projen
Version:
CDK for software projects
59 lines • 2 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.CompareCache = void 0;
/**
* Represents a cache for storing order between equal objects.
*
* This cache is used when an algorithm compares two objects and finds them to
* be equal but still needs to establish an order between those two objects.
* When two such objects `a` and `b` are passed to the `check` method, a random
* number is generated with `Math.random()`. If the random number is less than
* `0.5` it is assumed that `a < b` otherwise `a > b`. The random number along
* with `a` and `b` is stored in the cache, so that subsequent checks result
* in the same consistent result.
*
* The cache has a size limit which is defined on initialization.
*/
class CompareCache {
_limit;
_items = new Map();
/**
* Initializes a new instance of `CompareCache`.
*
* @param limit - maximum number of items to keep in the cache. When the limit
* is exceeded the first item is removed from the cache.
*/
constructor(limit = 1000) {
this._limit = limit;
}
/**
* Compares and caches the given objects. Returns `true` if `objA < objB` and
* `false` otherwise.
*
* @param objA - an item to compare
* @param objB - an item to compare
*/
check(objA, objB) {
if (this._items.get(objA) === objB)
return true;
else if (this._items.get(objB) === objA)
return false;
const result = (Math.random() < 0.5);
if (result) {
this._items.set(objA, objB);
}
else {
this._items.set(objB, objA);
}
if (this._items.size > this._limit) {
const it = this._items.keys().next();
/* istanbul ignore else */
if (!it.done) {
this._items.delete(it.value);
}
}
return result;
}
}
exports.CompareCache = CompareCache;
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