sun.misc.BASE64Decoder(Android Base64Jar包以及Java源代码)

/* * Copyright (C) 2010 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 android.util; import java.io.UnsupportedEncodingException; /** * Utilities for encoding and decoding the Base64 representation of * binary data. See RFCs <a * href="http://www.ietf.org/rfc/rfc2045.txt">2045</a> and <a * href="http://www.ietf.org/rfc/rfc3548.txt">3548</a>. */ public class Base64_k { /** * Default values for encoder/decoder flags. */ public static final int DEFAULT = 0; /** * Encoder flag bit to omit the padding '=' characters at the end * of the output (if any). */ public static final int NO_PADDING = 1; /** * Encoder flag bit to omit all line terminators (i.e., the output * will be on one long line). */ public static final int NO_WRAP = 2; /** * Encoder flag bit to indicate lines should be terminated with a * CRLF pair instead of just an LF. Has no effect if {@code * NO_WRAP} is specified as well. */ public static final int CRLF = 4; /** * Encoder/decoder flag bit to indicate using the "URL and * filename safe" variant of Base64 (see RFC 3548 section 4) where * {@code -} and {@code _} are used in place of {@code +} and * {@code /}. */ public static final int URL_SAFE = 8; /** * Flag to pass to {@link Base64OutputStream} to indicate that it * should not close the output stream it is wrapping when it * itself is closed. */ public static final int NO_CLOSE = 16; // -------------------------------------------------------- // shared code // -------------------------------------------------------- /* package */ static abstract class Coder { public byte[] output; public int op; /** * Encode/decode another block of input data. this.output is * provided by the caller, and must be big enough to hold all * the coded data. On exit, this.opwill be set to the length * of the coded data. * * @param finish true if this is the final call to process for * this object. Will finalize the coder state and * include any final bytes in the output. * * @return true if the input so far is good; false if some * error has been detected in the input stream.. */ public abstract boolean process(byte[] input, int offset, int len, boolean finish); /** * @return the maximum number of bytes a call to process() * could produce for the given number of input bytes. This may * be an overestimate. */ public abstract int maxOutputSize(int len); } // -------------------------------------------------------- // decoding // -------------------------------------------------------- /** * Decode the Base64-encoded data in input and return the data in * a new byte array. * * <p>The padding '=' characters at the end are considered optional, but * if any are present, there must be the correct number of them. * * @param str the input String to decode, which is converted to * bytes using the default charset * @param flags controls certain features of the decoded output. * Pass {@code DEFAULT} to decode standard Base64. * * @throws IllegalArgumentException if the input contains * incorrect padding */ public static byte[] decode(String str, int flags) { return decode(str.getBytes(), flags); } /** * Decode the Base64-encoded data in input and return the data in * a new byte array. * * <p>The padding '=' characters at the end are considered optional, but * if any are present, there must be the correct number of them. * * @param input the input array to decode * @param flags controls certain features of the decoded output. * Pass {@code DEFAULT} to decode standard Base64. * * @throws IllegalArgumentException if the input contains * incorrect padding */ public static byte[] decode(byte[] input, int flags) { return decode(input, 0, input.length, flags); } /** * Decode the Base64-encoded data in input and return the data in * a new byte array. * * <p>The padding '=' characters at the end are considered optional, but * if any are present, there must be the correct number of them. * * @param input the data to decode * @param offset the position within the input array at which to start * @param len the number of bytes of input to decode * @param flags controls certain features of the decoded output. * Pass {@code DEFAULT} to decode standard Base64. * * @throws IllegalArgumentException if the input contains * incorrect padding */ public static byte[] decode(byte[] input, int offset, int len, int flags) { // Allocate space for the most data the input could represent. // (It could contain less if it contains whitespace, etc.) Decoder decoder = new Decoder(flags, new byte[len*3/4]); if (!decoder.process(input, offset, len, true)) { throw new IllegalArgumentException("bad base-64"); } // Maybe we got lucky and allocated exactly enough output space. if (decoder.op == decoder.output.length) { return decoder.output; } // Need to shorten the array, so allocate a new one of the // right size and copy. byte[] temp = new byte[decoder.op]; System.arraycopy(decoder.output, 0, temp, 0, decoder.op); return temp; } /* package */ static class Decoder extends Coder { /** * Lookup table for turning bytes into their position in the * Base64 alphabet. */ private static final int DECODE[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, }; /** * Decode lookup table for the "web safe" variant (RFC 3548 * sec. 4) where - and _ replace + and /. */ private static final int DECODE_WEBSAF