std::basic_stringbuf - Man Page

typedef __string_type::size_type __size_type
typedef basic_streambuf< char_type, traits_type > __streambuf_type
typedef basic_string< char_type, _Traits, _Alloc > __string_type
typedef _Alloc allocator_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

basic_stringbuf ()
Starts with an empty string buffer.
basic_stringbuf (__string_type &&__s, ios_base::openmode __mode=ios_base::in|ios_base::out)
basic_stringbuf (basic_stringbuf &&__rhs)
basic_stringbuf (basic_stringbuf &&__rhs, const allocator_type &__a)
basic_stringbuf (const __string_type &__str, ios_base::openmode __mode=ios_base::in|ios_base::out)
Starts with an existing string buffer.
basic_stringbuf (const allocator_type &__a)
template<typename _SAlloc > basic_stringbuf (const basic_string< _CharT, _Traits, _SAlloc > &__s, const allocator_type &__a)
template<typename _SAlloc > basic_stringbuf (const basic_string< _CharT, _Traits, _SAlloc > &__s, ios_base::openmode __mode, const allocator_type &__a)
template<typename _SAlloc > basic_stringbuf (const basic_string< _CharT, _Traits, _SAlloc > &__s, ios_base::openmode __mode=ios_base::in|ios_base::out)
basic_stringbuf (const basic_stringbuf &)=delete
basic_stringbuf (ios_base::openmode __mode)
Starts with an empty string buffer.
basic_stringbuf (ios_base::openmode __mode, const allocator_type &__a)
allocator_type get_allocator () const noexcept
locale getloc () const
Locale access.
streamsize in_avail ()
Looking ahead into the stream.
basic_stringbuf & operator= (basic_stringbuf &&__rhs)
basic_stringbuf & operator= (const basic_stringbuf &)=delete
locale pubimbue (const locale &__loc)
Entry point for imbue().
int_type sbumpc ()
Getting the next character.
int_type sgetc ()
Getting the next character.
streamsize sgetn (char_type *__s, streamsize __n)
Entry point for xsgetn.
int_type snextc ()
Getting the next character.
int_type sputbackc (char_type __c)
Pushing characters back into the input stream.
int_type sputc (char_type __c)
Entry point for all single-character output functions.
streamsize sputn (const char_type *__s, streamsize __n)
Entry point for all single-character output functions.
__string_type str () &&
__string_type str () const &
Copying out the string buffer.
void str (__string_type &&__s)
void str (const __string_type &__s)
Setting a new buffer.
template<__allocator_like _SAlloc> basic_string< _CharT, _Traits, _SAlloc > str (const _SAlloc &__sa) const
template<__allocator_like _SAlloc>
requires (!is_same_v<_SAlloc, _Alloc>)void str (const basic_string< _CharT, _Traits, _SAlloc > &__s)"
int_type sungetc ()
Moving backwards in the input stream.
void swap (basic_stringbuf &__rhs) noexcept(_Noexcept_swap::value)
basic_string_view< char_type, traits_type > view () const noexcept

basic_streambuf * pubsetbuf (char_type *__s, streamsize __n)
Entry points for derived buffer functions.
pos_type pubseekoff (off_type __off, ios_base::seekdir __way, ios_base::openmode __mode=ios_base::in|ios_base::out)
Alters the stream position.
pos_type pubseekpos (pos_type __sp, ios_base::openmode __mode=ios_base::in|ios_base::out)
Alters the stream position.
int pubsync ()
Calls virtual sync function.

void __safe_gbump (streamsize __n)
void __safe_pbump (streamsize __n)
void _M_pbump (char_type *__pbeg, char_type *__pend, off_type __off)
void _M_stringbuf_init (ios_base::openmode __mode)
void _M_sync (char_type *__base, __size_type __i, __size_type __o)
void _M_update_egptr ()
void gbump (int __n)
Moving the read position.
virtual void imbue (const locale &__loc)
Changes translations.
virtual int_type overflow (int_type __c=traits_type::eof())
Consumes data from the buffer; writes to the controlled sequence.
virtual int_type pbackfail (int_type __c=traits_type::eof())
Tries to back up the input sequence.
void pbump (int __n)
Moving the write position.
virtual pos_type seekoff (off_type __off, ios_base::seekdir __way, ios_base::openmode __mode=ios_base::in|ios_base::out)
Alters the stream positions.
virtual pos_type seekpos (pos_type __sp, ios_base::openmode __mode=ios_base::in|ios_base::out)
Alters the stream positions.
virtual __streambuf_type * setbuf (char_type *__s, streamsize __n)
Manipulates the buffer.
void setg (char_type *__gbeg, char_type *__gnext, char_type *__gend)
Setting the three read area pointers.
void setp (char_type *__pbeg, char_type *__pend)
Setting the three write area pointers.
virtual streamsize showmanyc ()
Investigating the data available.
void swap (basic_streambuf &__sb)
virtual int sync ()
Synchronizes the buffer arrays with the controlled sequences.
virtual int_type uflow ()
Fetches more data from the controlled sequence.
virtual int_type underflow ()
Fetches more data from the controlled sequence.
virtual streamsize xsgetn (char_type *__s, streamsize __n)
Multiple character extraction.
virtual streamsize xsputn (const char_type *__s, streamsize __n)
Multiple character insertion.

