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/*
 * 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
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 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package android.util;

import static java.nio.charset.StandardCharsets.UTF_8;

/**
 * Utilities for encoding and decoding the Base64 representation of binary
 * data. See RFCs 2045 and
 * 3548.
 * 

* Original Author: iharder * Reference: http://iharder.sourceforge.net/current/java/base64/ *

* NOTE: Note that the class is updated to to match the android.util.Base64 * interface. Since that interface does not follow the Base64 standard this * class also does not entirely follow the standard, notably: *
    *
  • * Standard base64 will wrap at 76 characters per default, as * per RFC 2045, not only when requested as per RFC 3548. *
  • *
  • * Even {@link #URL_SAFE} encoding will both pad and wrap lines per default, * which frankly makes it neither safe for URLs nor filenames. *
  • *
  • * Line wrapping will only be applies as a splitter, it will never apply * to the end of the encoded string. This is a divergence from the * early implementation of the android.util.Base64 class at least. *
  • *
*/ public class Base64 { /* ******** P U B L I C F I E L D S ******** */ /** * Default values for encoder/decoder flags. */ public final static int DEFAULT = 0; /** * Encoder flag bit to omit the padding '=' characters at the end of the * output (if any). */ public final static int NO_PADDING = 1; /** Do not break lines when encoding. Value is 2. */ public final static 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 NO_WRAP is specified as well. */ public final static int CRLF = 4; /** * Encoder/decoder flag bit to indicate using the "URL and filename safe" * variant of Base64 (see RFC 3548 section 4) where - and _ are used in * place of + and /. * * URL_SAFE implies NO_WRAP and NO_PADDING. */ public final static int URL_SAFE = 8; /** * Flag to pass to Base64OutputStream to indicate that it should not * close the output stream it is wrapping when it itself is closed. */ public final static int NO_CLOSE = 16; /* ******** P R I V A T E F I E L D S ******** */ /** Maximum line length (76) of Base64 output. */ protected final static int MAX_LINE_LENGTH = 76; /** The equals sign (=) as a byte. */ protected final static byte EQUALS_SIGN = (byte) '='; /** The new carriage return (\r) as a byte. */ protected final static byte CR = (byte) '\r'; /** The new line character (\n) as a byte. */ protected final static byte LF = (byte) '\n'; protected final static byte WHITE_SPACE_ENC = -5; // Indicates white space in encoding private final static byte EQUALS_SIGN_ENC = -1; // Indicates equals sign in encoding /* ******** S T A N D A R D B A S E 6 4 A L P H A B E T ******** */ /** The 64 valid Base64 values. */ /* Host platform me be something funny like EBCDIC, so we hardcode these values. */ private final static byte[] _STANDARD_ALPHABET = { (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9', (byte) '+', (byte) '/' }; /** * Translates a Base64 value to either its 6-bit reconstruction value * or a negative number indicating some other meaning. **/ private final static byte[] _STANDARD_DECODABET = { -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 0 - 8 -5, -5, // Whitespace: Tab and Linefeed -9, -9, // Decimal 11 - 12 -5, // Whitespace: Carriage Return -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 14 - 26 -9, -9, -9, -9, -9, // Decimal 27 - 31 -5, // Whitespace: Space -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 33 - 