Signal model

• A newly constructed Signal starts with an empty wait queue.
• INIT performs no operation.
• wake and wakeOne release only contexts that are already waiting.
• No wake is remembered for later waiters.
• wait returns no status or result value and exposes no persistent state query.
• A Signal owns its waiter queue. Destroying a Signal with waiting contexts is invalid.

Signal

• INIT
• wait
• wake
• wakeOne

Methods

Waiting and cancellation semantics

• If the current context is already canceled when wait begins, wait returns immediately.
• If cancellation happens while the context is already waiting, the context is removed from the wait queue and resumed.
• wake affects every currently waiting context.
• wakeOne releases the oldest currently waiting context.
• No wake is remembered for later waiters.

Examples

FIFO wakeOne order

"sync/Signal" use
"sync/sync" use
"String" use
"control" use

{} Int32 {} [
  signal: Signal;
  one: {signal: @signal; CALL: [
    @signal.wait
    ("one" LF) printList
  ];} () spawn;
  two: {signal: @signal; CALL: [
    @signal.wait
    ("two" LF) printList
  ];} () spawn;
  yield
  @signal.wakeOne
  yield
  @signal.wakeOne
  @one.wait
  @two.wait
  0
] "main" exportFunction

Expected Output

one
two

Wake is not remembered

"sync/Signal" use
"sync/sync" use
"String" use
"control" use

{} Int32 {} [
  signal: Signal;
  @signal.wake
  context: {signal: @signal; CALL: [
    @signal.wait
    ("released" LF) printList
  ];} () spawn;
  yield
  context.done? [
    ("done" LF) printList
  ] [
    ("waiting" LF) printList
  ] if
  @signal.wakeOne
  @context.wait
  0
] "main" exportFunction

Expected Output

waiting
released

See also

• sync/Event: Persistent event state with clear, set, wait, wake, and wakeOne.
• sync/Context: Spawned context handle with waiting, output retrieval, and cancellation.
• sync/sync: Cross-platform scheduling, sleep, time, IPv4 formatting, and TCP helpers.