---
name: "std::basic_filebuf"
section: "3"
platform: "linux"
package: "gcc"
version: "16.2.1+r23+gd564253eb6c8-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/std::basic_filebuf"
---

# std::basic\_filebuf(3)

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

## NAME

std::basic\_filebuf\< \_CharT, \_Traits \> - The actual work of input and output (for files).

## SYNOPSIS

\#include \<fstream\>

Inherits **std::basic\_streambuf\< \_CharT, \_Traits \>**.

Inherited by **\_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>**.

### Public Types

typedef **codecvt**\< char\_type, char, \_\_state\_type \> **\_\_codecvt\_type**\
 typedef \_\_basic\_file\< char \> **\_\_file\_type**\
 typedef **basic\_filebuf**\< char\_type, traits\_type \> **\_\_filebuf\_type**\
 typedef traits\_type::state\_type **\_\_state\_type**\
 typedef **basic\_streambuf**\< char\_type, traits\_type \> **\_\_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\_filebuf** ()\
 Does not open any files.  **basic\_filebuf** (basic\_filebuf &&)\
 **basic\_filebuf** (const basic\_filebuf &)=delete\
 virtual **~basic\_filebuf** ()\
 The destructor closes the file first.  \_\_filebuf\_type \* **close** ()\
 Closes the currently associated file.  **locale** **getloc** () const\
 Locale access.  **streamsize** **in\_avail** ()\
 Looking ahead into the stream.  bool **is\_open** () const  throw ()\
 Returns true if the external file is open.  template\<typename \_Path\> \_If\_fs\_path\< \_Path, \_\_filebuf\_type \* \> **open** (const \_Path &\_\_s, **ios\_base::openmode** \_\_mode)\
 Opens an external file.  \_\_filebuf\_type \* **open** (const char \*\_\_s, **ios\_base::openmode** \_\_mode)\
 Opens an external file.  \_\_filebuf\_type \* **open** (const **std::string** &\_\_s, **ios\_base::openmode** \_\_mode)\
 Opens an external file.  **basic\_filebuf** & **operator=** (**basic\_filebuf** &&)\
 **basic\_filebuf** & **operator=** (const **basic\_filebuf** &)=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.  int\_type **sungetc** ()\
 Moving backwards in the input stream.  void **swap** (**basic\_filebuf** &)\

**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.

### Protected Member Functions

void **\_\_safe\_gbump** (**streamsize** \_\_n)\
 void **\_\_safe\_pbump** (**streamsize** \_\_n)\
 void **\_M\_allocate\_internal\_buffer** ()\
 bool **\_M\_convert\_to\_external** (char\_type \*, **streamsize**)\
 void **\_M\_create\_pback** ()\
 void **\_M\_destroy\_internal\_buffer** ()  throw ()\
 void **\_M\_destroy\_pback** ()  throw ()\
 int **\_M\_get\_ext\_pos** (\_\_state\_type &\_\_state)\
 pos\_type **\_M\_seek** (off\_type \_\_off, **ios\_base::seekdir** \_\_way, \_\_state\_type \_\_state)\
 void **\_M\_set\_buffer** (**streamsize** \_\_off)\
 bool **\_M\_terminate\_output** ()\
 void **gbump** (int \_\_n)\
 Moving the read position.  virtual void **imbue** (const **locale** &\_\_loc)\
 Changes translations.  virtual int\_type **overflow** (int\_type \_\_c=\_Traits::eof())\
 Consumes data from the buffer; writes to the controlled sequence.  virtual int\_type **pbackfail** (int\_type \_\_c=\_Traits::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 \_\_pos, **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.

