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/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
// This file contains variants of the random functions in random.c
// that store the state of the RNG in a context, allowing for multiple
// independant RNGs to be used simultaneously.
// The RNG behavior itself is the same.
#include "libs/compiler.h"
#define RANDOM2_INTERNAL
#include "random.h"
#include "libs/memlib.h"
#define A 16807 /* a relatively prime number -- also M div Q */
#define M 2147483647 /* 0xFFFFFFFF / 2 */
#define Q 127773 /* M div A */
#define R 2836 /* M mod A */
RandomContext *
RandomContext_New (void)
{
RandomContext *result = (RandomContext *) HMalloc (sizeof (RandomContext));
result->seed = 12345;
return result;
}
void
RandomContext_Delete (RandomContext *context)
{
HFree ((void *) context);
}
RandomContext *
RandomContext_Copy (const RandomContext *source)
{
RandomContext *result = (RandomContext *) HMalloc (sizeof (RandomContext));
*result = *source;
return result;
}
DWORD
RandomContext_Random (RandomContext *context)
{
context->seed = A * (context->seed % Q) - R * (context->seed / Q);
if (context->seed > M) {
context->seed -= M;
} else if (context->seed == 0)
context->seed = 1;
return context->seed;
}
DWORD
RandomContext_SeedRandom (RandomContext *context, DWORD new_seed)
{
DWORD old_seed;
/* coerce the seed to be in the range 1..M */
if (new_seed == 0) /* 0 becomes 1 */
new_seed = 1;
else if (new_seed > M) /* and less than M */
new_seed -= M;
old_seed = context->seed;
context->seed = new_seed;
return old_seed;
}
DWORD
RandomContext_GetSeed (RandomContext *context)
{
return context->seed;
}
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