libstdc++: std::basic_filebuf< _CharT, _Traits > Class Template Reference (original) (raw)

#include <[fstream](a00095%5Fsource.html)>

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

The actual work of input and output (for files).

Template Parameters

This class associates both its input and output sequence with an external disk file, and maintains a joint file position for both sequences. Many of its semantics are described in terms of similar behavior in the Standard C Library's FILE streams.

Requirements on traits_type, specific to this class:

• traits_type::pos_type must be fpos<traits_type::state_type>
• traits_type::off_type must be streamoff
• traits_type::state_type must be Assignable and DefaultConstructible,
• traits_type::state_type() must be the initial state for codecvt.

Definition at line 90 of file fstream.

◆ __codecvt_type

template<typename _CharT , typename _Traits >

◆ __file_type

template<typename _CharT , typename _Traits >

◆ __filebuf_type

template<typename _CharT , typename _Traits >

◆ __state_type

template<typename _CharT , typename _Traits >

◆ __streambuf_type

template<typename _CharT , typename _Traits >

◆ char_type

template<typename _CharT , typename _Traits >

◆ int_type

template<typename _CharT , typename _Traits >

◆ off_type

template<typename _CharT , typename _Traits >

◆ pos_type

template<typename _CharT , typename _Traits >

◆ traits_type

template<typename _CharT , typename _Traits >

template<typename _CharT , typename _Traits >

◆ basic_filebuf() [2/2]

◆ ~basic_filebuf()

template<typename _CharT , typename _Traits >

The destructor closes the file first.

Definition at line 256 of file fstream.

◆ __safe_gbump()

template<typename _CharT , typename _Traits >

◆ __safe_pbump()

template<typename _CharT , typename _Traits >

◆ _M_allocate_internal_buffer()

template<typename _CharT , typename _Traits >

◆ _M_convert_to_external()

template<typename _CharT , typename _Traits >

◆ _M_create_pback()

template<typename _CharT , typename _Traits >

Initializes pback buffers, and moves normal buffers to safety. Assumptions: _M_in_cur has already been moved back

Definition at line 209 of file fstream.

◆ _M_destroy_internal_buffer()

template<typename _CharT , typename _Traits >

◆ _M_destroy_pback()

template<typename _CharT , typename _Traits >

Deactivates pback buffer contents, and restores normal buffer. Assumptions: The pback buffer has only moved forward.

Definition at line 226 of file fstream.

◆ _M_get_ext_pos()

template<typename _CharT , typename _Traits >

◆ _M_seek()

template<typename _CharT , typename _Traits >

◆ _M_set_buffer()

template<typename _CharT , typename _Traits >

This function sets the pointers of the internal buffer, both get and put areas. Typically:

__off == egptr() - eback() upon underflow/uflow (read mode); __off == 0 upon overflow (write mode); __off == -1 upon open, setbuf, seekoff/pos (uncommitted mode).

NB: epptr() - pbase() == _M_buf_size - 1, since _M_buf_size reflects the actual allocated memory and the last cell is reserved for the overflow char of a full put area.

Definition at line 499 of file fstream.

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

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

◆ _M_terminate_output()

template<typename _CharT , typename _Traits >

◆ close()

template<typename _CharT , typename _Traits >

Closes the currently associated file.

Returns

this on success, NULL on failure

If no file is currently open, this function immediately fails.

If a put buffer area exists, overflow(eof) is called to flush all the characters. The file is then closed.

If any operations fail, this function also fails.

Definition at line 248 of file fstream.tcc.

References std::basic_filebuf< _CharT, _Traits >::_M_mode, std::basic_filebuf< _CharT, _Traits >::_M_pback_init, std::basic_filebuf< _CharT, _Traits >::_M_reading, and std::basic_filebuf< _CharT, _Traits >::_M_set_buffer().

Referenced by std::basic_ifstream< _CharT, _Traits >::close(), std::basic_ofstream< _CharT, _Traits >::close(), and std::basic_fstream< _CharT, _Traits >::close().

◆ eback()

template<typename _CharT , typename _Traits >

◆ egptr()

template<typename _CharT , typename _Traits >

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

Definition at line 495 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::_M_in_end.

Referenced by std::basic_streambuf< _CharT, _Traits >::in_avail(), std::basic_streambuf< _CharT, _Traits >::sbumpc(), std::basic_streambuf< _CharT, _Traits >::sgetc(), and std::basic_stringbuf< _CharT, _Traits, _Alloc >::showmanyc().

◆ epptr()

template<typename _CharT , typename _Traits >

◆ gbump()

template<typename _CharT , typename _Traits >

◆ getloc()

template<typename _CharT , typename _Traits >

◆ gptr()

template<typename _CharT , typename _Traits >

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

Definition at line 492 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::_M_in_cur.

Referenced by std::basic_streambuf< _CharT, _Traits >::in_avail(), std::basic_streambuf< _CharT, _Traits >::sbumpc(), std::basic_streambuf< _CharT, _Traits >::sgetc(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::showmanyc(), std::basic_streambuf< _CharT, _Traits >::sputbackc(), std::basic_streambuf< _CharT, _Traits >::sungetc(), and std::basic_streambuf< _CharT, _Traits >::uflow().

