/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_fir_sparse_f32.c
 * Description:  Floating-point sparse FIR filter processing function
 *
 * $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/filtering_functions.h"

/**
  @ingroup groupFilters
 */

/**
  @defgroup FIR_Sparse Finite Impulse Response (FIR) Sparse Filters

  This group of functions implements sparse FIR filters.
  Sparse FIR filters are equivalent to standard FIR filters except that most of the coefficients are equal to zero.
  Sparse filters are used for simulating reflections in communications and audio applications.

  There are separate functions for Q7, Q15, Q31, and floating-point data types.
  The functions operate on blocks  of input and output data and each call to the function processes
  <code>blockSize</code> samples through the filter.  <code>pSrc</code> and
  <code>pDst</code> points to input and output arrays respectively containing <code>blockSize</code> values.

  @par           Algorithm
                   The sparse filter instant structure contains an array of tap indices <code>pTapDelay</code> which specifies the locations of the non-zero coefficients.
                   This is in addition to the coefficient array <code>b</code>.
                   The implementation essentially skips the multiplications by zero and leads to an efficient realization.
  <pre>
      y[n] = b[0] * x[n-pTapDelay[0]] + b[1] * x[n-pTapDelay[1]] + b[2] * x[n-pTapDelay[2]] + ...+ b[numTaps-1] * x[n-pTapDelay[numTaps-1]]
  </pre>
  @par
                   \image html FIRSparse.gif "Sparse FIR filter.  b[n] represents the filter coefficients"
  @par
                   <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>;
                   <code>pTapDelay</code> points to an array of nonzero indices and is also of size <code>numTaps</code>;
                   <code>pState</code> points to a state array of size <code>maxDelay + blockSize</code>, where
                   <code>maxDelay</code> is the largest offset value that is ever used in the <code>pTapDelay</code> array.
                   Some of the processing functions also require temporary working buffers.

  @par           Instance Structure
                   The coefficients and state variables for a filter are stored together in an instance data structure.
                   A separate instance structure must be defined for each filter.
                   Coefficient and offset arrays may be shared among several instances while state variable arrays cannot be shared.
                   There are separate instance structure declarations for each of the 4 supported data types.

  @par           Initialization Functions
                   There is also an associated initialization function for each data type.
                   The initialization function performs the following operations:
                   - Sets the values of the internal structure fields.
                   - Zeros out the values in the state buffer.
                   To do this manually without calling the init function, assign the follow subfields of the instance structure:
                   numTaps, pCoeffs, pTapDelay, maxDelay, stateIndex, pState. Also set all of the values in pState to zero.
  @par
                   Use of the initialization function is optional.
                   However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
                   To place an instance structure into a const data section, the instance structure must be manually initialized.
                   Set the values in the state buffer to zeros before static initialization.
                   The code below statically initializes each of the 4 different data type filter instance structures
  <pre>
      arm_fir_sparse_instance_f32 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
      arm_fir_sparse_instance_q31 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
      arm_fir_sparse_instance_q15 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
      arm_fir_sparse_instance_q7 S =  {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
  </pre>

  @par           Fixed-Point Behavior
                   Care must be taken when using the fixed-point versions of the sparse FIR filter functions.
                   In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
                   Refer to the function specific documentation below for usage guidelines.
 */

/**
  @addtogroup FIR_Sparse
  @{
 */

/**
  @brief         Processing function for the floating-point sparse FIR filter.
  @param[in]     S           points to an instance of the floating-point sparse FIR structure
  @param[in]     pSrc        points to the block of input data
  @param[out]    pDst        points to the block of output data
  @param[in]     pScratchIn  points to a temporary buffer of size blockSize
  @param[in]     blockSize   number of input samples to process
  @return        none
 */

void arm_fir_sparse_f32(
        arm_fir_sparse_instance_f32 * S,
  const float32_t * pSrc,
        float32_t * pDst,
        float32_t * pScratchIn,
        uint32_t blockSize)
{
        float32_t *pState = S->pState;                 /* State pointer */
  const float32_t *pCoeffs = S->pCoeffs;               /* Coefficient pointer */
        float32_t *px;                                 /* Scratch buffer pointer */
        float32_t *py = pState;                        /* Temporary pointers for state buffer */
        float32_t *pb = pScratchIn;                    /* Temporary pointers for scratch buffer */
        float32_t *pOut;                               /* Destination pointer */
        int32_t *pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
        uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
        uint16_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter  */
        int32_t readIndex;                             /* Read index of the state buffer */
        uint32_t tapCnt, blkCnt;                       /* loop counters */
        float32_t coeff = *pCoeffs++;                  /* Read the first coefficient value */


  /* BlockSize of Input samples are copied into the state buffer */
  /* StateIndex points to the starting position to write in the state buffer */
  arm_circularWrite_f32((int32_t *) py, delaySize, &S->stateIndex, 1, (int32_t *) pSrc, 1, blockSize);

