/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_fir_sparse_q7.c
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* Description: Q7 sparse FIR filter processing function
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*
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* $Date: 18. March 2019
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* $Revision: V1.6.0
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*
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* Target Processor: Cortex-M cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "arm_math.h"
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/**
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@ingroup groupFilters
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*/
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/**
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@addtogroup FIR_Sparse
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@{
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*/
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/**
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@brief Processing function for the Q7 sparse FIR filter.
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@param[in] S points to an instance of the Q7 sparse FIR structure
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@param[in] pSrc points to the block of input data
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@param[out] pDst points to the block of output data
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@param[in] pScratchIn points to a temporary buffer of size blockSize
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@param[in] pScratchOut points to a temporary buffer of size blockSize
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@param[in] blockSize number of input samples to process
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@return none
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@par Scaling and Overflow Behavior
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The function is implemented using a 32-bit internal accumulator.
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Both coefficients and state variables are represented in 1.7 format and multiplications yield a 2.14 result.
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The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 format.
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There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
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The accumulator is then converted to 18.7 format by discarding the low 7 bits.
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Finally, the result is truncated to 1.7 format.
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*/
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void arm_fir_sparse_q7(
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arm_fir_sparse_instance_q7 * S,
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const q7_t * pSrc,
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q7_t * pDst,
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q7_t * pScratchIn,
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q31_t * pScratchOut,
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uint32_t blockSize)
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{
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q7_t *pState = S->pState; /* State pointer */
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const q7_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q7_t *px; /* Scratch buffer pointer */
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q7_t *py = pState; /* Temporary pointers for state buffer */
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q7_t *pb = pScratchIn; /* Temporary pointers for scratch buffer */
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q7_t *pOut = pDst; /* Destination pointer */
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int32_t *pTapDelay = S->pTapDelay; /* Pointer to the array containing offset of the non-zero tap values. */
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uint32_t delaySize = S->maxDelay + blockSize; /* state length */
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uint16_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
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int32_t readIndex; /* Read index of the state buffer */
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uint32_t tapCnt, blkCnt; /* loop counters */
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q31_t *pScr2 = pScratchOut; /* Working pointer for scratch buffer of output values */
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q31_t in;
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q7_t coeff = *pCoeffs++; /* Read the coefficient value */
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#if defined (ARM_MATH_LOOPUNROLL)
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q7_t in1, in2, in3, in4;
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#endif
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/* BlockSize of Input samples are copied into the state buffer */
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/* StateIndex points to the starting position to write in the state buffer */
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arm_circularWrite_q7(py, (int32_t) delaySize, &S->stateIndex, 1, pSrc, 1, blockSize);
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/* Loop over the number of taps. */
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tapCnt = numTaps;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1,
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pb, pb, (int32_t) blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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#if defined (ARM_MATH_LOOPUNROLL)
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/* Loop unrolling: Compute 4 outputs at a time. */
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blkCnt = blockSize >> 2U;
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while (blkCnt > 0U)
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{
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/* Perform multiplication and store in the scratch buffer */
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*pScratchOut++ = ((q31_t) *px++ * coeff);
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*pScratchOut++ = ((q31_t) *px++ * coeff);
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*pScratchOut++ = ((q31_t) *px++ * coeff);
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*pScratchOut++ = ((q31_t) *px++ * coeff);
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Loop unrolling: Compute remaining outputs */
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blkCnt = blockSize % 0x4U;
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#else
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/* Initialize blkCnt with number of samples */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
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while (blkCnt > 0U)
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{
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/* Perform Multiplication and store in the scratch buffer */
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*pScratchOut++ = ((q31_t) *px++ * coeff);
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Loop over the number of taps. */
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tapCnt = (uint32_t) numTaps - 2U;
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while (tapCnt > 0U)
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{
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1,
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pb, pb, (int32_t) blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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#if defined (ARM_MATH_LOOPUNROLL)
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/* Loop unrolling: Compute 4 outputs at a time. */
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blkCnt = blockSize >> 2U;
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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in = *pScratchOut + ((q31_t) * px++ * coeff);
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*pScratchOut++ = in;
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in = *pScratchOut + ((q31_t) * px++ * coeff);
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*pScratchOut++ = in;
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in = *pScratchOut + ((q31_t) * px++ * coeff);
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*pScratchOut++ = in;
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in = *pScratchOut + ((q31_t) * px++ * coeff);
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*pScratchOut++ = in;
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Loop unrolling: Compute remaining outputs */
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blkCnt = blockSize % 0x4U;
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#else
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/* Initialize blkCnt with number of samples */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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in = *pScratchOut + ((q31_t) *px++ * coeff);
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*pScratchOut++ = in;
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Decrement loop counter */
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tapCnt--;
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}
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/* Compute last tap without the final read of pTapDelay */
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1,
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pb, pb, (int32_t) blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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#if defined (ARM_MATH_LOOPUNROLL)
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/* Loop unrolling: Compute 4 outputs at a time. */
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blkCnt = blockSize >> 2U;
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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in = *pScratchOut + ((q31_t) *px++ * coeff);
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*pScratchOut++ = in;
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in = *pScratchOut + ((q31_t) *px++ * coeff);
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*pScratchOut++ = in;
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in = *pScratchOut + ((q31_t) *px++ * coeff);
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*pScratchOut++ = in;
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in = *pScratchOut + ((q31_t) *px++ * coeff);
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*pScratchOut++ = in;
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Loop unrolling: Compute remaining outputs */
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blkCnt = blockSize % 0x4U;
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#else
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/* Initialize blkCnt with number of samples */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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in = *pScratchOut + ((q31_t) *px++ * coeff);
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*pScratchOut++ = in;
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/* Decrement loop counter */
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blkCnt--;
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}
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/* All the output values are in pScratchOut buffer.
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Convert them into 1.15 format, saturate and store in the destination buffer. */
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#if defined (ARM_MATH_LOOPUNROLL)
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/* Loop unrolling: Compute 4 outputs at a time. */
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blkCnt = blockSize >> 2U;
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while (blkCnt > 0U)
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{
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in1 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
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in2 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
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in3 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
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in4 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
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write_q7x4_ia (&pOut, __PACKq7(in1, in2, in3, in4));
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Loop unrolling: Compute remaining outputs */
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blkCnt = blockSize % 0x4U;
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#else
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/* Initialize blkCnt with number of samples */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
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while (blkCnt > 0U)
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{
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*pOut++ = (q7_t) __SSAT(*pScr2++ >> 7, 8);
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/* Decrement loop counter */
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blkCnt--;
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}
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}
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/**
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@} end of FIR_Sparse group
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*/
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