std::strstreambuf::setbuf

 

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strstreambuf::setbuf

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protected: virtual streambuf* setbuf( char* s, std::streamsize n );

If s is a null pointer and n is zero, this function has no effect.

Otherwise, the effect is implementation-defined: some implementations do nothing, while some implementations deallocate the dynamic member array used as the buffer and begin using the user-supplied character array of size n, whose first element is pointed to by s.

This function is protected virtual, it may only be called through pubsetbuf() or from member functions of a user-defined class derived from std::strstreambuf.

Parameters

s	-	pointer to the first byte in the user-provided buffer
n	-	the number of bytes in the user-provided buffer

Return value

this

Example

Implementation test to check if setbuf() is supported on a dynamic strstream (output obtained with Sun Studio):

Run this code

#include <strstream>
#include <iostream>
 
int main()
{
    char a[100] = {};
    std::strstream str;
    str.rdbuf()->pubsetbuf(a, sizeof a);
    str << "Test string" << std::ends;
    std::cout << "user-provided buffer holds \"" << a << "\"\n";
}

Possible output:

user-provided buffer holds "Test string"

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 66	C++98	the effect of setbuf() was "performs an operation that is defined separately for each class derived from strstreambuf", but there are no classes derived from strstreambuf	the effect is implementation-defined

See also

pubsetbuf	invokes setbuf() (public member function of std::basic_streambuf<CharT,Traits>)
setbuf [virtual]	replaces the buffer with user-defined array, if permitted (virtual protected member function of std::basic_streambuf<CharT,Traits>)
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>)