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This commit is contained in:
jwellbelove 2017-01-04 16:33:44 +00:00
parent 4bde024c03
commit 5e77c55573
1 changed files with 50 additions and 40 deletions
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90
src/binary.h
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@ -71,12 +71,6 @@ namespace etl
template <const size_t NBITS>
const typename max_value_for_nbits_helper<NBITS>::value_type max_value_for_nbits_helper<NBITS>::value;
static const uint_least8_t bit_position_lookup[32] =
{
0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,
31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
};
}
/// Definition for non-zero NBITS.
@ -571,69 +565,85 @@ namespace etl
}
//***************************************************************************
/// Find the value of the first set bit.
/// Starts from LSB.
/// Count trailing zeros.
/// Uses a binary search.
//***************************************************************************
uint32_t first_set_bit(uint32_t value)
template <typename T>
typename etl::enable_if<etl::is_same<typename etl::make_unsigned<T>::type, uint32_t>::value, uint_least8_t>::type
count_trailing_zeros(uint32_t value)
{
return (uint32_t)(value & -value);
uint_least8_t count;
if (value & 0x1)
{
count = 0;
}
else
{
count = 1;
if ((value & 0xffff) == 0)
{
value >>= 16;
count += 16;
}
if ((value & 0xff) == 0)
{
value >>= 8;
count += 8;
}
if ((value & 0xf) == 0)
{
value >>= 4;
count += 4;
}
if ((value & 0x3) == 0)
{
value >>= 2;
count += 2;
}
count -= value & 0x1;
}
}
//***************************************************************************
/// Find the position of the first set bit.
/// Starts from LSB.
//***************************************************************************
uint_least8_t first_set_bit_position(uint32_t value)
template <typename T>
uint_least8_t first_set_bit_position(T value)
{
return __private_binary__::bit_position_lookup[(first_set_bit(value) * 0x077CB531U) >> 27];
}
//***************************************************************************
/// Find the value of the first clear bit.
/// Starts from LSB.
//***************************************************************************
uint32_t first_clear_bit(uint32_t value)
{
value = ~value;
return (uint32_t)(value & -value);
return count_trailing_zeros(value);
}
//***************************************************************************
/// Find the position of the first clear bit.
/// Starts from LSB.
//***************************************************************************
uint_least8_t first_clear_bit_position(uint32_t value)
template <typename T>
uint_least8_t first_clear_bit_position(T value)
{
value ~= value;
return __private_binary__::bit_position_lookup[((uint32_t)((value & -value) * 0x077CB531U)) >> 27];
return count_trailing_zeros(value);
}
//***************************************************************************
/// Find the position of the first bit that is clear or set.
/// Starts from LSB.
//***************************************************************************
uint_least8_t first_bit(bool state, uint32_t value)
template <typename T>
uint_least8_t first_bit_position(bool state, T value)
{
if (!state)
{
value ~= value;
}
return (uint32_t)(value & -value);
}
//***************************************************************************
/// Find the position of the first bit that is clear or set.
/// Starts from LSB.
//***************************************************************************
uint_least8_t first_bit_position(bool state, uint32_t value)
{
if (!state)
{
value ~= value;
}
return __private_binary__::bit_position_lookup[((uint32_t)((value & -value) * 0x077CB531U)) >> 27];
return count_trailing_zeros(value);
}
//***************************************************************************