Implementation of FFT for LC3

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 *

 *  Copyright 2021 The Android Open Source Project

 *

 *  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:

 *

 *  http://www.apache.org/licenses/LICENSE-2.0

 *

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 *  distributed under the License is distributed on an "AS IS" BASIS,

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 *  See the License for the specific language governing permissions and

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#ifndef __LC3_OWN_FFT_H

#define __LC3_OWN_FFT_H

#include <stdbool.h>

/**

 * Complex floating point number

 */

struct fft_complex {

  float re, im;

};

#ifdef __cplusplus

extern "C" {

#endif

/**

 * Perform FFT

 * inverse         True on inverse transform else forward

 * x, y0, y1       Input, and 2 scratch buffers of size `n`

 * n               Number of points 30, 40, 60, 80, 90, 120, 160, 180, 240

 * return          The buffer `y0` or `y1` that hold the result

 *

 * Input `x` can be the same as the `y0` second scratch buffer

 */

struct fft_complex* fft(bool inverse, const struct fft_complex* x, int n,

                        struct fft_complex* y0, struct fft_complex* y1);

#ifdef __cplusplus

}

#endif

#endif /* __LC3_OWN_FFT_H */

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