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 the function WebRtcSpl_ComplexBitReverse().
14  * The description header can be found in signal_processing_library.h
15  *
16  */
17 
18 #include "signal_processing_library.h"
19 
WebRtcSpl_ComplexBitReverse(WebRtc_Word16 frfi[],int stages)20 void WebRtcSpl_ComplexBitReverse(WebRtc_Word16 frfi[], int stages)
21 {
22     int mr, nn, n, l, m;
23     WebRtc_Word16 tr, ti;
24 
25     n = 1 << stages;
26 
27     mr = 0;
28     nn = n - 1;
29 
30     // decimation in time - re-order data
31     for (m = 1; m <= nn; ++m)
32     {
33         l = n;
34         do
35         {
36             l >>= 1;
37         } while (mr + l > nn);
38         mr = (mr & (l - 1)) + l;
39 
40         if (mr <= m)
41             continue;
42 
43         tr = frfi[2 * m];
44         frfi[2 * m] = frfi[2 * mr];
45         frfi[2 * mr] = tr;
46 
47         ti = frfi[2 * m + 1];
48         frfi[2 * m + 1] = frfi[2 * mr + 1];
49         frfi[2 * mr + 1] = ti;
50     }
51 }
52