Java tutorial
/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER. * * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved. * * The contents of this file are subject to the terms of either the GNU * General Public License Version 2 only ("GPL") or the Common Development * and Distribution License("CDDL") (collectively, the "License"). You * may not use this file except in compliance with the License. You can obtain * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html * or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific * language governing permissions and limitations under the License. * * When distributing the software, include this License Header Notice in each * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt. * Sun designates this particular file as subject to the "Classpath" exception * as provided by Sun in the GPL Version 2 section of the License file that * accompanied this code. If applicable, add the following below the License * Header, with the fields enclosed by brackets [] replaced by your own * identifying information: "Portions Copyrighted [year] * [name of copyright owner]" * * Contributor(s): * * If you wish your version of this file to be governed by only the CDDL or * only the GPL Version 2, indicate your decision by adding "[Contributor] * elects to include this software in this distribution under the [CDDL or GPL * Version 2] license." If you don't indicate a single choice of license, a * recipient has the option to distribute your version of this file under * either the CDDL, the GPL Version 2 or to extend the choice of license to * its licensees as provided above. However, if you add GPL Version 2 code * and therefore, elected the GPL Version 2 license, then the option applies * only if the new code is made subject to such option by the copyright * holder. */ /* * @(#)BASE64DecoderStream.java 1.16 07/05/04 */ import java.io.*; /** * This class implements a BASE64 Decoder. It is implemented as * a FilterInputStream, so one can just wrap this class around * any input stream and read bytes from this filter. The decoding * is done as the bytes are read out. * * @author John Mani * @author Bill Shannon */ public class BASE64DecoderStream extends FilterInputStream { // buffer of decoded bytes for single byte reads private byte[] buffer = new byte[3]; private int bufsize = 0; // size of the cache private int index = 0; // index into the cache // buffer for almost 8K of typical 76 chars + CRLF lines, // used by getByte method. this buffer contains encoded bytes. private byte[] input_buffer = new byte[78 * 105]; private int input_pos = 0; private int input_len = 0;; private boolean ignoreErrors = false; /** * Create a BASE64 decoder that decodes the specified input stream. * The System property <code>mail.mime.base64.ignoreerrors</code> * controls whether errors in the encoded data cause an exception * or are ignored. The default is false (errors cause exception). * * @param in the input stream */ public BASE64DecoderStream(InputStream in) { super(in); try { String s = System.getProperty("mail.mime.base64.ignoreerrors"); // default to false ignoreErrors = s != null && !s.equalsIgnoreCase("false"); } catch (SecurityException sex) { // ignore it } } /** * Create a BASE64 decoder that decodes the specified input stream. * * @param in the input stream * @param ignoreErrors ignore errors in encoded data? */ public BASE64DecoderStream(InputStream in, boolean ignoreErrors) { super(in); this.ignoreErrors = ignoreErrors; } /** * Read the next decoded byte from this input stream. The byte * is returned as an <code>int</code> in the range <code>0</code> * to <code>255</code>. If no byte is available because the end of * the stream has been reached, the value <code>-1</code> is returned. * This method blocks until input data is available, the end of the * stream is detected, or an exception is thrown. * * @return next byte of data, or <code>-1</code> if the end of the * stream is reached. * @exception IOException if an I/O error occurs. * @see java.io.FilterInputStream#in */ public int read() throws IOException { if (index >= bufsize) { bufsize = decode(buffer, 0, buffer.length); if (bufsize <= 0) // buffer is empty return -1; index = 0; // reset index into buffer } return