### Protected Attributes

char\_type \* **\_M\_buf**\
 Pointer to the beginning of internal buffer.  bool **\_M\_buf\_allocated**\
 **locale** **\_M\_buf\_locale**\
 Current locale setting.  size\_t **\_M\_buf\_size**\
 const \_\_codecvt\_type \* **\_M\_codecvt**\
 char \* **\_M\_ext\_buf**\
 **streamsize** **\_M\_ext\_buf\_size**\
 char \* **\_M\_ext\_end**\
 const char \* **\_M\_ext\_next**\
 \_\_file\_type **\_M\_file**\
 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.  \_\_c\_lock **\_M\_lock**\
 **ios\_base::openmode** **\_M\_mode**\
 Place to stash in \|\| out \|\| in \| out settings for current filebuf.  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.  bool **\_M\_reading**\
 \_\_state\_type **\_M\_state\_beg**\
 \_\_state\_type **\_M\_state\_cur**\
 \_\_state\_type **\_M\_state\_last**\
 bool **\_M\_writing**\

char\_type **\_M\_pback**\
 char\_type \* **\_M\_pback\_cur\_save**\
 char\_type \* **\_M\_pback\_end\_save**\
 bool **\_M\_pback\_init**\

### Friends

class **ios\_base**\

## Detailed Description

### template\<typename \_CharT, typename \_Traits\>

class std::basic\_filebuf\< \_CharT, \_Traits \>"The actual work of input and output (for files).

**Template Parameters**

*\_CharT* Type of character stream. \
 *\_Traits* Traits for character type, defaults to char\_traits\<\_CharT\>.

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.

## Constructor & Destructor Documentation

### template\<typename \_CharT, typename \_Traits\> std::basic\_filebuf\< \_CharT, \_Traits \>::basic\_filebuf ()

Does not open any files. The default constructor initializes the parent class using its own default ctor.

References **\_M\_buf**, **std::basic\_streambuf\< \_CharT, \_Traits \>::\_M\_buf\_locale**, **\_M\_buf\_size**, **\_M\_ext\_buf**, **\_M\_ext\_buf\_size**, **\_M\_ext\_next**, **\_M\_mode**, **\_M\_pback**, **\_M\_pback\_cur\_save**, **\_M\_pback\_end\_save**, **\_M\_pback\_init**, and **\_M\_reading**.

Referenced by **\_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf()**, and **close()**.

### template\<typename \_CharT, typename \_Traits\> virtual std::basic\_filebuf\< \_CharT, \_Traits \>::~basic\_filebuf () \[inline\], \[virtual\]

The destructor closes the file first.

## Member Function Documentation

### template\<typename \_CharT, typename \_Traits\> void std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_create\_pback () \[inline\], \[protected\]

Initializes pback buffers, and moves normal buffers to safety. Assumptions: \_M\_in\_cur has already been moved back

Referenced by **pbackfail()**.

### template\<typename \_CharT, typename \_Traits\> void std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_destroy\_pback () \[inline\], \[protected\]

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

Referenced by **overflow()**, **seekoff()**, **seekpos()**, **underflow()**, and **xsgetn()**.

### template\<typename \_CharT, typename \_Traits\> void std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_set\_buffer (streamsize \_\_off) \[inline\], \[protected\]

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.

Referenced by **\_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf()**, **\_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf()**, **close()**, **imbue()**, **open()**, **overflow()**, **pbackfail()**, **underflow()**, **xsgetn()**, and **xsputn()**.

### template\<typename \_CharT, typename \_Traits\> basic\_filebuf\< \_CharT, \_Traits \>::\_\_filebuf\_type \* std::basic\_filebuf\< \_CharT, \_Traits \>::close ()

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.

References **basic\_filebuf()**, **\_M\_mode**, **\_M\_pback\_init**, **\_M\_reading**, **\_M\_set\_buffer()**, and **is\_open()**.

Referenced by **std::basic\_filebuf\< char\_type, traits\_type \>::~basic\_filebuf()**, and **open()**.

### template\<typename \_CharT, typename \_Traits\> char\_type \* std::basic\_streambuf\< \_CharT, \_Traits \>::eback () const \[inline\], \[protected\], \[inherited\]

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::basic\_filebuf\< char\_type, traits\_type \>::\_M\_destroy\_pback()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::imbue()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::pbackfail()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::pbackfail()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekoff()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekpos()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sputbackc()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sungetc()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::underflow()**, and **std::basic\_filebuf\< \_CharT, \_Traits \>::xsgetn()**.

