isaac64.h

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/*
------------------------------------------------------------------------------
isaac64.h: Definitions for a fast cryptographic random number generator
Bob Jenkins, 1996, Public Domain
 
Modified for modularity by Tom Bartol and Rex Kerr
 
Reference:
http://burtleburtle.net/bob/rand/isaacafa.html
Jenkins, R.J. (1996) ISAAC, in Fast Software Encryption, vol. 1039,
    ed. Gollmann, D.  Spinger-Verlag, Cambridge
 
------------------------------------------------------------------------------
*/
#ifndef ISAAC64_H
#define ISAAC64_H
 
#include <nrnconf.h>
#if defined(HAVE_STDINT_H)
#include <stdint.h>
#endif
 
#define RANDSIZL (4) /* I recommend 8 for crypto, 4 for simulations */
#define RANDSIZ  (1 << RANDSIZL)
#define RANDMAX  (2 * RANDSIZ)
 
typedef unsigned long long ub8;
#if defined(uint32_t)
typedef uint32_t ub4;
#else
typedef unsigned int ub4;
#endif
typedef unsigned short int ub2;
typedef unsigned char ub1;
 
#define DBL32 (2.3283064365386962890625e-10)
#define DBL53 (1.1102230246251565404236316680908203125e-16)
#define DBL64 (5.42101086242752217003726400434970855712890625e-20)
#define MSK53 0x001FFFFFFFFFFFFFLL
 
struct isaac64_state {
    int randcnt;
    ub8 aa;
    ub8 bb;
    ub8 cc;
    ub8 randrsl[RANDSIZ];
    ub8 mm[RANDSIZ];
};
 
 
void isaac64_init(struct isaac64_state* rng, ub4 seed);
 
void isaac64_generate(struct isaac64_state* rng);
 
/*
------------------------------------------------------------------------------
Macros to get individual random numbers
------------------------------------------------------------------------------
*/
 
#define isaac64_uint32(rng)                                                \
    (rng->randcnt > 0 ? (*(((ub4*) (rng->randrsl)) + (rng->randcnt -= 1))) \
                      : (isaac64_generate(rng),                            \
                         rng->randcnt = RANDMAX - 1,                       \
                         *(((ub4*) (rng->randrsl)) + rng->randcnt)))
 
#define isaac64_uint64(rng)                                                         \
    (rng->randcnt > 1 ? (*((ub8*) (((ub4*) (rng->randrsl)) + (rng->randcnt -= 2)))) \
                      : (isaac64_generate(rng),                                     \
                         rng->randcnt = RANDMAX - 2,                                \
                         *((ub8*) (((ub4*) (rng->randrsl)) + rng->randcnt))))
 
#define isaac64_dbl32(rng)                                                           \
    (rng->randcnt > 0 ? (DBL32 * (*(((ub4*) (rng->randrsl)) + (rng->randcnt -= 1)))) \
                      : (isaac64_generate(rng),                                      \
                         rng->randcnt = RANDMAX - 1,                                 \
                         DBL32 * (*(((ub4*) (rng->randrsl)) + rng->randcnt))))
 
#define isaac64_dbl53(rng)                                                               \
    (rng->randcnt > 1                                                                    \
         ? (DBL53 * ((*((ub8*) (((ub4*) (rng->randrsl)) + (rng->randcnt -= 2)))) >> 11)) \
         : (isaac64_generate(rng),                                                       \
            rng->randcnt = RANDMAX - 2,                                                  \
            DBL64 * ((*((ub8*) (((ub4*) (rng->randrsl)) + rng->randcnt))) >> 11)))
 
#define isaac64_dbl64(rng)                                                                    \
    (rng->randcnt > 1 ? (DBL64 * (*((ub8*) (((ub4*) (rng->randrsl)) + (rng->randcnt -= 2))))) \
                      : (isaac64_generate(rng),                                               \
                         rng->randcnt = RANDMAX - 2,                                          \
                         DBL64 * (*((ub8*) (((ub4*) (rng->randrsl)) + rng->randcnt)))))
 
 
#endif /* ISAAC64_H */