Java tutorial
/******************************************************************************* * * A Base64 Encoder/Decoder. * * This class is used to encode and decode data in Base64 format as described in * RFC 1521. * * <p> * Copyright 2003: Christian d'Heureuse, Inventec Informatik AG, Switzerland.<br> * License: This is "Open Source" software and released under the <a * href="http://www.gnu.org/licenses/lgpl.html" target="_top">GNU/LGPL</a> * license. It is provided "as is" without warranty of any kind. Please contact * the author for other licensing arrangements.<br> * Home page: <a href="http://www.source-code.biz" * target="_top">www.source-code.biz</a><br> * * <p> * Version history:<br> * 2003-07-22 Christian d'Heureuse (chdh): Module created.<br> * 2005-08-11 chdh: Lincense changed from GPL to LGPL. * ******************************************************************************/ public class Base64Coder { // Mapping table from 6-bit nibbles to Base64 characters. private static char[] map1 = new char[64]; static { int i = 0; for (char c = 'A'; c <= 'Z'; c++) map1[i++] = c; for (char c = 'a'; c <= 'z'; c++) map1[i++] = c; for (char c = '0'; c <= '9'; c++) map1[i++] = c; map1[i++] = '+'; map1[i++] = '/'; } // Mapping table from Base64 characters to 6-bit nibbles. private static byte[] map2 = new byte[128]; static { for (int i = 0; i < map2.length; i++) map2[i] = -1; for (int i = 0; i < 64; i++) map2[map1[i]] = (byte) i; } /** * Encodes a string into Base64 format. No blanks or line breaks are inserted. * * @param s * a String to be encoded. * @return A String with the Base64 encoded data. */ public static String encode(String s) { return new String(encode(s.getBytes())); } /** * Encodes a byte array into Base64 format. No blanks or line breaks are * inserted. * * @param in * an array containing the data bytes to be encoded. * @return A character array with the Base64 encoded data. */ public static char[] encode(byte[] in) { int iLen = in.length; int oDataLen = (iLen * 4 + 2) / 3; // output length without padding int oLen = ((iLen + 2) / 3) * 4; // output length including padding char[] out = new char[oLen]; int ip = 0; int op = 0; while (ip < iLen) { int i0 = in[ip++] & 0xff; int i1 = ip < iLen ? in[ip++] & 0xff : 0; int i2 = ip < iLen ? in[ip++] & 0xff : 0; int o0 = i0 >>> 2; int o1 = ((i0 & 3) << 4) | (i1 >>> 4); int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6); int o3 = i2 & 0x3F; out[op++] = map1[o0]; out[op++] = map1[o1]; out[op] = op < oDataLen ? map1[o2] : '='; op++; out[op] = op < oDataLen ? map1[o3] : '='; op++; } return out; } /** * Decodes a Base64 string. * * @param s * a Base64 String to be decoded. * @return A String containing the decoded data. * @throws IllegalArgumentException * if the input is not valid Base64 encoded data. */ public static String decode(String s) { return new String(decode(s.toCharArray())); } /** * Decodes Base64 data. No blanks or line breaks are allowed within the Base64 * encoded data. * * @param in * a character array containing the Base64 encoded data. * @return An array containing the decoded data bytes. * @throws IllegalArgumentException * if the input is not valid Base64 encoded data. */ public static byte[] decode(char[] in) { int iLen = in.length; if (iLen % 4 != 0) throw new IllegalArgumentException("Length of Base64 encoded input string is not a multiple of 4."); while (iLen > 0 && in[iLen - 1] == '=') iLen--; int oLen = (iLen * 3) / 4; byte[] out = new byte[oLen]; int ip = 0; int op = 0; while (ip < iLen) { int i0 = in[ip++]; int i1 = in[ip++]; int i2 = ip < iLen ? in[ip++] : 'A'; int i3 = ip < iLen ? in[ip++] : 'A'; if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127) throw new IllegalArgumentException("Illegal character in Base64 encoded data."); int b0 = map2[i0]; int b1 = map2[i1]; int b2 = map2[i2]; int b3 = map2[i3]; if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0) throw new IllegalArgumentException("Illegal character in Base64 encoded data."); int o0 = (b0 << 2) | (b1 >>> 4); int o1 = ((b1 & 0xf) << 4) | (b2 >>> 2); int o2 = ((b2 & 3) << 6) | b3; out[op++] = (byte) o0; if (op < oLen) out[op++] = (byte) o1; if (op < oLen) out[op++] = (byte) o2; } return out; } }