Class Lock

A primitive lock is a synchronization primitive that is not owned by a particular coroutine when locked. A primitive lock is in one of two states, ‘locked’ or ‘unlocked’.

It is created in the unlocked state. It has two basic methods, acquire() and release(). When the state is unlocked, acquire() changes the state to locked and returns immediately. When the state is locked, acquire() blocks until a call to release() in another coroutine changes it to unlocked, then the acquire() call resets it to locked and returns. The release() method should only be called in the locked state; it changes the state to unlocked and returns immediately. If an attempt is made to release an unlocked lock, an Exception will be thrown.

When more than one coroutine is blocked in acquire() waiting for the state to turn to unlocked, only one coroutine proceeds when a release() call resets the state to unlocked; first coroutine which is blocked in acquire() is being processed.

acquire() is a coroutine.

This class is not thread safe.

Inherits from

• Object (base class)

Properties

Methods

Usage

lock = new Lock(); ... lock.acquire(); scope (exit) lock.release(); ...

Lock objects can be tested for locking state:

if (!lock.locked) lock.acquire(); else; // lock is acquired ...