Enum KeyHolderAlignment 

pub enum KeyHolderAlignment {
    Aligned,
    DataEncoding,
    Packed,
}

How the members of a key holder are aligned, which decides the KeyHash of every type with keys of different widths.

DDS-XTypes 1.3 §7.6.8 step 4 serialises the holder as PLAIN_CDR2 big-endian, so a member is aligned to its size capped at four, as in any XCDR2 body. Measured on the Linux test host with tools/keyhash-probe (types PadKey, WideKey, CharKey, StrKey, PathKey):

• Fast DDS 3.6.1, and Cyclone 11.0.1 and RTI Connext 7.7.0 under XCDR2, align as the clause says.
• Cyclone and RTI under XCDR1 align to the XCDR1 MAXALIGN of eight: @key short s; @key long long ll hashes as 0102 000000000000 0304… where the clause gives 0102 0000 0304…. RTI sends this in PID_KEY_HASH (plain and PL_CDR); Cyclone sends no PID_KEY_HASH.
• OpenSplice 6.9 writes the key fields back to back, measured on the wire: @key octet a; @key long b with a=0x11, b=0x22334455 goes out as 11223344 55000000 … where the clause gives 11000000 22334455 …, and a holder over sixteen octets is hashed without the padding too. Its DDSI2 source says so — KEYHASH_HAS_PADDING 0, “my current guess” (src/services/ddsi2e/code/q_osplser.c).

Variants

Aligned

Each member aligned to its size, capped at PLAIN_CDR2’s four. The clause.

DataEncoding

Each member aligned to its size, capped at the MAXALIGN of the encoding the data goes out in: eight under XCDR1, four under XCDR2. Cyclone and RTI under XCDR1.

Packed

No padding between members: every member at the next free octet. OpenSplice 6.9.

Implementations

impl KeyHolderAlignment

pub const ALL: [Self; 3]

All three.

pub const fn is_default(self) -> bool

Whether this is the default.

pub const fn max_alignment(self, encoding: Encoding) -> u8

The largest alignment a key holder member takes when the data goes out in encoding.

pub const fn as_str(self) -> &'static str

Short name, for configuration and diagnostics.

pub fn parse(value: &str) -> Option<Self>

Parse a configuration value.

An unknown value returns None rather than falling back to the default: a typo here changes every instance handle.

Trait Implementations

impl Clone for KeyHolderAlignment

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for KeyHolderAlignment

impl Debug for KeyHolderAlignment

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

Formats the value using the given formatter.

impl Default for KeyHolderAlignment

fn default() -> Self

Returns the “default value” for a type.

impl Eq for KeyHolderAlignment

impl Hash for KeyHolderAlignment

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 KeyHolderAlignment

fn cmp(&self, other: &Self) -> 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.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to)

Restrict a value to a certain range.

impl PartialEq for KeyHolderAlignment

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for KeyHolderAlignment

fn partial_cmp(&self, other: &Self) -> 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 StructuralPartialEq for KeyHolderAlignment