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/*
* Copyright (c) 2012 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.
*/
#include "common_audio/signal_processing/include/signal_processing_library.h"
/* Tables for data buffer indexes that are bit reversed and thus need to be
* swapped. Note that, index_7[{0, 2, 4, ...}] are for the left side of the swap
* operations, while index_7[{1, 3, 5, ...}] are for the right side of the
* operation. Same for index_8.
*/
/* Indexes for the case of stages == 7. */
static const int16_t index_7[112] = {
1, 64, 2, 32, 3, 96, 4, 16, 5, 80, 6, 48, 7, 112, 9, 72,
10, 40, 11, 104, 12, 24, 13, 88, 14, 56, 15, 120, 17, 68, 18, 36,
19, 100, 21, 84, 22, 52, 23, 116, 25, 76, 26, 44, 27, 108, 29, 92,
30, 60, 31, 124, 33, 66, 35, 98, 37, 82, 38, 50, 39, 114, 41, 74,
43, 106, 45, 90, 46, 58, 47, 122, 49, 70, 51, 102, 53, 86, 55, 118,
57, 78, 59, 110, 61, 94, 63, 126, 67, 97, 69, 81, 71, 113, 75, 105,
77, 89, 79, 121, 83, 101, 87, 117, 91, 109, 95, 125, 103, 115, 111, 123};
/* Indexes for the case of stages == 8. */
static const int16_t index_8[240] = {
1, 128, 2, 64, 3, 192, 4, 32, 5, 160, 6, 96, 7, 224, 8,
16, 9, 144, 10, 80, 11, 208, 12, 48, 13, 176, 14, 112, 15, 240,
17, 136, 18, 72, 19, 200, 20, 40, 21, 168, 22, 104, 23, 232, 25,
152, 26, 88, 27, 216, 28, 56, 29, 184, 30, 120, 31, 248, 33, 132,
34, 68, 35, 196, 37, 164, 38, 100, 39, 228, 41, 148, 42, 84, 43,
212, 44, 52, 45, 180, 46, 116, 47, 244, 49, 140, 50, 76, 51, 204,
53, 172, 54, 108, 55, 236, 57, 156, 58, 92, 59, 220, 61, 188, 62,
124, 63, 252, 65, 130, 67, 194, 69, 162, 70, 98, 71, 226, 73, 146,
74, 82, 75, 210, 77, 178, 78, 114, 79, 242, 81, 138, 83, 202, 85,
170, 86, 106, 87, 234, 89, 154, 91, 218, 93, 186, 94, 122, 95, 250,
97, 134, 99, 198, 101, 166, 103, 230, 105, 150, 107, 214, 109, 182, 110,
118, 111, 246, 113, 142, 115, 206, 117, 174, 119, 238, 121, 158, 123, 222,
125, 190, 127, 254, 131, 193, 133, 161, 135, 225, 137, 145, 139, 209, 141,
177, 143, 241, 147, 201, 149, 169, 151, 233, 155, 217, 157, 185, 159, 249,
163, 197, 167, 229, 171, 213, 173, 181, 175, 245, 179, 205, 183, 237, 187,
221, 191, 253, 199, 227, 203, 211, 207, 243, 215, 235, 223, 251, 239, 247};
void WebRtcSpl_ComplexBitReverse(int16_t* __restrict complex_data, int stages) {
/* For any specific value of stages, we know exactly the indexes that are
* bit reversed. Currently (Feb. 2012) in WebRTC the only possible values of
* stages are 7 and 8, so we use tables to save unnecessary iterations and
* calculations for these two cases.
*/
if (stages == 7 || stages == 8) {
int m = 0;
int length = 112;
const int16_t* index = index_7;
if (stages == 8) {
length = 240;
index = index_8;
}
/* Decimation in time. Swap the elements with bit-reversed indexes. */
for (m = 0; m < length; m += 2) {
/* We declare a int32_t* type pointer, to load both the 16-bit real
* and imaginary elements from complex_data in one instruction, reducing
* complexity.
*/
int32_t* complex_data_ptr = (int32_t*)complex_data;
int32_t temp = 0;
temp = complex_data_ptr[index[m]]; /* Real and imaginary */
complex_data_ptr[index[m]] = complex_data_ptr[index[m + 1]];
complex_data_ptr[index[m + 1]] = temp;
}
} else {
int m = 0, mr = 0, l = 0;
int n = 1 << stages;
int nn = n - 1;
/* Decimation in time - re-order data */
for (m = 1; m <= nn; ++m) {
int32_t* complex_data_ptr = (int32_t*)complex_data;
int32_t temp = 0;
/* Find out indexes that are bit-reversed. */
l = n;
do {
l >>= 1;
} while (l > nn - mr);
mr = (mr & (l - 1)) + l;
if (mr <= m) {
continue;
}
/* Swap the elements with bit-reversed indexes.
* This is similar to the loop in the stages == 7 or 8 cases.
*/
temp = complex_data_ptr[m]; /* Real and imaginary */
complex_data_ptr[m] = complex_data_ptr[mr];
complex_data_ptr[mr] = temp;
}
}
}
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