### template\<typename \_CharT, typename \_Traits\> char\_type \* std::basic\_streambuf\< \_CharT, \_Traits \>::egptr () const \[inline\], \[protected\], \[inherited\]

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::basic\_filebuf\< char\_type, traits\_type \>::\_M\_create\_pback()**, **std::basic\_streambuf\< char\_type, traits\_type \>::in\_avail()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sbumpc()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekoff()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekpos()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sgetc()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::showmanyc()**, **std::basic\_stringbuf\< char \>::showmanyc()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::underflow()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::underflow()**, **std::wbuffer\_convert\< \_Codecvt, \_Elem, \_Tr \>::underflow()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::xsgetn()**, and **xsgetn()**.

### template\<typename \_CharT, typename \_Traits\> char\_type \* std::basic\_streambuf\< \_CharT, \_Traits \>::epptr () const \[inline\], \[protected\], \[inherited\]

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

Referenced by **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekoff()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekpos()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sputc()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::xsputn()**, and **xsputn()**.

### template\<typename \_CharT, typename \_Traits\> void std::basic\_streambuf\< \_CharT, \_Traits \>::gbump (int \_\_n) \[inline\], \[protected\], \[inherited\]

Moving the read position.

**Parameters**

*\_\_n* The delta by which to move.

This just advances the read position without returning any data.

Referenced by **std::basic\_filebuf\< \_CharT, \_Traits \>::pbackfail()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::pbackfail()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sbumpc()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sputbackc()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sungetc()**, **std::basic\_streambuf\< char\_type, traits\_type \>::uflow()**, and **std::basic\_filebuf\< \_CharT, \_Traits \>::xsgetn()**.

### template\<typename \_CharT, typename \_Traits\> locale std::basic\_streambuf\< \_CharT, \_Traits \>::getloc () const \[inline\], \[inherited\]

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.

Referenced by **std::basic\_streambuf\< char\_type, traits\_type \>::pubimbue()**.

### template\<typename \_CharT, typename \_Traits\> char\_type \* std::basic\_streambuf\< \_CharT, \_Traits \>::gptr () const \[inline\], \[protected\], \[inherited\]

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::basic\_filebuf\< char\_type, traits\_type \>::\_M\_create\_pback()**, **std::basic\_filebuf\< char\_type, traits\_type \>::\_M\_destroy\_pback()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::imbue()**, **std::basic\_streambuf\< char\_type, traits\_type \>::in\_avail()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::pbackfail()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::pbackfail()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sbumpc()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekoff()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sgetc()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::showmanyc()**, **std::basic\_stringbuf\< char \>::showmanyc()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sputbackc()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sungetc()**, **std::basic\_streambuf\< char\_type, traits\_type \>::uflow()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::underflow()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::underflow()**, **std::wbuffer\_convert\< \_Codecvt, \_Elem, \_Tr \>::underflow()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::xsgetn()**, and **xsgetn()**.

### template\<typename \_CharT, typename \_Traits\> void std::basic\_filebuf\< \_CharT, \_Traits \>::imbue (const locale & \_\_loc) \[protected\], \[virtual\]

Changes translations.

**Parameters**

*\_\_loc* A new locale.

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 \>**.

References **\_M\_ext\_buf**, **\_M\_ext\_next**, **\_M\_mode**, **\_M\_reading**, **\_M\_set\_buffer()**, **std::ios\_base::cur**, **std::basic\_streambuf\< \_CharT, \_Traits \>::eback()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::gptr()**, **is\_open()**, and **seekoff()**.

### template\<typename \_CharT, typename \_Traits\> streamsize std::basic\_streambuf\< \_CharT, \_Traits \>::in\_avail () \[inline\], \[inherited\]

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().

### template\<typename \_CharT, typename \_Traits\> bool std::basic\_filebuf\< \_CharT, \_Traits \>::is\_open () const \[inline\], \[nodiscard\]

Returns true if the external file is open.

Referenced by **\_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf()**, **\_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf()**, **close()**, **imbue()**, **open()**, **seekoff()**, **seekpos()**, **setbuf()**, and **showmanyc()**.

### template\<typename \_CharT, typename \_Traits\> template\<typename \_Path\> \_If\_fs\_path\< \_Path, \_\_filebuf\_type \* \> std::basic\_filebuf\< \_CharT, \_Traits \>::open (const \_Path & \_\_s, ios\_base::openmode \_\_mode) \[inline\]

Opens an external file.