char_type * eback () const
Access to the get area.
char_type * gptr () const
Access to the get area.
char_type * egptr () const
Access to the get area.

char_type * pbase () const
Access to the put area.
char_type * pptr () const
Access to the put area.
char_type * epptr () const
Access to the put area.

locale _M_buf_locale
Current locale setting.
char_type * _M_in_beg
Start of get area.
char_type * _M_in_cur
Current read area.
char_type * _M_in_end
End of get area.
ios_base::openmode _M_mode
Place to stash in || out || in | out settings for current stringbuf.
char_type * _M_out_beg
Start of put area.
char_type * _M_out_cur
Current put area.
char_type * _M_out_end
End of put area.
__string_type _M_string

class std::basic_stringbuf< _CharT, _Traits, _Alloc >"The actual work of input and output (for std::string).

Template Parameters

This class associates either or both of its input and output sequences with a sequence of characters, which can be initialized from, or made available as, a std::basic_string. (Paraphrased from [27.7.1]/1.)

For this class, open modes (of type ios_base::openmode) have in set if the input sequence can be read, and out set if the output sequence can be written.

Starts with an empty string buffer. The default constructor initializes the parent class using its own default ctor.

Starts with an empty string buffer.

Parameters

The default constructor initializes the parent class using its own default ctor.

Starts with an existing string buffer.

Parameters

This constructor initializes the parent class using its own default ctor.

Access to the get area. These functions are only available to other protected functions, including derived classes.

• eback() returns the beginning pointer for the input sequence
• gptr() returns the next pointer for the input sequence
• egptr() returns the end pointer for the input sequence

Access to the get area. These functions are only available to other protected functions, including derived classes.

• eback() returns the beginning pointer for the input sequence
• gptr() returns the next pointer for the input sequence
• egptr() returns the end pointer for the input sequence

Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::underflow().

Access to the put area. These functions are only available to other protected functions, including derived classes.

• pbase() returns the beginning pointer for the output sequence
• pptr() returns the next pointer for the output sequence
• epptr() returns the end pointer for the output sequence

Moving the read position.

Parameters

This just advances the read position without returning any data.

Locale access.

Returns

The current locale in effect.

If pubimbue(loc) has been called, then the most recent loc is returned. Otherwise the global locale in effect at the time of construction is returned.

Access to the get area. These functions are only available to other protected functions, including derived classes.

• eback() returns the beginning pointer for the input sequence
• gptr() returns the next pointer for the input sequence
• egptr() returns the end pointer for the input sequence

Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::underflow().

Changes translations.

Parameters

Translations done during I/O which depend on the current locale are changed by this call. The standard adds, Between invocations of this function a class derived from streambuf can safely cache results of calls to locale functions and to members of facets so obtained.

Note

Base class version does nothing.

Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT > >, and std::basic_filebuf< char_type, traits_type >.

Looking ahead into the stream.

Returns

The number of characters available.

If a read position is available, returns the number of characters available for reading before the buffer must be refilled. Otherwise returns the derived showmanyc().

Consumes data from the buffer; writes to the controlled sequence.

Parameters

Returns

eof() to indicate failure, something else (usually __c, or not_eof())

Informally, this function is called when the output buffer is full (or does not exist, as buffering need not actually be done). If a buffer exists, it is consumed, with some effect on the controlled sequence. (Typically, the buffer is written out to the sequence verbatim.) In either case, the character c is also written out, if __c is not eof().

For a formal definition of this function, see a good text such as Langer & Kreft, or [27.5.2.4.5]/3-7.

A functioning output streambuf can be created by overriding only this function (no buffer area will be used).

Note

Base class version does nothing, returns eof().

