Java tutorial
/* * 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 "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. */ /* $Id: ASCII85OutputStream.java 426584 2006-07-28 16:01:47Z jeremias $ */ import java.io.OutputStream; import java.io.FilterOutputStream; import java.io.IOException; /** * This class applies a ASCII85 encoding to the stream. * * @version $Id: ASCII85OutputStream.java 426584 2006-07-28 16:01:47Z jeremias $ */ public class ASCII85OutputStream extends FilterOutputStream implements ASCII85Constants { private static final boolean DEBUG = false; private int pos = 0; private long buffer = 0; private int posinline = 0; private int bw = 0; /** @see java.io.FilterOutputStream **/ public ASCII85OutputStream(OutputStream out) { super(out); } /** @see java.io.FilterOutputStream **/ public void write(int b) throws IOException { if (pos == 0) { buffer += (b << 24) & 0xff000000L; } else if (pos == 1) { buffer += (b << 16) & 0xff0000L; } else if (pos == 2) { buffer += (b << 8) & 0xff00L; } else { buffer += b & 0xffL; } pos++; if (pos > 3) { checkedWrite(convertWord(buffer)); buffer = 0; pos = 0; } } /* UNUSED ATM private void checkedWrite(int b) throws IOException { if (posinline == 80) { out.write(EOL); bw++; posinline = 0; } checkedWrite(b); posinline++; bw++; }*/ private void checkedWrite(byte[] buf) throws IOException { checkedWrite(buf, buf.length, false); } private void checkedWrite(byte[] buf, boolean nosplit) throws IOException { checkedWrite(buf, buf.length, nosplit); } private void checkedWrite(byte[] buf, int len) throws IOException { checkedWrite(buf, len, false); } private void checkedWrite(byte[] buf, int len, boolean nosplit) throws IOException { if (posinline + len > 80) { int firstpart = (nosplit ? 0 : len - (posinline + len - 80)); if (firstpart > 0) { out.write(buf, 0, firstpart); } out.write(EOL); bw++; int rest = len - firstpart; if (rest > 0) { out.write(buf, firstpart, rest); } posinline = rest; } else { out.write(buf, 0, len); posinline += len; } bw += len; } /** * This converts a 32 bit value (4 bytes) into 5 bytes using base 85. * each byte in the result starts with zero at the '!' character so * the resulting base85 number fits into printable ascii chars * * @param word the 32 bit unsigned (hence the long datatype) word * @return 5 bytes (or a single byte of the 'z' character for word * values of 0) */ private byte[] convertWord(long word) { word = word & 0xffffffff; if (word == 0) { return ZERO_ARRAY; } else { if (word < 0) { word = -word; } byte c1 = (byte) ((word / POW85[0]) & 0xFF); byte c2 = (byte) (((word - (c1 * POW85[0])) / POW85[1]) & 0xFF); byte c3 = (byte) (((word - (c1 * POW85[0]) - (c2 * POW85[1])) / POW85[2]) & 0xFF); byte c4 = (byte) (((word - (c1 * POW85[0]) - (c2 * POW85[1]) - (c3 * POW85[2])) / POW85[3]) & 0xFF); byte c5 = (byte) (((word - (c1 * POW85[0]) - (c2 * POW85[1]) - (c3 * POW85[2]) - (c4 * POW85[3]))) & 0xFF); byte[] ret = { (byte) (c1 + START), (byte) (c2 + START), (byte) (c3 + START), (byte) (c4 + START), (byte) (c5 + START) }; if (DEBUG) { for (int i = 0; i < ret.length; i++) { if (ret[i] < 33 || ret[i] > 117) { System.out.println("Illegal char value " + new Integer(ret[i])); } } } return ret; } } /** @see Finalizable **/ public void finalizeStream() throws IOException { // now take care of the trailing few bytes. // with n leftover bytes, we append 0 bytes to make a full group of 4 // then convert like normal (except not applying the special zero rule) // and write out the first n+1 bytes from the result if (pos > 0) { int rest = pos; /* byte[] lastdata = new byte[4]; int i = 0; for (int j = 0; j < 4; j++) { if (j < rest) { lastdata[j] = data[i++]; } else { lastdata[j] = 0; } } long val = ((lastdata[0] << 24) & 0xff000000L) + ((lastdata[1] << 16) & 0xff0000L) + ((lastdata[2] << 8) & 0xff00L) + (lastdata[3] & 0xffL); */ byte[] conv; // special rule for handling zeros at the end if (buffer != 0) { conv = convertWord(buffer); } else { conv = new byte[5]; for (int j = 0; j < 5; j++) { conv[j] = (byte) '!'; } } // assert rest+1 <= 5 checkedWrite(conv, rest + 1); } // finally write the two character end of data marker checkedWrite(EOD, true); flush(); } /** @see java.io.FilterOutputStream **/ public void close() throws IOException { finalizeStream(); super.close(); } } /* * 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 "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. */ /* $Id: ASCII85Constants.java 426584 2006-07-28 16:01:47Z jeremias $ */ /** * This interface defines constants used by the ASCII85 filters. * * @version $Id: ASCII85Constants.java 426584 2006-07-28 16:01:47Z jeremias $ */ interface ASCII85Constants { /** Special character "z" stands for four NULL bytes (short-cut for !!!!!) */ public static final int ZERO = 0x7A; //"z" /** ZERO as a byte array */ public static final byte[] ZERO_ARRAY = { (byte) ZERO }; /** The start index for ASCII85 characters (!) */ public static final int START = 0x21; //"!" /** The end index for ASCII85 characters (u) */ public static final int END = 0x75; //"u" /** The EOL indicator (LF) */ public static final int EOL = 0x0A; //"\n" /** The EOD (end of data) indicator */ public static final byte[] EOD = { 0x7E, 0x3E }; //"~>" /** Array of powers of 85 (4, 3, 2, 1, 0) */ public static final long POW85[] = new long[] { 85 * 85 * 85 * 85, 85 * 85 * 85, 85 * 85, 85, 1 }; /* public static final long BASE85_4 = 85; public static final long BASE85_3 = BASE85_4 * BASE85_4; public static final long BASE85_2 = BASE85_3 * BASE85_4; public static final long BASE85_1 = BASE85_2 * BASE85_4; */ }