Edit
IABSD.fr/xenocara/lib/pixman/test/utils-prng.h
matthieu
- lib/pixman/test/utils-prng.h
-
/* * 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" /*****************************************************************************/ #ifdef HAVE_GCC_VECTOR_EXTENSIONS 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 HAVE_GCC_VECTOR_EXTENSIONS 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 HAVE_GCC_VECTOR_EXTENSIONS 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 HAVE_GCC_VECTOR_EXTENSIONS 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_00000000 = 4, /* ~25% chance for 0x00000000 clusters */ RANDMEMSET_MORE_FFFFFFFF = 8, /* ~25% chance for 0xFFFFFFFF clusters */ RANDMEMSET_MORE_00_AND_FF = (RANDMEMSET_MORE_00 | RANDMEMSET_MORE_00000000 | RANDMEMSET_MORE_FF | RANDMEMSET_MORE_FFFFFFFF) } 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