module tinymt32;
/**
* @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.
*
* The 3-clause BSD License is applied to this software, see
* LICENSE.txt
*/
uint UINT32_C(T)(T a)
{
    return cast(uint)a;
}

const TINYMT32_MEXP = 127;
const TINYMT32_SH0 = 1;
const TINYMT32_SH1 = 10;
const TINYMT32_SH8 = 8;
const TINYMT32_MASK = UINT32_C(0x7fffffff);
const TINYMT32_MUL = (1.0f / 16777216.0f);


/**
* tinymt32 internal state vector and parameters
*/
struct tinymt32_t {
    uint32_t[4] status;
    uint32_t mat1;
    uint32_t mat2;
    uint32_t tmat;
}


/**
* This function always returns 127
* @param random not used
* @return always 127
*/
static int tinymt32_get_mexp(tinymt32_t * random) {
    return TINYMT32_MEXP;
}

/**
* 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] ^= -(cast(int32_t)(y & 1)) & random.mat1;
    random.status[2] ^= -(cast(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];
    version(LINEARITY_CHECK)
    {
        t1 = random.status[0]
            ^ (random.status[2] >> TINYMT32_SH8);
    }
    else
    {
        t1 = random.status[0]
            + (random.status[2] >> TINYMT32_SH8);
    }
    t0 ^= t1;
    t0 ^= -(cast(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 Conv
    {
        uint32_t u;
        float f;
    }
    Conv conv;

    t0 = random.status[3];
    version(LINEARITY_CHECK)
        t1 = random.status[0]
        ^ (random.status[2] >> TINYMT32_SH8);
    else
        t1 = random.status[0]
        + (random.status[2] >> TINYMT32_SH8);
    t0 ^= t1;
    conv.u = ((t0 ^ (-(cast(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 Conv
    {
        uint32_t u;
        float f;
    }
    Conv conv;

    t0 = random.status[3];
    version(LINEARITY_CHECK)
        t1 = random.status[0]
        ^ (random.status[2] >> TINYMT32_SH8);
    else
        t1 = random.status[0]
        + (random.status[2] >> TINYMT32_SH8);
    t0 ^= t1;
    conv.u = ((t0 ^ (-(cast(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);
}

/**
* @file tinymt32.c
*
* @brief Tiny Mersenne Twister only 127 bit internal state
*
* @author Mutsuo Saito (Hiroshima University)
* @author Makoto Matsumoto (The University of Tokyo)
*
* Copyright (C) 2011 Mutsuo Saito, Makoto Matsumoto,
* Hiroshima University and The University of Tokyo.
* All rights reserved.
*
* The 3-clause BSD License is applied to this software, see
* LICENSE.txt
*/
const MIN_LOOP = 8;
const PRE_LOOP = 8;
alias uint32_t = uint;
alias int32_t = int;

/**
* This function represents a function used in the initialization
* by init_by_array
* @param x 32-bit integer
* @return 32-bit integer
*/
static uint32_t ini_func1(uint32_t x) {
    return (x ^ (x >> 27)) * UINT32_C(1664525);
}

/**
* This function represents a function used in the initialization
* by init_by_array
* @param x 32-bit integer
* @return 32-bit integer
*/
static uint32_t ini_func2(uint32_t x) {
    return (x ^ (x >> 27)) * UINT32_C(1566083941);
}

/**
* This function certificate the period of 2^127-1.
* @param random tinymt state vector.
*/
static void period_certification(tinymt32_t* random) {
    if ((random.status[0] & TINYMT32_MASK) == 0 &&
        random.status[1] == 0 &&
        random.status[2] == 0 &&
        random.status[3] == 0) {
            random.status[0] = 'T';
            random.status[1] = 'I';
            random.status[2] = 'N';
            random.status[3] = 'Y';
        }
}

/**
* This function initializes the internal state array with a 32-bit
* unsigned integer seed.
* @param random tinymt state vector.
* @param seed a 32-bit unsigned integer used as a seed.
*/
void tinymt32_init(tinymt32_t* random, uint32_t seed) {
    random.status[0] = seed;
    random.status[1] = random.mat1;
    random.status[2] = random.mat2;
    random.status[3] = random.tmat;
    for (int i = 1; i < MIN_LOOP; i++) {
        random.status[i & 3] ^= i + UINT32_C(1812433253)
            * (random.status[(i - 1) & 3]
               ^ (random.status[(i - 1) & 3] >> 30));
    }
    period_certification(random);
    for (int i = 0; i < PRE_LOOP; i++) {
        tinymt32_next_state(random);
    }
}

/**
* This function initializes the internal state array,
* with an array of 32-bit unsigned integers used as seeds
* @param random tinymt state vector.
* @param init_key the array of 32-bit integers, used as a seed.
* @param key_length the length of init_key.
*/
void tinymt32_init_by_array(tinymt32_t * random, uint32_t[] init_key, int key_length) {
    const int lag = 1;
    const int mid = 1;
    const int size = 4;
    int i, j;
    int count;
    uint32_t r;
    uint32_t * st = &random.status[0];

    st[0] = 0;
    st[1] = random.mat1;
    st[2] = random.mat2;
    st[3] = random.tmat;
    if (key_length + 1 > MIN_LOOP) {
        count = key_length + 1;
    } else {
        count = MIN_LOOP;
    }
    r = ini_func1(st[0] ^ st[mid % size]
                  ^ st[(size - 1) % size]);
    st[mid % size] += r;
    r += key_length;
    st[(mid + lag) % size] += r;
    st[0] = r;
    count--;
    for (i = 1, j = 0; (j < count) && (j < key_length); j++) {
        r = ini_func1(st[i % size]
                      ^ st[(i + mid) % size]
                      ^ st[(i + size - 1) % size]);
        st[(i + mid) % size] += r;
        r += init_key[j] + i;
        st[(i + mid + lag) % size] += r;
        st[i % size] = r;
        i = (i + 1) % size;
    }
    for (; j < count; j++) {
        r = ini_func1(st[i % size]
                      ^ st[(i + mid) % size]
                      ^ st[(i + size - 1) % size]);
        st[(i + mid) % size] += r;
        r += i;
        st[(i + mid + lag) % size] += r;
        st[i % size] = r;
        i = (i + 1) % size;
    }
    for (j = 0; j < size; j++) {
        r = ini_func2(st[i % size]
                      + st[(i + mid) % size]
                      + st[(i + size - 1) % size]);
        st[(i + mid) % size] ^= r;
        r -= i;
        st[(i + mid + lag) % size] ^= r;
        st[i % size] = r;
        i = (i + 1) % size;
    }
    period_certification(random);
    for (i = 0; i < PRE_LOOP; i++) {
        tinymt32_next_state(random);
    }
}
