Java tutorial
/* * * The contents of this [class] are subject to the Netscape Public * License Version 1.1 (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.mozilla.org/NPL/ * * Software distributed under the License is distributed on an "AS * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or * implied. See the License for the specific language governing * rights and limitations under the License. * * The Original Code is mozilla.org code. * * The Initial Developer of the Original Code is Netscape * Communications Corporation. Portions created by Netscape are * Copyright (C) 1999 Netscape Communications Corporation. All * Rights Reserved. * * Contributor(s): */ package org.exist.util; import org.apache.commons.io.output.ByteArrayOutputStream; /** * Base 64 text to byte decoder. To produce the binary array from * base 64 encoding call {@link #translate} for each sequence of * characters and {@link #getByteArray} to mark closure of the * character stream and retrieve the binary contents. * * @author Based on code from the Mozilla Directory SDK */ public final class Base64Decoder { private ByteArrayOutputStream out = new ByteArrayOutputStream(); private byte token[] = new byte[4]; // input buffer private byte bytes[] = new byte[3]; // output buffer private int token_length = 0; // input buffer length private static final byte NUL = 127; // must be out of range 0-64 private static final byte EOF = 126; // must be out of range 0-64 private static final byte SP = 125; // must be out of range 0-64 private static final byte[] map = { NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // x00 - x07 NUL, SP, SP, NUL, NUL, SP, NUL, NUL, // x08 - x0F NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // x10 - x17 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // x18 - x1F SP, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // x20 - x2F !"#$%&' NUL, NUL, NUL, 62, NUL, NUL, NUL, 63, // 050-057 ()*+,-./ 52, 53, 54, 55, 56, 57, 58, 59, // 060-067 01234567 60, 61, NUL, NUL, NUL, EOF, NUL, NUL, // 070-077 89:;<=>? NUL, 0, 1, 2, 3, 4, 5, 6, // 100-107 @ABCDEFG 7, 8, 9, 10, 11, 12, 13, 14, // 110-117 HIJKLMNO 15, 16, 17, 18, 19, 20, 21, 22, // 120-127 PQRSTUVW 23, 24, 25, NUL, NUL, NUL, NUL, NUL, // 130-137 XYZ[\]^_ NUL, 26, 27, 28, 29, 30, 31, 32, // 140-147 `abcdefg 33, 34, 35, 36, 37, 38, 39, 40, // 150-157 hijklmno 41, 42, 43, 44, 45, 46, 47, 48, // 160-167 pqrstuvw 49, 50, 51, NUL, NUL, NUL, NUL, NUL, // 170-177 xyz{|}~ NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 200-207 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 210-217 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 220-227 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 230-237 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 240-247 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 250-257 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 260-267 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 270-277 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 300-307 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 310-317 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 320-327 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 330-337 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 340-347 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 350-357 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 360-367 NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, // 370-377 }; // Fast routine that assumes full 4-char tokens with no '=' in them. // private void decode_token() { final int num = ((token[0] << 18) | (token[1] << 12) | (token[2] << 6) | (token[3])); bytes[0] = (byte) (0xFF & (num >> 16)); bytes[1] = (byte) (0xFF & (num >> 8)); bytes[2] = (byte) (0xFF & num); out.write(bytes, 0, 3); } // Hairier routine that deals with the final token, which can have fewer // than four characters, and that might be padded with '='. // private void decode_final_token() { byte b0 = token[0]; byte b1 = token[1]; byte b2 = token[2]; byte b3 = token[3]; int eq_count = 0; if (b0 == EOF) { b0 = 0; eq_count++; } if (b1 == EOF) { b1 = 0; eq_count++; } if (b2 == EOF) { b2 = 0; eq_count++; } if (b3 == EOF) { b3 = 0; eq_count++; } if (eq_count > 2) { throw new IllegalArgumentException( "The number of '=' signs at the end of a base64 value must not exceed 2"); } if (eq_count == 2 && (b1 & 0x0F) != 0) { throw new IllegalArgumentException( "In base64, if the value ends with '==' then the last character must be one of [AQgw]"); } if (eq_count == 1 && (b2 & 0x03) != 0) { throw new IllegalArgumentException( "In base64, if the value ends with '=' then the last character must be one of [AEIMQUYcgkosw048]"); } final int num = ((b0 << 18) | (b1 << 12) | (b2 << 6) | (b3)); // eq_count will be 0, 1, or 2. // No "=" padding means 4 bytes mapped to 3, the normal case, // not handled in this routine. // "xxx=" means 3 bytes mapped to 2. // "xx==" means 2 bytes mapped to 1. // "x===" can't happen, because "x" would then be encoding // only 6 bits, not 8, the minimum possible. out.write((byte) (num >> 16)); // byte 1, count = 0 or 1 or 2 if (eq_count <= 1) { out.write((byte) ((num >> 8) & 0xFF)); // byte 2, count = 0 or 1 if (eq_count == 0) { out.write((byte) (num & 0xFF)); // byte 3, count = 0 } } } /** * Decode the base 64 string into a byte array (which can subsequently be accessed using getByteArray() * @param str the base 64 string * @throws IllegalArgumentException if the base64 string is incorrectly formatted */ public final void translate(CharSequence str) throws IllegalArgumentException { if (token == null) // already saw eof marker? { return; } final int length = str.length(); int lengthAtEOF; int found_eq = 0; for (int i = 0; i < length; i++) { final char c = str.charAt(i); if (c > 127) { throw new IllegalArgumentException("non-ASCII character in Base64 value (at offset " + i + ')'); } byte t = map[c]; if (t == NUL) { throw new IllegalArgumentException( "invalid character '" + c + "' in Base64 value (at offset " + i + ')'); } if (found_eq > 0 && t != EOF && t != SP) { throw new IllegalArgumentException("In Base64, an '=' character can appear only at the end"); } if (t == EOF) { if (found_eq > 0) { found_eq++; if (found_eq > 2) { throw new IllegalArgumentException("Base64 value can contain at most two '=' characters"); } token_length = (token_length + 1) % 4; } else { found_eq = 1; lengthAtEOF = token_length; eof(); token_length = (lengthAtEOF + 1) % 4; } } else if (t != SP) { token[token_length++] = t; if (token_length == 4) { if (found_eq == 0) { decode_token(); } token_length = 0; } } } if (token_length != 0) { throw new IllegalArgumentException("Base64 input must be a multiple of four characters"); } } private void eof() { if (token != null && token_length != 0) { while (token_length < 4) { token[token_length++] = EOF; } decode_final_token(); } token_length = 0; token = new byte[4]; bytes = new byte[3]; } public byte[] getByteArray() { eof(); return out.toByteArray(); } public void reset() { out.reset(); } }