Blob.java

/**
 * Copyright 2008 - 2015 The Loon Game Engine Authors
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * 
 * @project loon
 * @author cping
 * @email：javachenpeng@yahoo.com
 * @version 0.5
 */
package loon.html5.gwt.preloader;

import java.io.IOException;
import java.io.InputStream;

import com.google.gwt.typedarrays.shared.Int8Array;

public final class Blob {

	private final Int8Array data;

	public Blob(Int8Array data) {
		this.data = data;
	}

	public int length() {
		return data.length();
	}

	public byte get(int i) {
		return data.get(i);
	}

	public InputStream read() {
		return new InputStream() {

			@Override
			public int read() throws IOException {
				if (pos == length())
					return -1;
				return get(pos++) & 0xff;
			}

			@Override
			public int available() {
				return length() - pos;
			}

			int pos;
		};
	}

	public String toBase64() {
		int length = data.length();
		String base64code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
		StringBuilder encoded = new StringBuilder(length * 4 / 3 + 2);
		for (int i = 0; i < length; i += 3) {
			if (length - i >= 3) {
				int j = ((data.get(i) & 0xff) << 16)
						+ ((data.get(i + 1) & 0xff) << 8)
						+ (data.get(i + 2) & 0xff);
				encoded.append(base64code.charAt((j >> 18) & 0x3f));
				encoded.append(base64code.charAt((j >> 12) & 0x3f));
				encoded.append(base64code.charAt((j >> 6) & 0x3f));
				encoded.append(base64code.charAt(j & 0x3f));
			} else if (length - i >= 2) {
				int j = ((data.get(i) & 0xff) << 16)
						+ ((data.get(i + 1) & 0xff) << 8);
				encoded.append(base64code.charAt((j >> 18) & 0x3f));
				encoded.append(base64code.charAt((j >> 12) & 0x3f));
				encoded.append(base64code.charAt((j >> 6) & 0x3f));
				encoded.append("=");
			} else {
				int j = ((data.get(i) & 0xff) << 16);
				encoded.append(base64code.charAt((j >> 18) & 0x3f));
				encoded.append(base64code.charAt((j >> 12) & 0x3f));
				encoded.append("==");
			}
		}
		return encoded.toString();
	}

}