Improve performance greatly (#337)

lib/util.js

@@ -0,0 +1,37 @@
+const stringReplaceAll = (string, substring, replacer) => {
+	let index = string.indexOf(substring);
+	if (index === -1) {
+		return string;
+	}
+
+	const subLen = substring.length;
+	let end = 0;
+	let res = '';
+	do {
+		res += string.substr(end, index - end) + replacer;
+		end = index + subLen;
+		index = string.indexOf(substring, end);
+	} while (index !== -1);
+
+	res += string.substr(end);
+	return res;
+};
+
+const stringEncaseCRLFWithFirstIndex = (string, prefix, postfix, index) => {
+	let end = 0;
+	let res = '';
+	do {
+		const gotCR = string[index - 1] === '\r';
+		res += string.substr(end, (gotCR ? index - 1 : index) - end) + prefix + (gotCR ? '\r\n' : '\n') + postfix;
+		end = index + 1;
+		index = string.indexOf('\n', end);
+	} while (index !== -1);
+
+	res += string.substr(end);
+	return res;
+};
+
+module.exports = {
+	stringReplaceAll,
+	stringEncaseCRLFWithFirstIndex
+};