[streambuf.virt.buffer]

# 31 Input/output library [[input.output]](./#input.output)

## 31.6 Stream buffers [[stream.buffers]](stream.buffers#streambuf.virt.buffer)

### 31.6.3 Class template basic_streambuf [[streambuf]](streambuf#virt.buffer)

#### 31.6.3.5 Virtual functions [[streambuf.virtuals]](streambuf.virtuals#streambuf.virt.buffer)

#### 31.6.3.5.2 Buffer management and positioning [streambuf.virt.buffer]

[🔗](#lib:setbuf,basic_streambuf)

`basic_streambuf* setbuf(char_type* s, streamsize n);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3619)

*Effects*: Influences stream buffering in a way that is defined separately for each class
derived frombasic_streambuf in this Clause ([[stringbuf.virtuals]](stringbuf.virtuals "31.8.2.5 Overridden virtual functions"), [[filebuf.virtuals]](filebuf.virtuals "31.10.3.5 Overridden virtual functions"))[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3626)

*Default behavior*: Does nothing[.](#2.sentence-1)

Returnsthis[.](#2.sentence-2)

[🔗](#lib:seekoff,basic_streambuf)

`pos_type seekoff(off_type off, ios_base::seekdir way,
                 ios_base::openmode which
                   = ios_base::in | ios_base::out);
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3641)

*Effects*: Alters the stream positions within one or more of
the controlled sequences in a way that is defined separately for each class
derived frombasic_streambuf in this Clause ([[stringbuf.virtuals]](stringbuf.virtuals "31.8.2.5 Overridden virtual functions"), [[filebuf.virtuals]](filebuf.virtuals "31.10.3.5 Overridden virtual functions"))[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3649)

*Default behavior*: Returnspos_type(off_type(-1))[.](#4.sentence-1)

[🔗](#lib:seekpos,basic_streambuf)

`pos_type seekpos(pos_type sp,
                 ios_base::openmode which
                   = ios_base::in | ios_base::out);
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3663)

*Effects*: Alters the stream positions within one or more of
the controlled sequences in a way that is defined separately for each class
derived frombasic_streambuf in this Clause ([[stringbuf]](stringbuf "31.8.2 Class template basic_­stringbuf"), [[filebuf]](filebuf "31.10.3 Class template basic_­filebuf"))[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3671)

*Default behavior*: Returnspos_type(off_type(-1))[.](#6.sentence-1)

[🔗](#lib:sync,basic_streambuf)

`int sync();
`

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3683)

*Effects*: Synchronizes the controlled sequences with the arrays[.](#7.sentence-1)

That is, ifpbase() is non-null the characters betweenpbase() andpptr() are written to the controlled sequence[.](#7.sentence-2)

The pointers may then be reset as appropriate[.](#7.sentence-3)

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3695)

*Returns*: -1 on failure[.](#8.sentence-1)

What constitutes failure is determined by each derived class ([[filebuf.virtuals]](filebuf.virtuals "31.10.3.5 Overridden virtual functions"))[.](#8.sentence-2)

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L3700)

*Default behavior*: Returns zero[.](#9.sentence-1)