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5
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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * bit_operations.c - Various bit level operations, such as bit reversal
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2006 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 *
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17 * This program is distributed in the hope that it will be useful,
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18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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20 * GNU General Public License for more details.
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21 *
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22 * You should have received a copy of the GNU General Public License
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23 * along with this program; if not, write to the Free Software
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24 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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25 *
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26 * $Id: bit_operations.c,v 1.5 2006/11/30 15:41:47 steveu Exp $
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27 */
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28
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29 /*! \file */
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30
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31 #ifdef HAVE_CONFIG_H
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32 #include "config.h"
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33 #endif
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34
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35 #include <inttypes.h>
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36 #include <stdlib.h>
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37 #include <fcntl.h>
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38 #include <string.h>
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39 #include <assert.h>
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40 #include <memory.h>
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41
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42 #include "spandsp/telephony.h"
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43 #include "spandsp/bit_operations.h"
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44
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45 uint16_t bit_reverse16(uint16_t x)
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46 {
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47 x = (x >> 8) | (x << 8);
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48 x = ((x & 0xF0F0) >> 4) | ((x & 0x0F0F) << 4);
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49 x = ((x & 0xCCCC) >> 2) | ((x & 0x3333) << 2);
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50 return ((x & 0xAAAA) >> 1) | ((x & 0x5555) << 1);
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51 }
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52 /*- End of function --------------------------------------------------------*/
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53
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54 uint32_t bit_reverse32(uint32_t x)
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55 {
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56 x = (x >> 16) | (x << 16);
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57 x = ((x & 0xFF00FF00) >> 8) | ((x & 0x00FF00FF) << 8);
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58 x = ((x & 0xF0F0F0F0) >> 4) | ((x & 0x0F0F0F0F) << 4);
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59 x = ((x & 0xCCCCCCCC) >> 2) | ((x & 0x33333333) << 2);
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60 return ((x & 0xAAAAAAAA) >> 1) | ((x & 0x55555555) << 1);
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61 }
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62 /*- End of function --------------------------------------------------------*/
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63
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64 uint32_t bit_reverse_4bytes(uint32_t x)
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65 {
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66 x = (x >> 4) | (x << 4);
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67 x = ((x & 0xCCCCCCCC) >> 2) | ((x & 0x33333333) << 2);
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68 return ((x & 0xAAAAAAAA) >> 1) | ((x & 0x55555555) << 1);
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69 }
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70 /*- End of function --------------------------------------------------------*/
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71
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72 int one_bits32(uint32_t x)
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73 {
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74 x = x - ((x >> 1) & 0x55555555);
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75 /* We now have 16 2-bit counts */
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76 x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
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77 /* We now have 8 4-bit counts */
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78 x = (x + (x >> 4)) & 0x0F0F0F0F;
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79 /* We now have 4 8-bit counts */
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80 #if defined(__i386__) || defined(__x86_64__)
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81 /* If multiply is fast */
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82 return (x*0x01010101) >> 24;
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83 #else
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84 /* If multiply is slow */
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85 x += (x >> 8);
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86 x += (x >> 16);
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87 return (x & 0x0000003F);
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88 #endif
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89 }
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90 /*- End of function --------------------------------------------------------*/
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91
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92 uint32_t make_mask32(uint32_t x)
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93 {
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94 x |= (x >> 1);
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95 x |= (x >> 2);
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96 x |= (x >> 4);
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97 x |= (x >> 8);
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98 x |= (x >> 16);
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99 return x;
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100 }
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101 /*- End of function --------------------------------------------------------*/
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102
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103 uint16_t make_mask16(uint16_t x)
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104 {
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105 x |= (x >> 1);
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106 x |= (x >> 2);
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107 x |= (x >> 4);
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108 x |= (x >> 8);
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109 return x;
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110 }
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111 /*- End of function --------------------------------------------------------*/
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112 /*- End of file ------------------------------------------------------------*/
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