lib_math.c
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/*
*********************************************************************************************************
* uC/LIB
* CUSTOM LIBRARY MODULES
*
* (c) Copyright 2004-2012; Micrium, Inc.; Weston, FL
*
* All rights reserved. Protected by international copyright laws.
*
* uC/LIB is provided in source form to registered licensees ONLY. It is
* illegal to distribute this source code to any third party unless you receive
* written permission by an authorized Micrium representative. Knowledge of
* the source code may NOT be used to develop a similar product.
*
* Please help us continue to provide the Embedded community with the finest
* software available. Your honesty is greatly appreciated.
*
* You can contact us at www.micrium.com.
*********************************************************************************************************
*/
/*
*********************************************************************************************************
*
* MATHEMATIC OPERATIONS
*
* Filename : lib_math.c
* Version : V1.37.01
* Programmer(s) : SR
* ITJ
*********************************************************************************************************
* Note(s) : (1) NO compiler-supplied standard library functions are used in library or product software.
*
* (a) ALL standard library functions are implemented in the custom library modules :
*
* (1) \<Custom Library Directory>\lib_*.*
*
* (2) \<Custom Library Directory>\Ports\<cpu>\<compiler>\lib*_a.*
*
* where
* <Custom Library Directory> directory path for custom library software
* <cpu> directory name for specific processor (CPU)
* <compiler> directory name for specific compiler
*
* (b) Product-specific library functions are implemented in individual products.
*
*********************************************************************************************************
* Notice(s) : (1) The Institute of Electrical and Electronics Engineers and The Open Group, have given
* us permission to reprint portions of their documentation. Portions of this text are
* reprinted and reproduced in electronic form from the IEEE Std 1003.1, 2004 Edition,
* Standard for Information Technology -- Portable Operating System Interface (POSIX),
* The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute
* of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
* discrepancy between these versions and the original IEEE and The Open Group Standard,
* the original IEEE and The Open Group Standard is the referee document. The original
* Standard can be obtained online at http://www.opengroup.org/unix/online.html.
*********************************************************************************************************
*/
/*
*********************************************************************************************************
* INCLUDE FILES
*********************************************************************************************************
*/
#define MICRIUM_SOURCE
#define LIB_MATH_MODULE
#include <lib_math.h>
/*$PAGE*/
/*
*********************************************************************************************************
* LOCAL DEFINES
*********************************************************************************************************
*/
/*
*********************************************************************************************************
* LOCAL CONSTANTS
*********************************************************************************************************
*/
/*
*********************************************************************************************************
* LOCAL DATA TYPES
*********************************************************************************************************
*/
/*
*********************************************************************************************************
* LOCAL TABLES
*********************************************************************************************************
*/
/*
*********************************************************************************************************
* LOCAL GLOBAL VARIABLES
*********************************************************************************************************
*/
RAND_NBR Math_RandSeedCur; /* Cur rand nbr seed. */
/*
*********************************************************************************************************
* LOCAL FUNCTION PROTOTYPES
*********************************************************************************************************
*/
/*
*********************************************************************************************************
* LOCAL CONFIGURATION ERRORS
*********************************************************************************************************
*/
/*$PAGE*/
/*
*********************************************************************************************************
* Math_Init()
*
* Description : (1) Initialize Mathematic Module :
*
* (a) Initialize random number seed value
*
*
* Argument(s) : none.
*
* Return(s) : none.
*
* Caller(s) : Application.
*
* Note(s) : (2) IEEE Std 1003.1, 2004 Edition, Section 'rand() : DESCRIPTION' states that "if rand()
* is called before any calls to srand() are made, the same sequence shall be generated
* as when srand() is first called with a seed value of 1".
*********************************************************************************************************
*/
void Math_Init (void)
{
Math_RandSetSeed((RAND_NBR)RAND_SEED_INIT_VAL); /* See Note #2. */
}
/*$PAGE*/
/*
*********************************************************************************************************
* Math_RandSetSeed()
*
* Description : Set the current pseudo-random number generator seed.
