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/*
 * 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: 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 $ */ 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 java.io.FilterInputStream **/ public ASCII85InputStream(InputStream in) { super(); this.in = in; } /** @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; } } }





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