Ifs is a null pointer andn is zero, the filebuf becomesunbuffered for output, meaningpbase() andpptr() are null and any output is immediately sent to file.

Otherwise, a call tosetbuf() replaces the internal buffer (the controlled character sequence) with the user-supplied character array whose first element is pointed to bys and allows thisstd::basic_filebuf object to use up ton bytes in that array for buffering.

This function is protected virtual, it may only be called throughpubsetbuf() or from member functions of a user-defined class derived fromstd::basic_filebuf.

[edit]Parameters

[edit]Return value

this

[edit]Notes

The conditions when this function may be used and the way in which the provided buffer is used is implementation-defined.

• GCC 4.6 libstdc++

setbuf() may only be called when thestd::basic_filebuf is not associated with a file (has no effect otherwise). With a user-provided buffer, reading from file readsn-1 bytes at a time.

• Clang++3.0 libc++

setbuf() may be called after opening the file, but before any I/O (may crash otherwise). With a user-provided buffer, reading from file reads largest multiples of 4096 that fit in the buffer.

• Visual Studio 2010

setbuf() may be called at any time, even after some I/O took place. Current contents of the buffer, if any, are lost.

The standard does not define any behavior for this function except thatsetbuf(0,0) called before any I/O has taken place is required to set unbuffered output.

[edit]Example

#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';}

356010

[edit]Defect reports

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

[edit]See also

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