/*
  * Copyright (c) 2013-2014 Mozilla Corporation
  *

  * This file is part of FFmpeg.

  *

  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *

  * FFmpeg is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**
  * @file
  * Celt non-power of 2 iMDCT
  */
 
 #include <float.h>
 #include <math.h>

 #include <stddef.h>
 
 #include "config.h"

 
 #include "libavutil/attributes.h"
 #include "libavutil/common.h"
 

 #include "avfft.h"

 #include "imdct15.h"

 #include "opus.h"

 
 // minimal iMDCT size to make SIMD opts easier
 #define CELT_MIN_IMDCT_SIZE 120

 
 // complex c = a * b
 #define CMUL3(cre, cim, are, aim, bre, bim)          \
 do {                                                 \
     cre = are * bre - aim * bim;                     \
     cim = are * bim + aim * bre;                     \
 } while (0)
 
 #define CMUL(c, a, b) CMUL3((c).re, (c).im, (a).re, (a).im, (b).re, (b).im)
 
 // complex c = a * b
 //         d = a * conjugate(b)
 #define CMUL2(c, d, a, b)                            \
 do {                                                 \
     float are = (a).re;                              \
     float aim = (a).im;                              \
     float bre = (b).re;                              \
     float bim = (b).im;                              \
     float rr  = are * bre;                           \
     float ri  = are * bim;                           \
     float ir  = aim * bre;                           \
     float ii  = aim * bim;                           \
     (c).re =  rr - ii;                               \
     (c).im =  ri + ir;                               \
     (d).re =  rr + ii;                               \
     (d).im = -ri + ir;                               \
 } while (0)
 

 av_cold void ff_imdct15_uninit(IMDCT15Context **ps)

 {

     IMDCT15Context *s = *ps;

     int i;
 
     if (!s)
         return;
 
     for (i = 0; i < FF_ARRAY_ELEMS(s->exptab); i++)
         av_freep(&s->exptab[i]);
 
     av_freep(&s->twiddle_exptab);
 
     av_freep(&s->tmp);
 
     av_freep(ps);
 }
 

 static void imdct15_half(IMDCT15Context *s, float *dst, const float *src,
                          ptrdiff_t stride, float scale);

 av_cold int ff_imdct15_init(IMDCT15Context **ps, int N)

 {

     IMDCT15Context *s;

     int len2 = 15 * (1 << N);
     int len  = 2 * len2;
     int i, j;
 

     if (len2 > CELT_MAX_FRAME_SIZE || len2 < CELT_MIN_IMDCT_SIZE)

         return AVERROR(EINVAL);
 
     s = av_mallocz(sizeof(*s));
     if (!s)
         return AVERROR(ENOMEM);
 
     s->fft_n = N - 1;
     s->len4 = len2 / 2;
     s->len2 = len2;
 

     s->tmp  = av_malloc_array(len, 2 * sizeof(*s->tmp));

     if (!s->tmp)
         goto fail;
 

     s->twiddle_exptab  = av_malloc_array(s->len4, sizeof(*s->twiddle_exptab));

     if (!s->twiddle_exptab)
         goto fail;
 
     for (i = 0; i < s->len4; i++) {
         s->twiddle_exptab[i].re = cos(2 * M_PI * (i + 0.125 + s->len4) / len);
         s->twiddle_exptab[i].im = sin(2 * M_PI * (i + 0.125 + s->len4) / len);
     }
 
     for (i = 0; i < FF_ARRAY_ELEMS(s->exptab); i++) {
         int N = 15 * (1 << i);
         s->exptab[i] = av_malloc(sizeof(*s->exptab[i]) * FFMAX(N, 19));
         if (!s->exptab[i])
             goto fail;
 
         for (j = 0; j < N; j++) {
             s->exptab[i][j].re = cos(2 * M_PI * j / N);
             s->exptab[i][j].im = sin(2 * M_PI * j / N);
         }
     }
 
     // wrap around to simplify fft15
     for (j = 15; j < 19; j++)
         s->exptab[0][j] = s->exptab[0][j - 15];
 

     s->imdct_half = imdct15_half;

 
     if (ARCH_AARCH64)

         ff_imdct15_init_aarch64(s);

     *ps = s;
 
     return 0;

 fail:

     ff_imdct15_uninit(&s);

     return AVERROR(ENOMEM);
 }
 

 static void fft5(FFTComplex *out, const FFTComplex *in, ptrdiff_t stride)

 {
     // [0] = exp(2 * i * pi / 5), [1] = exp(2 * i * pi * 2 / 5)
     static const FFTComplex fact[] = { { 0.30901699437494745,  0.95105651629515353 },
                                        { -0.80901699437494734, 0.58778525229247325 } };
 
     FFTComplex z[4][4];
 
