Java tutorial
// Portions copyright 2002, Google, Inc. // // 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.common.util; import com.google.common.annotations.GwtCompatible; // This code was converted from code at http://iharder.sourceforge.net/base64/ // Lots of extraneous features were removed. /* The original code said: * <p> * I am placing this code in the Public Domain. Do with it as you will. * This software comes with no guarantees or warranties but with * plenty of well-wishing instead! * Please visit * <a href="http://iharder.net/xmlizable">http://iharder.net/xmlizable</a> * periodically to check for updates or to contribute improvements. * </p> * * @author Robert Harder * @author rharder@usa.net * @version 1.3 */ /** * Base64 converter class. This code is not a full-blown MIME encoder; * it simply converts binary data to base64 data and back. * <p> * {@code CharBase64} differs from {@code Base64} (also in this package) in * that it does not use the {@code String.getBytes()} method or the * {@code String(byte[])} constructor. Also, {@code Base64} is not * GWT-compatible. * */ @GwtCompatible public final class CharBase64 { /** Specify encoding (value is {@code true}). */ public final static boolean ENCODE = true; /** Specify decoding (value is {@code false}). */ public final static boolean DECODE = false; /** * The equals sign (=), which is used as padding to make all base64 strings' * lengths a multiple of 4, as a char. */ private final static char PADDING_CHAR = '='; /** The new line character (\n) as a char. */ private final static char NEW_LINE = '\n'; /** The 64 valid Base64 values. */ private final static char[] ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" .toCharArray(); /** The 64 valid web safe Base64 values. */ private final static char[] WEBSAFE_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_" .toCharArray(); /** * Translates a Base64 value to either its 6-bit reconstruction value * or a negative number indicating some other meaning. **/ private final static byte[] 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 /* ,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 128 - 139 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 140 - 152 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 153 - 165 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 166 - 178 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 179 - 191 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 192 - 204 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 205 - 217 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 218 - 230 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 231 - 243 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9 // Decimal 244 - 255 */ }; /** The web safe decodabet */ private final static byte[] WEBSAFE_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, -9, -9, // Decimal 33 - 44 62, // Dash '-' sign at decimal 45 -9, -9, // Decimal 46-47 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 /* ,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 128 - 139 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 140 - 152 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 153 - 165 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 166 - 178 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 179 - 191 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 192 - 204 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 205 - 217 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 218 - 230 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 231 - 243 -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9 // Decimal 244 - 255 */ }; // Indicates white space in encoding private final static byte WHITE_SPACE_ENC = -5; // Indicates equals sign in encoding private final static byte EQUALS_SIGN_ENC = -1; /** Defeats instantiation. */ private CharBase64() { } /* ******** G E T T E R M E T H O D S ******** */ /** * Returns a clone of the alphabet array. */ public static final char[] getAlphabet() { // The following is not allowed by the GWT compiler: // return (char[]) ALPHABET.clone(); // It gives "[ERROR] ... Cannot invoke clone() on the array type char[]" char[] clone = new char[ALPHABET.length]; System.arraycopy(ALPHABET, 0, clone, 0, ALPHABET.length); return clone; } /** * Returns a clone of the web safe alphabet array. */ public static final char[] getWebSafeAlphabet() { // The following is not allowed by the GWT compiler: // return (char[]) WEBSAFE_ALPHABET.clone(); // It gives "[ERROR] ... Cannot invoke clone() on the array type char[]" char[] clone = new char[WEBSAFE_ALPHABET.length]; System.arraycopy(WEBSAFE_ALPHABET, 0, clone, 0, WEBSAFE_ALPHABET.length); return clone; } /* ******** E N C O D I N G M E T H O D S ******** */ /** * Encodes up to three bytes of the array <var>source</var> * and writes the resulting four Base64 bytes to <var>destination</var>. * The source and destination arrays can be manipulated * anywhere along their length by specifying * <var>srcOffset</var> and <var>destOffset</var>. * This method does not check to make sure your arrays * are large enough to accommodate <var>srcOffset</var> + 3 for * the <var>source</var> array or <var>destOffset</var> + 4 for * the <var>destination</var> array. * The actual number of significant bytes in your array is * given by <var>numSigBytes</var>. * * @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 alphabet is the encoding alphabet * @return the <var>destination</var> array */ private static char[] encode3to4(byte[] source, int srcOffset, int numSigBytes, char[] destination, int destOffset, char[] 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 destination; case 2: destination[destOffset] = alphabet[(inBuff >>> 18)]; destination[destOffset + 1] = alphabet[(inBuff >>> 12) & 0x3f]; destination[destOffset + 2] = alphabet[(inBuff >>> 6) & 0x3f]; destination[destOffset + 3] = PADDING_CHAR; return destination; case 1: destination[destOffset] = alphabet[(inBuff >>> 18)]; destination[destOffset + 1] = alphabet[(inBuff >>> 12) & 0x3f]; destination[destOffset + 2] = PADDING_CHAR; destination[destOffset + 3] = PADDING_CHAR; return destination; default: return destination; } // end switch } // end encode3to4 /** * Encodes a byte array into Base64 notation. * Equivalent to calling * {@code encodeBytes(source, 0, source.length)} * * @param source The data to convert */ public static String encode(byte[] source) { return encode(source, 0, source.length, ALPHABET, true); } /** * Encodes a byte array into web safe Base64 notation. * * @param source The data to convert * @param doPadding is {@code true} to pad result with '=' chars * if it does not fall on 3 byte boundaries */ public static String encodeWebSafe(byte[] source, boolean doPadding) { return encode(source, 0, source.length, WEBSAFE_ALPHABET, doPadding); } /** * 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 alphabet is the encoding alphabet * @param doPadding is {@code true} to pad result with '=' chars * if it does not fall on 3 byte boundaries */ public static String encode(byte[] source, int off, int len, char[] alphabet, boolean doPadding) { char[] outBuff = encode(source, off, len, alphabet, Integer.MAX_VALUE); int outLen = outBuff.length; // If doPadding is false, set length to truncate '=' // padding characters while (doPadding == false && outLen > 0) { if (outBuff[outLen - 1] != '=') { break; } outLen -= 1; } return new String(outBuff, 0, outLen); } /** * 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 alphabet is the encoding alphabet * @param maxLineLength maximum length of one line. * @return the BASE64-encoded char array */ public static char[] encode(byte[] source, int off, int len, char[] alphabet, int maxLineLength) { int lenDiv3 = (len + 2) / 3; // ceil(len / 3) int len43 = lenDiv3 * 4; char[] outBuff = new char[len43 // Main 4:3 + (len43 / maxLineLength)]; // New lines int d = 0; int e = 0; int len2 = len - 2; int lineLength = 0; for (; d < len2; d += 3, e += 4) { // The following block of code is the same as // encode3to4( source, d + off, 3, outBuff, e, alphabet ); // but inlined for faster encoding (~20% improvement) int inBuff = ((source[d + off] << 24) >>> 8) | ((source[d + 1 + off] << 24) >>> 16) | ((source[d + 2 + off] << 24) >>> 24); outBuff[e] = alphabet[(inBuff >>> 18)]; outBuff[e + 1] = alphabet[(inBuff >>> 12) & 0x3f]; outBuff[e + 2] = alphabet[(inBuff >>> 6) & 0x3f]; outBuff[e + 3] = alphabet[(inBuff) & 0x3f]; lineLength += 4; if (lineLength == maxLineLength) { outBuff[e + 4] = NEW_LINE; e++; lineLength = 0; } // end if: end of line } // end for: each piece of array if (d < len) { encode3to4(source, d + off, len - d, outBuff, e, alphabet); lineLength += 4; if (lineLength == maxLineLength) { // Add a last newline outBuff[e + 4] = NEW_LINE; e++; } e += 4; } assert (e == outBuff.length); return outBuff; } /* ******** D E C O D I N G M E T H O D S ******** */ /** * Decodes four chars from array <var>source</var> * and writes the resulting bytes (up to three of them) * to <var>destination</var>. * The source and destination arrays can be manipulated * anywhere along their length by specifying * <var>srcOffset</var> and <var>destOffset</var>. * This method does not check to make sure your arrays * are large enough to accommodate <var>srcOffset</var> + 4 for * the <var>source</var> array or <var>destOffset</var> + 3 for * the <var>destination</var> array. * This method returns the actual number of bytes that * were converted from the Base64 encoding. * * * @param source the array to convert * @param srcOffset the index where conversion begins * @param destination the array to hold the conversion * @param destOffset the index where output will be put * @param decodabet the decodabet for decoding Base64 content * @return the number of decoded bytes converted */ private static int decode4to3(char[] source, int srcOffset, byte[] destination, int destOffset, byte[] decodabet) { // Example: Dk== if (source[srcOffset + 2] == PADDING_CHAR) { int outBuff = ((decodabet[source[srcOffset]] << 24) >>> 6) | ((decodabet[source[srcOffset + 1]] << 24) >>> 12); destination[destOffset] = (byte) (outBuff >>> 16); return 1; } else if (source[srcOffset + 3] == PADDING_CHAR) { // Example: DkL= int outBuff = ((decodabet[source[srcOffset]] << 24) >>> 6) | ((decodabet[source[srcOffset + 1]] << 24) >>> 12) | ((decodabet[source[srcOffset + 2]] << 24) >>> 