Re: [dwm] [patch] simplification to drawtext
On Mon, Jun 02, 2008 at 10:16:34AM +0200, Premysl Hruby wrote: > On (02/06/08 09:56), Enno Gottox Boland wrote: > > To: dynamic window manager > > From: Enno Gottox Boland <[EMAIL PROTECTED]> > > Subject: Re: [dwm] [patch] simplification to drawtext > > Reply-To: dynamic window manager > > List-Id: dynamic window manager > > > > whoops... > > > > memcpy(&buf[MAX(0, len - 3)], "...", MIN(3, len)); > > > > Still, this is not needed, as buf is ALWAYS greater than 3 bytes. So: > > memcpy(&buf[MAX(0, len - 3)], "...", 3); > > is sufficent, this was my thought when I wrote this memcpy variant. Yes, I came to the same conclusion yesterday. Even if len < 3 it doesn't matter, because MAX(0, len - 3) will always evaluate to 0 for len <= 3 and sizeof buf > 3 is a precondition. However memcpy() might be slower than the following replacement: if(len < olen) for(i = len; i >= MAX(0, len - 3); buf[i--] = '.'); memcpy is an additional function call -- the for-solution might not be the fastest because a sane memcpy will attempt to copy 4xlong resp. 1 long in a step for speed reasons, however for the 3 dots this speed hack won't be used anyways. Kind regards, -- Anselm R. Garbe >< http://www.suckless.org/ >< GPG key: 0D73F361
Re: [dwm] [patch] simplification to drawtext
On (02/06/08 09:56), Enno Gottox Boland wrote: > To: dynamic window manager > From: Enno Gottox Boland <[EMAIL PROTECTED]> > Subject: Re: [dwm] [patch] simplification to drawtext > Reply-To: dynamic window manager > List-Id: dynamic window manager > > whoops... > > memcpy(&buf[MAX(0, len - 3)], "...", MIN(3, len)); > Still, this is not needed, as buf is ALWAYS greater than 3 bytes. So: memcpy(&buf[MAX(0, len - 3)], "...", 3); is sufficent, this was my thought when I wrote this memcpy variant. -Ph -- Premysl "Anydot" Hruby, http://www.redrum.cz/
Re: [dwm] [patch] simplification to drawtext
whoops... memcpy(&buf[MAX(0, len - 3)], "...", MIN(3, len)); 2008/6/1, Premysl Hruby <[EMAIL PROTECTED]>: > On (01/06/08 19:30), Enno Gottox Boland wrote: > > To: dynamic window manager > > From: Enno Gottox Boland <[EMAIL PROTECTED]> > > > Subject: Re: [dwm] [patch] simplification to drawtext > > > Reply-To: dynamic window manager > > List-Id: dynamic window manager > > > > > beware that it should be > > > > memcpy(&buf[MAX(0, len - 3)], "...", 4); > > > > not > > > > memcpy(&buf[MAX(0, len - 3)], "...", 3); > > > > otherwise it will overwrite the zero-terminator if len < 3. > > > This is REALLY OK, as that Xlib calls doesn't use zero-terminated > string, but string with length argument! > > > > > > Furthermore it will change the length of the string if len < 3, which > > has no impact on the output, as XDrawString respects len, but it's > > still ugly. > > > > So I still prefer strncpy as the result doing the same with memcopy > > should look like this to work properly: > > memcpy(&buf[MAX(0, len - 3)], "...", MAX(len, 3)); > > > That MAX is baaad, as if len > 4 it will copy some random data after > string "..." which is really bad. > > > > > > I also prefer strncpy over memcpy because we're not copy plain data, > > but strings. > > > No, at that point, we are copying plain data. Not strings[1] > > > > > regards > > Gottox > > > > [1]: meaned as C string == char[] which ends with zero-terminator > > > -- > Premysl "Anydot" Hruby, http://www.redrum.cz/ > > -- http://www.gnuffy.org - Real Community Distro http://www.gnuffy.org/index.php/GnuEm - Gnuffy on Ipaq (Codename Peggy)
