mirror of
https://github.com/oxen-io/session-android.git
synced 2023-12-14 02:53:01 +01:00
167 lines
5.2 KiB
Java
167 lines
5.2 KiB
Java
/*
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* Copyright (C) 2007 Esmertec AG.
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* Copyright (C) 2007 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package ws.com.google.android.mms.pdu;
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public class Base64 {
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/**
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* Used to get the number of Quadruples.
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*/
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static final int FOURBYTE = 4;
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/**
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* Byte used to pad output.
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*/
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static final byte PAD = (byte) '=';
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/**
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* The base length.
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*/
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static final int BASELENGTH = 255;
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// Create arrays to hold the base64 characters
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private static byte[] base64Alphabet = new byte[BASELENGTH];
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// Populating the character arrays
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static {
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for (int i = 0; i < BASELENGTH; i++) {
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base64Alphabet[i] = (byte) -1;
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}
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for (int i = 'Z'; i >= 'A'; i--) {
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base64Alphabet[i] = (byte) (i - 'A');
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}
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for (int i = 'z'; i >= 'a'; i--) {
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base64Alphabet[i] = (byte) (i - 'a' + 26);
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}
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for (int i = '9'; i >= '0'; i--) {
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base64Alphabet[i] = (byte) (i - '0' + 52);
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}
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base64Alphabet['+'] = 62;
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base64Alphabet['/'] = 63;
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}
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/**
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* Decodes Base64 data into octects
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*
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* @param base64Data Byte array containing Base64 data
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* @return Array containing decoded data.
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*/
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public static byte[] decodeBase64(byte[] base64Data) {
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// RFC 2045 requires that we discard ALL non-Base64 characters
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base64Data = discardNonBase64(base64Data);
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// handle the edge case, so we don't have to worry about it later
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if (base64Data.length == 0) {
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return new byte[0];
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}
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int numberQuadruple = base64Data.length / FOURBYTE;
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byte decodedData[] = null;
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byte b1 = 0, b2 = 0, b3 = 0, b4 = 0, marker0 = 0, marker1 = 0;
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// Throw away anything not in base64Data
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int encodedIndex = 0;
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int dataIndex = 0;
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{
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// this sizes the output array properly - rlw
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int lastData = base64Data.length;
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// ignore the '=' padding
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while (base64Data[lastData - 1] == PAD) {
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if (--lastData == 0) {
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return new byte[0];
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}
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}
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decodedData = new byte[lastData - numberQuadruple];
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}
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for (int i = 0; i < numberQuadruple; i++) {
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dataIndex = i * 4;
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marker0 = base64Data[dataIndex + 2];
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marker1 = base64Data[dataIndex + 3];
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b1 = base64Alphabet[base64Data[dataIndex]];
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b2 = base64Alphabet[base64Data[dataIndex + 1]];
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if (marker0 != PAD && marker1 != PAD) {
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//No PAD e.g 3cQl
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b3 = base64Alphabet[marker0];
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b4 = base64Alphabet[marker1];
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decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
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decodedData[encodedIndex + 1] =
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(byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
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decodedData[encodedIndex + 2] = (byte) (b3 << 6 | b4);
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} else if (marker0 == PAD) {
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//Two PAD e.g. 3c[Pad][Pad]
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decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
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} else if (marker1 == PAD) {
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//One PAD e.g. 3cQ[Pad]
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b3 = base64Alphabet[marker0];
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decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
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decodedData[encodedIndex + 1] =
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(byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
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}
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encodedIndex += 3;
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}
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return decodedData;
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}
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/**
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* Check octect wheter it is a base64 encoding.
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*
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* @param octect to be checked byte
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* @return ture if it is base64 encoding, false otherwise.
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*/
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private static boolean isBase64(byte octect) {
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if (octect == PAD) {
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return true;
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} else if (base64Alphabet[octect] == -1) {
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return false;
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} else {
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return true;
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}
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}
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/**
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* Discards any characters outside of the base64 alphabet, per
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* the requirements on page 25 of RFC 2045 - "Any characters
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* outside of the base64 alphabet are to be ignored in base64
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* encoded data."
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*
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* @param data The base-64 encoded data to groom
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* @return The data, less non-base64 characters (see RFC 2045).
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*/
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static byte[] discardNonBase64(byte[] data) {
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byte groomedData[] = new byte[data.length];
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int bytesCopied = 0;
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for (int i = 0; i < data.length; i++) {
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if (isBase64(data[i])) {
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groomedData[bytesCopied++] = data[i];
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}
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}
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byte packedData[] = new byte[bytesCopied];
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System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);
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return packedData;
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}
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}
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