std::basic_streambuf::pubsetbuf, std::basic_streambuf::setbuf

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Input/output library

I/O manipulators

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

strstreambuf (deprecated)

Streams

Abstractions

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I/O

basic_ifstream

basic_ofstream

basic_fstream

String I/O

basic_istringstream

basic_ostringstream

basic_stringstream

Array I/O

istrstream (deprecated)

ostrstream (deprecated)

strstream (deprecated)

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

 

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 byte in the user-provided buffer
n	-	the number of bytes in the user-provided buffer

Return value

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

2) this

Example

provide 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[10241];
 
    file.rdbuf()->pubsetbuf(buf, sizeof buf);
 
    file.open("/usr/share/dict/words");
 
    for (std::string line; getline(file, line);) {
        cnt++;
    }
 
    std::cout << cnt << '\n';
}

See also

setbuf [virtual]	attempts to replace the controlled character sequence with an array (virtual protected member function of std::basic_stringbuf)
setbuf [virtual]	provides user-supplied buffer or turns this filebuf unbuffered (virtual protected member function of std::basic_filebuf)
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)