/*  SSNES - A Super Nintendo Entertainment System (SNES) Emulator frontend for libsnes.
 *  Copyright (C) 2010-2012 - Hans-Kristian Arntzen
 *
 *  Some code herein may be based on code found in BSNES.
 * 
 *  SSNES is free software: you can redistribute it and/or modify it under the terms
 *  of the GNU General Public License as published by the Free Software Found-
 *  ation, either version 3 of the License, or (at your option) any later version.
 *
 *  SSNES 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along with SSNES.
 *  If not, see <http://www.gnu.org/licenses/>.
 */

// Bog-standard windowed SINC implementation.
// Only suitable as an upsampler, as there is no low-pass filter stage.

#include "resampler.h"
#include <math.h>
#include <stdint.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>

#if __SSE__
#include <xmmintrin.h>
#endif

#define PHASE_BITS 8
#define SUBPHASE_BITS 16

#define PHASES (1 << PHASE_BITS)
#define PHASES_SHIFT (SUBPHASE_BITS)
#define SUBPHASES (1 << SUBPHASE_BITS)
#define SUBPHASES_SHIFT 0
#define SUBPHASES_MASK ((1 << SUBPHASE_BITS) - 1)
#define PHASES_WRAP (1 << (PHASE_BITS + SUBPHASE_BITS))
#define FRAMES_SHIFT (PHASE_BITS + SUBPHASE_BITS)

#define SIDELOBES 8

struct ssnes_resampler
{
   float phase_table[PHASES + 1][SIDELOBES];
   float delta_table[PHASES + 1][SIDELOBES];
   float buffer_l[2 * SIDELOBES];
   float buffer_r[2 * SIDELOBES];

   uint32_t time;
};

static inline double sinc(double val)
{
   if (fabs(val) < 0.00001)
      return 1.0;
   else
      return sin(val) / val;
}

static inline double blackman(double index)
{
   index *= 0.5;
   index += 0.5;

   double alpha = 0.16;
   double a0 = (1.0 - alpha) / 2.0;
   double a1 = 0.5;
   double a2 = alpha / 2.0;

   return a0 - a1 * cos(2.0 * M_PI * index) + a2 * cos(4.0 * M_PI * index);
}

static void init_sinc_table(ssnes_resampler_t *resamp)
{
   for (unsigned i = 0; i <= PHASES; i++)
   {
      for (unsigned j = 0; j < SIDELOBES; j++)
      {
         double sinc_phase = M_PI * ((double)i / PHASES + (double)j);
         resamp->phase_table[i][j] = sinc(sinc_phase) * blackman(sinc_phase / SIDELOBES);
      }
   }

   // Optimize linear interpolation.
   for (unsigned i = 0; i < PHASES; i++)
      for (unsigned j = 0; j < SIDELOBES; j++)
         resamp->delta_table[i][j] = resamp->phase_table[i + 1][j] - resamp->phase_table[i][j];
}

ssnes_resampler_t *resampler_new(void)
{
   ssnes_resampler_t *re = (ssnes_resampler_t*)memalign(16, sizeof(*re));
   if (!re)
      return NULL;

   memset(re, 0, sizeof(*re));

   init_sinc_table(re);
   return re;
}

#if __SSE__
static void process_sinc(ssnes_resampler_t *resamp, float *out_buffer)
{
   __m128 sum_l = _mm_setzero_ps();
   __m128 sum_r = _mm_setzero_ps();

   const float *buffer_l = resamp->buffer_l;
   const float *buffer_r = resamp->buffer_r;

   unsigned phase = resamp->time >> PHASES_SHIFT;
   unsigned delta = (resamp->time >> SUBPHASES_SHIFT) & SUBPHASES_MASK;
   __m128 delta_f = _mm_set1_ps((float)delta / SUBPHASES);

   const float *phase_table = resamp->phase_table[phase];
   const float *delta_table = resamp->delta_table[phase];

   __m128 sinc_vals[SIDELOBES / 4];
   for (unsigned i = 0; i < SIDELOBES; i += 4)
   {
      __m128 phases    = _mm_load_ps(phase_table + i);
      __m128 deltas    = _mm_load_ps(delta_table + i);
      sinc_vals[i / 4] = _mm_add_ps(phases, _mm_mul_ps(deltas, delta_f));
   }

   // Older data.
   for (unsigned i = 0; i < SIDELOBES; i += 4)
   {
      __m128 buf_l = _mm_loadr_ps(buffer_l + SIDELOBES - 4 - i);
      sum_l        = _mm_add_ps(sum_l, _mm_mul_ps(buf_l, sinc_vals[i / 4]));

      __m128 buf_r = _mm_loadr_ps(buffer_r + SIDELOBES - 4 - i);
      sum_r        = _mm_add_ps(sum_r, _mm_mul_ps(buf_r, sinc_vals[i / 4]));
   }

