FIFOCache.ts
For the full content of this gist, refer to https://gist.github.com/CodingAbdullah/f163f84fe66eea64774b7bf65c63fada
McMaster. Software Engineer with a keen interest in blockchain and web3.
// FIFO cache implements a cache using queue properties
class FIFOCache {
queueCache: string[];
keyMap: Map<string, number>;
size: number;
constructor(size: number) {
this.queueCache = [];
this.keyMap = new Map<string, number>();
this.size = size < 0 ? 0 : size;
}
// Follow the FIFO principle for insertions and deletions of nodes
// If no key exists, a new one is being inserted, check eviction policy
// If at limit, evict the oldest key and delete from hash map
insertKey(key: string, value: number) {
if (this.keyMap.has(key)) {
this.keyMap.set(key, value); // If key exists, just simply update key value
}
else {
if (this.keyMap.size === this.size) {
let removeKey = this.evictKey();
this.keyMap.delete(removeKey!);
this.keyMap.set(key, value);
this.queueCache.push(key);
}
else {
// Very simple if no eviction is required
this.keyMap.set(key, value);
this.queueCache.push(key);
}
}
}
// Retrieve the value of the key
retrieveKey(key: string): number | null {
if (this.keyMap.has(key)) {
return this.keyMap.get(key)!;
}
else {
return null;
}
}
// Simply filter out the key from the queue
// Capture key value and return it
// Delete from hash map
deleteKey(key: string): number | undefined {
if (this.keyMap.has(key)) {
this.queueCache = this.queueCache.filter(i => i !== key); // Filter the key out of the queu
let value = this.keyMap.get(key);
this.keyMap.delete(key);
return value;
}
else {
return undefined;
}
}
// Delete and return the oldest key
evictKey(): string | undefined {
let key = this.queueCache.shift();
return key;
}
}