getHashDigest.js

"use strict";

const baseEncodeTables = {
	26: "abcdefghijklmnopqrstuvwxyz",
	32: "123456789abcdefghjkmnpqrstuvwxyz", // no 0lio
	36: "0123456789abcdefghijklmnopqrstuvwxyz",
	49: "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ", // no lIO
	52: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
	58: "123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ", // no 0lIO
	62: "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
	64: "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_"
};

function encodeBufferToBase(buffer, base) {
	const encodeTable = baseEncodeTables[base];
	if(!encodeTable) throw new Error("Unknown encoding base" + base);

	const readLength = buffer.length;

	const Big = require("big.js");
	Big.RM = Big.DP = 0;
	let b = new Big(0);
	for(let i = readLength - 1; i >= 0; i--) {
		b = b.times(256).plus(buffer[i]);
	}

	let output = "";
	while(b.gt(0)) {
		output = encodeTable[b.mod(base)] + output;
		b = b.div(base);
	}

	Big.DP = 20;
	Big.RM = 1;

	return output;
}

function getHashDigest(buffer, hashType, digestType, maxLength) {
	hashType = hashType || "md5";
	maxLength = maxLength || 9999;
	const hash = require("crypto").createHash(hashType);
	hash.update(buffer);
	if(digestType === "base26" || digestType === "base32" || digestType === "base36" ||
		digestType === "base49" || digestType === "base52" || digestType === "base58" ||
		digestType === "base62" || digestType === "base64") {
		return encodeBufferToBase(hash.digest(), digestType.substr(4)).substr(0, maxLength);
	} else {
		return hash.digest(digestType || "hex").substr(0, maxLength);
	}
}

module.exports = getHashDigest;