**Parameters**

*\_\_s* The name of the file, as a filesystem::path. \
 *\_\_mode* The open mode flags.

**Returns**

this on success, NULL on failure

### template\<typename \_CharT, typename \_Traits\> basic\_filebuf\< \_CharT, \_Traits \>::\_\_filebuf\_type \* std::basic\_filebuf\< \_CharT, \_Traits \>::open (const char \* \_\_s, ios\_base::openmode \_\_mode)

Opens an external file.

**Parameters**

*\_\_s* The name of the file. \
 *\_\_mode* The open mode flags.

**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                |
+---------------------------------------------------------+
```

References **\_M\_mode**, **\_M\_reading**, **\_M\_set\_buffer()**, **std::ios\_base::ate**, **close()**, **std::ios\_base::end**, **is\_open()**, and **seekoff()**.

Referenced by **std::basic\_filebuf\< char\_type, traits\_type \>::open()**, and **std::basic\_filebuf\< char\_type, traits\_type \>::open()**.

### template\<typename \_CharT, typename \_Traits\> \_\_filebuf\_type \* std::basic\_filebuf\< \_CharT, \_Traits \>::open (const std::string & \_\_s, ios\_base::openmode \_\_mode) \[inline\]

Opens an external file.

**Parameters**

*\_\_s* The name of the file. \
 *\_\_mode* The open mode flags.

**Returns**

this on success, NULL on failure

### template\<typename \_CharT, typename \_Traits\> basic\_filebuf\< \_CharT, \_Traits \>::int\_type std::basic\_filebuf\< \_CharT, \_Traits \>::overflow (int\_type \_\_c = \_Traits::eof()) \[protected\], \[virtual\]

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

**Parameters**

*\_\_c* An additional character to consume.

**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 **\_M\_buf\_size**, **\_M\_destroy\_pback()**, **\_M\_mode**, **\_M\_reading**, **\_M\_set\_buffer()**, **std::ios\_base::app**, **std::ios\_base::cur**, **std::ios\_base::out**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pbase()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pbump()**, and **std::basic\_streambuf\< \_CharT, \_Traits \>::pptr()**.

Referenced by **pbackfail()**, **sync()**, **underflow()**, and **xsgetn()**.

### template\<typename \_CharT, typename \_Traits\> basic\_filebuf\< \_CharT, \_Traits \>::int\_type std::basic\_filebuf\< \_CharT, \_Traits \>::pbackfail (int\_type \_\_c = \_Traits::eof()) \[protected\], \[virtual\]

Tries to back up the input sequence.

**Parameters**

*\_\_c* The character to be inserted back into the sequence.

**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 **\_M\_create\_pback()**, **\_M\_mode**, **\_M\_pback\_init**, **\_M\_reading**, **\_M\_set\_buffer()**, **std::ios\_base::cur**, **std::basic\_streambuf\< \_CharT, \_Traits \>::eback()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::gbump()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::gptr()**, **std::ios\_base::in**, **overflow()**, **seekoff()**, and **underflow()**.

### template\<typename \_CharT, typename \_Traits\> char\_type \* std::basic\_streambuf\< \_CharT, \_Traits \>::pbase () const \[inline\], \[protected\], \[inherited\]

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

Referenced by **std::basic\_filebuf\< \_CharT, \_Traits \>::overflow()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::seekoff()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekoff()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekpos()**, **std::basic\_stringbuf\< char \>::str()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::sync()**, and **std::basic\_filebuf\< \_CharT, \_Traits \>::xsputn()**.

### template\<typename \_CharT, typename \_Traits\> void std::basic\_streambuf\< \_CharT, \_Traits \>::pbump (int \_\_n) \[inline\], \[protected\], \[inherited\]

Moving the write position.

**Parameters**

*\_\_n* The delta by which to move.

This just advances the write position without returning any data.

Referenced by **std::basic\_filebuf\< \_CharT, \_Traits \>::overflow()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow()**, and **std::basic\_streambuf\< char\_type, traits\_type \>::sputc()**.

