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 * Licensed to the Apache Software Foundation (ASF) under one or more
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 * 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
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 *      http://www.apache.org/licenses/LICENSE-2.0
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/* $Id: ASCII85InputStream.java 1732018 2016-02-24 04:51:06Z gadams $ */

package org.apache.xmlgraphics.util.io;

import java.io.IOException;
import java.io.InputStream;

This class applies a ASCII85 decoding to the stream.

The class is derived from InputStream instead of FilteredInputStream because we can use the read(byte[], int, int) method from InputStream which simply delegates to read(). This makes the implementation easier.

The filter is described in chapter 3.13.3 of the PostScript Language Reference (third edition).

Version:$Id: ASCII85InputStream.java 1732018 2016-02-24 04:51:06Z gadams $
/** * This class applies a ASCII85 decoding to the stream. * <p> * The class is derived from InputStream instead of FilteredInputStream because * we can use the read(byte[], int, int) method from InputStream which simply * delegates to read(). This makes the implementation easier. * <p> * The filter is described in chapter 3.13.3 of the PostScript Language * Reference (third edition). * * @version $Id: ASCII85InputStream.java 1732018 2016-02-24 04:51:06Z gadams $ */
public class ASCII85InputStream extends InputStream implements ASCII85Constants { private InputStream in; private boolean eodReached; private int[] b = new int[4]; //decoded private int bSize; private int bIndex;
See Also:
/** @see java.io.FilterInputStream **/
public ASCII85InputStream(InputStream in) { super(); this.in = in; }
See Also:
/** @see java.io.FilterInputStream **/
public int read() throws IOException { //Check if we need to read the next tuple if (bIndex >= bSize) { if (eodReached) { return -1; } readNextTuple(); if (bSize == 0) { if (!eodReached) { throw new IllegalStateException("Internal error"); } return -1; } } int result = b[bIndex]; result = (result < 0 ? 256 + result : result); bIndex++; return result; } private int filteredRead() throws IOException { int buf; while (true) { buf = in.read(); switch (buf) { case 0: //null case 9: //tab case 10: //LF case 12: //FF case 13: //CR case 32: //space continue; //ignore case ZERO: case 126: //= EOD[0] = '~' return buf; default: if ((buf >= START) && (buf <= END)) { return buf; } else { throw new IOException("Illegal character detected: " + buf); } } } } private void handleEOD() throws IOException { final int buf = in.read(); if (buf != EOD[1]) { throw new IOException("'>' expected after '~' (EOD)"); } eodReached = true; bSize = 0; bIndex = 0; } private void readNextTuple() throws IOException { int buf; long tuple = 0; //Read ahead and check for special "z" buf = filteredRead(); if (buf == ZERO) { java.util.Arrays.fill(b, 0); bSize = 4; bIndex = 0; } else if (buf == EOD[0]) { handleEOD(); } else { int cIndex = 0; tuple = (buf - START) * POW85[cIndex]; cIndex++; while (cIndex < 5) { buf = filteredRead(); if (buf == EOD[0]) { handleEOD(); break; } else if (buf == ZERO) { //Violation 2 throw new IOException("Illegal 'z' within tuple"); } else { tuple += (buf - START) * POW85[cIndex]; cIndex++; } } int cSize = cIndex; if (cSize == 1) { //Violation 3 throw new IOException("Only one character in tuple"); } //Handle optional, trailing, incomplete tuple while (cIndex < 5) { tuple += POW85[cIndex - 1]; cIndex++; } if (tuple > (2L << 31) - 1) { //Violation 1 throw new IOException("Illegal tuple (> 2^32 - 1)"); } //Convert tuple b[0] = (byte)((tuple >> 24) & 0xFF); b[1] = (byte)((tuple >> 16) & 0xFF); b[2] = (byte)((tuple >> 8) & 0xFF); b[3] = (byte)((tuple) & 0xFF); bSize = cSize - 1; bIndex = 0; } } }