Enum PayloadPermission 

pub enum PayloadPermission {
    Permitted,
    Forbidden,
}

Whether an object carrying a given status may hold a non-empty payload.

Draft-15 Section 10.2.1.1 states the rule in one sentence — “Any object with a status code other than zero MUST have an empty payload” — and Section 10.2.1 says the same from the other side, listing the Object Payload as “Only present when ‘Object Status’ is Normal (0x0)”. On this draft the answer therefore falls out of the code being zero or not, and every status but ObjectStatus::Normal forbids a payload.

It is worth a type all the same, because that arithmetic is not something a consumer can safely perform on a raw wire code. A code draft-15 does not assign is not non-zero, and therefore forbidden: it is a code with no meaning at all, and the draft’s answer to it is to terminate the session, not to infer a payload rule. Handing back a PayloadPermission keeps the two apart, and lets a caller ask the question without restating the rule — or, worse, restating it slightly differently.

Variants

Permitted

The status permits a payload but does not require one: a zero-length object with such a status is well formed, and draft-15’s encodings have a way to spell it.

Forbidden

An object with such a status has an empty payload, and one carrying bytes is malformed.

Implementations

impl PayloadPermission

pub fn for_status(status: ObjectStatus) -> Self

The permission draft-15 gives objects carrying status.

Written as a match over every assigned status rather than as a test for zero, so that a status added to ObjectStatus later cannot quietly inherit not Normal, therefore forbidden — it stops the crate compiling until its own answer is written down. Drafts after 15 moved this rule into a column of the Object Status registry, where a future status may well permit a payload; the shape here does not have to change when a caller crosses that boundary.

pub fn permits(self) -> bool

true for PayloadPermission::Permitted.

The permission answers on its own, with no payload length in hand, which is the point of asking the status rather than the framing.

Trait Implementations

impl Clone for PayloadPermission

fn clone(&self) -> PayloadPermission

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for PayloadPermission

impl Debug for PayloadPermission

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

Formats the value using the given formatter.

impl Eq for PayloadPermission

impl PartialEq for PayloadPermission

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for PayloadPermission