Path: utzoo!mnetor!uunet!husc6!bloom-beacon!mcgill-vision!mouse
From: mouse@mcgill-vision.UUCP (der Mouse)
Newsgroups: comp.unix.questions
Subject: Re: Determining system memory
Message-ID: <1050@mcgill-vision.UUCP>
Date: 12 Apr 88 21:20:29 GMT
References: <248@lxn.UUCP>
Organization: McGill University, Montreal
Lines: 48

In article <248@lxn.UUCP>, chris@lxn.UUCP (Christopher D. Orr) writes:
> I have been trying to find a nice, clean way to determine system
> memory under SYS V 2.2.

> Solution 2:  [This is faster than Solution 1, but still slow]:
[program]

Well, you could speed it up by doing a more intelligent search
technique than linear search:

/****** UNTESTED (no SV system to test it on) ******/

#include <stdio.h>
#include <fcntl.h>

extern int errno;
static char buf;

main()
{
 long int l;
 long int m;
 long int h;
 int fd;

 fd = open("/dev/mem",O_RDONLY);
 /* check for fd<0 omitted for brevity */
 l = 1;
 h = 2;
 while (1)
  { lseek(fd,h,L_SET); /* or whatever the SV way is */
    if (read(fd,&buf,1) != 1) break;
    l = h;
    h *= 2;
  }
 while (h-l > 1)
  { m = (h + l) / 2;
    lseek(fd,m,L_SET); /* or whatever */
    if (read(fd,&buf,1) == 1) l = m; else h = m;
  }
 printf("%ld bytes accessible via /dev/mem\n",h);
 exit(0);
}

					der Mouse

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