From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:6f8:1178:4:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.72 #1 (Red Hat Linux)) id 1OPV40-00036N-HP for barebox@lists.infradead.org; Fri, 18 Jun 2010 06:28:29 +0000 Date: Fri, 18 Jun 2010 08:28:26 +0200 From: 'Sascha Hauer' Message-ID: <20100618062826.GP20799@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: barebox-bounces@lists.infradead.org Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH 04/11] include support for a simple pseudo number generator To: Andy Pont Cc: barebox@lists.infradead.org On Thu, Jun 17, 2010 at 02:26:58PM +0100, Andy Pont wrote: > Sascha Hauer wrote... > > > +#define RAND_MAX 32767 > > + > > +/* return a pseudo-random integer in the range [0, RAND_MAX] */ > > +unsigned int rand(void); > > *Snip* > > > +unsigned int rand(void) > > +{ > > + random_seed = random_seed * 1103515245 + 12345; > > + return (random_seed / 65536) % 32768; > > +} > > The return value on this function seems wrong as it will always return a > value between 0 and 32767 irrespective of what RAND_MAX is set to which > doesn't agree with the comment on the function prototype. Well the way the rand function is implemented it is not suitable for RAND_MAX > 32767. Ok, changed it for the attached patch. I originally thought there would be discussion about the pros and cons of random ethernet addresses, but about not this patch ;) Sascha commit dcd5248b7dceb918c5c5d9b045893421ddc6c112 Author: Sascha Hauer Date: Fri Jun 11 14:10:36 2010 +0200 include support for a simple pseudo number generator Signed-off-by: Sascha Hauer diff --git a/include/net.h b/include/net.h index 8db83d8..709e76c 100644 --- a/include/net.h +++ b/include/net.h @@ -16,6 +16,7 @@ #include #include #include +#include #include /* for nton* / ntoh* stuff */ diff --git a/include/stdlib.h b/include/stdlib.h new file mode 100644 index 0000000..dc72013 --- /dev/null +++ b/include/stdlib.h @@ -0,0 +1,16 @@ +#ifndef __STDLIB_H +#define __STDLIB_H + +#define RAND_MAX 32767 + +/* return a pseudo-random integer in the range [0, RAND_MAX] */ +unsigned int rand(void); + +/* set the seed for rand () */ +void srand(unsigned int seed); + +/* fill a buffer with pseudo-random data */ +void get_random_bytes(char *buf, int len); + + +#endif /* __STDLIB_H */ diff --git a/lib/Makefile b/lib/Makefile index b072fb6..4a33aaa 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -28,6 +28,7 @@ obj-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o obj-y += glob.o obj-y += notifier.o obj-y += copy_file.o +obj-y += random.o obj-y += lzo/ obj-$(CONFIG_LZO_DECOMPRESS) += decompress_unlzo.o obj-$(CONFIG_PROCESS_ESCAPE_SEQUENCE) += process_escape_sequence.o diff --git a/lib/random.c b/lib/random.c new file mode 100644 index 0000000..352d6bf --- /dev/null +++ b/lib/random.c @@ -0,0 +1,26 @@ +#include +#include + +static unsigned int random_seed; + +#if RAND_MAX > 32767 +#error this rand implementation is for RAND_MAX < 32678 only. +#endif + +unsigned int rand(void) +{ + random_seed = random_seed * 1103515245 + 12345; + return (random_seed / 65536) % (RAND_MAX + 1); +} + +void srand(unsigned int seed) +{ + random_seed = seed; +} + +void get_random_bytes(char *buf, int len) +{ + while (len--) + *buf++ = rand() % 256; +} + -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox