[fstream]how to set buffer

[Acer]

platform: freeBSD(gcc) Win32(MinGW)
I try follows:

char cbuf[buf_size];
ifstream fin;
fin.rdbuf()->pubsetbuf(cbuf,buf_size);

but I found it do not influence the I/O times when I increased or
decreased the buf_size

[Tom Widmer]

Acer wrote:

platform: freeBSD(gcc) Win32(MinGW)
I try follows:

char cbuf[buf_size];
ifstream fin;
fin.rdbuf()->pubsetbuf(cbuf,buf_size);
The behaviour of that is implementation defined, but I think it does
what you want on your compiler and platform. Make sure you set the
buffer before you open the file.
but I found it do not influence the I/O times when I increased or
decreased the buf_size

That implies that your I/O times are not being influenced by buffering.

Tom

[Sirish Kumar]

"Acer" <Ya******@gmail.com> wrote in message
news:11**********************@v46g2000cwv.googlegr oups.com...

platform: freeBSD(gcc) Win32(MinGW)
I try follows:

char cbuf[buf_size];
ifstream fin;
fin.rdbuf()->pubsetbuf(cbuf,buf_size);

but I found it do not influence the I/O times when I increased or
decreased the buf_size