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/* Cesar project {{{
 *
 * THIS FILE is Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji
 * Nishimura.  Please see below for more information.
 *
 * Include modification by Spidcom for constant time calls.
 *
 * }}} */
/**
 * \file    lib/src/mt19937ar.c
 * \brief   Random Number Generator implemented by MT19937.
 * \ingroup lib
 *
 * Please do not update formating or indent so that diffing is easy.
 */

/* 
   A C-program for MT19937, with initialization improved 2002/1/26.
   Coded by Takuji Nishimura and Makoto Matsumoto.

   Before using, initialize the state by using init_genrand(seed)  
   or init_by_array(init_key, key_length).

   Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
   All rights reserved.                          

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.

     2. 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.

     3. The names of its contributors may not 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.


   Any feedback is very welcome.
   http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
   email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
*/
#include "common/std.h"
#include "lib/rnd.h"

/* Do not generate N words at one time in order to limit maximum latency. */
#define LIB_MT_BURST 0

/* Period parameters */  
#define N LIB_MT_N
#define M 397
#define MATRIX_A 0x9908b0dfUL   /* constant vector a */
#define UPPER_MASK 0x80000000UL /* most significant w-r bits */
#define LOWER_MASK 0x7fffffffUL /* least significant r bits */

/* Use context instead of global variables. */
#define mt (ctx->state)
#define mti (ctx->state_index)

/**
 * Initialise a random number generator context.
 * \param  ctx  the rnd context to initialise.
 * \param  seed  32 bit random seed.
 */
void
lib_rnd_init (lib_rnd_t *ctx, u32 seed)
{
    dbg_assert (ctx);
    mt[0]= seed & 0xffffffffUL;
    for (mti=1; mti<N; mti++) {
        mt[mti] = 
	    (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti); 
        /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
        /* In the previous versions, MSBs of the seed affect   */
        /* only MSBs of the array mt[].                        */
        /* 2002/01/09 modified by Makoto Matsumoto             */
        mt[mti] &= 0xffffffffUL;
        /* for >32 bit machines */
    }
}

/**
 * Initialise a random number generator context using an array in order to
 * use a greater initialisation space.
 * \param  ctx  the rnd context to initialise.
 * \param  init_key  the array.
 * \param  key_length  the array length.
 */
void
lib_rnd_init_by_array (lib_rnd_t *ctx, const u32 init_key[], int key_length)
{
    int i, j, k;
    dbg_assert (ctx);
    dbg_assert (init_key);
    dbg_assert (key_length > 0);
    lib_rnd_init(ctx, 19650218UL);
    i=1; j=0;
    k = (N>key_length ? N : key_length);
    for (; k; k--) {
        mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525UL))
          + init_key[j] + j; /* non linear */
        mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
        i++; j++;
        if (i>=N) { mt[0] = mt[N-1]; i=1; }
        if (j>=key_length) j=0;
    }
    for (k=N-1; k; k--) {
        mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941UL))
          - i; /* non linear */
        mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
        i++;
        if (i>=N) { mt[0] = mt[N-1]; i=1; }
    }

    mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */ 
}

/**
 * Generates a random number on [0,0xffffffff]-interval.
 * \param  ctx  the rnd context.
 * \return the random number.
 */
u32
lib_rnd32 (lib_rnd_t *ctx)
{
    unsigned long y;
    static const unsigned long mag01[2]={0x0UL, MATRIX_A};
    /* mag01[x] = x * MATRIX_A  for x=0,1 */

    dbg_assert (ctx);

#if LIB_MT_BURST
    if (mti >= N) { /* generate N words at one time */
        int kk;

        if (mti == N+1)   /* if init_genrand() has not been called, */
            init_genrand(5489UL); /* a default initial seed is used */

        for (kk=0;kk<N-M;kk++) {
            y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
            mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1UL];
        }
        for (;kk<N-1;kk++) {
            y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
            mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
        }
        y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
        mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1UL];

        mti = 0;
    }
#else
    if (mti >= N)
        mti = 0;
    if (mti < N - M)
    {
        y = (mt[mti]&UPPER_MASK)|(mt[mti+1]&LOWER_MASK);
        mt[mti] = mt[mti+M] ^ (y >> 1) ^ mag01[y & 0x1UL];
    }
    else if (mti < N - 1)
    {
        y = (mt[mti]&UPPER_MASK)|(mt[mti+1]&LOWER_MASK);
        mt[mti] = mt[mti+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
    }
    else
    {
        y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
        mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1UL];
    }
#endif
  
    y = mt[mti++];

    /* Tempering */
    y ^= (y >> 11);
    y ^= (y << 7) & 0x9d2c5680UL;
    y ^= (y << 15) & 0xefc60000UL;
    y ^= (y >> 18);

    return y;
}

/* End of MT19937 code. */
#include "config/rnd/buffer/optimise.h"

/**
 * Generates a random number on [0,bound-1]-interval.
 * \param  ctx  the rnd context.
 * \param  bound  upper bound.
 * \return the random number.
 */
uint
lib_rnd_uniform (lib_rnd_t *ctx, uint bound)
{
    uint up;
    uint n;
    dbg_assert (ctx);
    dbg_assert (bound != 0);
    /* This is not optimal if bound is a power of two, but it is harder to
     * divide 2^32. */
    up = 0xffffffff - (0xffffffff % bound);
    do {
        n = lib_rnd32 (ctx);
    } while (n > up);
    return n % bound;
}

/**
 * Fill a buffer with random data.
 * \param  ctx  the rnd context
 * \param  buf  buffer to fill
 * \param  buf_size  buffer size
 *
 * The buffer need not to be word aligned.
 *
 * This will generate a reproducible buffer over big and little endian
 * machines.
 */
void
lib_rnd_buffer (lib_rnd_t *ctx, u8 *buf, uint buf_size)
{
    dbg_assert (ctx);
    dbg_assert_ptr (buf);
#if CONFIG_RND_BUFFER_OPTIMISE && !DEFS_BIG_ENDIAN
    /* Not needed yet. */
    dbg_assert_print (0, "not implemented");
#else /* !(CONFIG_RND_BUFFER_OPTIMISE && !DEFS_BIG_ENDIAN) */
    u32 r = 0;
    uint rb = 0;
    u8 *p = buf;
    u8 *pend = buf + buf_size;
    while (p != pend)
    {
        if (rb == 0)
        {
            r = lib_rnd32 (ctx);
            rb = 4;
        }
        *p++ = r & 0xff;
        r >>= 8;
        rb--;
    }
#endif /* !(CONFIG_RND_BUFFER_OPTIMISE && !DEFS_BIG_ENDIAN) */
}