Enum ShiftVariant 

#[repr(u8)]
pub enum ShiftVariant {
    Sll = 0,
    Slr = 1,
    Sar = 2,
    Rotr = 3,
    Sll32 = 4,
    Srl32 = 5,
    Sra32 = 6,
    Rotr32 = 7,
}

A different variants of shifting a value.

Note that there is no shift left arithmetic because it is redundant.

The discriminant is stored in a single byte.

Variants

Sll = 0

Shift logical left.

Slr = 1

Shift logical right.

Sar = 2

Shift arithmetic right.

This is similar to the logical shift right but instead of shifting in 0 bits it will replicate the sign bit.

Rotr = 3

Rotate right.

Rotates bits to the right, with bits shifted off the right end wrapping around to the left.

Sll32 = 4

Shift logical left on 32-bit halves.

Performs independent logical left shifts on the upper and lower 32-bit halves of the word. Only uses the lower 5 bits of the shift amount (0-31).

Srl32 = 5

Shift logical right on 32-bit halves.

Performs independent logical right shifts on the upper and lower 32-bit halves of the word. Only uses the lower 5 bits of the shift amount (0-31).

Sra32 = 6

Shift arithmetic right on 32-bit halves.

Performs independent arithmetic right shifts on the upper and lower 32-bit halves of the word. Sign extends each 32-bit half independently. Only uses the lower 5 bits of the shift amount (0-31).

Rotr32 = 7

Rotate right on 32-bit halves.

Performs independent rotate right operations on the upper and lower 32-bit halves of the word. Bits shifted off the right end wrap around to the left within each 32-bit half. Only uses the lower 5 bits of the shift amount (0-31).

Implementations

impl ShiftVariant

pub const ALL: [Self; 8]

Every variant, ordered so that the array index equals the discriminant.

Callers that must cover all variants iterate this: random fixtures, exhaustive checks.

pub const fn from_u8(byte: u8) -> Option<Self>

Decodes a variant from its u8 discriminant.

The discriminants match the #[repr(u8)] layout: 0..=7 map to the eight variants. Any other byte returns None.

pub const fn is_half_word(self) -> bool

Whether this variant operates on the two 32-bit halves independently.

• The *32 family shifts each half on its own.
• It reads only the lower 5 bits of the amount.
• Every other variant acts on the whole 64-bit word.

pub const fn is_cyclic(self) -> bool

Whether this variant wraps the bits it moves out, rather than discarding them.

A cyclic variant loses nothing, so any two of its shifts compose however far they move; every other variant drops what it carries past the end.

pub const fn max_amount(self) -> usize

The exclusive upper bound on a valid shift amount for this variant.

• Half-word (*32) variants read only the lower 5 bits, so amounts run 0..32.
• Full-width variants take amounts 0..64.

Construction, validation, and deserialization all enforce this same bound. A value that passes any of them therefore denotes the same shift everywhere.

pub fn apply(self, word: Word, amount: usize) -> Word

Applies this shift to a 64-bit word and returns the result.

Full-width variants act on the whole 64-bit word. The half-word variants act on the upper and lower 32-bit halves independently.

Arguments

• The word to shift.
• The shift amount in bits.

Performance

Which operation to run is decided on every call. To shift many words by one fixed variant, resolve the variant once instead.

pub fn write_shifted( self, out: &mut [MaybeUninit<Word>], src: &[Word], amount: u32, )

Applies this shift to each source word and writes the result to the matching output cell.

Every output cell is written, so the caller need not initialize them first. Cells past the end of either slice are left alone.

Arguments

• out: the cells to initialize, one per source word.
• src: the words to shift.
• amount: the shift amount in bits, below this variant’s upper bound.

pub fn xor_shifted(self, out: &mut [Word], src: &[Word], amount: u32)

Applies this shift to each source word and XORs the result into the matching output cell.

Cells past the end of either slice are left alone.

Arguments

• out: the cells to accumulate into, one per source word.
• src: the words to shift.
• amount: the shift amount in bits, below this variant’s upper bound.

Trait Implementations

impl Clone for ShiftVariant

fn clone(&self) -> ShiftVariant

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ShiftVariant

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl DeserializeBytes for ShiftVariant

fn deserialize(read_buf: impl Buf) -> Result<Self, SerializationError>

where Self: Sized,

impl Hash for ShiftVariant

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for ShiftVariant

fn cmp(&self, other: &ShiftVariant) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for ShiftVariant

fn eq(&self, other: &ShiftVariant) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for ShiftVariant

fn partial_cmp(&self, other: &ShiftVariant) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl SerializeBytes for ShiftVariant

fn serialize(&self, write_buf: impl BufMut) -> Result<(), SerializationError>

impl Copy for ShiftVariant

impl Eq for ShiftVariant

impl StructuralPartialEq for ShiftVariant