[GRASS5] segment lib speed patch

[Markus Neteler]

Hi,

I got some useful offlist comments. Find attached the modified
patch along with the suggested HAVE_LSEEK condition.
The '\n' were old stuff, I have taken them out.

Please have a look again.

Markus

On Mon, Jun 27, 2005 at 02:04:40PM -0700, Brad Douglas wrote:
> On Mon, 2005-06-27 at 17:03 +0200, Markus Neteler wrote:
> > Hi,
> > 
> > to speed up the creation of segments in lib/segment/format.c,
> > a colleague from ITC-irst proposes the attached patch.
> > I used it locally for quite a while without having problems.
> > 
> > I would like to hear you opinion:
> > - any objections to include it (removing the old version)?
> > - should it be conditionalized for GNU/Linux only or
> >   anything else (means: modifying the current condition ORIG)?
> 
> It's a basic POSIX function, so you're safe.  If you want to get
> technical about it, then you could surround it with #ifdef HAVE_LSEEK...
> generated by autoconf, which may arguably be better than #ifdef ORIG...
> 
> PS -
> You don't need the '\n' in G_warning(), unless you intend on a double
> carriage return.
> 
> 
> -- 
> Brad Douglas <rez at touchofmadness.com>
> 

-- 
Markus Neteler     <neteler itc it>       http://mpa.itc.it
ITC-irst -  Centro per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
Via Sommarive, 18        -       38050 Povo (Trento), Italy
-------------- next part --------------
Index: format.c
===================================================================
RCS file: /grassrepository/grass6/lib/segment/format.c,v
retrieving revision 2.0
diff -u -r2.0 format.c
--- format.c	9 Nov 2004 13:09:30 -0000	2.0
+++ format.c	28 Jun 2005 08:11:07 -0000
@@ -3,6 +3,7 @@
 #include <errno.h>
 #include <unistd.h>
 #include "segment.h"
+#include "config.h"
 
 static int _segment_format (int,int,int,int,int,int,int);
 static int write_int(int,int);
@@ -60,14 +61,14 @@
     if (nrows <= 0 || ncols <= 0 || len <= 0 || srows <= 0 || scols <= 0)
     {
 	G_warning (
-	    "segement_format(fd,%d,%d,%d,%d,%d): illegal value(s)\n",
+	    "segment_format(fd,%d,%d,%d,%d,%d): illegal value(s)",
 	    nrows, ncols, srows, scols, len);
 	return -3;
     }
 
     if (lseek (fd, 0L, 0) == (off_t)-1)
     {
-	G_warning ("Segment_format: %s\n",strerror(errno));
+	G_warning ("Segment_format: %s",strerror(errno));
 	return -1;
     }
 
@@ -107,12 +108,13 @@
     x = n;
 
     if((bytes_wrote = write (fd, &x, sizeof(int)) == sizeof(int) ) < 0)
-        G_warning("%s\n",strerror(errno));
+        G_warning("%s",strerror(errno));
     return bytes_wrote;
 }
 
 static int zero_fill(int fd, long nbytes)
 {
+#ifndef HAVE_LSEEK
     char buf[10240];
     register char *b;
     register int n;
@@ -127,10 +129,25 @@
     {
 	n = nbytes > sizeof(buf) ? sizeof(buf) : nbytes ;
 	if(write (fd, buf, n) != n) {
-            G_warning("%s\n",strerror(errno));
+            G_warning("%s",strerror(errno));
 	    return -1;
         }
 	nbytes -= n;
     }
     return 1;
+#else
+    char buf[10];
+
+    buf[0]=0x0;
+    G_debug(3,"Using new segmentation code...");
+    if ( lseek(fd,nbytes-1,SEEK_SET) < 0 ) { 
+            G_warning("%s",strerror(errno));
+	    return -1;
+    }
+    if(write (fd,buf, 1) != 1) {
+            G_warning("%s",strerror(errno));
+	    return -1;
+    }
+    return 1;
+#endif
 }