---
name: "std::basic_stringbuf"
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_stringbuf"
---

# std::basic\_stringbuf(3)

The actual work of input and output (for std::string).

## NAME

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

## SYNOPSIS

\#include \<sstream\>

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

### Public Types

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**\

### Public Member Functions

**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\> 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.

### Protected Member Functions

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.

### Protected Attributes

**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**\

## Detailed Description

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

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

**Template Parameters**

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

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.

## Constructor & Destructor Documentation

### template\<typename \_CharT, typename \_Traits, typename \_Alloc\> std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::basic\_stringbuf () \[inline\]

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

### template\<typename \_CharT, typename \_Traits, typename \_Alloc\> std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::basic\_stringbuf (ios\_base::openmode \_\_mode) \[inline\], \[explicit\]

Starts with an empty string buffer.

**Parameters**

*\_\_mode* Whether the buffer can read, or write, or both.

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

### template\<typename \_CharT, typename \_Traits, typename \_Alloc\> std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::basic\_stringbuf (const \_\_string\_type & \_\_str, ios\_base::openmode \_\_mode = ios\_base::in \| ios\_base::out) \[inline\], \[explicit\]

Starts with an existing string buffer.

**Parameters**

*\_\_str* A string to copy as a starting buffer. \
 *\_\_mode* Whether the buffer can read, or write, or both.

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

## Member Function Documentation

### 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\> virtual void std::basic\_streambuf\< \_CharT, \_Traits \>::imbue (const locale & \_\_loc) \[inline\], \[protected\], \[virtual\], \[inherited\]

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 in **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 \>**, **std::basic\_filebuf\< char\_type, traits\_type \>**, and **std::basic\_filebuf\< wchar\_t \>**.

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

### 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\<class \_CharT, class \_Traits, class \_Alloc\> basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::int\_type std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::overflow (int\_type \_\_c = traits\_type::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\_mode**, **std::basic\_string\< \_CharT, \_Traits, \_Alloc \>::assign()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::eback()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::egptr()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::epptr()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::gptr()**, **std::ios\_base::in**, **std::max()**, **std::min()**, **std::ios\_base::out**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pbase()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pbump()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pptr()**, **std::basic\_string\< \_CharT, \_Traits, \_Alloc \>::push\_back()**, **std::basic\_string\< \_CharT, \_Traits, \_Alloc \>::reserve()**, and **std::basic\_streambuf\< \_CharT, \_Traits \>::setg()**.

### template\<class \_CharT, class \_Traits, class \_Alloc\> basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::int\_type std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::pbackfail (int\_type \_\_c = traits\_type::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\_mode**, **std::basic\_streambuf\< \_CharT, \_Traits \>::eback()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::gbump()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::gptr()**, and **std::ios\_base::out**.

### 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\<class \_CharT, class \_Traits, class \_Alloc\> basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::pos\_type std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::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\_mode**, **std::ios\_base::cur**, **std::basic\_streambuf\< \_CharT, \_Traits \>::eback()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::egptr()**, **std::ios\_base::end**, **std::basic\_streambuf\< \_CharT, \_Traits \>::epptr()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::gptr()**, **std::ios\_base::in**, **std::ios\_base::out**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pbase()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pptr()**, and **std::basic\_streambuf\< \_CharT, \_Traits \>::setg()**.

### template\<class \_CharT, class \_Traits, class \_Alloc\> basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::pos\_type std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::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\_mode**, **std::basic\_streambuf\< \_CharT, \_Traits \>::eback()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::egptr()**, **std::basic\_streambuf\< \_CharT, \_Traits \>::epptr()**, **std::ios\_base::in**, **std::ios\_base::out**, **std::basic\_streambuf\< \_CharT, \_Traits \>::pbase()**, and **std::basic\_streambuf\< \_CharT, \_Traits \>::setg()**.

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

Manipulates the buffer.

**Parameters**

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

**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 \>**.

### 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, typename \_Alloc\> virtual streamsize std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::showmanyc () \[inline\], \[protected\], \[virtual\]

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 \>.**

### 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, typename \_Alloc\> \_\_string\_type std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::str () const & \[inline\], \[nodiscard\]

**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**

### template\<typename \_CharT, typename \_Traits, typename \_Alloc\> void std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::str (const \_\_string\_type & \_\_s) \[inline\]

**Setting a new buffer.**

**Parameters**

*\_\_s* **The string to use as a new sequence.**

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

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

**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 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 \>, std::basic\_filebuf\< char\_type, traits\_type \>, std::basic\_filebuf\< wchar\_t \>, and std::wbuffer\_convert\< \_Codecvt, \_Elem, \_Tr \>.**

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

### 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\<class \_CharT, class \_Traits, class \_Alloc\> basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::int\_type std::basic\_stringbuf\< \_CharT, \_Traits, \_Alloc \>::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\_mode, std::basic\_streambuf\< \_CharT, \_Traits \>::egptr(), std::basic\_streambuf\< \_CharT, \_Traits \>::gptr(), and std::ios\_base::in.**

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

**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 in 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 \>, and std::basic\_filebuf\< char\_type, traits\_type \>.**

**References egptr(), gptr(), std::min(), and uflow().**

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

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

**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 in 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 \>, and std::basic\_filebuf\< char\_type, traits\_type \>.**

**References epptr(), std::min(), overflow(), and pptr().**

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

## Member Data Documentation

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

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

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

### 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.**

## Author

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