Functions and macros that operate in a bitwise manner. More...
Collaboration diagram for Bit Manipulation:
|
Classes | |
| struct | embutil::countbits< tval > |
| Template struct for counting set bits and significant bits at compile-time. More... | |
Alignment Macros | |
| #define | align_up(num, align) (((num) + ((align)-1)) & ~((align)-1)) |
| Increase a number to the next aligned value. More... | |
| #define | IS_POWER_2(x) (!((x) & ((x)-1))) |
| Check if a number is a power of 2. More... | |
| #define | IS_ALIGNED(val, align) ((val & (align - 1)) == 0) |
| Check if a value is aligned. More... | |
Bitfield Macros | |
| #define | SET_BIT(x) (1 << x) |
| Set bit at position X. More... | |
| #define | EXTRACT_BITFIELD(value, high_bit, low_bit) (((value) >> (low_bit)) & N_SET_BITS((high_bit) - (low_bit) + 1)) |
| Extract a field of bits from a value. More... | |
Count Bits Macros | |
| #define | N_SET_BITS(n_ones) ((1 << (n_ones)) - 1) |
| Count the number of set bits. More... | |
Alignment Functions | |
| template<typename TIntegralType > | |
| constexpr bool | embutil::is_power_2 (TIntegralType val) noexcept |
| Check if a number is a power of 2. More... | |
| template<typename TType > | |
| constexpr bool | embutil::is_aligned (const TType val, const size_t align) noexcept |
| Checks if a value meets a specified alignment. More... | |
Bitfield Functions | |
| template<typename TIntegralType , typename... Args> | |
| constexpr TIntegralType | embutil::bitmask (Args &&... args) noexcept |
| A C++ 17 bitmask generator. More... | |
Detailed Description
Functions and macros that operate in a bitwise manner.
Class Documentation
◆ embutil::countbits
| struct embutil::countbits |
template<unsigned tval>
struct embutil::countbits< tval >
Template struct for counting set bits and significant bits at compile-time.
Examples:
countbits<8>::setbits == 1 (0b1000)
countbits<9>::setbits == 2 (0b1100)
countbits<8>::significant == 4 (0b1111)
countbits<9>::significant == 4 (0b1111)
- Template Parameters
-
tval Unsigned integral value to analyze.
Public Types | |
| using | t_ = countbits< tval/2 > |
Static Public Attributes | |
| static constexpr unsigned | set = ((tval & 1) != 0) ? t_::set + 1 : t_::set |
| Shows how many bits in the value are set. More... | |
| static constexpr unsigned | significant_bits = (tval != 0) ? t_::significant_bits + 1 : 0 |
| shows how many bits in the value matter More... | |
Member Typedef Documentation
◆ t_
template<unsigned tval>
| using embutil::countbits< tval >::t_ = countbits<tval / 2> |
Member Data Documentation
◆ set
template<unsigned tval>
|
static |
Shows how many bits in the value are set.
◆ significant_bits
template<unsigned tval>
|
static |
shows how many bits in the value matter
Macro Definition Documentation
◆ align_up
| #define align_up | ( | num, | |
| align | |||
| ) | (((num) + ((align)-1)) & ~((align)-1)) |
Increase a number to the next aligned value.
- Parameters
-
num The number to start with. align The target alignment.
- Returns
- The next value greater than num matching the target alignment.
◆ EXTRACT_BITFIELD
| #define EXTRACT_BITFIELD | ( | value, | |
| high_bit, | |||
| low_bit | |||
| ) | (((value) >> (low_bit)) & N_SET_BITS((high_bit) - (low_bit) + 1)) |
Extract a field of bits from a value.
Given a number, such as: 0b11010100
If we wanted to extract bits 7..5, we would supply: high_bit = 7 low_bit = 5
And the result would be 0b110
- Parameters
-
value The value to extract the bitfield from. high_bit the bit representing the upper limit of the bitfield. low_bit the bit representing the lower limit of the bitfield.
- Returns
- the extracted bitfield, shifted right by low_bit.
◆ IS_ALIGNED
| #define IS_ALIGNED | ( | val, | |
| align | |||
| ) | ((val & (align - 1)) == 0) |
Check if a value is aligned.
- Parameters
-
val The number to check. align The target alignment.
- Returns
- true if the number matches the target alignment, false otherwise.
◆ IS_POWER_2
| #define IS_POWER_2 | ( | x | ) | (!((x) & ((x)-1))) |
Check if a number is a power of 2.
- Parameters
-
x The number to check.
- Returns
- true if the number is a power of 2, false otherwise.
◆ N_SET_BITS
| #define N_SET_BITS | ( | n_ones | ) | ((1 << (n_ones)) - 1) |
Count the number of set bits.
- Parameters
-
n_ones The number to check.
- Returns
- the number of set bits.
◆ SET_BIT
| #define SET_BIT | ( | x | ) | (1 << x) |
Set bit at position X.
- Parameters
-
x The bit position to set.
- Returns
- A number with bit x set.
Function Documentation
◆ bitmask()
template<typename TIntegralType , typename... Args>
|
noexcept |
A C++ 17 bitmask generator.
This function was inspired by Martin Moene.
Example: bitmask<uint8_t>(6, 5, 0) -> 0b0110'0001
- Template Parameters
-
TIntegralType The desired type for the bitmask. Args A variadic list corresponding to bits to be set. Args is detected by the compiler.
- Parameters
-
args The variadic list of bits to set in the bitmask.
- Returns
- A number of type TIntegralType with the bits in the input list set.
◆ is_aligned()
template<typename TType >
|
inlinenoexcept |
Checks if a value meets a specified alignment.
Behavior for integral types: check if the value is aligned.
Behavior for pointers: check if the pointer is aligned.
Behavior for non-integral non-pointer types: Take the address and determine if it is aligned.
- Template Parameters
-
TType the type of data to check the alignment of. TType can be integral, pointer, or non-integral and non-pointer. The behavior of the function changes depending on the type.
- Parameters
-
val The value to check the alignment of. align The target alignment.
- Returns
- true if the value has the target alignment, false otherwise.
References IS_ALIGNED, and r.
Referenced by os::posix::Thread::Thread().
◆ is_power_2()
template<typename TIntegralType >
|
noexcept |
Check if a number is a power of 2.
- Template Parameters
-
TIntegralType The type of the number to check. This type does not need to be manually specified. The compiler should automatically deduce this type. TIntegralType must be an integral type.
- Parameters
-
val The number to evaluate.
- Returns
- true if the number is a power of 2, false otherwise.
References IS_POWER_2.