◆ imbue()

template<typename _CharT , typename _Traits >

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 from std::basic_streambuf< _CharT, _Traits >.

Definition at line 1025 of file fstream.tcc.

References std::ios_base::cur.

◆ in_avail()

template<typename _CharT , typename _Traits >

◆ is_open()

template<typename _CharT , typename _Traits >

◆ open() [1/3]

template<typename _CharT , typename _Traits >

template<typename _Path >

Opens an external file.

Parameters

Returns

this on success, NULL on failure

Definition at line 353 of file fstream.

◆ open() [2/3]

Opens an external file.

Parameters

Returns

this on success, NULL on failure

If a file is already open, this function immediately fails. Otherwise it tries to open the file named __s using the flags given in __mode.

Table 92, adapted here, gives the relation between openmode combinations and the equivalent fopen() flags. (NB: lines app, in|out|app, in|app, binary|app, binary|in|out|app, and binary|in|app per DR 596)

+---------------------------------------------------------+ | ios_base Flag combination stdio equivalent | |binary in out trunc app | +---------------------------------------------------------+ | + w | | + + a | | + a | | + + w | | + r | | + + r+ | | + + + w+ | | + + + a+ | | + + a+ | +---------------------------------------------------------+ | + + wb | | + + + ab | | + + ab | | + + + wb | | + + rb | | + + + r+b | | + + + + w+b | | + + + + a+b | | + + + a+b | +---------------------------------------------------------+

Definition at line 178 of file fstream.tcc.

References std::ios_base::ate, std::ios_base::end, and std::basic_filebuf< _CharT, _Traits >::open().

Referenced by std::basic_filebuf< _CharT, _Traits >::open(), std::basic_ifstream< _CharT, _Traits >::open(), std::basic_fstream< _CharT, _Traits >::open(), std::basic_ofstream< _CharT, _Traits >::open(), std::basic_ifstream< _CharT, _Traits >::open(), std::basic_fstream< _CharT, _Traits >::open(), and std::basic_ofstream< _CharT, _Traits >::open().

◆ open() [3/3]

template<typename _CharT , typename _Traits >

◆ operator=()

◆ overflow()

template<typename _CharT , typename _Traits >

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 >.

Definition at line 540 of file fstream.tcc.

References std::ios_base::app, std::ios_base::cur, and std::ios_base::out.

◆ pbackfail()

template<typename _CharT , typename _Traits >

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 >.

Definition at line 481 of file fstream.tcc.

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

◆ pbase()

template<typename _CharT , typename _Traits >

◆ pbump()

template<typename _CharT , typename _Traits >

◆ pptr()

template<typename _CharT , typename _Traits >

◆ pubimbue()

template<typename _CharT , typename _Traits >

◆ pubseekoff()

template<typename _CharT , typename _Traits >

◆ pubseekpos()

template<typename _CharT , typename _Traits >

◆ pubsetbuf()

template<typename _CharT , typename _Traits >

◆ pubsync()

template<typename _CharT , typename _Traits >

◆ sbumpc()

template<typename _CharT , typename _Traits >

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().

Definition at line 323 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::egptr(), std::basic_streambuf< _CharT, _Traits >::gbump(), std::basic_streambuf< _CharT, _Traits >::gptr(), and std::basic_streambuf< _CharT, _Traits >::uflow().

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

◆ seekoff()

template<typename _CharT , typename _Traits >

◆ seekpos()

template<typename _CharT , typename _Traits >

◆ setbuf()

template<typename _CharT , typename _Traits >

◆ setg()

template<typename _CharT , typename _Traits >

◆ setp()

template<typename _CharT , typename _Traits >

◆ sgetc()

template<typename _CharT , typename _Traits >

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.

Definition at line 345 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::egptr(), std::basic_streambuf< _CharT, _Traits >::gptr(), and std::basic_streambuf< _CharT, _Traits >::underflow().

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

◆ sgetn()

template<typename _CharT , typename _Traits >

◆ showmanyc()

template<typename _CharT , typename _Traits >

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 >.

Definition at line 296 of file fstream.tcc.

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

◆ snextc()

template<typename _CharT , typename _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().

Definition at line 305 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::sbumpc(), and std::basic_streambuf< _CharT, _Traits >::sgetc().

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

◆ sputbackc()

template<typename _CharT , typename _Traits >

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.

Definition at line 379 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::eback(), std::basic_streambuf< _CharT, _Traits >::gbump(), std::basic_streambuf< _CharT, _Traits >::gptr(), and std::basic_streambuf< _CharT, _Traits >::pbackfail().

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

◆ sputc()

template<typename _CharT , typename _Traits >

Entry point for all single-character output functions.

Parameters

Returns

__c, if possible.

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).

Definition at line 431 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::epptr(), std::basic_streambuf< _CharT, _Traits >::overflow(), std::basic_streambuf< _CharT, _Traits >::pbump(), and std::basic_streambuf< _CharT, _Traits >::pptr().

