perf(base-n): memoize value padding (encoding w/ size)

- migrate padding into BaseN class - add BaseN.clear() for clearing memoization cache
thi-ng · Jan 26, 2024 · 62ccf80 · 62ccf80
1 parent 5d39cda
commit 62ccf80
Showing 1 changed file with 17 additions and 10 deletions.
diff --git a/packages/base-n/src/base.ts b/packages/base-n/src/base.ts
@@ -14,6 +14,8 @@ export class BaseN implements IBase {
 	readonly N: number;
 	readonly index: Record<string, number>;
 
+	private __pc: string[] = [];
+
 	constructor(public readonly base: string) {
 		this.N = base.length;
 		this.index = [...base].reduce(
@@ -22,28 +24,32 @@ export class BaseN implements IBase {
 		);
 	}
 
+	clear() {
+		this.__pc.length = 0;
+	}
+
 	encode(x: number, size = 0) {
 		const { base, N } = this;
-		if (x === 0) return __pad(base[0], size, base[0]);
+		if (x === 0) return this.__pad(base[0], size);
 		let res = "";
 		while (x > 0) {
 			res = base[x % N] + res;
 			x = Math.floor(x / N);
 		}
-		return __pad(res, size, base[0]);
+		return this.__pad(res, size);
 	}
 
 	encodeBigInt(x: bigint, size = 0) {
 		if (x <= MAX_SAFE_INT) return this.encode(Number(x), size);
 		const { base, N } = this;
-		if (x === ZERO) return __pad(base[0], size, base[0]);
+		if (x === ZERO) return this.__pad(base[0], size);
 		const NN = BigInt(N);
 		let res = "";
 		while (x > ZERO) {
 			res = base[Number(x % NN)] + res;
 			x /= NN;
 		}
-		return __pad(res, size, base[0]);
+		return this.__pad(res, size);
 	}
 
 	encodeBytes(buf: Uint8Array, size = 0) {
@@ -87,13 +93,14 @@ export class BaseN implements IBase {
 	size(x: number) {
 		return Math.ceil(Math.log(x) / Math.log(this.N));
 	}
-}
 
-/** @internal */
-const __pad = (x: string, size: number, fill: string) => {
-	const d = size - x.length;
-	return d > 0 ? fill.repeat(d) + x : x;
-};
+	private __pad(x: string, size: number) {
+		const d = size - x.length;
+		return d > 0
+			? (this.__pc[d] || (this.__pc[d] = this.base[0].repeat(d))) + x
+			: x;
+	}
+}
 
 /** @internal */
 const __u8 = (x: number) =>