     CMUL2(z[0][0], z[0][3], in[1 * stride], fact[0]);
     CMUL2(z[0][1], z[0][2], in[1 * stride], fact[1]);
     CMUL2(z[1][0], z[1][3], in[2 * stride], fact[0]);
     CMUL2(z[1][1], z[1][2], in[2 * stride], fact[1]);
     CMUL2(z[2][0], z[2][3], in[3 * stride], fact[0]);
     CMUL2(z[2][1], z[2][2], in[3 * stride], fact[1]);
     CMUL2(z[3][0], z[3][3], in[4 * stride], fact[0]);
     CMUL2(z[3][1], z[3][2], in[4 * stride], fact[1]);
 
     out[0].re = in[0].re + in[stride].re + in[2 * stride].re + in[3 * stride].re + in[4 * stride].re;
     out[0].im = in[0].im + in[stride].im + in[2 * stride].im + in[3 * stride].im + in[4 * stride].im;
 
     out[1].re = in[0].re + z[0][0].re + z[1][1].re + z[2][2].re + z[3][3].re;
     out[1].im = in[0].im + z[0][0].im + z[1][1].im + z[2][2].im + z[3][3].im;
 
     out[2].re = in[0].re + z[0][1].re + z[1][3].re + z[2][0].re + z[3][2].re;
     out[2].im = in[0].im + z[0][1].im + z[1][3].im + z[2][0].im + z[3][2].im;
 
     out[3].re = in[0].re + z[0][2].re + z[1][0].re + z[2][3].re + z[3][1].re;
     out[3].im = in[0].im + z[0][2].im + z[1][0].im + z[2][3].im + z[3][1].im;
 
     out[4].re = in[0].re + z[0][3].re + z[1][2].re + z[2][1].re + z[3][0].re;
     out[4].im = in[0].im + z[0][3].im + z[1][2].im + z[2][1].im + z[3][0].im;
 }
 

 static void fft15(IMDCT15Context *s, FFTComplex *out, const FFTComplex *in,
                   ptrdiff_t stride)

 {
     const FFTComplex *exptab = s->exptab[0];
     FFTComplex tmp[5];
     FFTComplex tmp1[5];
     FFTComplex tmp2[5];
     int k;
 
     fft5(tmp,  in,              stride * 3);
     fft5(tmp1, in +     stride, stride * 3);
     fft5(tmp2, in + 2 * stride, stride * 3);
 
     for (k = 0; k < 5; k++) {
         FFTComplex t1, t2;
 
         CMUL(t1, tmp1[k], exptab[k]);
         CMUL(t2, tmp2[k], exptab[2 * k]);
         out[k].re = tmp[k].re + t1.re + t2.re;
         out[k].im = tmp[k].im + t1.im + t2.im;
 
         CMUL(t1, tmp1[k], exptab[k + 5]);
         CMUL(t2, tmp2[k], exptab[2 * (k + 5)]);
         out[k + 5].re = tmp[k].re + t1.re + t2.re;
         out[k + 5].im = tmp[k].im + t1.im + t2.im;
 
         CMUL(t1, tmp1[k], exptab[k + 10]);
         CMUL(t2, tmp2[k], exptab[2 * k + 5]);
         out[k + 10].re = tmp[k].re + t1.re + t2.re;
         out[k + 10].im = tmp[k].im + t1.im + t2.im;
     }
 }
 
 /*
  * FFT of the length 15 * (2^N)
  */

 static void fft_calc(IMDCT15Context *s, FFTComplex *out, const FFTComplex *in,

                      int N, ptrdiff_t stride)

 {
     if (N) {
         const FFTComplex *exptab = s->exptab[N];
         const int len2 = 15 * (1 << (N - 1));
         int k;
 
         fft_calc(s, out,        in,          N - 1, stride * 2);
         fft_calc(s, out + len2, in + stride, N - 1, stride * 2);
 
         for (k = 0; k < len2; k++) {
             FFTComplex t;
 
             CMUL(t, out[len2 + k], exptab[k]);
 
             out[len2 + k].re = out[k].re - t.re;
             out[len2 + k].im = out[k].im - t.im;
 
             out[k].re += t.re;
             out[k].im += t.im;
         }
     } else
         fft15(s, out, in, stride);
 }
 

 static void imdct15_half(IMDCT15Context *s, float *dst, const float *src,
                          ptrdiff_t stride, float scale)

 {
     FFTComplex *z = (FFTComplex *)dst;
     const int len8 = s->len4 / 2;
     const float *in1 = src;
     const float *in2 = src + (s->len2 - 1) * stride;
     int i;
 
     for (i = 0; i < s->len4; i++) {
         FFTComplex tmp = { *in2, *in1 };
         CMUL(s->tmp[i], tmp, s->twiddle_exptab[i]);
         in1 += 2 * stride;
         in2 -= 2 * stride;
     }
 
     fft_calc(s, z, s->tmp, s->fft_n, 1);
 
     for (i = 0; i < len8; i++) {
         float r0, i0, r1, i1;
 
         CMUL3(r0, i1, z[len8 - i - 1].im, z[len8 - i - 1].re,  s->twiddle_exptab[len8 - i - 1].im, s->twiddle_exptab[len8 - i - 1].re);
         CMUL3(r1, i0, z[len8 + i].im,     z[len8 + i].re,      s->twiddle_exptab[len8 + i].im,     s->twiddle_exptab[len8 + i].re);
         z[len8 - i - 1].re = scale * r0;
         z[len8 - i - 1].im = scale * i0;
         z[len8 + i].re     = scale * r1;
         z[len8 + i].im     = scale * i1;
     }
 }