/*
 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

/*
 * This file contains the function WebRtcSpl_ReflCoefToLpc().
 * The description header can be found in signal_processing_library.h
 *
 */

#include "common_audio/signal_processing/include/signal_processing_library.h"

void WebRtcSpl_ReflCoefToLpc(const int16_t* k, int use_order, int16_t* a) {
  int16_t any[WEBRTC_SPL_MAX_LPC_ORDER + 1];
  int16_t *aptr, *aptr2, *anyptr;
  const int16_t* kptr;
  int m, i;

  kptr = k;
  *a = 4096;  // i.e., (Word16_MAX >> 3)+1.
  *any = *a;
  a[1] = *k >> 3;

  for (m = 1; m < use_order; m++) {
    kptr++;
    aptr = a;
    aptr++;
    aptr2 = &a[m];
    anyptr = any;
    anyptr++;

    any[m + 1] = *kptr >> 3;
    for (i = 0; i < m; i++) {
      *anyptr = *aptr + (int16_t)((*aptr2 * *kptr) >> 15);
      anyptr++;
      aptr++;
      aptr2--;
    }

    aptr = a;
    anyptr = any;
    for (i = 0; i < (m + 2); i++) {
      *aptr = *anyptr;
      aptr++;
      anyptr++;
    }
  }
}