text: /* ----------------------------------------------------------------------
   * Project:      CMSIS DSP Library
   * Title:        arm_fir_interpolate_init_q15.c
   * Description:  Q15 FIR interpolator initialization function
   *
   * $Date:        27. January 2017
   * $Revision:    V.1.5.1
   *
   * Target Processor: Cortex-M cores
   * -------------------------------------------------------------------- */
  /*
   * Copyright (C) 2010-2017 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 "arm_math.h"
  
  /**
   * @ingroup groupFilters
   */
  
  /**
   * @addtogroup FIR_Interpolate
   * @{
   */
  
  /**
   * @brief  Initialization function for the Q15 FIR interpolator.
   * @param[in,out] *S        points to an instance of the Q15 FIR interpolator structure.
   * @param[in]     L         upsample factor.
   * @param[in]     numTaps   number of filter coefficients in the filter.
   * @param[in]     *pCoeffs  points to the filter coefficient buffer.
   * @param[in]     *pState   points to the state buffer.
   * @param[in]     blockSize number of input samples to process per call.
   * @return        The function returns ARM_MATH_SUCCESS if initialization was successful or ARM_MATH_LENGTH_ERROR if
   * the filter length <code>numTaps</code> is not a multiple of the interpolation factor <code>L</code>.
   *
   * <b>Description:</b>
   * \par
   * <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:
   * <pre>
   *    {b[numTaps-1], b[numTaps-2], b[numTaps-2], ..., b[1], b[0]}
   * </pre>
   * The length of the filter <code>numTaps</code> must be a multiple of the interpolation factor <code>L</code>.
   * \par
   * <code>pState</code> points to the array of state variables.
   * <code>pState</code> is of length <code>(numTaps/L)+blockSize-1</code> words
   * where <code>blockSize</code> is the number of input samples processed by each call to <code>arm_fir_interpolate_q15()</code>.
   */
  
  arm_status arm_fir_interpolate_init_q15(
    arm_fir_interpolate_instance_q15 * S,
    uint8_t L,
    uint16_t numTaps,
    q15_t * pCoeffs,
    q15_t * pState,
    uint32_t blockSize)
  {
    arm_status status;
  
    /* The filter length must be a multiple of the interpolation factor */
    if ((numTaps % L) != 0u)
    {
      /* Set status as ARM_MATH_LENGTH_ERROR */
      status = ARM_MATH_LENGTH_ERROR;
    }
    else
    {
  
      /* Assign coefficient pointer */
      S->pCoeffs = pCoeffs;
  
      /* Assign Interpolation factor */
      S->L = L;
  
      /* Assign polyPhaseLength */
      S->phaseLength = numTaps / L;
  
      /* Clear state buffer and size of buffer is always phaseLength + blockSize - 1 */
      memset(pState, 0,
             (blockSize + ((uint32_t) S->phaseLength - 1u)) * sizeof(q15_t));
  
      /* Assign state pointer */
      S->pState = pState;
  
      status = ARM_MATH_SUCCESS;
    }
  
    return (status);
  
  }
  
   /**
    * @} end of FIR_Interpolate group
    */
  