_gcount
protectedinherited

The documentation for this class was generated from the following file: