/* ====================================================================
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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namespace HH.WMS.Utils.NPOI.HSSF.Record.Crypto
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{
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using System;
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using System.IO;
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using HH.WMS.Utils.NPOI.Util;
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using HH.WMS.Utils.NPOI.HSSF.Record;
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/**
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*
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* @author Josh Micich
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*/
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public class Biff8DecryptingStream : BiffHeaderInput, ILittleEndianInput
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{
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private ILittleEndianInput _le;
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private Biff8RC4 _rc4;
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public Biff8DecryptingStream(Stream in1, int InitialOffSet, Biff8EncryptionKey key)
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{
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_rc4 = new Biff8RC4(InitialOffSet, key);
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if (in1 is ILittleEndianInput)
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{
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// accessing directly is an optimisation
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_le = (ILittleEndianInput)in1;
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}
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else
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{
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// less optimal, but should work OK just the same. Often occurs in junit tests.
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_le = new LittleEndianInputStream(in1);
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}
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}
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public int Available()
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{
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return _le.Available();
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}
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/**
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* Reads an unsigned short value without decrypting
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*/
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public int ReadRecordSID()
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{
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int sid = _le.ReadUShort();
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_rc4.SkipTwoBytes();
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_rc4.StartRecord(sid);
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return sid;
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}
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/**
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* Reads an unsigned short value without decrypting
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*/
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public int ReadDataSize()
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{
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int dataSize = _le.ReadUShort();
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_rc4.SkipTwoBytes();
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return dataSize;
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}
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public double ReadDouble()
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{
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long valueLongBits = ReadLong();
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double result = BitConverter.Int64BitsToDouble(valueLongBits);
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if (Double.IsNaN(result))
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{
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throw new Exception("Did not expect to read NaN"); // (Because Excel typically doesn't write NaN
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}
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return result;
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}
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public void ReadFully(byte[] buf)
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{
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ReadFully(buf, 0, buf.Length);
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}
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public void ReadFully(byte[] buf, int off, int len)
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{
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_le.ReadFully(buf, off, len);
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_rc4.Xor(buf, off, len);
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}
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public int ReadUByte()
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{
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return _rc4.XorByte(_le.ReadUByte());
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}
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public int ReadByte()
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{
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return _rc4.XorByte(_le.ReadUByte());
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}
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public int ReadUShort()
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{
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return _rc4.Xorshort(_le.ReadUShort());
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}
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public short ReadShort()
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{
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return (short)_rc4.Xorshort(_le.ReadUShort());
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}
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public int ReadInt()
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{
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return _rc4.XorInt(_le.ReadInt());
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}
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public long ReadLong()
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{
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return _rc4.XorLong(_le.ReadLong());
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}
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}
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}
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