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/*
* Copyright (C) 2007 Esmertec AG.
* Copyright (C) 2007 The Android Open Source Project
*
* 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.
*/
package com.google.android.mms.pdu;
public class Base64 {
/**
* Used to get the number of Quadruples.
*/
static final int FOURBYTE = 4;
/**
* Byte used to pad output.
*/
static final byte PAD = (byte) '=';
/**
* The base length.
*/
static final int BASELENGTH = 255;
// Create arrays to hold the base64 characters
private static byte[] base64Alphabet = new byte[BASELENGTH];
// Populating the character arrays
static {
for (int i = 0; i < BASELENGTH; i++) {
base64Alphabet[i] = (byte) -1;
}
for (int i = 'Z'; i >= 'A'; i--) {
base64Alphabet[i] = (byte) (i - 'A');
}
for (int i = 'z'; i >= 'a'; i--) {
base64Alphabet[i] = (byte) (i - 'a' + 26);
}
for (int i = '9'; i >= '0'; i--) {
base64Alphabet[i] = (byte) (i - '0' + 52);
}
base64Alphabet['+'] = 62;
base64Alphabet['/'] = 63;
}
/**
* Decodes Base64 data into octects
*
* @param base64Data Byte array containing Base64 data
* @return Array containing decoded data.
*/
public static byte[] decodeBase64(byte[] base64Data) {
// RFC 2045 requires that we discard ALL non-Base64 characters
base64Data = discardNonBase64(base64Data);
// handle the edge case, so we don't have to worry about it later
if (base64Data.length == 0) {
return new byte[0];
}
int numberQuadruple = base64Data.length / FOURBYTE;
byte decodedData[] = null;
byte b1 = 0, b2 = 0, b3 = 0, b4 = 0, marker0 = 0, marker1 = 0;
// Throw away anything not in base64Data
int encodedIndex = 0;
int dataIndex = 0;
{
// this sizes the output array properly - rlw
int lastData = base64Data.length;
// ignore the '=' padding
while (base64Data[lastData - 1] == PAD) {
if (--lastData == 0) {
return new byte[0];
}
}
decodedData = new byte[lastData - numberQuadruple];
}
for (int i = 0; i < numberQuadruple; i++) {
dataIndex = i * 4;
marker0 = base64Data[dataIndex + 2];
marker1 = base64Data[dataIndex + 3];
b1 = base64Alphabet[base64Data[dataIndex]];
b2 = base64Alphabet[base64Data[dataIndex + 1]];
if (marker0 != PAD && marker1 != PAD) {
//No PAD e.g 3cQl
b3 = base64Alphabet[marker0];
b4 = base64Alphabet[marker1];
decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
decodedData[encodedIndex + 1] =
(byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
decodedData[encodedIndex + 2] = (byte) (b3 << 6 | b4);
} else if (marker0 == PAD) {
//Two PAD e.g. 3c[Pad][Pad]
decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
} else if (marker1 == PAD) {
//One PAD e.g. 3cQ[Pad]
b3 = base64Alphabet[marker0];
decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
decodedData[encodedIndex + 1] =
(byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
}
encodedIndex += 3;
}
return decodedData;
}
/**
* Check octect wheter it is a base64 encoding.
*
* @param octect to be checked byte
* @return ture if it is base64 encoding, false otherwise.
*/
private static boolean isBase64(byte octect) {
if (octect == PAD) {
return true;
} else if (base64Alphabet[octect] == -1) {
return false;
} else {
return true;
}
}
/**
* Discards any characters outside of the base64 alphabet, per
* the requirements on page 25 of RFC 2045 - "Any characters
* outside of the base64 alphabet are to be ignored in base64
* encoded data."
*
* @param data The base-64 encoded data to groom
* @return The data, less non-base64 characters (see RFC 2045).
*/
static byte[] discardNonBase64(byte[] data) {
byte groomedData[] = new byte[data.length];
int bytesCopied = 0;
for (int i = 0; i < data.length; i++) {
if (isBase64(data[i])) {
groomedData[bytesCopied++] = data[i];
}
}
byte packedData[] = new byte[bytesCopied];
System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);
return packedData;
}
}
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