Enum Message 

pub enum Message<'a> {
    Push(Expression<'a>),
    Pull(Id),
    Resolve {
        export_id: Id,
        value: Expression<'a>,
    },
    Reject {
        export_id: Id,
        value: Expression<'a>,
    },
    Release {
        import_id: Id,
        refcount: u64,
    },
    Abort(Expression<'a>),
}

A top-level message in the Cap’n Web protocol

Variants

Push(Expression<'a>)

Asks the recipient to evaluate the given expression

The expression is implicitly assigned the next sequential import ID (in the positive direction). The recipient will evaluate the expression, delivering any calls therein to the application. The final result can be pulled, or used in promise pipelining.

Pull(Id)

Signals that the sender would like to receive a “resolve” message for the resolution of the given import, which must refer to a promise.

This is normally only used for imports created by a “push”, as exported promises are pulled automatically.

Resolve

Instructs the recipient to evaluate the given expression and use it as the resolution of the given promise export

Fields

export_id: Id

The ID of the export to resolve

value: Expression<'a>

The value to resolve the promise to

Reject

Instructs the recipient to evaluate the given expression and then use it to reject the given promise export.

The expression is not permitted to contain stubs. It typically evaluates to an Error, although technically JavaScript does not require that thrown values are Errors.

Fields

export_id: Id

The ID of the export to reject

value: Expression<'a>

The value to reject the promise with

Usually evaluates to an Expression::Error.

Release

Instructs the recipient to release the given entry in the import table, disposing whatever it is connected to.

If the import is a promise, the recipient is no longer obliged to send a “resolve” message for it, though it is still permitted to do so.

Fields

import_id: Id

The ID of the import to release

refcount: u64

The total number of times this import ID has been “introduced”

i.e. the number of times it has been the subject of an “export” or “promise” expression, plus 1 if it was created by a “push”. The refcount must be sent to avoid a race condition if the receiving side has recently exported the same ID again. The exporter remembers how many times they have exported this ID, decrementing it by the refcount of any release messages received, and only actually releases the ID when this count reaches zero.

Abort(Expression<'a>)

Indicates that the sender has experienced an error causing it to terminate the session

The expression evaluates to the error which caused the abort. No further messages will be sent nor received.

Trait Implementations

impl<'a> Debug for Message<'a>

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Message<'de>

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for Message<'_>

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.