*
* Argument(s) : seed Initial (or current) value to set for the pseudo-random number sequence.
*
* Return(s) : none.
*
* Caller(s) : Application.
*
* Note(s) : (1) IEEE Std 1003.1, 2004 Edition, Section 'rand() : DESCRIPTION' states that "srand()
* ... uses the argument as a seed for a new sequence of pseudo-random numbers to be
* returned by subsequent calls to rand()".
*
* (2) 'Math_RandSeedCur' MUST always be accessed exclusively in critical sections.
*
* See also 'Math_Rand() Note #1b'.
*********************************************************************************************************
*/
void Math_RandSetSeed (RAND_NBR seed)
{
CPU_SR_ALLOC();
CPU_CRITICAL_ENTER();
Math_RandSeedCur = seed;
CPU_CRITICAL_EXIT();
}
/*$PAGE*/
/*
*********************************************************************************************************
* Math_Rand()
*
* Description : Calculate the next pseudo-random number.
*
* Argument(s) : none.
*
* Return(s) : Next pseudo-random number in the sequence after 'Math_RandSeedCur'.
*
* Caller(s) : Application.
*
* Note(s) : (1) (a) The pseudo-random number generator is implemented as a Linear Congruential
* Generator (LCG).
*
* (b) The pseudo-random number generated is in the range [0, RAND_LCG_PARAM_M].
*
* See also 'Math_RandSeed() Note #1'.
*
* (2) (a) IEEE Std 1003.1, 2004 Edition, Section 'rand() : DESCRIPTION' states that "rand()
* ... need not be reentrant ... [and] is not required to be thread-safe".
*
* (b) However, in order to implement Math_Rand() as re-entrant; 'Math_RandSeedCur' MUST
* always be accessed & updated exclusively in critical sections.
*
* See also 'Math_RandSeed() Note #2'.
*********************************************************************************************************
*/
RAND_NBR Math_Rand (void)
{
RAND_NBR seed;
RAND_NBR rand_nbr;
CPU_SR_ALLOC();
CPU_CRITICAL_ENTER();
seed = Math_RandSeedCur;
rand_nbr = Math_RandSeed(seed);
Math_RandSeedCur = rand_nbr;
CPU_CRITICAL_EXIT();
return (rand_nbr);
}
/*$PAGE*/
/*
*********************************************************************************************************
* Math_RandSeed()
*
* Description : Calculate the next pseudo-random number.
*
* Argument(s) : seed Initial (or current) value for the pseudo-random number sequence.
*
* Return(s) : Next pseudo-random number in the sequence after 'seed'.
*
* Caller(s) : Math_Rand(),
* Application.
*
* Note(s) : (1) (a) BSD/ANSI-C implements rand() as a Linear Congruential Generator (LCG) :
*
* (A) random_number = [(a * random_number ) + b] modulo m
* n + 1 n
*
* where
* (1) (a) random_number Next random number to generate
* n+1
* (b) random_number Previous random number generated
* n
*
* (2) a = RAND_LCG_PARAM_A LCG multiplier
* (3) b = RAND_LCG_PARAM_B LCG incrementor
* (4) m = RAND_LCG_PARAM_M + 1 LCG modulus
*
* (b) The pseudo-random number generated is in the range [0, RAND_LCG_PARAM_M].
*
See also 'lib_math.h RANDOM NUMBER DEFINES Note #1b'.
*
* (2) (a) IEEE Std 1003.1, 2004 Edition, Section 'rand() : DESCRIPTION' states that "rand()
* ... need not be reentrant ... [and] is not required to be thread-safe".
*
* (b) However, Math_RandSeed() is re-entrant since it calculates the next random number
* using ONLY local variables.
*********************************************************************************************************
*/
RAND_NBR Math_RandSeed (RAND_NBR seed)
{
RAND_NBR rand_nbr;
rand_nbr = (((RAND_NBR)RAND_LCG_PARAM_A * seed) + (RAND_NBR)RAND_LCG_PARAM_B) % ((RAND_NBR)RAND_LCG_PARAM_M + 1u);
return (rand_nbr);
}