/**
 * @file tinymt32.h
 *
 * @brief Tiny Mersenne Twister only 127 bit internal state
 *
 * @author Mutsuo Saito (Hiroshima University)
 * @author Makoto Matsumoto (University of Tokyo)
 *
 ******************************************************************************
 * Copyright (c) 2011 Mutsuo Saito, Makoto Matsumoto, Hiroshima
 * University and The University of Tokyo. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *     * Neither the name of the Hiroshima University nor the names of
 *       its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written
 *       permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 ******************************************************************************
 */

#ifndef TINYMT32_H
#define TINYMT32_H


#include <stdint.h>
#include <inttypes.h>

#define TINYMT32_MEXP 127
#define TINYMT32_SH0 1
#define TINYMT32_SH1 10
#define TINYMT32_SH8 8
#define TINYMT32_MASK UINT32_C(0x7fffffff)
#define TINYMT32_MUL (1.0f / 16777216.0f)

#if defined(__cplusplus)
extern "C" {
#endif

/**
 * tinymt32 internal state vector and parameters
 */
struct TINYMT32_T {
    uint32_t status[4];
    uint32_t mat1;
    uint32_t mat2;
    uint32_t tmat;
};

typedef struct TINYMT32_T tinymt32_t;

void tinymt32_init(tinymt32_t * random, uint32_t seed);
void tinymt32_init_by_array(tinymt32_t * random, uint32_t init_key[],
                            int key_length);

#if defined(__GNUC__)
/**
 * This function always returns 127
 * @param random not used
 * @return always 127
 */
static int tinymt32_get_mexp(
    tinymt32_t * random  __attribute__((unused))) {
    return TINYMT32_MEXP;
}
#else
static int tinymt32_get_mexp(tinymt32_t * random) {
    return TINYMT32_MEXP;
}
#endif

/**
 * This function changes internal state of tinymt32.
 * Users should not call this function directly.
 * @param random tinymt internal status
 */
static void tinymt32_next_state(tinymt32_t * random) {
    uint32_t x;
    uint32_t y;

    y = random->status[3];
    x = (random->status[0] & TINYMT32_MASK)
        ^ random->status[1]
        ^ random->status[2];
    x ^= (x << TINYMT32_SH0);
    y ^= (y >> TINYMT32_SH0) ^ x;
    random->status[0] = random->status[1];
    random->status[1] = random->status[2];
    random->status[2] = x ^ (y << TINYMT32_SH1);
    random->status[3] = y;
    random->status[1] ^= -((int32_t)(y & 1)) & random->mat1;
    random->status[2] ^= -((int32_t)(y & 1)) & random->mat2;
}

/**
 * This function outputs 32-bit unsigned integer from internal state.
 * Users should not call this function directly.
 * @param random tinymt internal status
 * @return 32-bit unsigned pseudorandom number
 */
static uint32_t tinymt32_temper(tinymt32_t * random) {
    uint32_t t0, t1;
    t0 = random->status[3];
#if defined(LINEARITY_CHECK)
    t1 = random->status[0]
        ^ (random->status[2] >> TINYMT32_SH8);
#else
    t1 = random->status[0]
        + (random->status[2] >> TINYMT32_SH8);
#endif
    t0 ^= t1;
    t0 ^= -((int32_t)(t1 & 1)) & random->tmat;
    return t0;
}

/**
 * This function outputs floating point number from internal state.
 * Users should not call this function directly.
 * @param random tinymt internal status
 * @return floating point number r (1.0 <= r < 2.0)
 */
static float tinymt32_temper_conv(tinymt32_t * random) {
    uint32_t t0, t1;
    union {
        uint32_t u;
        float f;
    } conv;

    t0 = random->status[3];
#if defined(LINEARITY_CHECK)
    t1 = random->status[0]
        ^ (random->status[2] >> TINYMT32_SH8);
#else
    t1 = random->status[0]
        + (random->status[2] >> TINYMT32_SH8);
#endif
    t0 ^= t1;
    conv.u = ((t0 ^ (-((int32_t)(t1 & 1)) & random->tmat)) >> 9)
              | UINT32_C(0x3f800000);
    return conv.f;
}