Reimplemented from std::basic_streambuf< _CharT, _Traits >.

References std::basic_string< _CharT, _Traits, _Alloc >::assign(), std::ios_base::in, std::max(), std::min(), std::ios_base::out, std::basic_string< _CharT, _Traits, _Alloc >::push_back(), and std::basic_string< _CharT, _Traits, _Alloc >::reserve().

Tries to back up the input sequence.

Parameters

Returns

eof() on failure, some other value on success

Postcondition

The constraints of gptr(), eback(), and pptr() are the same as for underflow().

Note

Base class version does nothing, returns eof().

Reimplemented from std::basic_streambuf< _CharT, _Traits >.

References std::ios_base::out.

Access to the put area. These functions are only available to other protected functions, including derived classes.

• pbase() returns the beginning pointer for the output sequence
• pptr() returns the next pointer for the output sequence
• epptr() returns the end pointer for the output sequence

Moving the write position.

Parameters

This just advances the write position without returning any data.

Access to the put area. These functions are only available to other protected functions, including derived classes.

• pbase() returns the beginning pointer for the output sequence
• pptr() returns the next pointer for the output sequence
• epptr() returns the end pointer for the output sequence

Entry point for imbue().

Parameters

Returns

The previous locale.

Calls the derived imbue(__loc).

Alters the stream position.

Parameters

Calls virtual seekoff function.

Alters the stream position.

Parameters

Calls virtual seekpos function.

Entry points for derived buffer functions. The public versions of pubfoo dispatch to the protected derived foo member functions, passing the arguments (if any) and returning the result unchanged.

Calls virtual sync function.

Referenced by std::basic_istream< _CharT, _Traits >::sync(), and std::wbuffer_convert< _Codecvt, _Elem, _Tr >::sync().

Getting the next character.

Returns

The next character, or eof.

If the input read position is available, returns that character and increments the read pointer, otherwise calls and returns uflow().

Referenced by std::basic_istream< _CharT, char_traits< _CharT > >::get(), std::basic_istream< _CharT, _Traits >::ignore(), std::istreambuf_iterator< _CharT, _Traits >::operator++(), std::istreambuf_iterator< _CharT, _Traits >::operator++(), and std::basic_istream< _CharT, char_traits< _CharT > >::sync().

Alters the stream positions. Each derived class provides its own appropriate behavior.

Note

Base class version does nothing, returns a pos_type that represents an invalid stream position.

Reimplemented from std::basic_streambuf< _CharT, _Traits >.

References std::ios_base::cur, std::ios_base::end, std::ios_base::in, and std::ios_base::out.

Alters the stream positions. Each derived class provides its own appropriate behavior.

Note

Base class version does nothing, returns a pos_type that represents an invalid stream position.

Reimplemented from std::basic_streambuf< _CharT, _Traits >.

References std::ios_base::in, and std::ios_base::out.

Manipulates the buffer.

Parameters

Returns

this

If no buffer has already been created, and both __s and __n are non-zero, then __s is used as a buffer; see https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering for more.

Reimplemented from std::basic_streambuf< _CharT, _Traits >.

Setting the three read area pointers.

Parameters

Postcondition

Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::wbuffer_convert().

Setting the three write area pointers.

Parameters

Postcondition

Referenced by std::wbuffer_convert< _Codecvt, _Elem, _Tr >::wbuffer_convert().

Getting the next character.

Returns

The next character, or eof.

If the input read position is available, returns that character, otherwise calls and returns underflow(). Does not move the read position after fetching the character.

Referenced by std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< _CharT, char_traits< _CharT > >::get(), std::basic_istream< _CharT, _Traits >::ignore(), std::istreambuf_iterator< _CharT, _Traits >::operator++(), std::istreambuf_iterator< _CharT, _Traits >::operator++(), and std::basic_istream< _CharT, char_traits< _CharT > >::readsome().

Entry point for xsgetn.

Parameters

Returns xsgetn(__s,__n). The effect is to fill __s[0] through __s[__n-1] with characters from the input sequence, if possible.

Investigating the data available.

Returns

An estimate of the number of characters available in the input sequence, or -1.

If it returns a positive value, then successive calls to underflow() will not return traits::eof() until at least that number of characters have been supplied. If showmanyc() returns -1, then calls to underflow() or uflow() will fail. [27.5.2.4.3]/1

Note

Base class version does nothing, returns zero.

The standard adds that the intention is not only that the calls [to underflow or uflow] will not return eof() but that they will return immediately.

