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Embedded Template Library
Binary utilities
binary

binary

Header: binary.h
Since: TBC

Utility functions for manipulating binary numbers.

Rotate

Rotate the bits in the value left or right.

template <typename T>
ETL_CONSTEXPR14 T rotate_left(T value)

Return
value rotated left by one bit.

template <typename T>
ETL_CONSTEXPR14 T rotate_left(T value, size_t distance)

Return
value rotated left by distance.

template <typename T>
ETL_CONSTEXPR14 T rotate_right(T value)

Return
value rotated right by one bit.

template <typename T>
ETL_CONSTEXPR14 T rotate_right(T value, size_t distance)

Return
value rotated right by distance.

template <typename T>
ETL_CONSTEXPR14 T rotate(T value, typename etl::make_signed<size_t>::type distance)

Parameters
distance Positive is left, negative is right.
Return
value rotated left or right by distance.

reverse_bits

Reverse the order of the bits in a value.

template <typename T>
ETL_CONSTEXPR14 T reverse_bits(T value)

The structures below define a member constant value that is Value reversed in bits.

template <int8_t Value>
struct reverse_bits_const<int8_t, Value>
template <uint8_t Value>
struct reverse_bits_const<uint8_t, Value>
template <int16_t Value>
struct reverse_bits_const<int16_t, Value>
template <uint16_t Value>
struct reverse_bits_const<uint16_t, Value>
template <int32_t Value>
struct reverse_bits_const<int32_t, Value>
template <uint32_t Value>
struct reverse_bits_const<uint32_t, Value>
template <int64_t Value>
struct reverse_bits_const<int64_t, Value>
template <uint64_t Value>
struct reverse_bits_const<uint64_t, Value>

Defines value The reversed bits.

reverse_bytes

Reverse the order of the bytes in a value.

template <typename T>
ETL_CONSTEXPR14 T reverse_bytes(T value)

gray_to_binary 

template <typename T>
ETL_CONSTEXPR14 T gray_to_binary(T value)

Converts a gray code value to binary.

binary_to_gray 

template <typename T>
ETL_CONSTEXPR T binary_to_gray(T value)

Converts a binary value to the gray code equivalent.

count_bits 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t count_bits(T value)

Return
The number of set bits in value.

parity 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t parity(T value)

Return
1 if the parity of the value is odd, 0 if it is even.

max_value_for_nbits 

template <size_t NBits>
struct max_value_for_nbits

Return
Maximum unsigned value a particular number of bits can represent.

value_type The type for the value. value The maximum value.

fold_bits 

template <typename TReturn, size_t NBits, typename TValue>
ETL_CONSTEXPR14 TReturn fold_bits(TValue value)

Description
Fold a binary number down to a set number of bits using XOR.

Example
0xE8C9AACCBC3D9A8F folded down to 20 bits = 0x998E8

uint32_t result = etl::fold_bits<uint32_t, 20>(0xE8C9AACCBC3D9A8F);

sign_extend

Sign extends a binary number.

template <typename TReturn, size_t NBits, typename TValue>
ETL_CONSTEXPR14 TReturn sign_extend(TValue value)

Description
Converts an N bit binary number, where bit N-1 is the sign bit, to a signed integral type.

template <typename TReturn, size_t NBits, size_t Shift, typename TValue>
ETL_CONSTEXPR14 TReturn sign_extend(TValue value)

Description
Converts an N bit binary number, where bit N-1 is the sign bit, and Shift is the right shift amount, to a signed integral type.

template <typename TReturn, typename TValue>
ETL_CONSTEXPR14 TReturn sign_extend(TValue value, size_t nbits)

Description
Converts an N bit binary number, where bit N-1 is the sign bit, to a signed integral type.

template <typename TReturn, typename TValue>
ETL_CONSTEXPR14 TReturn sign_extend(TValue value, size_t nbits, size_t shift)

Description
Converts an N bit binary number, where bit N-1 is the sign bit, and shift is the right shift amount, to a signed integral type.

count_leading_zeros 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t count_leading_zeros(T value)

Description
Counts the number of leading zeros in a binary number

count_trailing_zeros 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t count_trailing_zeros(T value)

Description
Counts the number of trailing zeros in a binary number

count_leading_ones 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t count_leading_ones(T value)

Description
Counts the number of leading ones in a binary number

count_trailing_ones 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t count_trailing_ones(T value)

Description
Counts the number of trailing ones in a binary number

first_set_bit_position 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t first_set_bit_position(T value)

Description
Finds the index of the first set bit from lsb.

first_clear_bit_position 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t first_clear_bit_position(T value)

Description
Finds the index of the first clear bit from lsb.

first_bit_position 

template <typename T>
ETL_CONSTEXPR14 uint_least8_t first_bit_position(bool state, T value)

Description
Finds the index of the first bit in the specified state, from lsb.

binary_fill 

template <typename TResult, typename TValue>
ETL_CONSTEXPR TResult binary_fill(TValue value)

Fills a value of the specified width with a repeating binary pattern.
Run time

Generate 0x12121212

etl::binary_fill<uint32_t>(uint8_t(0x12));
template <typename TResult, typename TValue, TValue Value>
ETL_CONSTEXPR TResult binary_fill()

Partial compile time

Generate 0x12121212

etl::binary_fill<uint32_t, uint8_t, 0x12>();

has_zero_byte 

template <typename TValue>
ETL_CONSTEXPR14 bool has_zero_byte(TValue value)

Run time
Checks to see if a value contains a byte of value zero.

