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#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "main_FLP.h"

/* Apply sine window to signal vector   */

/* Window types:                        */

/*  1 -> sine window from 0 to pi/2     */

/*  2 -> sine window from pi/2 to pi    */

void silk_apply_sine_window_FLP(

    silk_float                      px_win[],                           /* O    Pointer to windowed signal                  */

    const silk_float                px[],                               /* I    Pointer to input signal                     */

    const opus_int                  win_type,                           /* I    Selects a window type                       */

    const opus_int                  length                              /* I    Window length, multiple of 4                */

)

{

    opus_int   k;

    silk_float freq, c, S0, S1;

    celt_assert( win_type == 1 || win_type == 2 );

    /* Length must be multiple of 4 */

    celt_assert( ( length & 3 ) == 0 );

    freq = PI / ( length + 1 );

    /* Approximation of 2 * cos(f) */

    c = 2.0f - freq * freq;

    /* Initialize state */

    if( win_type < 2 ) {

        /* Start from 0 */

        S0 = 0.0f;

        /* Approximation of sin(f) */

        S1 = freq;

    } else {

        /* Start from 1 */

        S0 = 1.0f;

        /* Approximation of cos(f) */

        S1 = 0.5f * c;

    }

    /* Uses the recursive equation:   sin(n*f) = 2 * cos(f) * sin((n-1)*f) - sin((n-2)*f)   */

    /* 4 samples at a time */

    for( k = 0; k < length; k += 4 ) {

        px_win[ k + 0 ] = px[ k + 0 ] * 0.5f * ( S0 + S1 );

        px_win[ k + 1 ] = px[ k + 1 ] * S1;

        S0 = c * S1 - S0;

        px_win[ k + 2 ] = px[ k + 2 ] * 0.5f * ( S1 + S0 );

        px_win[ k + 3 ] = px[ k + 3 ] * S0;

        S1 = c * S0 - S1;

    }

}