duk_util_tinyrandom.c File Reference

#include "duk_internal.h"

Go to the source code of this file.

Macros
#define	DUK__UPDATE_RND(rnd)
#define	DUK__RND_BIT(rnd)   ((rnd) >> 31) /* only use the highest bit */

Functions
DUK_INTERNAL duk_uint32_t	duk_util_tinyrandom_get_bits (duk_hthread *thr, duk_small_int_t n)
DUK_INTERNAL duk_double_t	duk_util_tinyrandom_get_double (duk_hthread *thr)

Macro Definition Documentation

DUK__RND_BIT

#define DUK__RND_BIT

(

rnd

)

((rnd) >> 31) /* only use the highest bit */

Definition at line 16 of file duktape-1.5.2/src-separate/duk_util_tinyrandom.c.

Referenced by duk_util_tinyrandom_get_bits(), and duk_util_tinyrandom_get_double().

DUK__UPDATE_RND

#define DUK__UPDATE_RND

(

rnd

)

Value:

        do { \
        (rnd) += ((rnd) * (rnd)) | 0x05; \
        (rnd) = ((rnd) & 0xffffffffU);       /* if duk_uint32_t is exactly 32 bits, this is a NOP */ \
    } while (0)

Definition at line 11 of file duktape-1.5.2/src-separate/duk_util_tinyrandom.c.

#define DUK__UPDATE_RND(rnd) do { \
        (rnd) += ((rnd) * (rnd)) | 0x05; \
        (rnd) = ((rnd) & 0xffffffffU);       /* if duk_uint32_t is exactly 32 bits, this is a NOP */ \
    } while (0)

Referenced by duk_util_tinyrandom_get_bits(), and duk_util_tinyrandom_get_double().

Function Documentation

duk_util_tinyrandom_get_bits()

DUK_INTERNAL duk_uint32_t duk_util_tinyrandom_get_bits	(	duk_hthread *	thr,
		duk_small_int_t	n )

Definition at line 18 of file duktape-1.5.2/src-separate/duk_util_tinyrandom.c.

                                                                                            {
    duk_small_int_t i;
    duk_uint32_t res = 0;
    duk_uint32_t rnd;
 
    rnd = thr->heap->rnd_state;
 
    for (i = 0; i < n; i++) {
        DUK__UPDATE_RND(rnd);
        res <<= 1;
        res += DUK__RND_BIT(rnd);
    }
 
    thr->heap->rnd_state = rnd;
 
    return res;
}

References DUK__RND_BIT, DUK__UPDATE_RND, duk_hthread::heap, and duk_heap::rnd_state.

duk_util_tinyrandom_get_double()

DUK_INTERNAL duk_double_t duk_util_tinyrandom_get_double

(

duk_hthread *

thr

)

Definition at line 36 of file duktape-1.5.2/src-separate/duk_util_tinyrandom.c.

                                                                           {
    duk_double_t t;
    duk_small_int_t n;
    duk_uint32_t rnd;
 
    /*
     *  XXX: could make this a lot faster if we create the double memory
     *  representation directly.  Feasible easily (must be uniform random).
     */
 
    rnd = thr->heap->rnd_state;
 
    n = 53;  /* enough to cover the whole mantissa */
    t = 0.0;
 
    do {
        DUK__UPDATE_RND(rnd);
        t += DUK__RND_BIT(rnd);
        t /= 2.0;
    } while (--n);
 
    thr->heap->rnd_state = rnd;
 
    DUK_ASSERT(t >= (duk_double_t) 0.0);
    DUK_ASSERT(t < (duk_double_t) 1.0);
 
    return t;
}

References DUK__RND_BIT, DUK__UPDATE_RND, DUK_ASSERT, duk_hthread::heap, and duk_heap::rnd_state.