44 lines
869 B
C
44 lines
869 B
C
/** @file
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*
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* Random number generation
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*
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <stdlib.h>
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#include <ipxe/timer.h>
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static int32_t rnd_seed = 0;
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/**
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* Seed the pseudo-random number generator
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*
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* @v seed Seed value
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*/
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void srandom ( unsigned int seed ) {
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rnd_seed = seed;
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if ( ! rnd_seed )
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rnd_seed = 4; /* Chosen by fair dice roll */
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}
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/**
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* Generate a pseudo-random number between 0 and 2147483647L or 2147483562?
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*
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* @ret rand Pseudo-random number
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*/
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long int random ( void ) {
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int32_t q;
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if ( ! rnd_seed ) /* Initialize linear congruential generator */
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srandom ( currticks() );
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/* simplified version of the LCG given in Bruce Schneier's
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"Applied Cryptography" */
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q = ( rnd_seed / 53668 );
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rnd_seed = ( 40014 * ( rnd_seed - 53668 * q ) - 12211 * q );
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if ( rnd_seed < 0 )
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rnd_seed += 2147483563L;
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return rnd_seed;
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}
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