42 62, // Plus sign at decimal 43 -9, -9, -9, // Decimal 44 - 46 63, // Slash at decimal 47 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // Numbers zero through nine -9, -9, -9, // Decimal 58 - 60 -1, // Equals sign at decimal 61 -9, -9, -9, // Decimal 62 - 64 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, // Letters 'A' through 'N' 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // Letters 'O' through 'Z' -9, -9, -9, -9, -9, -9, // Decimal 91 - 96 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, // Letters 'a' through 'm' 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // Letters 'n' through 'z' -9, -9, -9, -9, -9, // Decimal 123 - 127 }; /* ******** U R L S A F E B A S E 6 4 A L P H A B E T ******** */ /** * Used in the URL- and Filename-safe dialect described in Section 4 of RFC3548: * http://www.faqs.org/rfcs/rfc3548.html. * Notice that the last two bytes become "hyphen" and "underscore" instead of "plus" and "slash." */ private final static byte[] _URL_SAFE_ALPHABET = { (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9', (byte) '-', (byte) '_' }; /** * Used in decoding URL- and Filename-safe dialects of Base64. */ private final static byte[] _URL_SAFE_DECODABET = { -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 0 - 8 -5, -5, // Whitespace: Tab and Linefeed -9, -9, // Decimal 11 - 12 -5, // Whitespace: Carriage Return -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 14 - 26 -9, -9, -9, -9, -9, // Decimal 27 - 31 -5, // Whitespace: Space -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 33 - 42 -9, // Plus sign at decimal 43 -9, // Decimal 44 62, // Minus sign at decimal 45 -9, // Decimal 46 -9, // Slash at decimal 47 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // Numbers zero through nine -9, -9, -9, // Decimal 58 - 60 -1, // Equals sign at decimal 61 -9, -9, -9, // Decimal 62 - 64 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, // Letters 'A' through 'N' 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // Letters 'O' through 'Z' -9, -9, -9, -9, // Decimal 91 - 94 63, // Underscore at decimal 95 -9, // Decimal 96 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, // Letters 'a' through 'm' 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // Letters 'n' through 'z' -9, -9, -9, -9, -9, // Decimal 123 - 127 }; /* ******** D E T E R M I N E W H I C H A L H A B E T ******** */ /** * Returns one of the _SOMETHING_ALPHABET byte arrays depending on * the options specified. * It's possible, though silly, to specify ORDERED and URLSAFE * in which case one of them will be picked, though there is * no guarantee as to which one will be picked. * * @param options Option used to determine alphabet. * @return The alphabet pos to byte value array. */ protected static byte[] getAlphabet(int options) { if ((options & URL_SAFE) == URL_SAFE) { return _URL_SAFE_ALPHABET; } else { return _STANDARD_ALPHABET; } } // end getAlphabet /** * Returns one of the _SOMETHING_DECODABET byte arrays depending on * the options specified. * It's possible, though silly, to specify ORDERED and URL_SAFE * in which case one of them will be picked, though there is * no guarantee as to which one will be picked. * * @param options Option used to determine decodabet. * @return The decodabet pos to byte value array. */ protected static byte[] getDecodabet(int options) { if ((options & URL_SAFE) == URL_SAFE) { return _URL_SAFE_DECODABET; } else { return _STANDARD_DECODABET; } } // end getAlphabet /** Defeats instantiation. */ private Base64() { } /* ******** E N C O D I N G M E T H O D S ******** */ /** *

