Re: [ros-kernel] New proposed fix: for getchar

[KJK::Hyperion <no...@li...>]

At 10.16 03/05/2002, you wrote:
> >not sure. Stdio FILE objects are supposed, AFAIK, to maintain their
> >internal buffer, exactly to avoid the overhead of a system call to
> >read a single character
>I think you're right (btw wine's msvcrt functions call readconsole 1 char 
>at a time, so porting may be a bad idea after all).

argh. Not only a system call, but a potential RPC call at each character read!

[...]
>BUT _read (in msvcrt\io\read.c) doesn't want to return until it's read the 
>size requested (filebuf asks for 4096), even if enter is pressed. So it 
>seems that's the problem. If we wanted buffered reading to limit system 
>call overhead, then _read must return if enter is pressed and the file in 
>use is stdin. What do you think about this?

This behavior of read() is non-standard (I don't know if it's done for 
compatibility with Microsoft's CRT). A call to read() reading less than 
expected is still considered successful:

"[...]
If a read() is interrupted by a signal after it has successfully read some 
data, it will return the number of bytes read.
[...]"