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#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "SigProc_FIX.h"

#include "define.h"

#define QA                          24

#define A_LIMIT                     SILK_FIX_CONST( 0.99975, QA )

#define MUL32_FRAC_Q(a32, b32, Q)   ((opus_int32)(silk_RSHIFT_ROUND64(silk_SMULL(a32, b32), Q)))

/* Compute inverse of LPC prediction gain, and                          */

/* test if LPC coefficients are stable (all poles within unit circle)   */

static opus_int32 LPC_inverse_pred_gain_QA_c(               /* O   Returns inverse prediction gain in energy domain, Q30    */

    opus_int32           A_QA[ SILK_MAX_ORDER_LPC ],        /* I   Prediction coefficients                                  */

    const opus_int       order                              /* I   Prediction order                                         */

)

{

    opus_int   k, n, mult2Q;

    opus_int32 invGain_Q30, rc_Q31, rc_mult1_Q30, rc_mult2, tmp1, tmp2;

    invGain_Q30 = SILK_FIX_CONST( 1, 30 );

    for( k = order - 1; k > 0; k-- ) {

        /* Check for stability */

        if( ( A_QA[ k ] > A_LIMIT ) || ( A_QA[ k ] < -A_LIMIT ) ) {

            return 0;

        }

        /* Set RC equal to negated AR coef */

        rc_Q31 = -silk_LSHIFT( A_QA[ k ], 31 - QA );

        /* rc_mult1_Q30 range: [ 1 : 2^30 ] */

        rc_mult1_Q30 = silk_SUB32( SILK_FIX_CONST( 1, 30 ), silk_SMMUL( rc_Q31, rc_Q31 ) );

        silk_assert( rc_mult1_Q30 > ( 1 << 15 ) );                   /* reduce A_LIMIT if fails */

        silk_assert( rc_mult1_Q30 <= ( 1 << 30 ) );

        /* Update inverse gain */

        /* invGain_Q30 range: [ 0 : 2^30 ] */

        invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );

        silk_assert( invGain_Q30 >= 0           );

        silk_assert( invGain_Q30 <= ( 1 << 30 ) );

        if( invGain_Q30 < SILK_FIX_CONST( 1.0f / MAX_PREDICTION_POWER_GAIN, 30 ) ) {

            return 0;

        }

        /* rc_mult2 range: [ 2^30 : silk_int32_MAX ] */

        mult2Q = 32 - silk_CLZ32( silk_abs( rc_mult1_Q30 ) );

        rc_mult2 = silk_INVERSE32_varQ( rc_mult1_Q30, mult2Q + 30 );

        /* Update AR coefficient */

        for( n = 0; n < (k + 1) >> 1; n++ ) {

            opus_int64 tmp64;

            tmp1 = A_QA[ n ];

            tmp2 = A_QA[ k - n - 1 ];

            tmp64 = silk_RSHIFT_ROUND64( silk_SMULL( silk_SUB_SAT32(tmp1,

                  MUL32_FRAC_Q( tmp2, rc_Q31, 31 ) ), rc_mult2 ), mult2Q);

            if( tmp64 > silk_int32_MAX || tmp64 < silk_int32_MIN ) {

               return 0;

            }

            A_QA[ n ] = ( opus_int32 )tmp64;

            tmp64 = silk_RSHIFT_ROUND64( silk_SMULL( silk_SUB_SAT32(tmp2,

                  MUL32_FRAC_Q( tmp1, rc_Q31, 31 ) ), rc_mult2), mult2Q);

            if( tmp64 > silk_int32_MAX || tmp64 < silk_int32_MIN ) {

               return 0;

            }

            A_QA[ k - n - 1 ] = ( opus_int32 )tmp64;

        }

    }

    /* Check for stability */

    if( ( A_QA[ k ] > A_LIMIT ) || ( A_QA[ k ] < -A_LIMIT ) ) {

        return 0;

    }

    /* Set RC equal to negated AR coef */

    rc_Q31 = -silk_LSHIFT( A_QA[ 0 ], 31 - QA );

    /* Range: [ 1 : 2^30 ] */

    rc_mult1_Q30 = silk_SUB32( SILK_FIX_CONST( 1, 30 ), silk_SMMUL( rc_Q31, rc_Q31 ) );

    /* Update inverse gain */

    /* Range: [ 0 : 2^30 ] */

    invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );

    silk_assert( invGain_Q30 >= 0           );

    silk_assert( invGain_Q30 <= ( 1 << 30 ) );

    if( invGain_Q30 < SILK_FIX_CONST( 1.0f / MAX_PREDICTION_POWER_GAIN, 30 ) ) {

        return 0;

    }

    return invGain_Q30;

}

/* For input in Q12 domain */

opus_int32 silk_LPC_inverse_pred_gain_c(            /* O   Returns inverse prediction gain in energy domain, Q30        */

    const opus_int16            *A_Q12,             /* I   Prediction coefficients, Q12 [order]                         */

    const opus_int              order               /* I   Prediction order                                             */

)

{

    opus_int   k;

    opus_int32 Atmp_QA[ SILK_MAX_ORDER_LPC ];

    opus_int32 DC_resp = 0;

    /* Increase Q domain of the AR coefficients */

    for( k = 0; k < order; k++ ) {

        DC_resp += (opus_int32)A_Q12[ k ];

        Atmp_QA[ k ] = silk_LSHIFT32( (opus_int32)A_Q12[ k ], QA - 12 );

    }

    /* If the DC is unstable, we don't even need to do the full calculations */

    if( DC_resp >= 4096 ) {

        return 0;

    }

    return LPC_inverse_pred_gain_QA_c( Atmp_QA, order );

}