text: /* ----------------------------------------------------------------------
   * Project:      CMSIS DSP Library
   * Title:        arm_sin_q31.c
   * Description:  Fast sine calculation for Q31 values
   *
   * $Date:        23 April 2021
   * $Revision:    V1.9.0
   *
   * Target Processor: Cortex-M and Cortex-A cores
   * -------------------------------------------------------------------- */
  /*
   * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
   *
   * SPDX-License-Identifier: Apache-2.0
   *
   * Licensed under the Apache License, Version 2.0 (the License); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an AS IS BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include "dsp/fast_math_functions.h"
  #include "arm_common_tables.h"
  
  /**
    @ingroup groupFastMath
   */
  
  /**
    @addtogroup sin
    @{
   */
  
  /**
    @brief         Fast approximation to the trigonometric sine function for Q31 data.
    @param[in]     x  Scaled input value in radians
    @return        sin(x)
  
    The Q31 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*PI).
   */
  
  q31_t arm_sin_q31(
    q31_t x)
  {
    q31_t sinVal;                                  /* Temporary variables for input, output */
    int32_t index;                                 /* Index variable */
    q31_t a, b;                                    /* Two nearest output values */
    q31_t fract;                                   /* Temporary values for fractional values */
  
    if (x < 0)
    { /* convert negative numbers to corresponding positive ones */
      x = (uint32_t)x + 0x80000000;
    }
  
    /* Calculate the nearest index */
    index = (uint32_t)x >> FAST_MATH_Q31_SHIFT;
  
    /* Calculation of fractional value */
    fract = (x - (index << FAST_MATH_Q31_SHIFT)) << 9;
  
    /* Read two nearest values of input value from the sin table */
    a = sinTable_q31[index];
    b = sinTable_q31[index+1];
  
    /* Linear interpolation process */
    sinVal = (q63_t) (0x80000000 - fract) * a >> 32;
    sinVal = (q31_t) ((((q63_t) sinVal << 32) + ((q63_t) fract * b)) >> 32);
  
    /* Return output value */
    return (sinVal << 1);
  }
  
  /**
    @} end of sin group
   */
  