std::strstreambuf::underflow

 

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::strstreambuf

Public member functions

strstreambuf::strstreambuf

strstreambuf::~strstreambuf

strstreambuf::freeze

strstreambuf::str

strstreambuf::pcount

Protected member functions

strstreambuf::underflow

strstreambuf::pbackfail

strstreambuf::overflow

strstreambuf::setbuf

strstreambuf::seekoff

strstreambuf::seekpos

 

protected: virtual streambuf<char>* 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'

See also

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