buffer[index++] & 0xff; // Zero off the MSB } /** * Reads up to <code>len</code> decoded bytes of data from this input stream * into an array of bytes. This method blocks until some input is * available. * <p> * * @param buf the buffer into which the data is read. * @param off the start offset of the data. * @param len the maximum number of bytes read. * @return the total number of bytes read into the buffer, or * <code>-1</code> if there is no more data because the end of * the stream has been reached. * @exception IOException if an I/O error occurs. */ public int read(byte[] buf, int off, int len) throws IOException { // empty out single byte read buffer int off0 = off; while (index < bufsize && len > 0) { buf[off++] = buffer[index++]; len--; } if (index >= bufsize) bufsize = index = 0; int bsize = (len / 3) * 3; // round down to multiple of 3 bytes if (bsize > 0) { int size = decode(buf, off, bsize); off += size; len -= size; if (size != bsize) { // hit EOF? if (off == off0) // haven't returned any data return -1; else // returned some data before hitting EOF return off - off0; } } // finish up with a partial read if necessary for (; len > 0; len--) { int c = read(); if (c == -1) // EOF break; buf[off++] = (byte) c; } if (off == off0) // haven't returned any data return -1; else // returned some data before hitting EOF return off - off0; } /** * Tests if this input stream supports marks. Currently this class * does not support marks */ public boolean markSupported() { return false; // Maybe later .. } /** * Returns the number of bytes that can be read from this input * stream without blocking. However, this figure is only * a close approximation in case the original encoded stream * contains embedded CRLFs; since the CRLFs are discarded, not decoded */ public int available() throws IOException { // This is only an estimate, since in.available() // might include CRLFs too .. return ((in.available() * 3) / 4 + (bufsize - index)); } /** * This character array provides the character to value map * based on RFC1521. */ private final static char pem_array[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', // 0 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 1 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 2 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', // 3 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 4 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', // 5 'w', 'x', 'y', 'z', '0', '1', '2', '3', // 6 '4', '5', '6', '7', '8', '9', '+', '/' // 7 }; private final static byte pem_convert_array[] = new byte[256]; static { for (int i = 0; i < 255; i++) pem_convert_array[i] = -1; for (int i = 0; i < pem_array.length; i++) pem_convert_array[pem_array[i]] = (byte) i; } /** * The decoder algorithm. Most of the complexity here is dealing * with error cases. Returns the number of bytes decoded, which * may be zero. Decoding is done by filling an int with 4 6-bit * values by shifting them in from the bottom and then extracting * 3 8-bit bytes from the int by shifting them out from the bottom. * * @param outbuf the buffer into which to put the decoded bytes * @param pos position in the buffer to start filling * @param len the number of bytes to fill * @return the number of bytes filled, always a multiple * of three, and may be zero * @exception IOException if the data is incorrectly formatted */ private int decode(byte[] outbuf, int pos, int len) throws IOException { int pos0 = pos; while (len >= 3) { /* * We need 4 valid base64 characters before we start decoding. * We skip anything that's not a valid base64 character (usually * just CRLF). */ int got = 0; int val = 0; while (got < 4) { int i = getByte(); if (i == -1 || i == -2) { boolean atEOF; if (i == -1) { if (got == 0) return pos - pos0; if (!ignoreErrors) throw new IOException("Error in encoded stream: " + "needed 4 valid base64 characters " + "but only got " + got + " before EOF" + recentChars()); atEOF = true; // don't read any more } else { // i == -2 // found a padding character, we're at EOF // XXX - should do something to make EOF "sticky" if (got < 2 && !ignoreErrors) throw new IOException("Error in encoded stream: " + "needed at least 2 valid base64 characters," + " but only got " + got + " before padding character (=)" + recentChars()); // didn't get any characters before padding character? if (got == 0) return pos - pos0; atEOF = false; // need to keep reading } // pad partial result with zeroes // how many bytes will we produce on output? // (got always < 4, so size always < 3) int size = got - 1; if (size == 0) size = 1; // handle the one padding character we've seen got++; val <<= 6; while (got < 4) { if (!atEOF) { // consume the rest of the padding characters, // filling with zeroes i = getByte(); if (i == -1) { if (!ignoreErrors) throw new IOException("Error in encoded stream: " + "hit EOF while looking for " + "padding characters (=)" + recentChars()); } else if (i != -2) { if (!ignoreErrors) throw new IOException( "Error in encoded stream: " + "found valid base64 character after " + "a padding character (=)" + recentChars()); } } val <<= 6; got++; } // now pull out however many valid bytes we got val >>= 8; // always skip first one if (size == 2) outbuf[pos + 1] = (byte) (val & 0xff); val >>= 8; outbuf[pos] = (byte) (val & 0xff); // len -= size; // not needed, return below pos += size; return pos - pos0; } else { // got a valid byte val <<= 6; got++; val |= i; } } // read 4 valid characters, now extract 3 bytes outbuf[pos + 2] = (byte) (val & 0xff); val >>= 8; outbuf[pos + 1] = (byte) (val & 0xff); val >>= 8; outbuf[pos] = (byte) (val & 0xff); len -= 3; pos += 3; } return pos - pos0; } /** * Read the next valid byte from the input stream. * Buffer lots of data from underlying stream in input_buffer, * for efficiency. * * @return the next byte, -1 on EOF, or -2 if next byte is '=' * (padding at end of encoded data) */ private int getByte() throws IOException { int c; do { if (input_pos >= input_len) { try { input_len = in.read(input_buffer); } catch (EOFException ex) { return -1; } if (input_len <= 0) return -1; input_pos = 0; } // get the next byte in the buffer c = input_buffer[input_pos++] & 0xff; // is it a padding byte? if (c == '=') return -2; // no, convert it c = pem_convert_array[c]; // loop until we get a legitimate byte } while (c == -1); return c; } /** * Return the most recent characters, for use in an error message. */ private String recentChars() { // reach into the input buffer and extract up to 10 // recent characters, to help in debugging. String errstr = ""; int nc = input_pos > 10 ? 10 : input_pos; if (nc > 0) { errstr += ", the " + nc + " most recent characters were: \""; for (int k = input_pos - nc; k < input_pos; k++) { char c = (char) (input_buffer[k] & 0xff); switch (c) { case '\r': errstr += "\\r"; break; case '\n': errstr += "\\n"; break; case '\t': errstr += "\\t"; break; default: if (c >= ' ' && c < 0177) errstr += c; else errstr += ("\\" + (int) c); } } errstr += "\""; } return errstr; } /** * Base64 decode a byte array. No line breaks are allowed. * This method is suitable for short strings, such as those * in the IMAP AUTHENTICATE protocol, but not to decode the * entire content of a MIME part. * * NOTE: inbuf may only contain valid base64 characters. * Whitespace is not ignored. */ public static byte[] decode(byte[] inbuf) { int size = (inbuf.length / 4) * 3; if (size == 0) return inbuf; if (inbuf[inbuf.length - 1] == '=') { size--; if (inbuf[inbuf.length - 2] == '=') size--; } byte[] outbuf = new byte[size]; int inpos = 0, outpos = 0; size = inbuf.length; while (size > 0) { int val; int osize = 3; val = pem_convert_array[inbuf[inpos++] & 0xff]; val <<= 6; val |= pem_convert_array[inbuf[inpos++] & 0xff]; val <<= 6; if (inbuf[inpos] != '=') // End of this BASE64 encoding val |= pem_convert_array[inbuf[inpos++] & 0xff]; else osize--; val <<= 6; if (inbuf[inpos] != '=') // End of this BASE64 encoding val |= pem_convert_array[inbuf[inpos++] & 0xff]; else osize--; if (osize > 2) outbuf[outpos + 2] = (byte) (val & 0xff); val >>= 8; if (osize > 1) outbuf[outpos + 1] = (byte) (val & 0xff); val >>= 8; outbuf[outpos] = (byte) (val & 0xff); outpos += osize; size -= 4; } return outbuf; } /*** begin TEST program *** public static void main(String argv[]) throws Exception { FileInputStream infile = new FileInputStream(argv[0]); BASE64DecoderStream decoder = new BASE64DecoderStream(infile); int c; while ((c = decoder.read()) != -1) System.out.print((char)c); System.out.flush(); } *** end TEST program ***/ }