### template\<typename \_CharT, typename \_Traits\> char\_type \* std::basic\_streambuf\< \_CharT, \_Traits \>::pptr () const \[inline\], \[protected\], \[inherited\]

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

Referenced by **std::basic\_filebuf\< \_CharT, \_Traits \>::overflow()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::seekoff()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekoff()**, **std::basic\_streambuf\< char\_type, traits\_type \>::sputc()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::sync()**, **std::basic\_filebuf\< \_CharT, \_Traits \>::xsputn()**, and **xsputn()**.

### template\<typename \_CharT, typename \_Traits\> locale std::basic\_streambuf\< \_CharT, \_Traits \>::pubimbue (const locale & \_\_loc) \[inline\], \[inherited\]

Entry point for imbue().

**Parameters**

*\_\_loc* The new locale.

**Returns**

The previous locale.

Calls the derived imbue(\_\_loc).

### template\<typename \_CharT, typename \_Traits\> pos\_type std::basic\_streambuf\< \_CharT, \_Traits \>::pubseekoff (off\_type \_\_off, ios\_base::seekdir \_\_way, ios\_base::openmode \_\_mode = ios\_base::in \| ios\_base::out) \[inline\], \[inherited\]

Alters the stream position.

**Parameters**

*\_\_off* Offset. \
 *\_\_way* Value for ios\_base::seekdir. \
 *\_\_mode* Value for ios\_base::openmode.

Calls virtual seekoff function.

### template\<typename \_CharT, typename \_Traits\> pos\_type std::basic\_streambuf\< \_CharT, \_Traits \>::pubseekpos (pos\_type \_\_sp, ios\_base::openmode \_\_mode = ios\_base::in \| ios\_base::out) \[inline\], \[inherited\]

Alters the stream position.

**Parameters**

*\_\_sp* Position \
 *\_\_mode* Value for ios\_base::openmode.

Calls virtual seekpos function.

### template\<typename \_CharT, typename \_Traits\> basic\_streambuf \* std::basic\_streambuf\< \_CharT, \_Traits \>::pubsetbuf (char\_type \* \_\_s, streamsize \_\_n) \[inline\], \[inherited\]

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.

### template\<typename \_CharT, typename \_Traits\> int std::basic\_streambuf\< \_CharT, \_Traits \>::pubsync () \[inline\], \[inherited\]

Calls virtual sync function.

Referenced by **std::basic\_istream\< \_CharT, \_Traits \>::sync()**.

### template\<typename \_CharT, typename \_Traits\> int\_type std::basic\_streambuf\< \_CharT, \_Traits \>::sbumpc () \[inline\], \[inherited\]

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, \_Traits \>::ignore()**, **std::basic\_streambuf\< char\_type, traits\_type \>::snextc()**, and **std::basic\_istream\< \_CharT, char\_traits\< \_CharT \> \>::unget()**.

### template\<typename \_CharT, typename \_Traits\> basic\_filebuf\< \_CharT, \_Traits \>::pos\_type std::basic\_filebuf\< \_CharT, \_Traits \>::seekoff (off\_type , ios\_base::seekdir , ios\_base::openmode = ios\_base::in \| ios\_base::out) \[protected\], \[virtual\]

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 **\_M\_destroy\_pback()**, **\_M\_reading**, **std::ios\_base::cur**, **is\_open()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pbase()**, and **std::basic\_streambuf\< \_CharT, \_Traits \>::pptr()**.

Referenced by **imbue()**, **open()**, and **pbackfail()**.

### template\<typename \_CharT, typename \_Traits\> basic\_filebuf\< \_CharT, \_Traits \>::pos\_type std::basic\_filebuf\< \_CharT, \_Traits \>::seekpos (pos\_type , ios\_base::openmode = ios\_base::in \| ios\_base::out) \[protected\], \[virtual\]

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 **\_M\_destroy\_pback()**, **std::ios\_base::beg**, and **is\_open()**.

### template\<typename \_CharT, typename \_Traits\> basic\_filebuf\< \_CharT, \_Traits \>::\_\_streambuf\_type \* std::basic\_filebuf\< \_CharT, \_Traits \>::setbuf (char\_type \* \_\_s, streamsize \_\_n) \[protected\], \[virtual\]

Manipulates the buffer.

**Parameters**

*\_\_s* Pointer to a buffer area. \
 *\_\_n* Size of *\_\_s*.

**Returns**

this

If no file has been opened, and both *\_\_s* and *\_\_n* are zero, then the stream becomes unbuffered. Otherwise, \_\_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 \>**.

