/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date: 16/10/14 6:01p $Revision:  V.1.4.5
*
* Project:      CMSIS DSP Library
* Title:        arm_sin_q15.c
*
* Description:  Fast sine calculation for Q15 values.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
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*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
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*   - Neither the name of ARM LIMITED 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
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* -------------------------------------------------------------------- */

#include "arm_math.h"
#include "arm_common_tables.h"

/**
 * @ingroup groupFastMath
 */

/**
* @addtogroup sin
* @{
*/

/**
 * @brief Fast approximation to the trigonometric sine function for Q15 data.
 * @param[in] x Scaled input value in radians.
 * @return  sin(x).
 *
 * The Q15 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*pi).
 */

q15_t arm_sin_q15(
    q15_t x)
{
    q15_t sinVal;                                  /* Temporary variables for input, output */
    int32_t index;                                 /* Index variables */
    q15_t a, b;                                    /* Four nearest output values */
    q15_t fract;                                   /* Temporary values for fractional values */

    /* Calculate the nearest index */
    index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;

    /* Calculation of fractional value */
    fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;

    /* Read two nearest values of input value from the sin table */
    a = sinTable_q15[index];
    b = sinTable_q15[index + 1];

    /* Linear interpolation process */
    sinVal = (q31_t)(0x8000 - fract) * a >> 16;
    sinVal = (q15_t)((((q31_t)sinVal << 16) + ((q31_t)fract * b)) >> 16);

    return sinVal << 1;
}

/**
 * @} end of sin group
 */
