1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16#define LOG_TAG "EFFECTSMATH"
17//#define LOG_NDEBUG 0
18
19#include <assert.h>
20
21#include <android/log.h>
22
23#include "EffectsMath.h"
24
25// gLogTab contains pre-calculated values of log2(1 + ai5*2^-1 + ai4*2^-2 + ai3*2^-3 + ai2*2^-4 + ai1*2^-5 + ai0*2^-6)
26// for integers in the range 0 to 63 (i = ai5*2^5 + ai4*2^4 + ai3*2^3 + ai2*2^2 + ai1*2^1 + ai0*2^0)
27// It is used for a better than piece wise approximation of lin to log2 conversion
28
29static const uint16_t gLogTab[] =
30{
31    0, 733, 1455, 2166,
32    2866, 3556, 4236, 4907,
33    5568, 6220, 6863, 7498,
34    8124, 8742, 9352, 9954,
35    10549, 11136, 11716, 12289,
36    12855, 13415, 13968, 14514,
37    15055, 15589, 16117, 16639,
38    17156, 17667, 18173, 18673,
39    19168, 19658, 20143, 20623,
40    21098, 21568, 22034, 22495,
41    22952, 23404, 23852, 24296,
42    24736, 25172, 25604, 26031,
43    26455, 26876, 27292, 27705,
44    28114, 28520, 28922, 29321,
45    29717, 30109, 30498, 30884,
46    31267, 31647, 32024, 32397,
47    32768
48};
49
50int32_t Effects_log2(uint32_t x) {
51    int32_t exp = 31 - __builtin_clz(x);
52    uint32_t segStart = x >> (exp - 6);
53    uint32_t i = segStart & 0x3F;
54    int32_t log = (int32_t)gLogTab[i];
55    int32_t logEnd = (int32_t)gLogTab[i+1];
56    segStart <<= exp - 6;
57
58    return (exp << 15) + log + (((x - segStart) * (logEnd - log)) >> (exp - 6));
59}
60
61// gExpTab[i] = (2^(i>>6)) << 22
62static const uint32_t gExpTab[] = {
63            4194304, 4239977, 4286147, 4332820,
64            4380002, 4427697, 4475911, 4524651,
65            4573921, 4623728, 4674077, 4724974,
66            4776426, 4828438, 4881016, 4934167,
67            4987896, 5042211, 5097117, 5152621,
68            5208729, 5265449, 5322786, 5380747,
69            5439339, 5498570, 5558445, 5618973,
70            5680159, 5742012, 5804539, 5867746,
71            5931642, 5996233, 6061528, 6127533,
72            6194258, 6261709, 6329894, 6398822,
73            6468501, 6538938, 6610143, 6682122,
74            6754886, 6828442, 6902799, 6977965,
75            7053950, 7130763, 7208412, 7286906,
76            7366255, 7446469, 7527555, 7609525,
77            7692387, 7776152, 7860829, 7946428,
78            8032959, 8120432, 8208857, 8298246,
79            8388608
80};
81
82
83uint32_t Effects_exp2(int32_t x) {
84    int32_t i = x >> 15;
85    assert(i < 32);
86    x &= (1 << 15) - 1;
87    int32_t j = x >> 9;
88    x &= (1 << 9) - 1;
89    uint32_t exp = gExpTab[j];
90    uint32_t expEnd = gExpTab[j+1];
91
92    return ((exp << 9) + (expEnd - exp) * x) >> (31 - i);
93}
94
95
96int16_t Effects_MillibelsToLinear16 (int32_t nGain)
97{
98    nGain = ((nGain + MB_TO_LIN_K1) << 15 ) / MB_TO_LIN_K2;
99    uint32_t exp2 = Effects_exp2(nGain);
100
101    if (exp2 > 32767) exp2 = 32767;
102
103    return (int16_t)exp2;
104}
105
106
107int16_t Effects_Linear16ToMillibels (int32_t nGain)
108{
109    return (int16_t)(((MB_TO_LIN_K2*Effects_log2(nGain))>>15)-MB_TO_LIN_K1);
110}
111
112
113int32_t Effects_Sqrt(int32_t in)
114{
115    int32_t tmp;
116    int32_t out = 0;
117    int32_t i;
118    int32_t j;
119
120
121    if (in == 0) return 0;
122
123    if (in >= 0x10000000)
124    {
125        out = 0x4000;
126        in -= 0x10000000;
127    }
128
129    j = 32 - __builtin_clz(in);
130
131    if (j & 1) j++;
132    j >>= 1;
133
134    for (i = j; i > 0; i--) {
135        tmp = (out << i) + (1 << ((i - 1)*2));
136        if (in >= tmp)
137        {
138            out += 1 << (i-1);
139            in -= tmp;
140        }
141    }
142
143    return out;
144}
145
146