1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_bitreversal.c
4 * Description: Bitreversal functions
5 *
6 * $Date: 23 April 2021
7 * $Revision: V1.9.0
8 *
9 * Target Processor: Cortex-M and Cortex-A cores
10 * -------------------------------------------------------------------- */
11 /*
12 * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
13 *
14 * SPDX-License-Identifier: Apache-2.0
15 *
16 * Licensed under the Apache License, Version 2.0 (the License); you may
17 * not use this file except in compliance with the License.
18 * You may obtain a copy of the License at
19 *
20 * www.apache.org/licenses/LICENSE-2.0
21 *
22 * Unless required by applicable law or agreed to in writing, software
23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
25 * See the License for the specific language governing permissions and
26 * limitations under the License.
27 */
28
29 #include "dsp/transform_functions.h"
30 #include "arm_common_tables.h"
31
32
33 /**
34 @brief In-place floating-point bit reversal function.
35 @param[in,out] pSrc points to in-place floating-point data buffer
36 @param[in] fftSize length of FFT
37 @param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
38 @param[in] pBitRevTab points to bit reversal table
39 @return none
40 */
41
arm_bitreversal_f32(float32_t * pSrc,uint16_t fftSize,uint16_t bitRevFactor,const uint16_t * pBitRevTab)42 void arm_bitreversal_f32(
43 float32_t * pSrc,
44 uint16_t fftSize,
45 uint16_t bitRevFactor,
46 const uint16_t * pBitRevTab)
47 {
48 uint16_t fftLenBy2, fftLenBy2p1;
49 uint16_t i, j;
50 float32_t in;
51
52 /* Initializations */
53 j = 0U;
54 fftLenBy2 = fftSize >> 1U;
55 fftLenBy2p1 = (fftSize >> 1U) + 1U;
56
57 /* Bit Reversal Implementation */
58 for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
59 {
60 if (i < j)
61 {
62 /* pSrc[i] <-> pSrc[j]; */
63 in = pSrc[2U * i];
64 pSrc[2U * i] = pSrc[2U * j];
65 pSrc[2U * j] = in;
66
67 /* pSrc[i+1U] <-> pSrc[j+1U] */
68 in = pSrc[(2U * i) + 1U];
69 pSrc[(2U * i) + 1U] = pSrc[(2U * j) + 1U];
70 pSrc[(2U * j) + 1U] = in;
71
72 /* pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
73 in = pSrc[2U * (i + fftLenBy2p1)];
74 pSrc[2U * (i + fftLenBy2p1)] = pSrc[2U * (j + fftLenBy2p1)];
75 pSrc[2U * (j + fftLenBy2p1)] = in;
76
77 /* pSrc[i+fftLenBy2p1+1U] <-> pSrc[j+fftLenBy2p1+1U] */
78 in = pSrc[(2U * (i + fftLenBy2p1)) + 1U];
79 pSrc[(2U * (i + fftLenBy2p1)) + 1U] =
80 pSrc[(2U * (j + fftLenBy2p1)) + 1U];
81 pSrc[(2U * (j + fftLenBy2p1)) + 1U] = in;
82
83 }
84
85 /* pSrc[i+1U] <-> pSrc[j+1U] */
86 in = pSrc[2U * (i + 1U)];
87 pSrc[2U * (i + 1U)] = pSrc[2U * (j + fftLenBy2)];
88 pSrc[2U * (j + fftLenBy2)] = in;
89
90 /* pSrc[i+2U] <-> pSrc[j+2U] */
91 in = pSrc[(2U * (i + 1U)) + 1U];
92 pSrc[(2U * (i + 1U)) + 1U] = pSrc[(2U * (j + fftLenBy2)) + 1U];
93 pSrc[(2U * (j + fftLenBy2)) + 1U] = in;
94
95 /* Reading the index for the bit reversal */
96 j = *pBitRevTab;
97
98 /* Updating the bit reversal index depending on the fft length */
99 pBitRevTab += bitRevFactor;
100 }
101 }
102
103
104 /**
105 @brief In-place Q31 bit reversal function.
106 @param[in,out] pSrc points to in-place Q31 data buffer.
107 @param[in] fftLen length of FFT.
