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/*************************************************
* Bit/Word Operations Source File *
* (C) 1999-2006 The Botan Project *
*************************************************/
#include <botan/bit_ops.h>
namespace Botan {
/*************************************************
* XOR arrays together *
*************************************************/
void xor_buf(byte data[], const byte mask[], u32bit length)
{
while(length >= 8)
{
data[0] ^= mask[0]; data[1] ^= mask[1];
data[2] ^= mask[2]; data[3] ^= mask[3];
data[4] ^= mask[4]; data[5] ^= mask[5];
data[6] ^= mask[6]; data[7] ^= mask[7];
data += 8; mask += 8; length -= 8;
}
for(u32bit j = 0; j != length; ++j)
data[j] ^= mask[j];
}
void xor_buf(byte out[], const byte in[], const byte mask[], u32bit length)
{
while(length >= 8)
{
out[0] = in[0] ^ mask[0]; out[1] = in[1] ^ mask[1];
out[2] = in[2] ^ mask[2]; out[3] = in[3] ^ mask[3];
out[4] = in[4] ^ mask[4]; out[5] = in[5] ^ mask[5];
out[6] = in[6] ^ mask[6]; out[7] = in[7] ^ mask[7];
in += 8; out += 8; mask += 8; length -= 8;
}
for(u32bit j = 0; j != length; ++j)
out[j] = in[j] ^ mask[j];
}
/*************************************************
* Return true iff arg is 2**n for some n > 0 *
*************************************************/
bool power_of_2(u64bit arg)
{
if(arg == 0 || arg == 1)
return false;
if((arg & (arg-1)) == 0)
return true;
return false;
}
/*************************************************
* Return the index of the highest set bit *
*************************************************/
u32bit high_bit(u64bit n)
{
for(u32bit count = 64; count > 0; --count)
if((n >> (count - 1)) & 0x01)
return count;
return 0;
}
/*************************************************
* Return the index of the lowest set bit *
*************************************************/
u32bit low_bit(u64bit n)
{
for(u32bit count = 0; count != 64; ++count)
if((n >> count) & 0x01)
return (count + 1);
return 0;
}
/*************************************************
* Return the number of significant bytes in n *
*************************************************/
u32bit significant_bytes(u64bit n)
{
for(u32bit j = 0; j != 8; ++j)
if(get_byte(j, n))
return 8-j;
return 0;
}
/*************************************************
* Return the Hamming weight of n *
*************************************************/
u32bit hamming_weight(u64bit n)
{
u32bit weight = 0;
for(u32bit j = 0; j != 64; ++j)
if((n >> j) & 0x01)
++weight;
return weight;
}
}
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