NAME¶

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

Synopsis¶

public: (1)
basic_streambuf<CharT, Traits>* pubsetbuf( char_type* s, std::streamsize n )
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';
}

Possible output:¶

356010

Defect reports

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

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

See also¶

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

setbuf attempts to replace the controlled character sequence with an array
[virtual] (virtual protected member function of std::strstreambuf)
setbuf sets the buffer for a file stream
(function)