Re: [PATCH 2/2] ios: Introduce IO stream device for stdin, stdout, stderr.

[Jose E. Marchesi]

Hi Ege!

Super nice stuff!  Thanks to this we will have support for writing poke
filters and much more :)

Before reviewing more in deep, I have a comment:

    +  if (!strcmp (handler, "stdin"))
    +    {
    +      sio->file = stdin;
    +      sio->flags = IOS_F_READ;
    +    }
    +  else if (!strcmp (handler, "stdout"))
    +    {
    +      sio->file = stdout;
    +      sio->flags = IOS_F_WRITE;
    +    }
    +  else if (!strcmp (handler, "stderr"))
    +    {
    +      sio->file = stderr;
    +      sio->flags = IOS_F_WRITE;
    +    }

I always had the idea that the IO spaces 0, 1 and 2 would exist by
default, i.e. ios_init would actually open these streams and make them
available as IOS 0 (for stdin) 1 (for stdout) and 2 (for stderr).

We will of course define variables in the standard library, for the
user's commodity:

defvar stdin = 0;
defvar stdout = 1;
defvar stderr = 2;

A good outcome of this approach is that "stdin", "stdout" and "stderr"
won't be special handlers anymore, i.e. you could open a perfectly
regular file called "stdout" for example.