TableturfBattleApp/TableturfBattleClient/src/Base64.ts

// Adapted from https://github.com/mdn/content/blob/main/files/en-us/glossary/base64/index.md
class Base64 {
	// Array of bytes to Base64 string decoding
	private static b64ToUint6(nChr: number) {
		return nChr > 64 && nChr < 91
			? nChr - 65
			: nChr > 96 && nChr < 123
			? nChr - 71
			: nChr > 47 && nChr < 58
			? nChr + 4
			: nChr === 43
			? 62
			: nChr === 47
			? 63
			: 0;
	}

	static base64DecToArr(sBase64: string, nBlocksSize?: number) {
		const sB64Enc = sBase64.replace(/[^A-Za-z0-9+/]/g, "");
		const nInLen = sB64Enc.length;
		const nOutLen = nBlocksSize
			? Math.ceil(((nInLen * 3 + 1) >> 2) / nBlocksSize) * nBlocksSize
			: (nInLen * 3 + 1) >> 2;
		const taBytes = new Uint8Array(nOutLen);

		let nMod3;
		let nMod4;
		let nUint24 = 0;
		let nOutIdx = 0;
		for (let nInIdx = 0; nInIdx < nInLen; nInIdx++) {
			nMod4 = nInIdx & 3;
			nUint24 |= Base64.b64ToUint6(sB64Enc.charCodeAt(nInIdx)) << (6 * (3 - nMod4));
			if (nMod4 === 3 || nInLen - nInIdx === 1) {
				nMod3 = 0;
				while (nMod3 < 3 && nOutIdx < nOutLen) {
					taBytes[nOutIdx] = (nUint24 >>> ((16 >>> nMod3) & 24)) & 255;
					nMod3++;
					nOutIdx++;
				}
				nUint24 = 0;
			}
		}

		return taBytes;
	}

	/* Base64 string to array encoding */
	private static uint6ToB64(nUint6: number) {
		return nUint6 < 26
			? nUint6 + 65
			: nUint6 < 52
			? nUint6 + 71
			: nUint6 < 62
			? nUint6 - 4
			: nUint6 === 62
			? 43
			: nUint6 === 63
			? 47
			: 65;
	}

	static base64EncArr(aBytes: Uint8Array) {
		let nMod3 = 2;
		let sB64Enc = "";

		const nLen = aBytes.length;
		let nUint24 = 0;
		for (let nIdx = 0; nIdx < nLen; nIdx++) {
			nMod3 = nIdx % 3;
			if (nIdx > 0 && ((nIdx * 4) / 3) % 76 === 0) {
				sB64Enc += "\r\n";
			}

			nUint24 |= aBytes[nIdx] << ((16 >>> nMod3) & 24);
			if (nMod3 === 2 || aBytes.length - nIdx === 1) {
				sB64Enc += String.fromCodePoint(
					Base64.uint6ToB64((nUint24 >>> 18) & 63),
					Base64.uint6ToB64((nUint24 >>> 12) & 63),
					Base64.uint6ToB64((nUint24 >>> 6) & 63),
					Base64.uint6ToB64(nUint24 & 63)
				);
				nUint24 = 0;
			}
		}
		return (
			sB64Enc.substring(0, sB64Enc.length - 2 + nMod3) +
			(nMod3 === 2 ? "" : nMod3 === 1 ? "=" : "==")
		);
	}
}