Re: /dev/clipboard pasting with small read() buffer

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

On Aug 16 14:11, Thomas Wolff wrote:
> Hi Corinna,
> 
> On 16.08.2012 11:33, Corinna Vinschen wrote:
> >Hi Thomas,
> >
> >thanks for the patch.   I have a few minor nits:
> >
> >On Aug 14 22:56, Thomas Wolff wrote:
> >>--- sav/fhandler_clipboard.cc	2012-07-08 02:36:47.000000000 +0200
> >>+++ ./fhandler_clipboard.cc	2012-08-14 18:25:14.903255600 +0200
> >>...
> >See (*) below.
> >
> >>...
> >>+	  char * _ptr = (char *) ptr;
> >>+	  size_t _len = len;
> >I would prefer to have local variable names here which don't just
> >differ by a leading underscore.  It's a bit confusing.  What about,
> >say, tmp_ptr/tmp_len, or use_ptr/use_len or something like that?
> tmp_OK
> 
> >>+	  char cprabuf [8 + 1];	/* need this length for surrogates */
> >>+	  if (len < 8)
> >>+	    {
> >>+	      _ptr = cprabuf;
> >>+	      _len = 8;
> >>+	    }
> >8?  Why 8?  The size appears to be rather artificial.  The code should
> >use MB_CUR_MAX instead.
> MB_CUR_MAX does not work because its value is 1 at this point

So what about MB_LEN_MAX then?  There's no problem using a multiplier,
but a symbolic constant is always better than a numerical constant.

> >>+	      /* If using read-ahead buffer, copy to class read-ahead buffer
> >>+	         and deliver first byte. */
> >>+	      if (_ptr == cprabuf)
> >>+		{
> >>+		  puts_readahead (cprabuf, ret);
> >>+		  * (char *) ptr = get_readahead ();
> >>+		  ret = 1;
> >(*) Ok, that works, but wouldn't it be more efficient to do that in
> >a tiny loop along the lines of
> >
> >		  int x;
> >		  ret = 0;
> >                   while (ret < len && (x = get_readahead ()) >= 0)
> >		    ptr++ = x;
> >		    ret++;
> >
> >?
> I can add it if you prefer; I just didn't think it's worth the
> effort and concerning efficiency, after that prior trial-and-error
> count-down-loop...

Yeah, that's a valid point.  But maybe we shouldn't make it slower
than necessary?  If you have a good idea how to avoid the other
loop, don't hesitate to submit a patch.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat