/* ----------------------------------------------------------------------
* 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_biquad_cascade_df1_q31.c
*
* Description:  Processing function for the
*               Q31 Biquad cascade filter
*
* 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
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - 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
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup BiquadCascadeDF1
 * @{
 */

/**
 * @brief Processing function for the Q31 Biquad cascade filter.
 * @param[in]  *S         points to an instance of the Q31 Biquad cascade structure.
 * @param[in]  *pSrc      points to the block of input data.
 * @param[out] *pDst      points to the block of output data.
 * @param[in]  blockSize  number of samples to process per call.
 * @return none.
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using an internal 64-bit accumulator.
 * The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
 * Thus, if the accumulator result overflows it wraps around rather than clip.
 * In order to avoid overflows completely the input signal must be scaled down by 2 bits and lie in the range [-0.25 +0.25).
 * After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to
 * 1.31 format by discarding the low 32 bits.
 *
 * \par
 * Refer to the function <code>arm_biquad_cascade_df1_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.
 */

void arm_biquad_cascade_df1_q31(
    const arm_biquad_casd_df1_inst_q31 * S,
    q31_t * pSrc,
    q31_t * pDst,
    uint32_t blockSize)
{
    q63_t acc;                                     /*  accumulator                   */
    uint32_t uShift = ((uint32_t) S->postShift + 1u);
    uint32_t lShift = 32u - uShift;                /*  Shift to be applied to the output */
    q31_t *pIn = pSrc;                             /*  input pointer initialization  */
    q31_t *pOut = pDst;                            /*  output pointer initialization */
    q31_t *pState = S->pState;                     /*  pState pointer initialization */
    q31_t *pCoeffs = S->pCoeffs;                   /*  coeff pointer initialization  */
    q31_t Xn1, Xn2, Yn1, Yn2;                      /*  Filter state variables        */
    q31_t b0, b1, b2, a1, a2;                      /*  Filter coefficients           */
    q31_t Xn;                                      /*  temporary input               */
    uint32_t sample, stage = S->numStages;         /*  loop counters                     */


#ifndef ARM_MATH_CM0_FAMILY_FAMILY

    q31_t acc_l, acc_h;                            /*  temporary output variables    */

    /* Run the below code for Cortex-M4 and Cortex-M3 */

    do
    {
        /* Reading the coefficients */
        b0 = *pCoeffs++;
        b1 = *pCoeffs++;
        b2 = *pCoeffs++;
        a1 = *pCoeffs++;
        a2 = *pCoeffs++;

        /* Reading the state values */
        Xn1 = pState[0];
        Xn2 = pState[1];
        Yn1 = pState[2];
        Yn2 = pState[3];

        /* Apply loop unrolling and compute 4 output values simultaneously. */
        /*      The variable acc hold output values that are being computed:
         *
         *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
         */

        sample = blockSize >> 2u;

        /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
         ** a second loop below computes the remaining 1 to 3 samples. */
        while(sample > 0u)
        {
            /* Read the input */
            Xn = *pIn++;

            /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */

            /* acc =  b0 * x[n] */
            acc = (q63_t) b0 * Xn;
            /* acc +=  b1 * x[n-1] */
            acc += (q63_t) b1 * Xn1;
            /* acc +=  b[2] * x[n-2] */
            acc += (q63_t) b2 * Xn2;
            /* acc +=  a1 * y[n-1] */
            acc += (q63_t) a1 * Yn1;
            /* acc +=  a2 * y[n-2] */
            acc += (q63_t) a2 * Yn2;

            /* The result is converted to 1.31 , Yn2 variable is reused */

            /* Calc lower part of acc */
            acc_l = acc & 0xffffffff;

            /* Calc upper part of acc */
            acc_h = (acc >> 32) & 0xffffffff;

            /* Apply shift for lower part of acc and upper part of acc */
            Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;

            /* Store the output in the destination buffer. */
            *pOut++ = Yn2;

            /* Read the second input */
            Xn2 = *pIn++;

            /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */

            /* acc =  b0 * x[n] */
            acc = (q63_t) b0 * Xn2;
            /* acc +=  b1 * x[n-1] */
            acc += (q63_t) b1 * Xn;
            /* acc +=  b[2] * x[n-2] */
            acc += (q63_t) b2 * Xn1;
            /* acc +=  a1 * y[n-1] */
            acc += (q63_t) a1 * Yn2;
            /* acc +=  a2 * y[n-2] */
            acc += (q63_t) a2 * Yn1;


            /* The result is converted to 1.31, Yn1 variable is reused  */

            /* Calc lower part of acc */
            acc_l = acc & 0xffffffff;

            /* Calc upper part of acc */
            acc_h = (acc >> 32) & 0xffffffff;


            /* Apply shift for lower part of acc and upper part of acc */
            Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;

            /* Store the output in the destination buffer. */
            *pOut++ = Yn1;

            /* Read the third input  */
            Xn1 = *pIn++;

            /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */

            /* acc =  b0 * x[n] */
            acc = (q63_t) b0 * Xn1;
            /* acc +=  b1 * x[n-1] */
            acc += (q63_t) b1 * Xn2;
            /* acc +=  b[2] * x[n-2] */
            acc += (q63_t) b2 * Xn;
            /* acc +=  a1 * y[n-1] */
            acc += (q63_t) a1 * Yn1;
            /* acc +=  a2 * y[n-2] */
            acc += (q63_t) a2 * Yn2;

            /* The result is converted to 1.31, Yn2 variable is reused  */
            /* Calc lower part of acc */
            acc_l = acc & 0xffffffff;

