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 /*
13  * This file contains implementations of the divisions
14  * WebRtcSpl_DivU32U16()
15  * WebRtcSpl_DivW32W16()
16  * WebRtcSpl_DivW32W16ResW16()
17  * WebRtcSpl_DivResultInQ31()
18  * WebRtcSpl_DivW32HiLow()
19  *
20  * The description header can be found in signal_processing_library.h
21  *
22  */
23 
24 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
25 
WebRtcSpl_DivU32U16(uint32_t num,uint16_t den)26 uint32_t WebRtcSpl_DivU32U16(uint32_t num, uint16_t den)
27 {
28     // Guard against division with 0
29     if (den != 0)
30     {
31         return (uint32_t)(num / den);
32     } else
33     {
34         return (uint32_t)0xFFFFFFFF;
35     }
36 }
37 
WebRtcSpl_DivW32W16(int32_t num,int16_t den)38 int32_t WebRtcSpl_DivW32W16(int32_t num, int16_t den)
39 {
40     // Guard against division with 0
41     if (den != 0)
42     {
43         return (int32_t)(num / den);
44     } else
45     {
46         return (int32_t)0x7FFFFFFF;
47     }
48 }
49 
WebRtcSpl_DivW32W16ResW16(int32_t num,int16_t den)50 int16_t WebRtcSpl_DivW32W16ResW16(int32_t num, int16_t den)
51 {
52     // Guard against division with 0
53     if (den != 0)
54     {
55         return (int16_t)(num / den);
56     } else
57     {
58         return (int16_t)0x7FFF;
59     }
60 }
61 
WebRtcSpl_DivResultInQ31(int32_t num,int32_t den)62 int32_t WebRtcSpl_DivResultInQ31(int32_t num, int32_t den)
63 {
64     int32_t L_num = num;
65     int32_t L_den = den;
66     int32_t div = 0;
67     int k = 31;
68     int change_sign = 0;
69 
70     if (num == 0)
71         return 0;
72 
73     if (num < 0)
74     {
75         change_sign++;
76         L_num = -num;
77     }
78     if (den < 0)
79     {
80         change_sign++;
81         L_den = -den;
82     }
83     while (k--)
84     {
85         div <<= 1;
86         L_num <<= 1;
87         if (L_num >= L_den)
88         {
89             L_num -= L_den;
90             div++;
91         }
92     }
93     if (change_sign == 1)
94     {
95         div = -div;
96     }
97     return div;
98 }
99 
WebRtcSpl_DivW32HiLow(int32_t num,int16_t den_hi,int16_t den_low)100 int32_t WebRtcSpl_DivW32HiLow(int32_t num, int16_t den_hi, int16_t den_low)
101 {
102     int16_t approx, tmp_hi, tmp_low, num_hi, num_low;
103     int32_t tmpW32;
104 
105     approx = (int16_t)WebRtcSpl_DivW32W16((int32_t)0x1FFFFFFF, den_hi);
106     // result in Q14 (Note: 3FFFFFFF = 0.5 in Q30)
107 
108     // tmpW32 = 1/den = approx * (2.0 - den * approx) (in Q30)
109     tmpW32 = (den_hi * approx << 1) + ((den_low * approx >> 15) << 1);
110     // tmpW32 = den * approx
111 
112     tmpW32 = (int32_t)0x7fffffffL - tmpW32; // result in Q30 (tmpW32 = 2.0-(den*approx))
113 
114     // Store tmpW32 in hi and low format
115     tmp_hi = (int16_t)(tmpW32 >> 16);
116     tmp_low = (int16_t)((tmpW32 - ((int32_t)tmp_hi << 16)) >> 1);
117 
118     // tmpW32 = 1/den in Q29
119     tmpW32 = (tmp_hi * approx + (tmp_low * approx >> 15)) << 1;
120 
121     // 1/den in hi and low format
122     tmp_hi = (int16_t)(tmpW32 >> 16);
123     tmp_low = (int16_t)((tmpW32 - ((int32_t)tmp_hi << 16)) >> 1);
124 
125     // Store num in hi and low format
126     num_hi = (int16_t)(num >> 16);
127     num_low = (int16_t)((num - ((int32_t)num_hi << 16)) >> 1);
128 
129     // num * (1/den) by 32 bit multiplication (result in Q28)
130 
131     tmpW32 = num_hi * tmp_hi + (num_hi * tmp_low >> 15) +
132         (num_low * tmp_hi >> 15);
133 
134     // Put result in Q31 (convert from Q28)
135     tmpW32 = WEBRTC_SPL_LSHIFT_W32(tmpW32, 3);
136 
137     return tmpW32;
138 }
139