18); destination[destOffset] = (byte) (outBuff >>> 16); destination[destOffset + 1] = (byte) (outBuff >>> 8); return 2; } else { // Example: DkLE int outBuff = ((decodabet[source[srcOffset]] << 24) >>> 6) | ((decodabet[source[srcOffset + 1]] << 24) >>> 12) | ((decodabet[source[srcOffset + 2]] << 24) >>> 18) | ((decodabet[source[srcOffset + 3]] << 24) >>> 24); destination[destOffset] = (byte) (outBuff >> 16); destination[destOffset + 1] = (byte) (outBuff >> 8); destination[destOffset + 2] = (byte) (outBuff); return 3; } } // end decodeToBytes /** * Decodes data from Base64 notation. * * @param s the string to decode (decoded in default encoding) * @return the decoded data */ public static byte[] decode(String s) throws Base64DecoderException { char[] chars = s.toCharArray(); return decode(chars, 0, chars.length); } /** * Decodes data from web safe Base64 notation. * Web safe encoding uses '-' instead of '+', '_' instead of '/' * * @param s the string to decode (decoded in default encoding) * @return the decoded data */ public static byte[] decodeWebSafe(String s) throws Base64DecoderException { char[] chars = s.toCharArray(); return decodeWebSafe(chars, 0, chars.length); } /** * Decodes Base64 content in char array format and returns * the decoded byte array. * * @param source The Base64 encoded data * @return decoded data */ public static byte[] decode(char[] source) throws Base64DecoderException { return decode(source, 0, source.length); } /** * Decodes web safe Base64 content in char array format and returns * the decoded data. * Web safe encoding uses '-' instead of '+', '_' instead of '/' * * @param source the string to decode (decoded in default encoding) * @return the decoded data */ public static byte[] decodeWebSafe(char[] source) throws Base64DecoderException { return decodeWebSafe(source, 0, source.length); } /** * Decodes Base64 content in char array format and returns * the decoded byte array. * * @param source The Base64 encoded data * @param off The offset of where to begin decoding * @param len The length of characters to decode * @return decoded data */ public static byte[] decode(char[] source, int off, int len) throws Base64DecoderException { return decode(source, off, len, DECODABET); } /** * Decodes web safe Base64 content in char array format and returns * the decoded byte array. * Web safe encoding uses '-' instead of '+', '_' instead of '/' * * @param source The Base64 encoded data * @param off The offset of where to begin decoding * @param len The length of characters to decode * @return decoded data */ public static byte[] decodeWebSafe(char[] source, int off, int len) throws Base64DecoderException { return decode(source, off, len, WEBSAFE_DECODABET); } /** * Decodes Base64 content using the supplied decodabet and returns * the decoded byte array. * * @param source The Base64 encoded data * @param off The offset of where to begin decoding * @param len The length of characters to decode * @param decodabet the decodabet for decoding Base64 content * @return decoded data */ public static byte[] decode(char[] source, int off, int len, byte[] decodabet) throws Base64DecoderException { int len34 = len * 3 / 4; byte[] outBuff = new byte[2 + len34]; // Upper limit on size of output int outBuffPosn = 0; char[] c4 = new char[4]; int c4Posn = 0; int i = 0; char sbiCrop = 0; byte sbiDecode = 0; boolean paddingCharSeen = false; for (i = 0; i < len; i++) { char sbiRaw = source[i + off]; sbiCrop = (char) (sbiRaw & 0x7f); // Only the low seven bits sbiDecode = decodabet[sbiCrop]; if (sbiCrop == sbiRaw // Verify that discarded upper bits were actually 0 && sbiDecode < WHITE_SPACE_ENC) { // White space Equals sign or better throw new Base64DecoderException( "Bad Base64 input character at " + i + ": " + (int) source[i + off] + "(decimal)"); } if (sbiDecode >= EQUALS_SIGN_ENC) { if (sbiCrop == PADDING_CHAR) { if (paddingCharSeen) { continue; } // Padding must not occur at position 0 or 1 and must be the last // char[s] in the encoded value if (i < 2) { throw new Base64DecoderException("Invalid padding char found in position " + i); } paddingCharSeen = true; char lastChar = (char) (source[len - 1 + off] & 0x7f); if (lastChar != PADDING_CHAR && lastChar != NEW_LINE) { throw new Base64DecoderException("encoded value has invalid trailing char"); } } else if (paddingCharSeen) { throw new Base64DecoderException("Data found after trailing padding char at index " + i); } else { c4[c4Posn++] = sbiCrop; if (c4Posn == 4) { outBuffPosn += decode4to3(c4, 0, outBuff, outBuffPosn, decodabet); c4Posn = 0; } } } } // Because web safe encoding allows non padding base64 encodes, we // need to pad the rest of the c4 buffer with equal signs when // c4Posn != 0. There can be at most 2 equal signs at the end of // four characters, so the c4 buffer must have two or three // characters. This also catches the case where the input is // padded. if (c4Posn != 0) { if (c4Posn == 1) { throw new Base64DecoderException("single trailing character at offset " + (len - 1)); } c4[c4Posn] = PADDING_CHAR; outBuffPosn += decode4to3(c4, 0, outBuff, outBuffPosn, decodabet); } byte[] out = new byte[outBuffPosn]; System.arraycopy(outBuff, 0, out, 0, outBuffPosn); return out; } }