#ifndef _AVFFT_H_e01ea90e_
#define _AVFFT_H_e01ea90e_

/*
 * This file was stolen from ffmpeg and modified for usability here.
 *  The original does not have a "copyright by" line.
 *
 * This version is a derivative work of that version.  It is not free
 *  software; it is licensed under the GNU Lesser General Public
 *  License version 2.1, which places nontrivial restrictions on what
 *  may be done with it.  (I'm not terribly happy about that, but for
 *  my purposes accepting LGPL-infected code is a lower price than
 *  reimplementing it all myself.)
 *
 * The LGPL v2.1 as distributed with ffmpeg is in the accompanying file
 *  `LGPL-v2.1'.
 */

typedef float FFTSample;

typedef struct FFTComplex {
    FFTSample re, im;
} FFTComplex;

typedef struct FFTContext FFTContext;

/**
 * Set up a complex FFT.
 * @param nbits           log2 of the length of the input array
 * @param inverse         if 0 perform the forward transform, if 1 perform the inverse
 */
FFTContext *av_fft_init(int nbits, int inverse);

/**
 * Do the permutation needed BEFORE calling ff_fft_calc().
 */
void av_fft_permute(FFTContext *s, FFTComplex *z);

/**
 * Do a complex FFT with the parameters defined in av_fft_init(). The
 * input data must be permuted before. No 1.0/sqrt(n) normalization is done.
 */
void av_fft_calc(FFTContext *s, FFTComplex *z);

void av_fft_end(FFTContext *s);

FFTContext *av_mdct_init(int nbits, int inverse, double scale);
void av_imdct_calc(FFTContext *s, FFTSample *output, const FFTSample *input);
void av_imdct_half(FFTContext *s, FFTSample *output, const FFTSample *input);
void av_mdct_calc(FFTContext *s, FFTSample *output, const FFTSample *input);
void av_mdct_end(FFTContext *s);

/* Real Discrete Fourier Transform */

enum RDFTransformType {
    DFT_R2C,
    IDFT_C2R,
    IDFT_R2C,
    DFT_C2R,
};

typedef struct RDFTContext RDFTContext;

/**
 * Set up a real FFT.
 * @param nbits           log2 of the length of the input array
 * @param trans           the type of transform
 */
RDFTContext *av_rdft_init(int nbits, enum RDFTransformType trans);
void av_rdft_calc(RDFTContext *s, FFTSample *data);
void av_rdft_end(RDFTContext *s);

/* Discrete Cosine Transform */

typedef struct DCTContext DCTContext;

enum DCTTransformType {
    DCT_II = 0,
    DCT_III,
    DCT_I,
    DST_I,
};

/**
 * Set up DCT.
 * @param nbits           size of the input array:
 *                        (1 << nbits)     for DCT-II, DCT-III and DST-I
 *                        (1 << nbits) + 1 for DCT-I
 *
 * @note the first element of the input of DST-I is ignored
 */
DCTContext *av_dct_init(int nbits, enum DCTTransformType type);
void av_dct_calc(DCTContext *s, FFTSample *data);
void av_dct_end (DCTContext *s);

#endif