1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_bitreversal_f16.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_f16.h"
30
31 /*
32 * @brief In-place bit reversal function.
33 * @param[in, out] *pSrc points to the in-place buffer of floating-point data type.
34 * @param[in] fftSize length of the FFT.
35 * @param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table.
36 * @param[in] *pBitRevTab points to the bit reversal table.
37 * @return none.
38 */
39
40 #if defined(ARM_FLOAT16_SUPPORTED)
41
arm_bitreversal_f16(float16_t * pSrc,uint16_t fftSize,uint16_t bitRevFactor,const uint16_t * pBitRevTab)42 void arm_bitreversal_f16(
43 float16_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 float16_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 #endif /* #if defined(ARM_FLOAT16_SUPPORTED) */