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/*
* Copyright © 2012 Siarhei Siamashka <siarhei.siamashka@gmail.com>
*
* Based on the public domain implementation of small noncryptographic PRNG
* authored by Bob Jenkins: http://burtleburtle.net/bob/rand/smallprng.html
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#ifndef __UTILS_PRNG_H__
#define __UTILS_PRNG_H__
/*
* This file provides a fast SIMD-optimized noncryptographic PRNG (pseudorandom
* number generator), with the output good enough to pass "Big Crush" tests
* from TestU01 (http://en.wikipedia.org/wiki/TestU01).
*
* SIMD code uses http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html
* which is a GCC specific extension. There is also a slower alternative
* code path, which should work with any C compiler.
*
* The "prng_t" structure keeps the internal state of the random number
* generator. It is possible to have multiple instances of the random number
* generator active at the same time, in this case each of them needs to have
* its own "prng_t". All the functions take a pointer to "prng_t"
* as the first argument.
*
* Functions:
*
* ----------------------------------------------------------------------------
* void prng_srand_r (prng_t *prng, uint32_t seed);
*
* Initialize the pseudorandom number generator. The sequence of preudorandom
* numbers is deterministic and only depends on "seed". Any two generators
* initialized with the same seed will produce exactly the same sequence.
*
* ----------------------------------------------------------------------------
* uint32_t prng_rand_r (prng_t *prng);
*
* Generate a single uniformly distributed 32-bit pseudorandom value.
*
* ----------------------------------------------------------------------------
* void prng_randmemset_r (prng_t *prng,
* void *buffer,
* size_t size,
* prng_randmemset_flags_t flags);
*
* Fills the memory buffer "buffer" with "size" bytes of pseudorandom data.
* The "flags" argument may be used to tweak some statistics properties:
* RANDMEMSET_MORE_00 - set ~25% of bytes to 0x00
* RANDMEMSET_MORE_FF - set ~25% of bytes to 0xFF
* The flags can be combined. This allows a bit better simulation of typical
* pixel data, which normally contains a lot of fully transparent or fully
* opaque pixels.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "pixman-private.h"
/*****************************************************************************/
#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7))
#define GCC_VECTOR_EXTENSIONS_SUPPORTED
typedef uint32_t uint32x4 __attribute__ ((vector_size(16)));
typedef uint8_t uint8x16 __attribute__ ((vector_size(16)));
#endif
typedef struct
{
uint32_t a, b, c, d;
} smallprng_t;
typedef struct
{
#ifdef GCC_VECTOR_EXTENSIONS_SUPPORTED
uint32x4 a, b, c, d;
#else
smallprng_t p1, p2, p3, p4;
#endif
smallprng_t p0;
} prng_t;
typedef union
{
uint8_t b[16];
uint32_t w[4];
#ifdef GCC_VECTOR_EXTENSIONS_SUPPORTED
uint8x16 vb;
uint32x4 vw;
#endif
} prng_rand_128_data_t;
/*****************************************************************************/
static force_inline uint32_t
smallprng_rand_r (smallprng_t *x)
{
uint32_t e = x->a - ((x->b << 27) + (x->b >> (32 - 27)));
x->a = x->b ^ ((x->c << 17) ^ (x->c >> (32 - 17)));
x->b = x->c + x->d;
x->c = x->d + e;
x->d = e + x->a;
return x->d;
}
/* Generate 4 bytes (32-bits) of random data */
static force_inline uint32_t
prng_rand_r (prng_t *x)
{
return smallprng_rand_r (&x->p0);
}
/* Generate 16 bytes (128-bits) of random data */
static force_inline void
prng_rand_128_r (prng_t *x, prng_rand_128_data_t *data)
{
#ifdef GCC_VECTOR_EXTENSIONS_SUPPORTED
uint32x4 e = x->a - ((x->b << 27) + (x->b >> (32 - 27)));
x->a = x->b ^ ((x->c << 17) ^ (x->c >> (32 - 17)));
x->b = x->c + x->d;
x->c = x->d + e;
x->d = e + x->a;
data->vw = x->d;
#else
data->w[0] = smallprng_rand_r (&x->p1);
data->w[1] = smallprng_rand_r (&x->p2);
data->w[2] = smallprng_rand_r (&x->p3);
data->w[3] = smallprng_rand_r (&x->p4);
#endif
}
typedef enum
{
RANDMEMSET_MORE_00 = 1, /* ~25% chance for 0x00 bytes */
RANDMEMSET_MORE_FF = 2, /* ~25% chance for 0xFF bytes */
RANDMEMSET_MORE_00_AND_FF = (RANDMEMSET_MORE_00 | RANDMEMSET_MORE_FF)
} prng_randmemset_flags_t;
/* Set the 32-bit seed for PRNG */
void prng_srand_r (prng_t *prng, uint32_t seed);
/* Fill memory buffer with random data */
void prng_randmemset_r (prng_t *prng,
void *buffer,
size_t size,
prng_randmemset_flags_t flags);
#endif
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