IOTConnect-Web/node_modules/fast-unique-numbers/build/es2019/factories/generate-unique-number.js

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2024-05-09 01:49:52 +00:00
/*
* The value of the constant Number.MAX_SAFE_INTEGER equals (2 ** 53 - 1) but it
* is fairly new.
*/
const MAX_SAFE_INTEGER = Number.MAX_SAFE_INTEGER === undefined ? 9007199254740991 : Number.MAX_SAFE_INTEGER;
const TWO_TO_THE_POWER_OF_TWENTY_NINE = 536870912;
const TWO_TO_THE_POWER_OF_THIRTY = TWO_TO_THE_POWER_OF_TWENTY_NINE * 2;
export const createGenerateUniqueNumber = (cache, lastNumberWeakMap) => {
return (collection) => {
const lastNumber = lastNumberWeakMap.get(collection);
/*
* Let's try the cheapest algorithm first. It might fail to produce a new
* number, but it is so cheap that it is okay to take the risk. Just
* increase the last number by one or reset it to 0 if we reached the upper
* bound of SMIs (which stands for small integers). When the last number is
* unknown it is assumed that the collection contains zero based consecutive
* numbers.
*/
let nextNumber = lastNumber === undefined ? collection.size : lastNumber < TWO_TO_THE_POWER_OF_THIRTY ? lastNumber + 1 : 0;
if (!collection.has(nextNumber)) {
return cache(collection, nextNumber);
}
/*
* If there are less than half of 2 ** 30 numbers stored in the collection,
* the chance to generate a new random number in the range from 0 to 2 ** 30
* is at least 50%. It's benifitial to use only SMIs because they perform
* much better in any environment based on V8.
*/
if (collection.size < TWO_TO_THE_POWER_OF_TWENTY_NINE) {
while (collection.has(nextNumber)) {
nextNumber = Math.floor(Math.random() * TWO_TO_THE_POWER_OF_THIRTY);
}
return cache(collection, nextNumber);
}
// Quickly check if there is a theoretical chance to generate a new number.
if (collection.size > MAX_SAFE_INTEGER) {
throw new Error('Congratulations, you created a collection of unique numbers which uses all available integers!');
}
// Otherwise use the full scale of safely usable integers.
while (collection.has(nextNumber)) {
nextNumber = Math.floor(Math.random() * MAX_SAFE_INTEGER);
}
return cache(collection, nextNumber);
};
};
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