@thermopylae/lib.cache/dist/policies/eviction/arc.js

Modular cache.

import { DoublyLinkedList } from "../../data-structures/list/doubly-linked.js";
import { CircularBuffer } from "../../data-structures/circular-buffer.js";
import { createException } from "../../error.js";
const SEGMENT_TYPE_SYM = Symbol('ARC_SEGMENT_TYPE_SYM');
class ArcEvictionPolicy {
    segments;
    deleteFromCache;
    constructor(cacheMaxCapacity) {
        if (cacheMaxCapacity < 2) {
            throw createException("INVALID_CACHE_MAX_CAPACITY" , `Cache maximum capacity needs to be at least 2.`);
        }
        this.segments = {
            [0 ]: {
                capacity: Math.round(cacheMaxCapacity / 2),
                block: new DoublyLinkedList(),
                ghosts: new CircularBuffer(Math.round(cacheMaxCapacity / 2))
            },
            [1 ]: {
                capacity: 0,
                block: new DoublyLinkedList(),
                ghosts: new CircularBuffer(Math.round(cacheMaxCapacity / 2))
            }
        };
        this.segments[1 ].capacity = cacheMaxCapacity - this.segments[0 ].capacity;
    }
    onHit(entry) {
        if (entry[SEGMENT_TYPE_SYM] === 0 ) {
            if (this.segments[1 ].capacity === 0) {
                this.segments[0 ].block.toTail(entry);
                return 1 ;
            }
            this.segments[0 ].block.remove(entry);
            this.insertInT2(entry);
            return 1 ;
        }
        this.segments[1 ].block.toFront(entry);
        return 1 ;
    }
    onMiss(key) {
        if (this.segments[0 ].ghosts.has(key)) {
            if (this.segments[1 ].capacity === 0) {
                return;
            }
            this.segments[0 ].capacity += 1;
            this.segments[1 ].capacity -= 1;
            if (this.segments[1 ].block.size > this.segments[1 ].capacity) {
                this.deleteFromCache(this.segments[1 ].block.tail); 
            }
            return;
        }
        if (this.segments[1 ].ghosts.has(key)) {
            if (this.segments[0 ].capacity === 0) {
                return;
            }
            this.segments[1 ].capacity += 1;
            this.segments[0 ].capacity -= 1;
            if (this.segments[0 ].block.size > this.segments[0 ].capacity) {
                this.deleteFromCache(this.segments[0 ].block.head); 
            }
        }
    }
    onSet(entry) {
        this.insertInT1(entry);
    }
    onUpdate() {
        return undefined;
    }
    onDelete(entry) {
        this.segments[entry[SEGMENT_TYPE_SYM]].block.remove(entry);
        this.segments[entry[SEGMENT_TYPE_SYM]].ghosts.add(entry.key);
        entry[SEGMENT_TYPE_SYM] = undefined; 
    }
    onClear() {
        this.segments[0 ].block.clear();
        this.segments[0 ].ghosts.clear();
        this.segments[1 ].block.clear();
        this.segments[1 ].ghosts.clear();
        const cacheMaxCapacity = this.segments[0 ].capacity + this.segments[1 ].capacity;
        this.segments[0 ].capacity = Math.round(cacheMaxCapacity / 2);
        this.segments[1 ].capacity = cacheMaxCapacity - this.segments[0 ].capacity;
    }
    setDeleter(deleter) {
        this.deleteFromCache = deleter;
    }
    insertInT1(entry) {
        if (this.segments[0 ].capacity === 0) {
            this.insertInT2(entry);
            return;
        }
        if (this.segments[0 ].block.size === this.segments[0 ].capacity) {
            this.deleteFromCache(this.segments[0 ].block.head); 
        }
        entry[SEGMENT_TYPE_SYM] = 0 ;
        this.segments[0 ].block.push(entry);
    }
    insertInT2(entry) {
        if (this.segments[1 ].block.size === this.segments[1 ].capacity) {
            this.deleteFromCache(this.segments[1 ].block.tail); 
        }
        entry[SEGMENT_TYPE_SYM] = 1 ;
        this.segments[1 ].block.unshift(entry);
    }
}
export { ArcEvictionPolicy, SEGMENT_TYPE_SYM };