1 /** @file 2 * 3 * Random number generation 4 * 5 */ 6 7 FILE_LICENCE ( GPL2_OR_LATER ); 8 9 #include <stdlib.h> 10 #include <gpxe/timer.h> 11 12 static int32_t rnd_seed = 0; 13 14 /** 15 * Seed the pseudo-random number generator 16 * 17 * @v seed Seed value 18 */ 19 void srandom ( unsigned int seed ) { 20 rnd_seed = seed; 21 } 22 23 /** 24 * Generate a pseudo-random number between 0 and 2147483647L or 2147483562? 25 * 26 * @ret rand Pseudo-random number 27 */ 28 long int random ( void ) { 29 int32_t q; 30 31 if ( ! rnd_seed ) /* Initialize linear congruential generator */ 32 srandom ( currticks() ); 33 34 /* simplified version of the LCG given in Bruce Schneier's 35 "Applied Cryptography" */ 36 q = ( rnd_seed / 53668 ); 37 rnd_seed = ( 40014 * ( rnd_seed - 53668 * q ) - 12211 * q ); 38 if ( rnd_seed < 0 ) 39 rnd_seed += 2147483563L; 40 return rnd_seed; 41 } 42
