std::basic_streambuf<CharT,Traits>::pubsetbuf, std::basic_streambuf<CharT,Traits>::setbuf

 

C++

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Symbols index

External libraries

 

Input/output library

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C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

basic_spanbuf (C++23)

strstreambuf (deprecated in C++98)

basic_syncbuf (C++20)

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ios_base

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basic_stringstream

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basic_ispanstream (C++23)

basic_ospanstream (C++23)

basic_spanstream (C++23)

istrstream (deprecated in C++98)

ostrstream (deprecated in C++98)

strstream (deprecated in C++98)

Synchronized Output

basic_osyncstream (C++20)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

std::basic_streambuf

Public member functions

basic_streambuf::~basic_streambuf

Locales

basic_streambuf::pubimbue

basic_streambuf::getloc

Positioning

basic_streambuf::pubsetbuf

basic_streambuf::pubseekoff

basic_streambuf::pubseekpos

basic_streambuf::pubsync

Get area

basic_streambuf::in_avail

basic_streambuf::snextc

basic_streambuf::sbumpc

basic_streambuf::sgetc

basic_streambuf::sgetn

Put area

basic_streambuf::sputc

basic_streambuf::sputn

Putback

basic_streambuf::sputbackc

basic_streambuf::sungetc

Protected member functions

basic_streambuf::basic_streambuf

basic_streambuf::operator= (C++11)

basic_streambuf::swap (C++11)

Locales

basic_streambuf::imbue

Positioning

basic_streambuf::setbuf

basic_streambuf::seekoff

basic_streambuf::seekpos

basic_streambuf::sync

Get area

basic_streambuf::showmanyc

basic_streambuf::underflow

basic_streambuf::uflow

basic_streambuf::xsgetn

basic_streambuf::ebackbasic_streambuf::gptrbasic_streambuf::egptr

basic_streambuf::gbump

basic_streambuf::setg

Put area

basic_streambuf::xsputn

basic_streambuf::overflow

basic_streambuf::pbasebasic_streambuf::pptrbasic_streambuf::epptr

basic_streambuf::pbump

basic_streambuf::setp

Putback

basic_streambuf::pbackfail

 

public: basic_streambuf<CharT, Traits>* pubsetbuf( char_type* s, std::streamsize n )	(1)
protected: virtual basic_streambuf<CharT, Traits>* setbuf( char_type* s, std::streamsize n )	(2)

1) Calls setbuf(s, n) of the most derived class.

2) The base class version of this function has no effect. The derived classes may override this function to allow removal or replacement of the controlled character sequence (the buffer) with a user-provided array, or for any other implementation-specific purpose.

Parameters

s	-	pointer to the first CharT in the user-provided buffer
n	-	the number of CharT elements in the user-provided buffer

Return value

1) The return value of setbuf(s, n)

2) this

Example

Provides a 10k buffer for reading. On linux, the strace utility may be used to observe the actual number of bytes read.

Run this code

#include <fstream>
#include <iostream>
#include <string>
 
int main()
{
    int cnt = 0;
    std::ifstream file;
    char buf[1024*10 + 1];
 
    file.rdbuf()->pubsetbuf(buf, sizeof buf);
 
    file.open("/usr/share/dict/words");
 
    for (std::string line; getline(file, line);)
        cnt++;
 
    std::cout << cnt << '\n';
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 158	C++98	the default behavior of setbuf was only specified if gptr() is not null and not equal to egptr()	specified as no-op for all cases

See also

setbuf [virtual]	attempts to replace the controlled character sequence with an array (virtual protected member function of std::basic_stringbuf<CharT,Traits,Allocator>)
setbuf [virtual]	provides user-supplied buffer or turns this filebuf unbuffered (virtual protected member function of std::basic_filebuf<CharT,Traits>)
setbuf [virtual]	attempts to replace the controlled character sequence with an array (virtual protected member function of std::strstreambuf)
setbuf	sets the buffer for a file stream (function)