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Added find first set/clear bit functions.

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This commit is contained in:
jwellbelove 2017-01-04 11:23:16 +00:00
parent a371b27c2a
commit c24d007d5c
1 changed files with 39 additions and 0 deletions
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39
src/binary.h
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@ -71,6 +71,12 @@ 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.
@ -564,6 +570,39 @@ namespace etl
return signed_value;
}
//***************************************************************************
/// Find the position of the first set bit.
/// Starts from LSB.
//***************************************************************************
uint_least8_t find_first_set_bit(uint32_t value)
{
return __private_binary__::bit_position_lookup[((uint32_t)((value & -value) * 0x077CB531U)) >> 27];
}
//***************************************************************************
/// Find the position of the first clear bit.
/// Starts from LSB.
//***************************************************************************
uint_least8_t find_first_clear_bit(uint32_t value)
{
value ~= value;
return __private_binary__::bit_position_lookup[((uint32_t)((value & -value) * 0x077CB531U)) >> 27];
}
//***************************************************************************
/// Find the position of the first bit that is clear or set.
/// Starts from LSB.
//***************************************************************************
uint_least8_t find_first_bit(bool state, uint32_t value)
{
if (!state)
{
value ~= value;
}
return __private_binary__::bit_position_lookup[((uint32_t)((value & -value) * 0x077CB531U)) >> 27];
}
//***************************************************************************
/// 8 bit binary constants.
//***************************************************************************