tor-browser

The Tor Browser
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division_operations.c (3157B)

      1 /*
      2 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
      3 *
      4 *  Use of this source code is governed by a BSD-style license
      5 *  that can be found in the LICENSE file in the root of the source
      6 *  tree. An additional intellectual property rights grant can be found
      7 *  in the file PATENTS.  All contributing project authors may
      8 *  be found in the AUTHORS file in the root of the source tree.
      9 */
     10 
     11 /*
     12 * This file contains implementations of the divisions
     13 * WebRtcSpl_DivU32U16()
     14 * WebRtcSpl_DivW32W16()
     15 * WebRtcSpl_DivW32W16ResW16()
     16 * WebRtcSpl_DivResultInQ31()
     17 * WebRtcSpl_DivW32HiLow()
     18 *
     19 * The description header can be found in signal_processing_library.h
     20 *
     21 */
     22 
     23 #include "common_audio/signal_processing/include/signal_processing_library.h"
     24 #include "rtc_base/sanitizer.h"
     25 
     26 uint32_t WebRtcSpl_DivU32U16(uint32_t num, uint16_t den) {
     27  // Guard against division with 0
     28  if (den != 0) {
     29    return (uint32_t)(num / den);
     30  } else {
     31    return (uint32_t)0xFFFFFFFF;
     32  }
     33 }
     34 
     35 int32_t WebRtcSpl_DivW32W16(int32_t num, int16_t den) {
     36  // Guard against division with 0
     37  if (den != 0) {
     38    return (int32_t)(num / den);
     39  } else {
     40    return (int32_t)0x7FFFFFFF;
     41  }
     42 }
     43 
     44 int16_t WebRtcSpl_DivW32W16ResW16(int32_t num, int16_t den) {
     45  // Guard against division with 0
     46  if (den != 0) {
     47    return (int16_t)(num / den);
     48  } else {
     49    return (int16_t)0x7FFF;
     50  }
     51 }
     52 
     53 int32_t WebRtcSpl_DivResultInQ31(int32_t num, int32_t den) {
     54  int32_t L_num = num;
     55  int32_t L_den = den;
     56  int32_t div = 0;
     57  int k = 31;
     58  int change_sign = 0;
     59 
     60  if (num == 0)
     61    return 0;
     62 
     63  if (num < 0) {
     64    change_sign++;
     65    L_num = -num;
     66  }
     67  if (den < 0) {
     68    change_sign++;
     69    L_den = -den;
     70  }
     71  while (k--) {
     72    div <<= 1;
     73    L_num <<= 1;
     74    if (L_num >= L_den) {
     75      L_num -= L_den;
     76      div++;
     77    }
     78  }
     79  if (change_sign == 1) {
     80    div = -div;
     81  }
     82  return div;
     83 }
     84 
     85 int32_t WebRtcSpl_DivW32HiLow(int32_t num, int16_t den_hi, int16_t den_low) {
     86  int16_t approx, tmp_hi, tmp_low, num_hi, num_low;
     87  int32_t tmpW32;
     88 
     89  approx = (int16_t)WebRtcSpl_DivW32W16((int32_t)0x1FFFFFFF, den_hi);
     90  // result in Q14 (Note: 3FFFFFFF = 0.5 in Q30)
     91 
     92  // tmpW32 = 1/den = approx * (2.0 - den * approx) (in Q30)
     93  tmpW32 = (den_hi * approx << 1) + ((den_low * approx >> 15) << 1);
     94  // tmpW32 = den * approx
     95 
     96  // result in Q30 (tmpW32 = 2.0-(den*approx))
     97  tmpW32 = (int32_t)((int64_t)0x7fffffffL - tmpW32);
     98 
     99  // Store tmpW32 in hi and low format
    100  tmp_hi = (int16_t)(tmpW32 >> 16);
    101  tmp_low = (int16_t)((tmpW32 - ((int32_t)tmp_hi << 16)) >> 1);
    102 
    103  // tmpW32 = 1/den in Q29
    104  tmpW32 = (tmp_hi * approx + (tmp_low * approx >> 15)) << 1;
    105 
    106  // 1/den in hi and low format
    107  tmp_hi = (int16_t)(tmpW32 >> 16);
    108  tmp_low = (int16_t)((tmpW32 - ((int32_t)tmp_hi << 16)) >> 1);
    109 
    110  // Store num in hi and low format
    111  num_hi = (int16_t)(num >> 16);
    112  num_low = (int16_t)((num - ((int32_t)num_hi << 16)) >> 1);
    113 
    114  // num * (1/den) by 32 bit multiplication (result in Q28)
    115 
    116  tmpW32 =
    117      num_hi * tmp_hi + (num_hi * tmp_low >> 15) + (num_low * tmp_hi >> 15);
    118 
    119  // Put result in Q31 (convert from Q28)
    120  tmpW32 = WEBRTC_SPL_LSHIFT_W32(tmpW32, 3);
    121 
    122  return tmpW32;
    123 }