diff --git a/util.js b/src/util.js
copy from util.js
copy to src/util.js
--- a/util.js
+++ b/src/util.js
@@ -1,10 +1,10 @@
-const MASK=0xffffffff;
+export const MASK=0xffffffff;
 
-function bytes2int32(arr){
+export function bytes2int32(arr){
 	return arr.reduce((acc,b,i)=>acc|b<<(i*8));
 }
 
-function bytes2int32s(arr){
+export function bytes2int32s(arr){
 	let res=[];
 	for(let i=0;i<arr.length;i+=4){
 		res.push(bytes2int32(arr.slice(i,i+4)));
@@ -12,7 +12,7 @@ function bytes2int32s(arr){
 	return res;
 }
 
-function int322bytes(x){
+export function int322bytes(x){
 	let res=[];
 	for(let i=0;i<4;i++){
 		res.push(x&0xff);
@@ -21,15 +21,15 @@ function int322bytes(x){
 	return res;
 }
 
-function int32s2bytes(arr){
+export function int32s2bytes(arr){
 	return arr.map(int322bytes).reduce((acc,bytes)=>acc.concat(bytes));
 }
 
-function bytes2hex(arr){
+export function bytes2hex(arr){
 	return arr.map(x=>x.toString(16).padStart(2,"0")).join("");
 }
 
-function str2utf8(s){
+export function str2utf8(s){
 	let res=[];
 	let c=s.codePointAt(0);
 	for(let i=0; c!==undefined; i++,c=s.codePointAt(i)){
@@ -54,7 +54,7 @@ function str2utf8(s){
 	return res;
 }
 
-function utf82str(arr){
+export function utf82str(arr){
 	let res=[];
 	for(let i=0;i<arr.length;i++){
 		let x=arr[i];
@@ -80,13 +80,3 @@ function utf82str(arr){
 	}
 	return res.map(x=>String.fromCodePoint(x)).join("");
 }
-
-if(typeof module!=='undefined'&&module.hasOwnProperty('exports')){
-	module.exports.bytes2int32=bytes2int32;
-	module.exports.bytes2int32s=bytes2int32s;
-	module.exports.int322bytes=int322bytes;
-	module.exports.int32s2bytes=int32s2bytes;
-	module.exports.bytes2hex=bytes2hex;
-	module.exports.str2utf8=str2utf8;
-	module.exports.utf82str=utf82str;
-}