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/************************************************************
* lib/stdlib/lib_rand.c
*
* Copyright (C) 2007, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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. Neither the name NuttX 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.
*
************************************************************/
/************************************************************
* Compilation Switches
************************************************************/
/************************************************************
* Included Files
************************************************************/
#include <sys/types.h>
#include <stdlib.h>
/************************************************************
* Definitions
************************************************************/
#ifndef CONFIG_LIB_RAND_ORDER
#define CONFIG_LIB_RAND_ORDER 1
#endif
/* Values needed by the random number generator */
#define RND1_CONSTK 470001
#define RND1_CONSTP 999563
#define RND2_CONSTK1 366528
#define RND2_CONSTK2 508531
#define RND2_CONSTP 998917
#define RND3_CONSTK1 360137
#define RND3_CONSTK2 519815
#define RND3_CONSTK3 616087
#define RND3_CONSTP 997783
#if CONFIG_LIB_RAND_ORDER == 1
# define RND_CONSTP RND1_CONSTP
#elif CONFIG_LIB_RAND_ORDER == 2
# define RND_CONSTP RND2_CONSTP
#else
# define RND_CONSTP RND3_CONSTP
#endif
/************************************************************
* Private Type Declarations
************************************************************/
/************************************************************
* Private Function Prototypes
************************************************************/
static unsigned int nrand(unsigned int nLimit);
static double_t frand1(void);
#if (CONFIG_LIB_RAND_ORDER > 1)
static double_t frand2(void);
#if (CONFIG_LIB_RAND_ORDER > 2)
static double_t frand3(void);
#endif
#endif
/**********************************************************
* Global Constant Data
**********************************************************/
/************************************************************
* Global Variables
************************************************************/
/**********************************************************
* Private Constant Data
**********************************************************/
/************************************************************
* Private Variables
************************************************************/
static unsigned long g_nRandInt1;
#if (CONFIG_LIB_RAND_ORDER > 1)
static unsigned long g_nRandInt2;
#if (CONFIG_LIB_RAND_ORDER > 2)
static unsigned long g_nRandInt3;
#endif
#endif
/************************************************************
* Private Functions
************************************************************/
static unsigned int nrand(unsigned int nLimit)
{
unsigned long nResult;
double_t fRatio;
/* Loop to be sure a legal random number is generated */
do {
/* Get a random integer in the requested range */
#if (CONFIG_LIB_RAND_ORDER == 1)
fRatio = frand1();
#elif (CONFIG_LIB_RAND_ORDER == 2)
fRatio = frand2();
#else
fRatio = frand3();
#endif
/* Then, produce the return-able value */
nResult = (unsigned long)(((double_t)nLimit) * fRatio);
} while (nResult >= (unsigned long)nLimit);
return (unsigned int)nResult;
} /* end nrand */
static double_t frand1(void)
{
unsigned long nRandInt;
/* First order congruential generator */
nRandInt = (RND1_CONSTK * g_nRandInt1) % RND1_CONSTP;
g_nRandInt1 = nRandInt;
/* Construct an floating point value in the range from 0.0 up to 1.0 */
return ((double_t)nRandInt) / ((double_t)RND_CONSTP);
} /* end frand */
#if (CONFIG_LIB_RAND_ORDER > 1)
static double_t frand2(void)
{
unsigned long nRandInt;
/* Second order congruential generator */
nRandInt = (RND2_CONSTK1 * g_nRandInt1 + RND2_CONSTK2 * g_nRandInt2) %
RND2_CONSTP;
g_nRandInt2 = g_nRandInt1;
g_nRandInt1 = nRandInt;
/* Construct an floating point value in the range from 0.0 up to 1.0 */
return ((double_t)nRandInt) / ((double_t)RND_CONSTP);
} /* end frand */
#if (CONFIG_LIB_RAND_ORDER > 2)
static double_t frand3(void)
{
unsigned long nRandInt;
/* Third order congruential generator */
nRandInt = (RND3_CONSTK1 * g_nRandInt1 + RND3_CONSTK2 * g_nRandInt2 +
RND3_CONSTK2 * g_nRandInt3) % RND3_CONSTP;
g_nRandInt3 = g_nRandInt2;
g_nRandInt2 = g_nRandInt1;
g_nRandInt1 = nRandInt;
/* Construct an floating point value in the range from 0.0 up to 1.0 */
return ((double_t)nRandInt) / ((double_t)RND_CONSTP);
} /* end frand */
#endif
#endif
/************************************************************
* Public Functions
************************************************************/
/************************************************************
* Function: srand, rand
************************************************************/
void srand(unsigned int seed)
{
g_nRandInt1 = seed;
#if (CONFIG_LIB_RAND_ORDER > 1)
g_nRandInt2 = seed;
(void)frand1();
#if (CONFIG_LIB_RAND_ORDER > 2)
g_nRandInt3 = seed;
(void)frand2();
#endif
#endif
} /* end srand */
int rand(void)
{
return (int)nrand(32768);
} /* end rand */
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