Encodes up to three bytes of the array source * and writes the resulting four Base64 bytes to destination. * The source and destination arrays can be manipulated * anywhere along their length by specifying * srcOffset and destOffset. * This method does not check to make sure your arrays * are large enough to accomodate srcOffset + 3 for * the source array or destOffset + 4 for * the destination array. * The actual number of significant bytes in your array is * given by numSigBytes.

*

This is the lowest level of the encoding methods with * all possible parameters.

* * @param source the array to convert * @param srcOffset the index where conversion begins * @param numSigBytes the number of significant bytes in your array * @param destination the array to hold the conversion * @param destOffset the index where output will be put * @param noPadding True if no padding should be added. * @param alphabet The alphabet to use. * @return the destination array * @since 1.3 */ protected static int encode3to4(byte[] source, int srcOffset, int numSigBytes, byte[] destination, int destOffset, boolean noPadding, byte[] alphabet) { // 1 2 3 // 01234567890123456789012345678901 Bit position // --------000000001111111122222222 Array position from threeBytes // --------| || || || | Six bit groups to index ALPHABET // >>18 >>12 >> 6 >> 0 Right shift necessary // 0x3f 0x3f 0x3f Additional AND // Create buffer with zero-padding if there are only one or two // significant bytes passed in the array. // We have to shift left 24 in order to flush out the 1's that appear // when Java treats a value as negative that is cast from a byte to an int. int inBuff = (numSigBytes > 0 ? ((source[srcOffset] << 24) >>> 8) : 0) | (numSigBytes > 1 ? ((source[srcOffset + 1] << 24) >>> 16) : 0) | (numSigBytes > 2 ? ((source[srcOffset + 2] << 24) >>> 24) : 0); switch (numSigBytes) { case 3: destination[destOffset] = alphabet[(inBuff >>> 18)]; destination[destOffset + 1] = alphabet[(inBuff >>> 12) & 0x3f]; destination[destOffset + 2] = alphabet[(inBuff >>> 6) & 0x3f]; destination[destOffset + 3] = alphabet[(inBuff) & 0x3f]; return 4; case 2: destination[destOffset] = alphabet[(inBuff >>> 18)]; destination[destOffset + 1] = alphabet[(inBuff >>> 12) & 0x3f]; destination[destOffset + 2] = alphabet[(inBuff >>> 6) & 0x3f]; if (noPadding) { return 3; } destination[destOffset + 3] = EQUALS_SIGN; return 4; case 1: destination[destOffset] = alphabet[(inBuff >>> 18)]; destination[destOffset + 1] = alphabet[(inBuff >>> 12) & 0x3f]; if (noPadding) { return 2; } destination[destOffset + 2] = EQUALS_SIGN; destination[destOffset + 3] = EQUALS_SIGN; return 4; default: return 0; } // end switch } // end encode3to4 /** * Encodes a byte array into Base64 notation. * * @param source The data to convert * @param options Specified options * @return The Base64-encoded data as a String * @see Base64#NO_WRAP * @throws NullPointerException if source array is null * @since 2.0 */ public static String encodeToString(byte[] source, int options) { return encodeToString(source, 0, source.length, options); } // end encodeToString /** * Encodes a byte array into Base64 notation. * * @param source The data to convert * @param off Offset in array where conversion should begin * @param len Length of data to convert * @param options Specified options * @return The Base64-encoded data as a String * @see Base64#NO_WRAP * @throws NullPointerException if source array is null * @throws IllegalArgumentException if source array, offset, or length are invalid * @since 2.0 */ public static String encodeToString(byte[] source, int off, int len, int options) { byte[] encoded = encode(source, off, len, options); return new String(encoded, UTF_8); } // end encodeToString /** * Similar to {@link #encodeToString(byte[], int, int, int)} but returns * a byte array instead of instantiating a String. This is more efficient * if you're working with I/O streams and have large data sets to encodeToString. * * @param source The data to convert * @param off Offset in array where conversion should begin * @param len Length of data