i_rand.h

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/*
------------------------------------------------------------------------------
rand.h: definitions for a random number generator
MODIFIED:
	960327: Creation (addition of randinit, really)
	970719: use context, not global variables, for internal state
	980324: renamed seed to flag
	980605: recommend RANDSIZL=4 for noncryptography.
------------------------------------------------------------------------------
*/
#ifndef STANDARD
#include "i_std.h"
#endif

#ifndef RAND
#define RAND
#define RANDSIZL   (8)  /* I recommend 8 for crypto, 4 for simulations */
#define RANDSIZ    (1<<RANDSIZL)

/* context of random number generator */
struct randctx
{
	ub4 randcnt;
	ub4 randrsl[RANDSIZ];
	ub4 randmem[RANDSIZ];
	ub4 randa;
	ub4 randb;
	ub4 randc;
};
typedef struct randctx randctx;

/*
------------------------------------------------------------------------------
 If (flag==TRUE), then use the contents of randrsl[0..RANDSIZ-1] as the seed.
------------------------------------------------------------------------------
*/

void randinit(randctx *ctx, word flag);
void isaac(randctx *ctx);

/*
------------------------------------------------------------------------------
 Call rand(/o_ randctx *r _o/) to retrieve a single 32-bit random value
------------------------------------------------------------------------------
*/
#define isaac_rand(r) \
	(!(r)->randcnt-- ? \
		(isaac(r), (r)->randcnt=RANDSIZ-1, \
			(r)->randrsl[(r)->randcnt]) : \
			(r)->randrsl[(r)->randcnt])

#endif  /* RAND */