On Thu, Nov 10, 2011 at 11:10:34PM -0600, Abel Abraham Camarillo Ojeda wrote:
> On Thu, Nov 10, 2011 at 9:26 PM, Michael W. Bombardieri <m...@ii.net> wrote:
> > Hi tech,
> >
> > I have a diff for the patch(1) tool which copies
> > one included in NetBSD two years ago...
> >
> > Source: NetBSD src/usr.bin/patch/inp.c revision 1.23
> > Purpose: Don't bother mmap'ing an empty file
> >
> > Comments/OK?
> >
> > - Michael
> >
> >
> > Index: inp.c
> > ===================================================================
> > RCS file: /usr/src/cvs/src/usr.bin/patch/inp.c,v
> > retrieving revision 1.35
> > diff -u -r1.35 inp.c
> > --- inp.c ?? ?? ?? 27 Oct 2009 23:59:41 -0000 ?? ?? ??1.35
> > +++ inp.c ?? ?? ?? 11 Nov 2011 03:12:10 -0000
> > @@ -243,12 +243,16 @@
> > ?? ?? ?? ??if ((ifd = open(filename, O_RDONLY)) < 0)
> > ?? ?? ?? ?? ?? ?? ?? ??pfatal("can't open file %s", filename);
> >
> > - ?? ?? ?? i_womp = mmap(NULL, i_size, PROT_READ, MAP_PRIVATE, ifd, 0);
> > - ?? ?? ?? if (i_womp == MAP_FAILED) {
> > - ?? ?? ?? ?? ?? ?? ?? perror("mmap failed");
> > + ?? ?? ?? if (i_size == 0)
> > ?? ?? ?? ?? ?? ?? ?? ??i_womp = NULL;
> > - ?? ?? ?? ?? ?? ?? ?? close(ifd);
> > - ?? ?? ?? ?? ?? ?? ?? return false;
> > + ?? ?? ?? else {
> > + ?? ?? ?? ?? ?? ?? ?? i_womp = mmap(NULL, i_size, PROT_READ, MAP_PRIVATE,
> > ifd, 0);
> > + ?? ?? ?? ?? ?? ?? ?? if (i_womp == MAP_FAILED) {
> > + ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? perror("mmap failed");
> > + ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? i_womp = NULL;
> > + ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? close(ifd);
> > + ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? return false;
> > + ?? ?? ?? ?? ?? ?? ?? }
> > ?? ?? ?? ??}
> >
> > ?? ?? ?? ??close(ifd);
> >
> >
>
> if "if (i_size == 0) {...}" returns, there's still need for an else block?...
>
> Just asking...
Thanks for your comment.
>From what I can see, plan_a() should return true in any case when we get
an empty file, so it should be fairly safe to return directly here as
you mentioned.
I have tested the following diff on i386; it appears to produce the same
behaviour as my previous diff. If this works for you, I'm happy to go
with the simpler diff rather than blindly following the NetBSD code.
- Michael
Index: inp.c
===================================================================
RCS file: /usr/src/cvs/src/usr.bin/patch/inp.c,v
retrieving revision 1.35
diff -u -r1.35 inp.c
--- inp.c 27 Oct 2009 23:59:41 -0000 1.35
+++ inp.c 11 Nov 2011 05:27:41 -0000
@@ -243,6 +243,8 @@
if ((ifd = open(filename, O_RDONLY)) < 0)
pfatal("can't open file %s", filename);
+ if (i_size == 0)
+ return true;
i_womp = mmap(NULL, i_size, PROT_READ, MAP_PRIVATE, ifd, 0);
if (i_womp == MAP_FAILED) {
perror("mmap failed");
