Enum CollectionDelimiterPolicy 

pub enum CollectionDelimiterPolicy {
    Specification,
    EnumIsPrimitive,
    Never,
}

Which collections carry a DHEADER under XCDR2.

XTypes 1.3 §7.4.3.5 rules (8) through (13): a collection of a primitive element type serialises identically under both versions, and every other collection is delimited under XCDR2. §7.2.2.2 lists the primitive types; an enumeration is a constructed type under §7.2.2.4.1 and is therefore not one.

The three implementations disagree

Measured on 2026-08-09, XCDR2 little-endian, payload bytes:

element type	Cyclone	RTI 7.7	Fast DDS
@final struct Cell, Cell items[2]	20	16	20
@final struct Cell, sequence<Cell>	24	20	24
@appendable struct, sequence<>	32	28	32
enum Colour, Colour cs[2]	12	8	8
enum Colour, sequence<Colour>	16	12	12

The runs are in tests/fixtures/vendor_bytes.md. Only Cyclone matches the specification on every row.

Changing this changes the bytes on the wire. Unlike the length-code policy, a conforming reader cannot absorb the difference: there is no flag in the stream saying whether the four bytes it is looking at are a delimiter or the first element.

Variants

Specification

Delimit every collection whose element type is not primitive, enumerations included.

The default, because it is what §7.4.3.5 says and what Cyclone DDS emits.

EnumIsPrimitive

Treat an enumeration as if it were primitive, and delimit the rest.

What Fast DDS emits. Select it to interoperate with a Fast DDS peer over a topic whose type has an enum collection.

Never

Never delimit a collection, whatever its element type.

What RTI Connext 7.7 emits. Element-level delimiters an @appendable element type calls for are still written; this policy is only about the collection’s own.

Implementations

impl CollectionDelimiterPolicy

pub const ALL: [Self; 3]

Every policy.

pub const fn is_default(self) -> bool

Whether this is the default.

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 in a wire-affecting setting must be loud.

Trait Implementations

impl Clone for CollectionDelimiterPolicy

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 CollectionDelimiterPolicy

impl Debug for CollectionDelimiterPolicy

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

Formats the value using the given formatter.

impl Default for CollectionDelimiterPolicy

fn default() -> Self

Returns the “default value” for a type.

impl Eq for CollectionDelimiterPolicy

impl Hash for CollectionDelimiterPolicy

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 CollectionDelimiterPolicy

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 CollectionDelimiterPolicy

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for CollectionDelimiterPolicy

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 CollectionDelimiterPolicy