            /* Calc upper part of acc */
            acc_h = (acc >> 32) & 0xffffffff;


            /* Apply shift for lower part of acc and upper part of acc */
            Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;

            /* Store the output in the destination buffer. */
            *pOut++ = Yn2;

            /* Read the forth input */
            Xn = *pIn++;

            /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */

            /* acc =  b0 * x[n] */
            acc = (q63_t) b0 * Xn;
            /* acc +=  b1 * x[n-1] */
            acc += (q63_t) b1 * Xn1;
            /* acc +=  b[2] * x[n-2] */
            acc += (q63_t) b2 * Xn2;
            /* acc +=  a1 * y[n-1] */
            acc += (q63_t) a1 * Yn2;
            /* acc +=  a2 * y[n-2] */
            acc += (q63_t) a2 * Yn1;

            /* The result is converted to 1.31, Yn1 variable is reused  */
            /* Calc lower part of acc */
            acc_l = acc & 0xffffffff;

            /* Calc upper part of acc */
            acc_h = (acc >> 32) & 0xffffffff;

            /* Apply shift for lower part of acc and upper part of acc */
            Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;

            /* Every time after the output is computed state should be updated. */
            /* The states should be updated as:  */
            /* Xn2 = Xn1    */
            /* Xn1 = Xn     */
            /* Yn2 = Yn1    */
            /* Yn1 = acc    */
            Xn2 = Xn1;
            Xn1 = Xn;

            /* Store the output in the destination buffer. */
            *pOut++ = Yn1;

            /* decrement the loop counter */
            sample--;
        }

        /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
         ** No loop unrolling is used. */
        sample = (blockSize & 0x3u);

        while(sample > 0u)
        {
            /* Read the input */
            Xn = *pIn++;

            /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */

            /* acc =  b0 * x[n] */
            acc = (q63_t) b0 * Xn;
            /* acc +=  b1 * x[n-1] */
            acc += (q63_t) b1 * Xn1;
            /* acc +=  b[2] * x[n-2] */
            acc += (q63_t) b2 * Xn2;
            /* acc +=  a1 * y[n-1] */
            acc += (q63_t) a1 * Yn1;
            /* acc +=  a2 * y[n-2] */
            acc += (q63_t) a2 * Yn2;

            /* The result is converted to 1.31  */
            acc = acc >> lShift;

            /* Every time after the output is computed state should be updated. */
            /* The states should be updated as:  */
            /* Xn2 = Xn1    */
            /* Xn1 = Xn     */
            /* Yn2 = Yn1    */
            /* Yn1 = acc    */
            Xn2 = Xn1;
            Xn1 = Xn;
            Yn2 = Yn1;
            Yn1 = (q31_t) acc;

            /* Store the output in the destination buffer. */
            *pOut++ = (q31_t) acc;

            /* decrement the loop counter */
            sample--;
        }

        /*  The first stage goes from the input buffer to the output buffer. */
        /*  Subsequent stages occur in-place in the output buffer */
        pIn = pDst;

        /* Reset to destination pointer */
        pOut = pDst;

        /*  Store the updated state variables back into the pState array */
        *pState++ = Xn1;
        *pState++ = Xn2;
        *pState++ = Yn1;
        *pState++ = Yn2;

    }
    while(--stage);

#else

    /* Run the below code for Cortex-M0 */

    do
    {
        /* Reading the coefficients */
        b0 = *pCoeffs++;
        b1 = *pCoeffs++;
        b2 = *pCoeffs++;
        a1 = *pCoeffs++;
        a2 = *pCoeffs++;

        /* Reading the state values */
        Xn1 = pState[0];
        Xn2 = pState[1];
        Yn1 = pState[2];
        Yn2 = pState[3];

        /*      The variables acc holds the output value that is computed:
         *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
         */

        sample = blockSize;

        while(sample > 0u)
        {
            /* Read the input */
            Xn = *pIn++;

            /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
            /* acc =  b0 * x[n] */
            acc = (q63_t) b0 * Xn;

            /* acc +=  b1 * x[n-1] */
            acc += (q63_t) b1 * Xn1;
            /* acc +=  b[2] * x[n-2] */
            acc += (q63_t) b2 * Xn2;
            /* acc +=  a1 * y[n-1] */
            acc += (q63_t) a1 * Yn1;
            /* acc +=  a2 * y[n-2] */
            acc += (q63_t) a2 * Yn2;

            /* The result is converted to 1.31  */
            acc = acc >> lShift;

            /* Every time after the output is computed state should be updated. */
            /* The states should be updated as:  */
            /* Xn2 = Xn1    */
            /* Xn1 = Xn     */
            /* Yn2 = Yn1    */
            /* Yn1 = acc    */
            Xn2 = Xn1;
            Xn1 = Xn;
            Yn2 = Yn1;
            Yn1 = (q31_t) acc;

            /* Store the output in the destination buffer. */
            *pOut++ = (q31_t) acc;

            /* decrement the loop counter */
            sample--;
        }

        /*  The first stage goes from the input buffer to the output buffer. */
        /*  Subsequent stages occur in-place in the output buffer */
        pIn = pDst;

        /* Reset to destination pointer */
        pOut = pDst;

        /*  Store the updated state variables back into the pState array */
        *pState++ = Xn1;
        *pState++ = Xn2;
        *pState++ = Yn1;
        *pState++ = Yn2;

    }
    while(--stage);

#endif /*  #ifndef ARM_MATH_CM0_FAMILY_FAMILY */
}




/**
  * @} end of BiquadCascadeDF1 group
  */
