/****************************************************************
* Licensed to the Apache Software Foundation (ASF) under one *
* or more contributor license agreements. See the NOTICE file *
* distributed with this work for additional information *
* regarding copyright ownership. The ASF licenses this file *
* to you 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. *
****************************************************************/
/**
* Modified to improve efficiency by Android 21-Aug-2009
*/
package org.apache.james.mime4j.decoder;
import java.io.IOException;
import java.io.InputStream;
/**
* Performs Base-64 decoding on an underlying stream.
*
*
* @version $Id: Base64InputStream.java,v 1.3 2004/11/29 13:15:47 ntherning Exp $
*/
public class Base64InputStream extends InputStream {
private final InputStream s;
private int outCount = 0;
private int outIndex = 0;
private final int[] outputBuffer = new int[3];
private final byte[] inputBuffer = new byte[4];
private boolean done = false;
public Base64InputStream(InputStream s) {
this.s = s;
}
/**
* Closes the underlying stream.
*
* @throws IOException on I/O errors.
*/
@Override
public void close() throws IOException {
s.close();
}
@Override
public int read() throws IOException {
if (outIndex == outCount) {
fillBuffer();
if (outIndex == outCount) {
return -1;
}
}
return outputBuffer[outIndex++];
}
/**
* Retrieve data from the underlying stream, decode it,
* and put the results in the byteq.
* @throws IOException
*/
private void fillBuffer() throws IOException {
outCount = 0;
outIndex = 0;
int inCount = 0;
int i;
// "done" is needed for the two successive '=' at the end
while (!done) {
switch (i = s.read()) {
case -1:
// No more input - just return, let outputBuffer drain out, and be done
return;
case '=':
// once we meet the first '=', avoid reading the second '='
done = true;
decodeAndEnqueue(inCount);
return;
default:
byte sX = TRANSLATION[i];
if (sX < 0) continue;
inputBuffer[inCount++] = sX;
if (inCount == 4) {
decodeAndEnqueue(inCount);
return;
}
break;
}
}
}
private void decodeAndEnqueue(int len) {
int accum = 0;
accum |= inputBuffer[0] << 18;
accum |= inputBuffer[1] << 12;
accum |= inputBuffer[2] << 6;
accum |= inputBuffer[3];
// There's a bit of duplicated code here because we want to have straight-through operation
// for the most common case of len==4
if (len == 4) {
outputBuffer[0] = (accum >> 16) & 0xFF;
outputBuffer[1] = (accum >> 8) & 0xFF;
outputBuffer[2] = (accum) & 0xFF;
outCount = 3;
return;
} else if (len == 3) {
outputBuffer[0] = (accum >> 16) & 0xFF;
outputBuffer[1] = (accum >> 8) & 0xFF;
outCount = 2;
return;
} else { // len == 2
outputBuffer[0] = (accum >> 16) & 0xFF;
outCount = 1;
return;
}
}
private static byte[] TRANSLATION = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x00 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x10 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, /* 0x20 */
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, /* 0x30 */
-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 0x40 */
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, /* 0x50 */
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, /* 0x60 */
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, /* 0x70 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x80 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x90 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xA0 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xB0 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xC0 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xD0 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xE0 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 /* 0xF0 */
};
}