Referenced by std::ostreambuf_iterator< _CharT, _Traits >::operator=().

◆ sputn()

template<typename _CharT , typename _Traits >

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.

Definition at line 457 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::xsputn().

◆ sungetc()

template<typename _CharT , typename _Traits >

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.

Definition at line 404 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::eback(), std::basic_streambuf< _CharT, _Traits >::gbump(), std::basic_streambuf< _CharT, _Traits >::gptr(), and std::basic_streambuf< _CharT, _Traits >::pbackfail().

◆ swap() [1/2]

◆ swap() [2/2]

template<typename _CharT , typename _Traits >

◆ sync()

template<typename _CharT , typename _Traits >

Synchronizes the buffer arrays with the controlled sequences.

Returns

-1 on failure.

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

Note

Base class version does nothing, returns zero.

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

Definition at line 1008 of file fstream.tcc.

◆ uflow()

template<typename _CharT , typename _Traits >

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 >.

Definition at line 707 of file streambuf.

References std::basic_streambuf< _CharT, _Traits >::gbump(), std::basic_streambuf< _CharT, _Traits >::gptr(), and std::basic_streambuf< _CharT, _Traits >::underflow().

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

◆ underflow()

template<typename _CharT , typename _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 >.

Definition at line 322 of file fstream.tcc.

References std::ios_base::in.

◆ xsgetn()

template<typename _CharT , typename _Traits >

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 from std::basic_streambuf< _CharT, _Traits >.

Definition at line 668 of file fstream.tcc.

References std::ios_base::in.

◆ xsputn()

template<typename _CharT , typename _Traits >

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 from std::basic_streambuf< _CharT, _Traits >.

Definition at line 754 of file fstream.tcc.

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

◆ ios_base

template<typename _CharT , typename _Traits >

◆ _M_buf

template<typename _CharT , typename _Traits >

Pointer to the beginning of internal buffer.

Definition at line 146 of file fstream.

◆ _M_buf_allocated

template<typename _CharT , typename _Traits >

◆ _M_buf_locale

template<typename _CharT , typename _Traits >

◆ _M_buf_size

template<typename _CharT , typename _Traits >

Actual size of internal buffer. This number is equal to the size of the put area + 1 position, reserved for the overflow char of a full area.

Definition at line 153 of file fstream.

◆ _M_codecvt

template<typename _CharT , typename _Traits >

◆ _M_ext_buf

template<typename _CharT , typename _Traits >

Buffer for external characters. Used for input when codecvt::always_noconv() == false. When valid, this corresponds to eback().

Definition at line 188 of file fstream.

◆ _M_ext_buf_size

template<typename _CharT , typename _Traits >

Size of buffer held by _M_ext_buf.

Definition at line 193 of file fstream.

◆ _M_ext_end

template<typename _CharT , typename _Traits >

◆ _M_ext_next

template<typename _CharT , typename _Traits >

Pointers into the buffer held by _M_ext_buf that delimit a subsequence of bytes that have been read but not yet converted. When valid, _M_ext_next corresponds to egptr().

Definition at line 200 of file fstream.

◆ _M_file

template<typename _CharT , typename _Traits >

◆ _M_in_beg

template<typename _CharT , typename _Traits >

◆ _M_in_cur

template<typename _CharT , typename _Traits >

◆ _M_in_end

template<typename _CharT , typename _Traits >

◆ _M_lock

template<typename _CharT , typename _Traits >

◆ _M_mode

template<typename _CharT , typename _Traits >

◆ _M_out_beg

template<typename _CharT , typename _Traits >

◆ _M_out_cur

template<typename _CharT , typename _Traits >

◆ _M_out_end

template<typename _CharT , typename _Traits >

◆ _M_pback

template<typename _CharT , typename _Traits >

Necessary bits for putback buffer management.

Note

pbacks of over one character are not currently supported.

Definition at line 174 of file fstream.

◆ _M_pback_cur_save

template<typename _CharT , typename _Traits >

Necessary bits for putback buffer management.

Note

pbacks of over one character are not currently supported.

Definition at line 175 of file fstream.

◆ _M_pback_end_save

template<typename _CharT , typename _Traits >

Necessary bits for putback buffer management.

Note

pbacks of over one character are not currently supported.

Definition at line 176 of file fstream.

◆ _M_pback_init

template<typename _CharT , typename _Traits >

◆ _M_reading

template<typename _CharT , typename _Traits >

_M_reading == false && _M_writing == false for uncommitted mode; _M_reading == true for read mode; _M_writing == true for write mode;

NB: _M_reading == true && _M_writing == true is unused.

Definition at line 165 of file fstream.

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

◆ _M_state_beg

template<typename _CharT , typename _Traits >

◆ _M_state_cur

template<typename _CharT , typename _Traits >

◆ _M_state_last

template<typename _CharT , typename _Traits >

◆ _M_writing

template<typename _CharT , typename _Traits >

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

• fstream
• fstream.tcc