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package org.eclipse.swt.internal.image; |
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/* |
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Licensed to the Apache Software Foundation (ASF) under one or more |
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contributor license agreements. See the NOTICE file distributed with |
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this work for additional information regarding copyright ownership. |
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The ASF licenses this file to You under the Apache License, Version 2.0 |
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(the "License"); you may not use this file except in compliance with |
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the License. You may obtain a copy of the License at |
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|
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http://www.apache.org/licenses/LICENSE-2.0 |
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|
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Unless required by applicable law or agreed to in writing, software |
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distributed under the License is distributed on an "AS IS" BASIS, |
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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See the License for the specific language governing permissions and |
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limitations under the License. |
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|
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*/ |
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|
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/** |
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* A class for performing LZW decoding. |
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* |
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* @version $Id$ |
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*/ |
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public class TIFFLZWDecoder { |
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|
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byte[][] stringTable; |
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byte[] data = null; |
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byte[] uncompData; |
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int tableIndex, bitsToGet = 9; |
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int bytePointer, bitPointer; |
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int dstIndex; |
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int w, h; |
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int predictor, samplesPerPixel; |
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int nextData = 0; |
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int nextBits = 0; |
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|
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int[] andTable = { |
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511, |
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1023, |
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2047, |
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4095 |
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}; |
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public TIFFLZWDecoder(int w, int predictor, int samplesPerPixel) { |
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this.w = w; |
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this.predictor = predictor; |
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this.samplesPerPixel = samplesPerPixel; |
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} |
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|
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/** |
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* Method to decode LZW compressed data. |
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* |
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* @param data The compressed data. |
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* @param uncompData Array to return the uncompressed data in. |
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* @param h The number of rows the compressed data contains. |
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*/ |
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public int decode(byte[] data, byte[] uncompData, int destIndex, int h) { |
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|
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if(data[0] == (byte)0x00 && data[1] == (byte)0x01) { |
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throw new UnsupportedOperationException("TIFFLZWDecoder0"); |
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} |
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initializeStringTable(); |
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this.data = data; |
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this.h = h; |
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this.uncompData = uncompData; |
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// Initialize pointers |
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bytePointer = 0; |
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bitPointer = 0; |
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dstIndex = destIndex; |
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nextData = 0; |
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nextBits = 0; |
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|
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int code, oldCode = 0; |
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byte[] string; |
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|
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while ( ((code = getNextCode()) != 257) && |
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dstIndex != uncompData.length) { |
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if (code == 256) { |
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initializeStringTable(); |
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code = getNextCode(); |
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if (code == 257) { |
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break; |
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} |
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writeString(stringTable[code]); |
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oldCode = code; |
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} else { |
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if (code < tableIndex) { |
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string = stringTable[code]; |
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writeString(string); |
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addStringToTable(stringTable[oldCode], string[0]); |
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oldCode = code; |
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} else { |
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string = stringTable[oldCode]; |
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string = composeString(string, string[0]); |
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writeString(string); |
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addStringToTable(string); |
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oldCode = code; |
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} |
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|
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} |
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|
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} |
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|
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// Horizontal Differencing Predictor |
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if (predictor == 2) { |
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int count; |
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for (int j = 0; j < h; j++) { |
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count = samplesPerPixel * (j * w + 1)+ destIndex; |
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for (int i = samplesPerPixel; i < w * samplesPerPixel; i++) { |
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uncompData[count] += uncompData[count - samplesPerPixel]; |
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count++; |
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} |
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} |
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} |
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return dstIndex; |
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} |
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/** |
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* Initialize the string table. |
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*/ |
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public void initializeStringTable() { |
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stringTable = new byte[4096][]; |
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for (int i=0; i<256; i++) { |
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stringTable[i] = new byte[1]; |
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stringTable[i][0] = (byte)i; |
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} |
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tableIndex = 258; |
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bitsToGet = 9; |
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} |
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/** |
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* Write out the string just uncompressed. |
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*/ |
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public void writeString(byte[] string) { |
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for (int i=0; i<string.length; i++) { |
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uncompData[dstIndex++] = string[i]; |
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} |
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} |
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/** |
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* Add a new string to the string table. |
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*/ |
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public void addStringToTable(byte[] oldString, byte newString) { |
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int length = oldString.length; |
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byte[] string = new byte[length + 1]; |
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System.arraycopy(oldString, 0, string, 0, length); |
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string[length] = newString; |
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// Add this new String to the table |
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stringTable[tableIndex++] = string; |
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if (tableIndex == 511) { |
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bitsToGet = 10; |
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} else if (tableIndex == 1023) { |
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bitsToGet = 11; |
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} else if (tableIndex == 2047) { |
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bitsToGet = 12; |
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} |
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} |
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/** |
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* Add a new string to the string table. |
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*/ |
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public void addStringToTable(byte[] string) { |
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// Add this new String to the table |
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stringTable[tableIndex++] = string; |
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if (tableIndex == 511) { |
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bitsToGet = 10; |
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} else if (tableIndex == 1023) { |
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bitsToGet = 11; |
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} else if (tableIndex == 2047) { |
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bitsToGet = 12; |
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} |
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} |
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/** |
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* Append <code>newString</code> to the end of <code>oldString</code>. |
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*/ |
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public byte[] composeString(byte[] oldString, byte newString) { |
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int length = oldString.length; |
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byte[] string = new byte[length + 1]; |
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System.arraycopy(oldString, 0, string, 0, length); |
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string[length] = newString; |
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return string; |
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} |
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// Returns the next 9, 10, 11 or 12 bits |
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public int getNextCode() { |
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// Attempt to get the next code. The exception is caught to make |
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// this robust to cases wherein the EndOfInformation code has been |
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// omitted from a strip. Examples of such cases have been observed |
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// in practice. |
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try { |
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nextData = (nextData << 8) | (data[bytePointer++] & 0xff); |
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nextBits += 8; |
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if (nextBits < bitsToGet) { |
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nextData = (nextData << 8) | (data[bytePointer++] & 0xff); |
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nextBits += 8; |
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} |
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int code = |
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(nextData >> (nextBits - bitsToGet)) & andTable[bitsToGet-9]; |
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nextBits -= bitsToGet; |
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return code; |
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} catch(ArrayIndexOutOfBoundsException e) { |
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// Strip not terminated as expected: return EndOfInformation code. |
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return 257; |
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} |
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} |
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} |