[Bochs-developers] [PATCH] faster bximage

[tal b. <tal-ba@NewMail.Net>]

  bximage-seek.patch

this little patch brings a significant speed improvement
to
the bximage utility. when bximage creates a disk image,
it writes
a lot of zeros, as much zeros as the size of the image
file should be.
this takes quite a while for large images (at least in
my win98/cygwin box).
a faster way to create the image file is to seek to its
end and write a
single byte.
to see the speed improvement, create a 100mb image with
the old bximge.
then apply this patch and do the same.

to apply the path, cd to bochs root directory (for
example: cd bochs-1.4), and type:
  patch -p1 < bximage-seek.patch
  make bximage

diff was made against:
 $Id: bximage.c,v 1.6 2001/12/08 17:46:02 bdenney Exp
$
Prereq: 1.6

*** bochs-1.4/misc/bximage.c Sat Dec  8 19:46:02 2001

--- bochs-1.4.work/misc/bximage.c Fri May 17 22:08:20
2002
*************** int make_image (int sec, char *filename)

*** 207,231 ****
      perror (buffer);
  #endif
      fatal ("ERROR: Could not write disk image");
    }
!   // clear the buffer
!   for (i=0; i<512; i++)
!     buffer[i] = 0;
!   // write it however many times
    printf ("\nWriting: [");
!   for (i=0; i<sec; i++) {
!     n = (unsigned int) fwrite (buffer, 512, 1, fp);

!     if (n != 1) {
!       printf ("\nWrite failed with %d sectors written\n",
i);
!       fclose (fp);
!       fatal ("ERROR: The disk image is not complete!");

!     }
!     if ((i%2048) == 0) {
!       printf (".");
!       fflush (stdout);
!     }
    }
    printf ("] Done.\n");
    fclose (fp);
    return 0;
  }
--- 207,239 ----
      perror (buffer);
  #endif
      fatal ("ERROR: Could not write disk image");
    }
!
    printf ("\nWriting: [");
!
!   /*
!    * seek to sec*512-1 and write a signle character.

!    * can't just do: fseek(fp, 512*sec-1, SEEK_SET)

!    * because 512*sec may be too large for signed int.

!    */
!   while (sec > 0)
!   {
!     /* temp <-- min(sec, 4194303)
!      * 4194303 is (int)(0x7FFFFFFF/512)
!      */
!     int temp = ((sec < 4194303) ? sec : 4194303);
!     fseek(fp, 512*temp, SEEK_CUR);
!     sec -= temp;
    }
+
+   fseek(fp, -1, SEEK_CUR);
+   if (fputc('\0', fp) == EOF)
+   {
+     fclose (fp);
+     fatal ("ERROR: The disk image is not complete!");

+   }
+
    printf ("] Done.\n");
    fclose (fp);
    return 0;
  }


_________________________________________
Free web based e-mail with Pop access at http://www.newmail.net