to convert * @param options Specified options * @return The Base64-encoded data as a String * @see Base64#NO_WRAP * @see Base64#URL_SAFE * @see Base64#CRLF * @throws NullPointerException if source array is null * @throws IllegalArgumentException if source array, offset, or length are invalid * @since 2.3.1 */ public static byte[] encode(final byte[] source, final int off, final int len, final int options) { if (source == null) { throw new NullPointerException("Cannot serialize a null array."); } // end if: null if (off < 0) { throw new IllegalArgumentException("Cannot have negative offset: " + off); } // end if: off < 0 if (len < 0) { throw new IllegalArgumentException("Cannot have length offset: " + len); } // end if: len < 0 if (off + len > source.length) { throw new IllegalArgumentException(String.format( "Cannot have offset of %d and length of %d with array of length %d", off, len, source.length)); } // end if: off < 0 if (len == 0) { return new byte[0]; } final boolean breakLines = (options & (Base64.NO_WRAP)) == 0; final boolean crlf = (options & Base64.CRLF) != 0; final boolean noPadding = (options & (Base64.NO_PADDING)) != 0; final byte[] alphabet = getAlphabet(options); //int len43 = len * 4 / 3; //byte[] outBuff = new byte[ ( len43 ) // Main 4:3 // + ( (len % 3) > 0 ? 4 : 0 ) // Account for padding // + (breakLines ? ( len43 / MAX_LINE_LENGTH ) : 0) ]; // New lines // Try to determine more precisely how big the array needs to be. // If we get it right, we don't have to do an array copy, and // we save a bunch of memory. int bufLen = (len / 3) * 4 + (len % 3 > 0 ? 4 : 0); // Bytes needed for actual encoding if (breakLines) { int lines = bufLen / MAX_LINE_LENGTH; // Plus extra newline characters bufLen += crlf ? lines * 2 : lines; } byte[] dest = new byte[bufLen]; int srcPos = 0; int destPos = 0; int lineLength = 0; final int len2 = len - 2; for (; srcPos < len2; srcPos += 3) { if (breakLines && lineLength >= MAX_LINE_LENGTH) { if (crlf) { dest[destPos++] = CR; } dest[destPos++] = LF; lineLength = 0; } int l = encode3to4(source, srcPos + off, 3, dest, destPos, noPadding, alphabet); destPos += l; lineLength += l; } // end for: each piece of array if (srcPos < len) { if (breakLines && lineLength >= MAX_LINE_LENGTH) { if (crlf) { dest[destPos++] = CR; } dest[destPos++] = LF; } destPos += encode3to4(source, srcPos + off, len - srcPos, dest, destPos, noPadding, alphabet); } // end if: some padding needed // Only resize array if we didn't guess it right. if (destPos < dest.length) { // If breaking lines and the last byte falls right at // the line length (76 bytes per line), there will be // one extra byte, and the array will need to be resized. // Not too bad of an estimate on array size, I'd say. byte[] finalOut = new byte[destPos]; System.arraycopy(dest, 0, finalOut, 0, destPos); return finalOut; } else { return dest; } } // end encode /** * Similar to {@link #encodeToString(byte[], int, int, int)} but returns * a byte array instead of instantiating a String. This is more efficient * if you're working with I/O streams and have large data sets to encodeToString. * * * @param source The data to convert * @param options Specified options * @return The Base64-encoded data as a String * @see Base64#NO_WRAP * @throws NullPointerException if source array is null * @throws IllegalArgumentException if source array, offset, or length are invalid * @since 2.3.1 */ public static byte[] encode(byte[] source, int options) { return encode(source, 0, source.length, options); } /* ******** D E C O D I N G M E T H O D S ******** */ /** * Decodes four bytes from array source * and writes the resulting bytes (up to three of them) * to destination. * The source and destination arrays can be manipulated * anywhere along their length by specifying * srcOffset and destOffset. * This method does not check to make sure your arrays * are large enough to accomodate srcOffset + 4 for * the source array or destOffset + 3 for * the destination array. * This method returns the actual number of bytes that * were converted from the Base64 encoding. *

