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6-symbol.js
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88 lines (76 loc) · 2.15 KB
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'use strict';
const poolified = Symbol('poolified');
const mixSymbol = { [poolified]: true };
const duplicate = (factory, n) =>
new Array(n).fill(null).map(() => {
const instance = factory();
return Object.assign(instance, mixSymbol);
});
const provide = (callback) => (data) => {
setImmediate(() => {
callback(data);
});
};
const poolify = (factory, { size, max }) => {
let allocated = size;
const instances = duplicate(factory, size);
const delayed = [];
const acquire = (callback) => {
const request = provide(callback);
if (instances.length === 0 && allocated < max) {
const grow = Math.min(max - allocated, size - instances.length);
allocated += grow;
const addition = duplicate(factory, grow);
instances.push(...addition);
}
const instance = instances.pop();
if (instance) request(instance);
else delayed.push(request);
};
const release = (instance) => {
if (!instance[poolified]) return;
if (delayed.length > 0) {
const request = delayed.shift();
return void request(instance);
}
if (instances.length < max) {
instances.push(instance);
}
};
return { acquire, release };
};
// Usage
const adder = (a) => (b) => adder(a + b);
const pool = poolify(adder, { size: 2, max: 3 });
console.log('request Item1');
pool.acquire((instance1) => {
console.log('get instance1');
console.log('request instance2');
pool.acquire((instance2) => {
console.log('get instance2');
console.log('request instance3');
pool.acquire((instance3) => {
console.log('get instance3');
setTimeout(() => {
pool.release(instance3);
console.log('recycle instance3');
}, 50);
});
console.log('request instance4');
pool.acquire((instance4) => {
console.log('get instance4');
setTimeout(() => {
pool.release(instance4);
console.log('recycle instance4');
}, 20);
});
setTimeout(() => {
pool.release(instance1);
console.log('recycle instance1');
setTimeout(() => {
pool.release(instance2);
console.log('recycle instance2');
}, 10);
}, 10);
});
});