  /* Read Index, from where the state buffer should be read, is calculated. */
  readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;

  /* Wraparound of readIndex */
  if (readIndex < 0)
  {
    readIndex += (int32_t) delaySize;
  }

  /* Working pointer for state buffer is updated */
  py = pState;

  /* blockSize samples are read from the state buffer */
  arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
                       (int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize);

  /* Working pointer for the scratch buffer of state values */
  px = pb;

  /* Working pointer for scratch buffer of output values */
  pOut = pDst;


#if defined (ARM_MATH_LOOPUNROLL)

  /* Loop unrolling: Compute 4 outputs at a time. */
  blkCnt = blockSize >> 2U;

  while (blkCnt > 0U)
  {
    /* Perform Multiplications and store in destination buffer */
    *pOut++ = *px++ * coeff;

    *pOut++ = *px++ * coeff;

    *pOut++ = *px++ * coeff;

    *pOut++ = *px++ * coeff;

    /* Decrement loop counter */
    blkCnt--;
  }

  /* Loop unrolling: Compute remaining outputs */
  blkCnt = blockSize % 0x4U;

#else

  /* Initialize blkCnt with number of samples */
  blkCnt = blockSize;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

  while (blkCnt > 0U)
  {
    /* Perform Multiplication and store in destination buffer */
    *pOut++ = *px++ * coeff;

    /* Decrement loop counter */
    blkCnt--;
  }

  /* Load the coefficient value and
   * increment the coefficient buffer for the next set of state values */
  coeff = *pCoeffs++;

  /* Read Index, from where the state buffer should be read, is calculated. */
  readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;

  /* Wraparound of readIndex */
  if (readIndex < 0)
  {
    readIndex += (int32_t) delaySize;
  }

  /* Loop over the number of taps. */
  tapCnt = (uint32_t) numTaps - 2U;

  while (tapCnt > 0U)
  {
    /* Working pointer for state buffer is updated */
    py = pState;

    /* blockSize samples are read from the state buffer */
    arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
                         (int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize);

    /* Working pointer for the scratch buffer of state values */
    px = pb;

    /* Working pointer for scratch buffer of output values */
    pOut = pDst;


#if defined (ARM_MATH_LOOPUNROLL)

    /* Loop unrolling: Compute 4 outputs at a time. */
    blkCnt = blockSize >> 2U;

    while (blkCnt > 0U)
    {
      /* Perform Multiply-Accumulate */
      *pOut++ += *px++ * coeff;

      *pOut++ += *px++ * coeff;

      *pOut++ += *px++ * coeff;

      *pOut++ += *px++ * coeff;

      /* Decrement loop counter */
      blkCnt--;
    }

    /* Loop unrolling: Compute remaining outputs */
    blkCnt = blockSize % 0x4U;

#else

    /* Initialize blkCnt with number of samples */
    blkCnt = blockSize;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

    while (blkCnt > 0U)
    {
      /* Perform Multiply-Accumulate */
      *pOut++ += *px++ * coeff;

      /* Decrement loop counter */
      blkCnt--;
    }

    /* Load the coefficient value and
     * increment the coefficient buffer for the next set of state values */
    coeff = *pCoeffs++;

    /* Read Index, from where the state buffer should be read, is calculated. */
    readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;

    /* Wraparound of readIndex */
    if (readIndex < 0)
    {
      readIndex += (int32_t) delaySize;
    }

    /* Decrement tap loop counter */
    tapCnt--;
  }

  /* Compute last tap without the final read of pTapDelay */

  /* Working pointer for state buffer is updated */
  py = pState;

  /* blockSize samples are read from the state buffer */
  arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
                       (int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize);

  /* Working pointer for the scratch buffer of state values */
  px = pb;

  /* Working pointer for scratch buffer of output values */
  pOut = pDst;


#if defined (ARM_MATH_LOOPUNROLL)

  /* Loop unrolling: Compute 4 outputs at a time. */
  blkCnt = blockSize >> 2U;

  while (blkCnt > 0U)
  {
    /* Perform Multiply-Accumulate */
    *pOut++ += *px++ * coeff;
    *pOut++ += *px++ * coeff;
    *pOut++ += *px++ * coeff;
    *pOut++ += *px++ * coeff;

    /* Decrement loop counter */
    blkCnt--;
  }

  /* Loop unrolling: Compute remaining outputs */
  blkCnt = blockSize % 0x4U;

#else

  /* Initialize blkCnt with number of samples */
  blkCnt = blockSize;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

  while (blkCnt > 0U)
  {
    /* Perform Multiply-Accumulate */
    *pOut++ += *px++ * coeff;

    /* Decrement loop counter */
    blkCnt--;
  }

}

/**
  @} end of FIR_Sparse group
 */