108 @param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
109 @param[in] pBitRevTab points to bit reversal table
110 @return none
111 */
112
arm_bitreversal_q31(q31_t * pSrc,uint32_t fftLen,uint16_t bitRevFactor,const uint16_t * pBitRevTab)113 void arm_bitreversal_q31(
114 q31_t * pSrc,
115 uint32_t fftLen,
116 uint16_t bitRevFactor,
117 const uint16_t * pBitRevTab)
118 {
119 uint32_t fftLenBy2, fftLenBy2p1, i, j;
120 q31_t in;
121
122 /* Initializations */
123 j = 0U;
124 fftLenBy2 = fftLen / 2U;
125 fftLenBy2p1 = (fftLen / 2U) + 1U;
126
127 /* Bit Reversal Implementation */
128 for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
129 {
130 if (i < j)
131 {
132 /* pSrc[i] <-> pSrc[j]; */
133 in = pSrc[2U * i];
134 pSrc[2U * i] = pSrc[2U * j];
135 pSrc[2U * j] = in;
136
137 /* pSrc[i+1U] <-> pSrc[j+1U] */
138 in = pSrc[(2U * i) + 1U];
139 pSrc[(2U * i) + 1U] = pSrc[(2U * j) + 1U];
140 pSrc[(2U * j) + 1U] = in;
141
142 /* pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
143 in = pSrc[2U * (i + fftLenBy2p1)];
144 pSrc[2U * (i + fftLenBy2p1)] = pSrc[2U * (j + fftLenBy2p1)];
145 pSrc[2U * (j + fftLenBy2p1)] = in;
146
147 /* pSrc[i+fftLenBy2p1+1U] <-> pSrc[j+fftLenBy2p1+1U] */
148 in = pSrc[(2U * (i + fftLenBy2p1)) + 1U];
149 pSrc[(2U * (i + fftLenBy2p1)) + 1U] =
150 pSrc[(2U * (j + fftLenBy2p1)) + 1U];
151 pSrc[(2U * (j + fftLenBy2p1)) + 1U] = in;
152
153 }
154
155 /* pSrc[i+1U] <-> pSrc[j+1U] */
156 in = pSrc[2U * (i + 1U)];
157 pSrc[2U * (i + 1U)] = pSrc[2U * (j + fftLenBy2)];
158 pSrc[2U * (j + fftLenBy2)] = in;
159
160 /* pSrc[i+2U] <-> pSrc[j+2U] */
161 in = pSrc[(2U * (i + 1U)) + 1U];
162 pSrc[(2U * (i + 1U)) + 1U] = pSrc[(2U * (j + fftLenBy2)) + 1U];
163 pSrc[(2U * (j + fftLenBy2)) + 1U] = in;
164
165 /* Reading the index for the bit reversal */
166 j = *pBitRevTab;
167
168 /* Updating the bit reversal index depending on the fft length */
169 pBitRevTab += bitRevFactor;
170 }
171 }
172
173
174
175 /**
176 @brief In-place Q15 bit reversal function.
177 @param[in,out] pSrc16 points to in-place Q15 data buffer
178 @param[in] fftLen length of FFT
179 @param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
180 @param[in] pBitRevTab points to bit reversal table
181 @return none
182 */
183
arm_bitreversal_q15(q15_t * pSrc16,uint32_t fftLen,uint16_t bitRevFactor,const uint16_t * pBitRevTab)184 void arm_bitreversal_q15(
185 q15_t * pSrc16,
186 uint32_t fftLen,
187 uint16_t bitRevFactor,
188 const uint16_t * pBitRevTab)
189 {
190 q31_t *pSrc = (q31_t *) pSrc16;
191 q31_t in;
192 uint32_t fftLenBy2, fftLenBy2p1;
193 uint32_t i, j;
194
195 /* Initializations */
196 j = 0U;
197 fftLenBy2 = fftLen / 2U;
198 fftLenBy2p1 = (fftLen / 2U) + 1U;
199
200 /* Bit Reversal Implementation */
201 for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
202 {
203 if (i < j)
204 {
205 /* pSrc[i] <-> pSrc[j]; */
206 /* pSrc[i+1U] <-> pSrc[j+1U] */
207 in = pSrc[i];
208 pSrc[i] = pSrc[j];
209 pSrc[j] = in;
210
211 /* pSrc[i + fftLenBy2p1] <-> pSrc[j + fftLenBy2p1]; */
212 /* pSrc[i + fftLenBy2p1+1U] <-> pSrc[j + fftLenBy2p1+1U] */
213 in = pSrc[i + fftLenBy2p1];
214 pSrc[i + fftLenBy2p1] = pSrc[j + fftLenBy2p1];
215 pSrc[j + fftLenBy2p1] = in;
216 }
217
218 /* pSrc[i+1U] <-> pSrc[j+fftLenBy2]; */
219 /* pSrc[i+2] <-> pSrc[j+fftLenBy2+1U] */
220 in = pSrc[i + 1U];
221 pSrc[i + 1U] = pSrc[j + fftLenBy2];
222 pSrc[j + fftLenBy2] = in;
223
224 /* Reading the index for the bit reversal */
225 j = *pBitRevTab;
226
227 /* Updating the bit reversal index depending on the fft length */
228 pBitRevTab += bitRevFactor;
229 }
230 }
231