Base64Utils.java

package com.akjava.gwt.lib.client;

import com.akjava.gwt.html5.client.file.Uint8Array;
import com.google.common.io.BaseEncoding;
/**
 * @author aki
 *
 */
public class Base64Utils {
	private Base64Utils(){}
public static final String DATA_BASE64_KEY=";base64,";
	public static String getDataUrlHeader(String mimeType){
		return "data:"+mimeType+DATA_BASE64_KEY;
	}
	
	public static String toDataUrl(String mimeType,String base64){
		return getDataUrlHeader(mimeType)+base64;
	}
	public static String toDataUrl(String mimeType,byte[] data){
		return getDataUrlHeader(mimeType)+encode(data);
	}
	public static String toDataUrl(String mimeType,Uint8Array array){
		return getDataUrlHeader(mimeType)+encodeBase64(array);
	}
	
	public static String encode(byte[] data){
		return BaseEncoding.base64().encode(data);
	}
	
	
	/**
	 * don't use dataurl that contain header,use fromDataUrl();
	 * @param data
	 * @return
	 */
	public static byte[] decode(String data){
		
		return BaseEncoding.base64().decode(data);
	}
	//TODO be careful
	public static byte[] fromDataUrl(String url){
		int index=url.indexOf(DATA_BASE64_KEY);
		if(index!=-1){
			
			return BaseEncoding.base64Url().decode(url.substring(DATA_BASE64_KEY.length()));
		}else{
			return BaseEncoding.base64Url().decode(url);
		}
	}
	public static String cutHeader(String url){
		int index=url.indexOf(DATA_BASE64_KEY);
		if(index!=-1){
			return url.substring(index+DATA_BASE64_KEY.length());
		}else{
			return url;
		}
	}
	
	/**
	 * based http://stackoverflow.com/questions/12710001/how-to-convert-uint8-array-to-base64-encoded-string
	 * @param u8Arr
	 * @return
	 */
	public  static  native final String encodeBase64(Uint8Array u8Arr)/*-{
	
	  var CHUNK_SIZE = 0x8000; //arbitrary number
var index = 0;
var length = u8Arr.length;
var result = '';
var slice;
while (index < length) {
  slice = u8Arr.subarray(index, Math.min(index + CHUNK_SIZE, length)); 
  result += String.fromCharCode.apply(null, slice);
  index += CHUNK_SIZE;
}
return btoa(result);

	}-*/;
}