#include "SampleFilter.h"

static double filter_taps[SAMPLEFILTER_TAP_NUM] = {
  0.008343267095683641,
  0.007149583224306389,
  0.0014492517668354074,
  -0.013310605694094289,
  -0.03450422491286543,
  -0.05367579867194659,
  -0.058668616471107396,
  -0.038574347326520715,
  0.010331418196167608,
  0.08087666209830409,
  0.15569629640166385,
  0.21287259655532492,
  0.23427451265344573,
  0.21287259655532492,
  0.15569629640166385,
  0.08087666209830409,
  0.010331418196167608,
  -0.038574347326520715,
  -0.058668616471107396,
  -0.05367579867194659,
  -0.03450422491286543,
  -0.013310605694094289,
  0.0014492517668354074,
  0.007149583224306389,
  0.008343267095683641
};

void SampleFilter_init(SampleFilter* f) {
  int i;
  for(i = 0; i < SAMPLEFILTER_TAP_NUM; ++i)
    f->history[i] = 0;
  f->last_index = 0;
}

void SampleFilter_put(SampleFilter* f, double input) {
  f->history[f->last_index++] = input;
  if(f->last_index == SAMPLEFILTER_TAP_NUM)
    f->last_index = 0;
}

double SampleFilter_get(SampleFilter* f) {
  double acc = 0;
  int index = f->last_index, i;
  for(i = 0; i < SAMPLEFILTER_TAP_NUM; ++i) {
    index = index != 0 ? index-1 : SAMPLEFILTER_TAP_NUM-1;
    acc += f->history[index] * filter_taps[i];
  };
  return acc;
}