   // Newer data.
   unsigned reverse_phase = PHASES_WRAP - resamp->time;
   phase   = reverse_phase >> PHASES_SHIFT;
   delta   = (reverse_phase >> SUBPHASES_SHIFT) & SUBPHASES_MASK;
   delta_f = _mm_set1_ps((float)delta / SUBPHASES);

   phase_table = resamp->phase_table[phase];
   delta_table = resamp->delta_table[phase];

   for (unsigned i = 0; i < SIDELOBES; i += 4)
   {
      __m128 phases    = _mm_load_ps(phase_table + i);
      __m128 deltas    = _mm_load_ps(delta_table + i);
      sinc_vals[i / 4] = _mm_add_ps(phases, _mm_mul_ps(deltas, delta_f));
   }

   for (unsigned i = 0; i < SIDELOBES; i += 4)
   {
      __m128 buf_l = _mm_load_ps(buffer_l + SIDELOBES + i);
      sum_l        = _mm_add_ps(sum_l, _mm_mul_ps(buf_l, sinc_vals[i / 4]));

      __m128 buf_r = _mm_load_ps(buffer_r + SIDELOBES + i);
      sum_r        = _mm_add_ps(sum_r, _mm_mul_ps(buf_r, sinc_vals[i / 4]));
   }

   // This can be done faster with _mm_hadd_ps(), but it's SSE3 :(
   __m128 sum_shuf_l = _mm_shuffle_ps(sum_l, sum_r, _MM_SHUFFLE(1, 0, 1, 0));
   __m128 sum_shuf_r = _mm_shuffle_ps(sum_l, sum_r, _MM_SHUFFLE(3, 2, 3, 2));
   __m128 sum        = _mm_add_ps(sum_shuf_l, sum_shuf_r);

   union
   {
      float f[4];
      __m128 v;
   } u;
   u.v = sum;

   out_buffer[0] = u.f[0] + u.f[1];
   out_buffer[1] = u.f[2] + u.f[3];
}
#else // Plain ol' C99
static void process_sinc(ssnes_resampler_t *resamp, float *out_buffer)
{
   float sum_l = 0.0f;
   float sum_r = 0.0f;
   const float *buffer_l = resamp->buffer_l;
   const float *buffer_r = resamp->buffer_r;

   unsigned phase = resamp->time >> PHASES_SHIFT;
   unsigned delta = (resamp->time >> SUBPHASES_SHIFT) & SUBPHASES_MASK;
   float delta_f = (float)delta / SUBPHASES;

   const float *phase_table = resamp->phase_table[phase];
   const float *delta_table = resamp->delta_table[phase];

   float sinc_vals[SIDELOBES];
   for (unsigned i = 0; i < SIDELOBES; i++)
      sinc_vals[i] = phase_table[i] + delta_f * delta_table[i];

   // Older data.
   for (unsigned i = 0; i < SIDELOBES; i++)
   {
      sum_l += buffer_l[SIDELOBES - 1 - i] * sinc_vals[i];
      sum_r += buffer_r[SIDELOBES - 1 - i] * sinc_vals[i];
   }

   // Newer data.
   unsigned reverse_phase = PHASES_WRAP - resamp->time;
   phase   = reverse_phase >> PHASES_SHIFT;
   delta   = (reverse_phase >> SUBPHASES_SHIFT) & SUBPHASES_MASK;
   delta_f = (float)delta / SUBPHASES;

   phase_table = resamp->phase_table[phase];
   delta_table = resamp->delta_table[phase];

   for (unsigned i = 0; i < SIDELOBES; i++)
      sinc_vals[i] = phase_table[i] + delta_f * delta_table[i];

   for (unsigned i = 0; i < SIDELOBES; i++)
   {
      sum_l += buffer_l[SIDELOBES + i] * sinc_vals[i];
      sum_r += buffer_r[SIDELOBES + i] * sinc_vals[i];
   }

   out_buffer[0] = sum_l;
   out_buffer[1] = sum_r;
}
#endif

void resampler_process(ssnes_resampler_t *re, struct resampler_data *data)
{
   uint32_t ratio = PHASES_WRAP / data->ratio;

   const float *input = data->data_in;
   float *output = data->data_out;
   size_t frames = data->input_frames;
   size_t out_frames = 0;

   while (frames)
   {
      process_sinc(re, output);
      output += 2;
      out_frames++;

      re->time += ratio;
      while (re->time >= PHASES_WRAP)
      {
         memmove(re->buffer_l, re->buffer_l + 1,
               sizeof(re->buffer_l) - sizeof(float));
         memmove(re->buffer_r, re->buffer_r + 1,
               sizeof(re->buffer_r) - sizeof(float));

         re->buffer_l[2 * SIDELOBES - 1] = *input++;
         re->buffer_r[2 * SIDELOBES - 1] = *input++;

         re->time -= PHASES_WRAP;
         frames--;
      }
   }

   data->output_frames = out_frames;
}

void resampler_free(ssnes_resampler_t *re)
{
   free(re);
}