References **\_M\_buf**, **\_M\_buf\_size**, and **is\_open()**.

### template\<typename \_CharT, typename \_Traits\> void std::basic\_streambuf\< \_CharT, \_Traits \>::setg (char\_type \* \_\_gbeg, char\_type \* \_\_gnext, char\_type \* \_\_gend) \[inline\], \[protected\], \[inherited\]

Setting the three read area pointers.

**Parameters**

*\_\_gbeg* A pointer. \
 *\_\_gnext* A pointer. \
 *\_\_gend* A pointer.

**Postcondition**

*\_\_gbeg* == eback(), *\_\_gnext* == gptr(), and *\_\_gend* == egptr()

Referenced by **std::wbuffer\_convert\< \_Codecvt, \_Elem, \_Tr \>::wbuffer\_convert()**, **std::basic\_filebuf\< char\_type, traits\_type \>::\_M\_create\_pback()**, **std::basic\_filebuf\< char\_type, traits\_type \>::\_M\_destroy\_pback()**, **std::basic\_filebuf\< char\_type, traits\_type \>::\_M\_set\_buffer()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekoff()**, **std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::seekpos()**, and **std::basic\_filebuf\< \_CharT, \_Traits \>::xsgetn()**.

### template\<typename \_CharT, typename \_Traits\> void std::basic\_streambuf\< \_CharT, \_Traits \>::setp (char\_type \* \_\_pbeg, char\_type \* \_\_pend) \[inline\], \[protected\], \[inherited\]

Setting the three write area pointers.

**Parameters**

*\_\_pbeg* A pointer. \
 *\_\_pend* A pointer.

**Postcondition**

*\_\_pbeg* == pbase(), *\_\_pbeg* == pptr(), and *\_\_pend* == epptr()

Referenced by **std::wbuffer\_convert\< \_Codecvt, \_Elem, \_Tr \>::wbuffer\_convert()**, and **std::basic\_filebuf\< char\_type, traits\_type \>::\_M\_set\_buffer()**.

### template\<typename \_CharT, typename \_Traits\> int\_type std::basic\_streambuf\< \_CharT, \_Traits \>::sgetc () \[inline\], \[inherited\]

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, \_Traits \>::get()**, **std::basic\_istream\< \_CharT, \_Traits \>::ignore()**, **std::basic\_istream\< \_CharT, char\_traits\< \_CharT \> \>::readsome()**, and **std::basic\_streambuf\< char\_type, traits\_type \>::snextc()**.

### template\<typename \_CharT, typename \_Traits\> streamsize std::basic\_streambuf\< \_CharT, \_Traits \>::sgetn (char\_type \* \_\_s, streamsize \_\_n) \[inline\], \[inherited\]

Entry point for xsgetn.

**Parameters**

*\_\_s* A buffer area. \
 *\_\_n* A count.

Returns xsgetn(\_\_s,\_\_n). The effect is to fill *\_\_s*\[0\] through *\_\_s*\[\_\_n-1\] with characters from the input sequence, if possible.

### template\<typename \_CharT, typename \_Traits\> streamsize std::basic\_filebuf\< \_CharT, \_Traits \>::showmanyc () \[protected\], \[virtual\]

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 \>.**

**References \_M\_mode, std::ios\_base::binary, std::basic\_streambuf\< \_CharT, \_Traits \>::egptr(), std::basic\_streambuf\< \_CharT, \_Traits \>::gptr(), std::ios\_base::in, and is\_open().**

### template\<typename \_CharT, typename \_Traits\> int\_type std::basic\_streambuf\< \_CharT, \_Traits \>::snextc () \[inline\], \[inherited\]

**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\_iostream\< char\_type, traits\_type \>::ignore(), and std::basic\_istream\< \_CharT, char\_traits\< \_CharT \> \>::readsome().**

### template\<typename \_CharT, typename \_Traits\> int\_type std::basic\_streambuf\< \_CharT, \_Traits \>::sputbackc (char\_type \_\_c) \[inline\], \[inherited\]

**Pushing characters back into the input stream.**

**Parameters**

*\_\_c* **The character to push back.**

**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().**

### template\<typename \_CharT, typename \_Traits\> int\_type std::basic\_streambuf\< \_CharT, \_Traits \>::sputc (char\_type \_\_c) \[inline\], \[inherited\]

**Entry point for all single-character output functions.**

**Parameters**

*\_\_c* **A character to output.**

**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)**.**

**Referenced by std::wbuffer\_convert\< \_Codecvt, \_Elem, \_Tr \>::overflow().**

### template\<typename \_CharT, typename \_Traits\> streamsize std::basic\_streambuf\< \_CharT, \_Traits \>::sputn (const char\_type \* \_\_s, streamsize \_\_n) \[inline\], \[inherited\]

**Entry point for all single-character output functions.**

**Parameters**

*\_\_s* **A buffer read area.** \
