ref: 710b205e19d68d14516c76c86f3d27e83e8a4827
parent: aed66866cc63b01f8d66e1f381ca7a26c514887d
author: menno <menno>
date: Wed Aug 14 06:55:03 EDT 2002
Better random function for PNS
--- a/libfaad/pns.c
+++ b/libfaad/pns.c
@@ -16,7 +16,7 @@
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
**
-** $Id: pns.c,v 1.7 2002/06/13 11:03:27 menno Exp $
+** $Id: pns.c,v 1.8 2002/08/14 10:55:03 menno Exp $
**/
#include "common.h"
@@ -40,14 +40,30 @@
*/
+static const unsigned char Parity [256] = { // parity+ 0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
+ 1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
+ 1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
+ 0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
+ 1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
+ 0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
+ 0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
+ 1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0
+};
-static INLINE int32_t random2()
+static unsigned int __r1 = 1;
+static unsigned int __r2 = 1;
+
+static INLINE uint32_t random2()
{- static int32_t state = 1;
+ uint32_t t1, t2, t3, t4;
- state = (1664525L * state) + 1013904223L; /* Numerical recipes */
+ t3 = t1 = __r1; t4 = t2 = __r2; // Parity calculation is done via table lookup, this is also available
+ t1 &= 0xF5; t2 >>= 25; // on CPUs without parity, can be implemented in C and avoid unpredictable
+ t1 = Parity [t1]; t2 &= 0x63; // jumps and slow rotate through the carry flag operations.
+ t1 <<= 31; t2 = Parity [t2];
- return state;
+ return (__r1 = (t3 >> 1) | t1 ) ^ (__r2 = (t4 + t4) | t2 );
}
/* The function gen_rand_vector(addr, size) generates a vector of length