Created
January 27, 2019 13:34
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crappy lock mechanism for js, "minor projects"
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function deferred() { | |
let r; | |
let p = new Promise(a => r = a); | |
p.r = r; | |
return p; | |
} | |
function lock() { | |
let queue = []; | |
let locked = false; | |
return { | |
lock() { | |
if(locked) { | |
let q = deferred(); | |
queue.push(q); | |
return q; | |
} | |
locked = true; | |
}, | |
unlock() { | |
if (!locked) throw new Error('already unlocked'); | |
if(queue.length > 0) { | |
let q = queue.shift(); | |
q.r(); | |
} else { | |
locked = false; | |
} | |
} | |
} | |
} |
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let s = lock(); | |
for(let i = 0; i<5; i++) { | |
(async () => { | |
try { | |
console.log('trigger' + i); | |
await s.lock(); | |
console.log('lock' + i); | |
await new Promise(resolve => setTimeout(resolve, 1000 + Math.random() * 5000)); | |
} finally { | |
console.log('unlock' + i); | |
s.unlock(); | |
} | |
})(); | |
} | |
/* | |
trigger0 | |
trigger1 | |
trigger2 | |
trigger3 | |
trigger4 | |
lock0 | |
... | |
unlock0 | |
lock1 | |
... | |
unlock1 | |
lock2 | |
... | |
unlock2 | |
lock3 | |
... | |
unlock3 | |
lock4 | |
... | |
unlock4 | |
*/ |
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