The standard adds that the morphemes of showmanyc are es-how-many-see, not show-manic.

Reimplemented from std::basic_streambuf< _CharT, _Traits >.

Getting the next character.

Returns

The next character, or eof.

Calls sbumpc(), and if that function returns traits::eof(), so does this function. Otherwise, sgetc().

Referenced by std::basic_istream< _CharT, char_traits< _CharT > >::get(), std::basic_istream< _CharT, char_traits< _CharT > >::ignore(), std::basic_istream< _CharT, char_traits< _CharT > >::operator>>(), and std::basic_istream< _CharT, char_traits< _CharT > >::putback().

Pushing characters back into the input stream.

Parameters

Returns

The previous character, if possible.

Similar to sungetc(), but __c is pushed onto the stream instead of the previous character. If successful, the next character fetched from the input stream will be __c.

Referenced by std::basic_istream< _CharT, _Traits >::putback().

Entry point for all single-character output functions.

Parameters

Returns

One of two public output functions.

If a write position is available for the output sequence (i.e., the buffer is not full), stores __c in that position, increments the position, and returns traits::to_int_type(__c). If a write position is not available, returns overflow(__c).

Referenced by std::ostreambuf_iterator< _CharT, _Traits >::operator=(), and std::wbuffer_convert< _Codecvt, _Elem, _Tr >::overflow().

Entry point for all single-character output functions.

Parameters

One of two public output functions.

Returns xsputn(__s,__n). The effect is to write __s[0] through __s[__n-1] to the output sequence, if possible.

Copying out the string buffer.

Returns

A copy of one of the underlying sequences.

If the buffer is only created in input mode, the underlying character sequence is equal to the input sequence; otherwise, it is equal to the output sequence. [27.7.1.2]/1

Setting a new buffer.

Parameters

Deallocates any previous stored sequence, then copies s to use as a new one.

Moving backwards in the input stream.

Returns

The previous character, if possible.

If a putback position is available, this function decrements the input pointer and returns that character. Otherwise, calls and returns pbackfail(). The effect is to unget the last character gotten.

Synchronizes the buffer arrays with the controlled sequences.

Returns

Each derived class provides its own appropriate behavior, including the definition of failure.

Note

Base class version does nothing, returns zero.

Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT > >, std::basic_filebuf< char_type, traits_type >, and std::wbuffer_convert< _Codecvt, _Elem, _Tr >.

Fetches more data from the controlled sequence.

Returns

The first character from the pending sequence.

Informally, this function does the same thing as underflow(), and in fact is required to call that function. It also returns the new character, like underflow() does. However, this function also moves the read position forward by one.

Reimplemented in __gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >.

Fetches more data from the controlled sequence.

Returns

The first character from the pending sequence.

Informally, this function is called when the input buffer is exhausted (or does not exist, as buffering need not actually be done). If a buffer exists, it is refilled. In either case, the next available character is returned, or traits::eof() to indicate a null pending sequence.

For a formal definition of the pending sequence, see a good text such as Langer & Kreft, or [27.5.2.4.3]/7-14.

A functioning input streambuf can be created by overriding only this function (no buffer area will be used). For an example, see https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html

Note

Base class version does nothing, returns eof().

Reimplemented from std::basic_streambuf< _CharT, _Traits >.

References std::ios_base::in.

Multiple character extraction.

Parameters

Returns

The number of characters assigned.

Fills __s[0] through __s[__n-1] with characters from the input sequence, as if by sbumpc(). Stops when either __n characters have been copied, or when traits::eof() would be copied.

It is expected that derived classes provide a more efficient implementation by overriding this definition.

Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT > >, and std::basic_filebuf< char_type, traits_type >.

References std::min().

Multiple character insertion.

Parameters

Returns

The number of characters written.

Writes __s[0] through __s[__n-1] to the output sequence, as if by sputc(). Stops when either n characters have been copied, or when sputc() would return traits::eof().

It is expected that derived classes provide a more efficient implementation by overriding this definition.

Reimplemented in std::basic_filebuf< _CharT, _Traits >, std::basic_filebuf< _CharT, encoding_char_traits< _CharT > >, std::basic_filebuf< _CharT, std::char_traits< _CharT > >, and std::basic_filebuf< char_type, traits_type >.

References std::min().

Current locale setting.

Referenced by std::basic_filebuf< _CharT, _Traits >::basic_filebuf().

Start of get area.

Current read area.

End of get area.

Place to stash in || out || in | out settings for current stringbuf.

Start of put area.

Current put area.

End of put area.