/**
 * This function outputs floating point number from internal state.
 * Users should not call this function directly.
 * @param random tinymt internal status
 * @return floating point number r (1.0 < r < 2.0)
 */
static float tinymt32_temper_conv_open(tinymt32_t * random) {
    uint32_t t0, t1;
    union {
        uint32_t u;
        float f;
    } conv;

    t0 = random->status[3];
#if defined(LINEARITY_CHECK)
    t1 = random->status[0]
        ^ (random->status[2] >> TINYMT32_SH8);
#else
    t1 = random->status[0]
        + (random->status[2] >> TINYMT32_SH8);
#endif
    t0 ^= t1;
    conv.u = ((t0 ^ (-((int32_t)(t1 & 1)) & random->tmat)) >> 9)
              | UINT32_C(0x3f800001);
    return conv.f;
}

/**
 * This function outputs 32-bit unsigned integer from internal state.
 * @param random tinymt internal status
 * @return 32-bit unsigned integer r (0 <= r < 2^32)
 */
static uint32_t tinymt32_generate_uint32(tinymt32_t * random) {
    tinymt32_next_state(random);
    return tinymt32_temper(random);
}

/**
 * This function outputs floating point number from internal state.
 * This function is implemented using multiplying by (1 / 2^24).
 * floating point multiplication is faster than using union trick in
 * my Intel CPU.
 * @param random tinymt internal status
 * @return floating point number r (0.0 <= r < 1.0)
 */
static float tinymt32_generate_float(tinymt32_t * random) {
    tinymt32_next_state(random);
    return (tinymt32_temper(random) >> 8) * TINYMT32_MUL;
}

/**
 * This function outputs floating point number from internal state.
 * This function is implemented using union trick.
 * @param random tinymt internal status
 * @return floating point number r (1.0 <= r < 2.0)
 */
static float tinymt32_generate_float12(tinymt32_t * random) {
    tinymt32_next_state(random);
    return tinymt32_temper_conv(random);
}

/**
 * This function outputs floating point number from internal state.
 * This function is implemented using union trick.
 * @param random tinymt internal status
 * @return floating point number r (0.0 <= r < 1.0)
 */
static float tinymt32_generate_float01(tinymt32_t * random) {
    tinymt32_next_state(random);
    return tinymt32_temper_conv(random) - 1.0f;
}

/**
 * This function outputs floating point number from internal state.
 * This function may return 1.0 and never returns 0.0.
 * @param random tinymt internal status
 * @return floating point number r (0.0 < r <= 1.0)
 */
static float tinymt32_generate_floatOC(tinymt32_t * random) {
    tinymt32_next_state(random);
    return 1.0f - tinymt32_generate_float(random);
}

/**
 * This function outputs floating point number from internal state.
 * This function returns neither 0.0 nor 1.0.
 * @param random tinymt internal status
 * @return floating point number r (0.0 < r < 1.0)
 */
static float tinymt32_generate_floatOO(tinymt32_t * random) {
    tinymt32_next_state(random);
    return tinymt32_temper_conv_open(random) - 1.0f;
}

/**
 * This function outputs double precision floating point number from
 * internal state. The returned value has 32-bit precision.
 * In other words, this function makes one double precision floating point
 * number from one 32-bit unsigned integer.
 * @param random tinymt internal status
 * @return floating point number r (0.0 <= r < 1.0)
 */
static double tinymt32_generate_32double(tinymt32_t * random) {
    tinymt32_next_state(random);
    return tinymt32_temper(random) * (1.0 / 4294967296.0);
}

#if defined(__cplusplus)
}
#endif

#endif

