Help on Research Project

Tux-O-Matic · 09-28-2006, 02:34 PM

I'm doing a research project on the random number theory, and I'm attempting to emulate srand. However, the file is encrypted. Does anyone have the source code, the writer of srand, or someone that may know the ins and outs of srand?
And if anyone tells me to look at the man page, I already have: no author is listed.

Tinkster · 09-29-2006, 02:07 AM

What do you mean by "the file is encrypted"?

Cheers,
Tink

Tux-O-Matic · 09-29-2006, 03:48 PM

When I used vim srand (when I got to the folder), I saw some garbage like this:
@@@@@@@[^@@@@@@@@@@@@[^[^@@@@@@

haertig · 09-29-2006, 04:02 PM

Quote:

Originally Posted by Tux-O-Matic

When I used vim srand...

Well, you'll always see garbage like that if you try to edit a binary file.

I wasn't aware of a commandline program named "srand" (it's a C library function) but the context of your description makes me think you found one. And then tried to edit it.

Tux-O-Matic · 09-29-2006, 04:21 PM

Thanks, but could someone please answer my original question please?

Tinkster · 09-29-2006, 05:13 PM

If you told what that file you're talking about is, maybe?

Cheers,
Tink

haertig · 09-29-2006, 05:59 PM

Quote:

Originally Posted by Tux-O-Matic

Thanks, but could someone please answer my original question please?

Unfortunately, I really can't tell what your original question was. I believe your inital assumption about an encrypted file is incorrect. I think you must be vi-ing some binary file and misinterpretting the non-ASCII characters as encryption. But I can't really tell that for sure, your description was not detailed enough. I'm just guessing. You need to give us more information.

If you're looking for the source code for the C library call srand(), I'd start off with something like the commands below to attempt to find it. I don't know if this will find the code for you, but at least it should give you some idea of where to look. You will need to have your kernel sources installed.

Code:

# cd /usr/include
# find . -type f -print | xargs fgrep srand
# cd /usr/src/linux
# find . -type f -name *.c -print | xargs fgrep srand
# find . -type f -name *.h -print | xargs fgrep srand

You can skip the -name parameter to find if you have just installed your kernel sources but not compiled. After a compile you'll have lots of object files in there and you certainly don't need to be grepping through those. Or, you can run a "make clean" to get rid of the object files before running the find.

Tinkster · 09-29-2006, 09:59 PM

Quote:

Originally Posted by haertig

Code:

# cd /usr/include
# find . -type f -print | xargs fgrep srand
# cd /usr/src/linux
# find . -type f -name *.c -print | xargs fgrep srand
# find . -type f -name *.h -print | xargs fgrep srand

Code:

find -type f -name "*srand*.[ch]

No need for two runs, or pipe and xargs. Think lazy ;}

Cheers,
Tink

haertig · 09-29-2006, 10:32 PM

Quote:

Originally Posted by Tinkster

find -type f -name "*srand*.[ch]

I was trying to locate a sourcefile that contains the text "srand", not a file with srand in it's filename. Who knows what the actual sourcefile name is.

Tinkster · 10-02-2006, 12:09 PM

Of course - had a blonde moment. but you can still get away with one run,
and without xargs :}

Code:

find -type f -name "*.[ch]" -exec grep srand {} \;

Cheers,
Tink

haertig · 10-02-2006, 12:39 PM

Code:

find -type f -name "*.[ch]" -exec grep srand {} \;

Gotcha! I typically use that "*.[ch]" type of specification myself, but didn't in my example, for some unexplained reason.

As far as -exec grep srand {} \;, my poor little brain recognizes | xargs grep srand much more readily. Habit and old age I guess! (Note: I still use -print with find too. Not really required these days, but it used to be. At least on older System V, SunOS, etc. Another archiac habit of mine.)

Tux-O-Matic · 10-02-2006, 01:59 PM

Could someone please get me what I want. I don't mean to be hasty

. If it's illegal to see the source code, it's okay to just tell me.

ethics · 10-02-2006, 02:44 PM

Ahhhh you want the source code, you won't get that by opening the binary with a text editor (as stated) you can search for the sourcefile (as stated).

Why ask a question when you dont want an answer?

Go to the authors website (been a longtime since i saw a developer without one) see what license it is under, see if it's there?

I honestly can't believe how rude some people are

haertig · 10-02-2006, 04:14 PM

Quote:

Originally Posted by Tux-O-Matic

Could someone please get me what I want.

OK!

From .../glibc-2.5/stdlib/srand48.c

Code:

#include <stdlib.h>
void
srand48 (seedval)
     long seedval;
{
  (void) __srand48_r (seedval, &__libc_drand48_data);
}

If that's not enough, more from .../glibc-2.5/stdlib/srand48_r.c

Code:

#include <stdlib.h>
#include <limits.h>

int
__srand48_r (seedval, buffer)
     long int seedval;
     struct drand48_data *buffer;
{
  /* The standards say we only have 32 bits.  */
  if (sizeof (long int) > 4)
    seedval &= 0xffffffffl;

  buffer->__x[2] = seedval >> 16;
  buffer->__x[1] = seedval & 0xffffl;
  buffer->__x[0] = 0x330e;

  buffer->__a = 0x5deece66dull;
  buffer->__c = 0xb;
  buffer->__init = 1;

  return 0;
}
weak_alias (__srand48_r, srand48_r)

If you want the whole enchilada, I'd recommend

Code:

$ wget ftp://ftp.gnu.org/gnu/glibc/glibc-2.5.tar.gz
$ tar xzvf glibc-2.5.tar.gz
$ cd glibc-2.5
$ find . -name "*srand*" -print

... and continue on from there ...

Tux-O-Matic · 10-02-2006, 04:19 PM

Okay...Thanks.