channel (slug)

slug.channel

slug.channel — channel-based concurrency primitives

Provides buffered and unbuffered channels for communicating between concurrent tasks, following Slug’s structured concurrency model.

Channels are created with chan() and closed with close(). Use send and recv for blocking operations, or trySend/tryRecv for non-blocking variants. Use await to block until a spawned task completes.

Example

val { chan, send, recv, close } = import("slug.channel")

val ch = chan()

nursery {
  spawn { send(ch, "hello") }
  val msg = recv(ch)
  println(msg)  // => "hello"
}

close(ch)

Timeouts

Both recv and await accept an optional timeout in milliseconds. A timeout of 0 (default) means wait indefinitely. When a timeout elapses a TimeoutError is thrown.

TOC

• await(handle, timeout)
• chan(capacity)
• close(channel)
• recv(channel, timeout)
• send(channel, payload)
• tryRecv(channel)
• trySend(channel, payload)

Functions

await(handle, timeout)

fn slug.channel#await(handle:task, timeout:num = 0):any

waits for a spawned task to complete and returns its result.

If timeout is greater than 0 and the task does not complete within that many milliseconds, a TimeoutError is thrown.

Throws: Error{type:TimeoutError}

chan(capacity)

fn slug.channel#chan(capacity:num = 0):chan<any|nil>

creates a new channel with an optional buffer capacity.

An unbuffered channel (capacity 0) blocks the sender until a receiver is ready. A buffered channel allows up to capacity messages to be queued before blocking.

close(channel)

fn slug.channel#close(channel:chan<any|nil>):nil

closes a channel, signalling that no more values will be sent.

Receivers on a closed channel return nil. Sending to a closed channel is a runtime error.

recv(channel, timeout)

fn slug.channel#recv(channel:chan<any|nil>, timeout:num = 0):any

receives a value from a channel, blocking until one is available.

If timeout is greater than 0 and no value arrives within that many milliseconds, a TimeoutError is thrown.

Throws: Error{type:TimeoutError}

send(channel, payload)

fn slug.channel#send(channel:chan<any|nil>, payload):any

sends a value to a channel, blocking until a receiver is ready.

payload must not be nil.

Returns the channel, allowing chains: ch /> send("a") /> send("b")

tryRecv(channel)

fn slug.channel#tryRecv(channel:chan<any|nil>):any

attempts to receive a value from a channel without blocking.

Returns the next value if one is immediately available, nil otherwise.

trySend(channel, payload)

fn slug.channel#trySend(channel:chan<any|nil>, payload):any

attempts to send a value to a channel without blocking.

payload must not be nil.

Returns the channel if the send succeeded, nil if the channel was full.