This is the lowest level of the decoding methods with * all possible parameters.

* * * @param src the array to convert * @param len The number of bytes to read within src. * @param dest the array to hold the conversion * @param offset the index where output will be put * @param decodabet alphabet type is pulled from this (standard, url-safe, ordered) * @return the number of decoded bytes converted * @throws NullPointerException if source or destination arrays are null * @throws IllegalArgumentException if srcOffset or destOffset are invalid * or there is not enough room in the array. * @since 1.3 */ protected static int decode4to3(byte[] src, int len, byte[] dest, int offset, byte[] decodabet) { // Example: Dk or Dk== if (len == 2 || (src[2] == EQUALS_SIGN && src[3] == EQUALS_SIGN)) { int outBuff = (validate(decodabet, src[0]) << 18) | (validate(decodabet, src[1]) << 12); dest[offset] = (byte) (outBuff >>> 16); return 1; } // Example: DkL or DkL= if (len == 3 || src[3] == EQUALS_SIGN) { int outBuff = (validate(decodabet, src[0]) << 18) | (validate(decodabet, src[1]) << 12) | (validate(decodabet, src[2]) << 6); dest[offset] = (byte) (outBuff >>> 16); dest[offset + 1] = (byte) (outBuff >>> 8); return 2; } // Example: DkLE int outBuff = (validate(decodabet, src[0]) << 18) | (validate(decodabet, src[1]) << 12) | (validate(decodabet, src[2]) << 6) | (validate(decodabet, src[3])); dest[offset] = (byte) (outBuff >>> 16); dest[offset + 1] = (byte) (outBuff >>> 8); dest[offset + 2] = (byte) (outBuff); return 3; } /** * Validate char byte and revalculate to data byte value or throw IllegalArgumentException. * @param decodabet The decodabet to use. * @param from The char byte to check. * @return The value byte. * @throws IllegalArgumentException If the char is not valid for the alphabet. */ private static int validate(byte[] decodabet, byte from) { byte b = decodabet[from & 0x7F]; if (b < 0) { throw new IllegalArgumentException(String.format( "Bad Base64%s character '%s'", (decodabet == _URL_SAFE_DECODABET ? " url safe" : ""), escape(from))); } return b; } /** * Decode the Base64-encoded data in input and return the data in a new * byte array. * * The padding '=' characters at the end are considered optional, but if * any are present, there must be the correct number of them. * * @param source The data to decode * @param options controls certain features of the decoded output. Pass * DEFAULT to decode standard Base64. * @return decoded data */ public static byte[] decode(byte[] source, int options) { if (source == null) { throw new IllegalArgumentException("Cannot decode null source array."); } return decode(source, 0, source.length, options); } /** * Decode the Base64-encoded data in input and return the data in a new * byte array. * * The padding '=' characters at the end are considered optional, but if * any are present, there must be the correct number of them. * * @param source The data to decode * @param offset The offset within the input array at which to start * @param len The number of byte sof input to decode. * @param options controls certain features of the decoded output. Pass * DEFAULT to decode standard Base64. * @return decoded data */ public static byte[] decode(byte[] source, int offset, int len, int options) { if (source == null) { throw new IllegalArgumentException("Cannot decode null source array."); } if (offset < 0 || offset + len > source.length) { throw new IllegalArgumentException(String.format( "Source array with length %d cannot have offset of %d and process %d bytes.", source.length, offset, len)); } if (len == 0) { return new byte[0]; } byte[] decodabet = getDecodabet(options); int len34 = len * 3 / 4; // Estimate on array size byte[] outBuff = new byte[len34]; // Upper limit on size of output int outBuffPosn = 0; // Keep track of where we're writing byte[] b4 = new byte[4]; // Four byte buffer from source, eliminating white space int b4Posn = 0; // Keep track of four byte input buffer int i; // Source array counter byte sbiDecode; // Special value from DECODABET for (i = offset; i < offset + len; i++) { // Loop through source sbiDecode = decodabet[source[i] & 0x7F]; // White space, Equals sign, or legit Base64 character // Note the values such as -5 and -9 in the // DECODABETs at the top of the file. if (sbiDecode >= WHITE_SPACE_ENC) { if (sbiDecode >= EQUALS_SIGN_ENC) { b4[b4Posn++] = source[i]; if (b4Posn > 3) { outBuffPosn += decode4to3(b4, 4, outBuff, outBuffPosn, decodabet); b4Posn = 0; } } } else { // There's a bad input character in the Base64 stream. throw new IllegalArgumentException(String.format( "Bad%s Base64 character '%s' in array position %d", (decodabet == _URL_SAFE_DECODABET ? " url safe" : ""), escape(source[i]), i)); } } if (b4Posn > 0) { outBuffPosn += decode4to3(b4, b4Posn, outBuff, outBuffPosn, decodabet); } if (outBuffPosn < outBuff.length) { byte[] out = new byte[outBuffPosn]; System.arraycopy(outBuff, 0, out, 0, outBuffPosn); return out; } return outBuff; } // end decode /** * Decodes data from Base64 notation, automatically * detecting gzip-compressed data and decompressing it. * * @param s the string to decode * @param options encodeToString options such as URL_SAFE * @return the decoded data * @throws NullPointerException if s is null */ public static byte[] decode(String s, int options) { if (s == null) { throw new IllegalArgumentException("Input string was null."); } byte[] bytes = s.getBytes(UTF_8); return decode(bytes, 0, bytes.length, options); } private static String escape(byte b) { if (b == '\"') { return "\\\""; } else if (b == '\'') { return "\\\'"; } else if (b < 0) { return String.format("\\u%04x", ((int) b + 0x100)); } else if (b < 32 || b == 127) { return String.format("\\%03o", (int) b); } return String.valueOf((char) b); } }




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