 *\_\_n* **A count.**

**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.**

### template\<typename \_CharT, typename \_Traits\> int\_type std::basic\_streambuf\< \_CharT, \_Traits \>::sungetc () \[inline\], \[inherited\]

**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***.**

**Referenced by std::basic\_istream\< \_CharT, \_Traits \>::unget().**

### template\<typename \_CharT, typename \_Traits\> int std::basic\_filebuf\< \_CharT, \_Traits \>::sync () \[protected\], \[virtual\]

**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 \>.**

**References overflow(), std::basic\_streambuf\< \_CharT, \_Traits \>::pbase(), and std::basic\_streambuf\< \_CharT, \_Traits \>::pptr().**

### template\<typename \_CharT, typename \_Traits\> virtual int\_type std::basic\_streambuf\< \_CharT, \_Traits \>::uflow () \[inline\], \[protected\], \[virtual\], \[inherited\]

**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 \>.**

**Referenced by std::basic\_streambuf\< char\_type, traits\_type \>::sbumpc(), and xsgetn().**

### template\<typename \_CharT, typename \_Traits\> basic\_filebuf\< \_CharT, \_Traits \>::int\_type std::basic\_filebuf\< \_CharT, \_Traits \>::underflow () \[protected\], \[virtual\]

**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 \_M\_buf\_size, \_M\_destroy\_pback(), \_M\_mode, \_M\_set\_buffer(), std::basic\_streambuf\< \_CharT, \_Traits \>::eback(), std::basic\_streambuf\< \_CharT, \_Traits \>::egptr(), std::basic\_streambuf\< \_CharT, \_Traits \>::gptr(), std::ios\_base::in, and overflow().**

**Referenced by pbackfail().**

### template\<typename \_CharT, typename \_Traits\> streamsize std::basic\_filebuf\< \_CharT, \_Traits \>::xsgetn (char\_type \* \_\_s, streamsize \_\_n) \[protected\], \[virtual\]

**Multiple character extraction.**

**Parameters**

*\_\_s* **A buffer area.** \
 *\_\_n* **Maximum number of characters to assign.**

**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 \>.**

**References \_M\_buf\_size, \_M\_destroy\_pback(), \_M\_mode, \_M\_pback\_init, \_M\_reading, \_M\_set\_buffer(), std::basic\_streambuf\< \_CharT, \_Traits \>::eback(), std::basic\_streambuf\< \_CharT, \_Traits \>::egptr(), std::basic\_streambuf\< \_CharT, \_Traits \>::gbump(), std::basic\_streambuf\< \_CharT, \_Traits \>::gptr(), std::ios\_base::in, overflow(), std::basic\_streambuf\< \_CharT, \_Traits \>::setg(), and std::basic\_streambuf\< char\_type, traits\_type \>::xsgetn().**

### template\<typename \_CharT, typename \_Traits\> streamsize std::basic\_filebuf\< \_CharT, \_Traits \>::xsputn (const char\_type \* \_\_s, streamsize \_\_n) \[protected\], \[virtual\]

**Multiple character insertion.**

**Parameters**

*\_\_s* **A buffer area.** \
 *\_\_n* **Maximum number of characters to write.**

**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 \>.**

**References \_M\_buf\_size, \_M\_mode, \_M\_reading, \_M\_set\_buffer(), std::ios\_base::app, std::basic\_streambuf\< \_CharT, \_Traits \>::epptr(), std::ios\_base::out, std::basic\_streambuf\< \_CharT, \_Traits \>::pbase(), std::basic\_streambuf\< \_CharT, \_Traits \>::pptr(), and std::basic\_streambuf\< char\_type, traits\_type \>::xsputn().**

## Member Data Documentation

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_buf \[protected\]

**Pointer to the beginning of internal buffer.**

**Referenced by basic\_filebuf(), and setbuf().**

### template\<typename \_CharT, typename \_Traits\> locale std::basic\_streambuf\< \_CharT, \_Traits \>::\_M\_buf\_locale \[protected\], \[inherited\]

**Current locale setting.**

**Referenced by std::basic\_filebuf\< \_CharT, \_Traits \>::basic\_filebuf().**

### template\<typename \_CharT, typename \_Traits\> size\_t std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_buf\_size \[protected\]

**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.**

**Referenced by basic\_filebuf(), \_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf(), \_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf(), overflow(), setbuf(), underflow(), xsgetn(), and xsputn().**

### template\<typename \_CharT, typename \_Traits\> char\* std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_ext\_buf \[protected\]

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

