240 lines
7.9 KiB
C#
240 lines
7.9 KiB
C#
using System;
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using System.IO;
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using System.Collections;
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/*
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* Copyright 2002-2008 by Paulo Soares.
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*
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* This code was originally released in 2001 by SUN (see class
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* com.sun.media.imageioimpl.plugins.tiff.TIFFLZWDecompressor.java)
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* using the BSD license in a specific wording. In a mail dating from
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* January 23, 2008, Brian Burkhalter (@sun.com) gave us permission
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* to use the code under the following version of the BSD license:
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*
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* Copyright (c) 2005 Sun Microsystems, Inc. All Rights Reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistribution of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistribution in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* Neither the name of Sun Microsystems, Inc. or the names of
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* This software is provided "AS IS," without a warranty of any
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* kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
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* WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
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* EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL
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* NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
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* USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
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* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
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* ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
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* CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
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* REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
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* INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGES.
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*
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* You acknowledge that this software is not designed or intended for
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* use in the design, construction, operation or maintenance of any
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* nuclear facility.
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*/
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namespace iTextSharp.text.pdf {
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/**
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* A class for performing LZW decoding.
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*
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*
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*/
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public class LZWDecoder {
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byte[][] stringTable;
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byte[] data = null;
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Stream uncompData;
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int tableIndex, bitsToGet = 9;
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int bytePointer;
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int nextData = 0;
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int nextBits = 0;
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internal 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 LZWDecoder() {
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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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*/
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public void Decode(byte[] data, Stream uncompData) {
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if (data[0] == (byte)0x00 && data[1] == (byte)0x01) {
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throw new Exception("LZW flavour not supported.");
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}
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InitializeStringTable();
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this.data = data;
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this.uncompData = uncompData;
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// Initialize pointers
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bytePointer = 0;
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nextData = 0;
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nextBits = 0;
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int code, oldCode = 0;
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byte[] str;
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while ((code = this.NextCode) != 257) {
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if (code == 256) {
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InitializeStringTable();
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code = NextCode;
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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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str = stringTable[code];
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WriteString(str);
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AddStringToTable(stringTable[oldCode], str[0]);
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oldCode = code;
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} else {
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str = stringTable[oldCode];
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str = ComposeString(str, str[0]);
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WriteString(str);
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AddStringToTable(str);
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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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* Initialize the string table.
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*/
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public void InitializeStringTable() {
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stringTable = new byte[8192][];
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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[] str) {
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uncompData.Write(str, 0, str.Length);
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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[] str = new byte[length + 1];
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Array.Copy(oldstring, 0, str, 0, length);
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str[length] = newstring;
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// Add this new string to the table
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stringTable[tableIndex++] = str;
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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[] str) {
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// Add this new string to the table
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stringTable[tableIndex++] = str;
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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[] str = new byte[length + 1];
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Array.Copy(oldstring, 0, str, 0, length);
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str[length] = newstring;
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return str;
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}
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// Returns the next 9, 10, 11 or 12 bits
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public int NextCode {
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get {
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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 {
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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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}
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}
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} |