/usr/include/botan/bit_ops.h is in libbotan1.8-dev 1.8.13-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 | /*
* Bit/Word Operations
* (C) 1999-2008 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#ifndef BOTAN_BIT_OPS_H__
#define BOTAN_BIT_OPS_H__
#include <botan/types.h>
namespace Botan {
/*
* Return true iff arg is 2**n for some n > 0
* T should be an unsigned integer type
*/
template<typename T>
inline bool power_of_2(T arg)
{
return ((arg != 0 && arg != 1) && ((arg & (arg-1)) == 0));
}
/*
* Return the index of the highest set bit
* T is an unsigned integer type
*/
template<typename T>
inline u32bit high_bit(T n)
{
for(u32bit i = 8*sizeof(T); i > 0; --i)
if((n >> (i - 1)) & 0x01)
return i;
return 0;
}
/*
* Return the index of the lowest set bit
*/
template<typename T>
inline u32bit low_bit(T n)
{
for(u32bit i = 0; i != 8*sizeof(T); ++i)
if((n >> i) & 0x01)
return (i + 1);
return 0;
}
/*
* Return the number of significant bytes in n
*/
template<typename T>
inline u32bit significant_bytes(T n)
{
for(u32bit j = 0; j != sizeof(T); ++j)
if(get_byte(j, n))
return sizeof(T)-j;
return 0;
}
/*
* Return the Hamming weight of n
*/
template<typename T>
inline u32bit hamming_weight(T n)
{
const byte NIBBLE_WEIGHTS[] = {
0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
u32bit weight = 0;
for(u32bit i = 0; i != 2*sizeof(T); ++i)
weight += NIBBLE_WEIGHTS[(n >> (4*i)) & 0x0F];
return weight;
}
/*
* Count the trailing zero bits in n
*/
template<typename T>
inline u32bit ctz(T n)
{
for(u32bit i = 0; i != 8*sizeof(T); ++i)
if((n >> i) & 0x01)
return i;
return 8*sizeof(T);
}
}
#endif
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