**Referenced by basic\_filebuf(), and imbue().**

### template\<typename \_CharT, typename \_Traits\> streamsize std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_ext\_buf\_size \[protected\]

**Size of buffer held by \_M\_ext\_buf.**

**Referenced by basic\_filebuf().**

### template\<typename \_CharT, typename \_Traits\> const char\* std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_ext\_next \[protected\]

**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().**

**Referenced by basic\_filebuf(), and imbue().**

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_streambuf\< \_CharT, \_Traits \>::\_M\_in\_beg \[protected\], \[inherited\]

**Start of get area.**

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_streambuf\< \_CharT, \_Traits \>::\_M\_in\_cur \[protected\], \[inherited\]

**Current read area.**

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_streambuf\< \_CharT, \_Traits \>::\_M\_in\_end \[protected\], \[inherited\]

**End of get area.**

### template\<typename \_CharT, typename \_Traits\> ios\_base::openmode std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_mode \[protected\]

**Place to stash in \|\| out \|\| in \| out settings for current filebuf.**

**Referenced by basic\_filebuf(), \_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf(), \_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf(), close(), imbue(), open(), overflow(), pbackfail(), showmanyc(), underflow(), xsgetn(), and xsputn().**

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_streambuf\< \_CharT, \_Traits \>::\_M\_out\_beg \[protected\], \[inherited\]

**Start of put area.**

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_streambuf\< \_CharT, \_Traits \>::\_M\_out\_cur \[protected\], \[inherited\]

**Current put area.**

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_streambuf\< \_CharT, \_Traits \>::\_M\_out\_end \[protected\], \[inherited\]

**End of put area.**

### template\<typename \_CharT, typename \_Traits\> char\_type std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_pback \[protected\]

**Necessary bits for putback buffer management.**

**Note**

**pbacks of over one character are not currently supported.**

**Referenced by basic\_filebuf().**

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_pback\_cur\_save \[protected\]

**Necessary bits for putback buffer management.**

**Note**

**pbacks of over one character are not currently supported.**

**Referenced by basic\_filebuf().**

### template\<typename \_CharT, typename \_Traits\> char\_type\* std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_pback\_end\_save \[protected\]

**Necessary bits for putback buffer management.**

**Note**

**pbacks of over one character are not currently supported.**

**Referenced by basic\_filebuf().**

### template\<typename \_CharT, typename \_Traits\> bool std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_pback\_init \[protected\]

**Necessary bits for putback buffer management.**

**Note**

**pbacks of over one character are not currently supported.**

**Referenced by basic\_filebuf(), close(), pbackfail(), and xsgetn().**

### template\<typename \_CharT, typename \_Traits\> bool std::basic\_filebuf\< \_CharT, \_Traits \>::\_M\_reading \[protected\]

**\_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.**

**Referenced by basic\_filebuf(), \_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf(), \_\_gnu\_cxx::stdio\_filebuf\< \_CharT, \_Traits \>::stdio\_filebuf(), close(), imbue(), open(), overflow(), pbackfail(), seekoff(), xsgetn(), and xsputn().**

## Author

**Generated automatically by Doxygen for libstdc++ from the source code.**