Example
etl::has_zero_byte(uint32_t(0x01234567)) == false
etl::has_zero_byte(uint32_t(0x01230067)) == true

template <typename TValue, TValue Value>
ETL_CONSTEXPR14 bool has_zero_byte()

Checks to see if Value contains a byte of value zero. Compile time value

has_byte_n

Checks to see if a value contains a byte of a particular value.

template <typename TValue>
ETL_CONSTEXPR14 bool has_byte_n(TValue value, uint8_t n)

Run time

etl::has_byte_n(uint32_t(0x01234567), 0x12) == false
etl::has_byte_n(uint32_t(0x01234567), 0x45) == true
template <typename TValue, TValue Value>
ETL_CONSTEXPR14 bool has_byte_n(TValue value)

Partial compile time

etl::has_byte_n<0x12>(uint32_t(0x01234567)) == false
etl::has_byte_n<0x45>(uint32_t(0x01234567)) == true

binary_merge

Merges two binary values according to a mask.
Bits set in the mask select bits in the first value, clear bits select those in the second.

template <typename T>
ETL_CONSTEXPR T binary_merge(T first, T second, T mask)
uint8_t first  = 0x12;
uint8_t second = 0x34;

const uint8_t mask = 0xF0;

etl::binary_merge(first, second, mask) Equals 0x14
template <typename T, T Mask>
ETL_CONSTEXPR T binary_merge(T first, T second)
uint8_t first  = 0x12;
uint8_t second = 0x34;

const uint8_t mask = 0xF0;

etl::binary_merge<uint8_t, mask>(first, second) Equals 0x14

binary_interleave

Interleaves two values such that bits abcd and efgh will result in eafbgchd.

ETL_CONSTEXPR14 uint16_t binary_interleave(uint8_t  first, uint8_t  second);
ETL_CONSTEXPR14 uint32_t binary_interleave(uint16_t first, uint16_t second);
ETL_CONSTEXPR14 uint64_t binary_interleave(uint32_t first, uint32_t second);

Odd / Even

Determines the odd or evenness of a value.

template <typename T>
ETL_CONSTEXPR bool is_odd(T value)
template <typename T>
ETL_CONSTEXPR bool is_even(T value)

Constants 

enum binary_constant

An enumeration of 256 constants from b00000000 to b11111111 (0 to 255)

enum bit_constant

An enumeration of 32 constants from b0 to b31 (1 to 4294967296)

template <size_t Position>
struct bit

value_type The type of the value.
value The value of the bit at Position.

Creating bit masks

These classes and constexpr functions help create lsb and msb masks.

template <typename T, size_t NBits>
class lsb_mask;

Defines the member constant value as a binary value of NBits 1 shift to the LSB.
e.g. lsb_mask<int8_t, 3>::value == 0b00000111
From: 20.34.0

template <typename T>
ETL_CONSTEXPR T make_lsb_mask(size_t nbits)

Returns a binary value of nbits 1 shift to the LSB. e.g. make_lsb_mask<int8_t>(3) == 0b00000111
From: 20.34.0

template <typename T, size_t NBits>
ETL_CONSTEXPR T make_lsb_mask()

Description
Returns a binary value of nbits 1 shift to the LSB.
e.g. make_lsb_mask<int8_t, 3>() == 0b00000111
From: 20.38.7

template <typename T, size_t NBits>
class msb_mask;

Return
A binary value of nbits 1 shift to the MSB.
e.g. msb_mask<int8_t, 3>::value == 0b11100000
From: 20.34.0

template <typename T>
ETL_CONSTEXPR T make_msb_mask(size_t nbits)

Description
Defines the member constant value as a binary value of NBits 1 shift to the MSB.
e.g. make_msb_mask<int8_t>(3) == 0b11100000
20.34.0

template <typename T, size_t NBits>
ETL_CONSTEXPR T make_msb_mask()

Description
Defines the member constant value as a binary value of NBits 1 shift to the MSB.
e.g. make_msb_mask<int8_t, 3>() == 0b11100000
From: 20.38.7

Bit manipulation functors

These functors are most useful where lambdas are not available.

binary_not 

template <typename T>
struct binary_not : public etl::unary_function<T, T>;

From: 20.38.11

ETL_CONSTEXPR
binary_not()

Description
Default constructor.

ETL_CONSTEXPR
ETL_NODISCARD
T operator()(T value) const ETL_NOEXCEPT

Return
~value.

binary_and 

template <typename T>
struct binary_and : public etl::unary_function<T, T>;

From: 20.38.11

ETL_CONSTEXPR
explicit binary_and(T and_value)

Description
Constructor.

ETL_CONSTEXPR
ETL_NODISCARD
T operator()(T value) const ETL_NOEXCEPT

Return
value & and_value.

binary_or 

template <typename T>
struct binary_or : public etl::unary_function<T, T>;

From: 20.38.11

ETL_CONSTEXPR
explicit binary_or(T or_value)

Description
Constructor.

ETL_CONSTEXPR
ETL_NODISCARD
T operator()(T value) const ETL_NOEXCEPT

Return
value | or_value.

binary_xor 

template <typename T>
struct binary_xor : public etl::unary_function<T, T>;

From: 20.38.11

ETL_CONSTEXPR
explicit binary_xor(T xor_value)

Description
Constructor.

ETL_CONSTEXPR
ETL_NODISCARD
T operator()(T value) const ETL_NOEXCEPT

Return
value ^ xor_value.

bit