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372
iTechSharp/srcbc/crypto/BufferedBlockCipher.cs
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372
iTechSharp/srcbc/crypto/BufferedBlockCipher.cs
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using System;
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using System.Diagnostics;
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using Org.BouncyCastle.Crypto.Parameters;
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namespace Org.BouncyCastle.Crypto
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{
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/**
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* A wrapper class that allows block ciphers to be used to process data in
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* a piecemeal fashion. The BufferedBlockCipher outputs a block only when the
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* buffer is full and more data is being added, or on a doFinal.
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* <p>
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* Note: in the case where the underlying cipher is either a CFB cipher or an
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* OFB one the last block may not be a multiple of the block size.
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* </p>
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*/
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public class BufferedBlockCipher
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: BufferedCipherBase
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{
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internal byte[] buf;
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internal int bufOff;
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internal bool forEncryption;
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internal IBlockCipher cipher;
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/**
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* constructor for subclasses
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*/
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protected BufferedBlockCipher()
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{
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}
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/**
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* Create a buffered block cipher without padding.
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*
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* @param cipher the underlying block cipher this buffering object wraps.
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* false otherwise.
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*/
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public BufferedBlockCipher(
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IBlockCipher cipher)
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{
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if (cipher == null)
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throw new ArgumentNullException("cipher");
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this.cipher = cipher;
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buf = new byte[cipher.GetBlockSize()];
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bufOff = 0;
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}
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public override string AlgorithmName
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{
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get { return cipher.AlgorithmName; }
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}
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/**
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* initialise the cipher.
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*
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* @param forEncryption if true the cipher is initialised for
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* encryption, if false for decryption.
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* @param param the key and other data required by the cipher.
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* @exception ArgumentException if the parameters argument is
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* inappropriate.
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*/
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// Note: This doubles as the Init in the event that this cipher is being used as an IWrapper
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public override void Init(
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bool forEncryption,
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ICipherParameters parameters)
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{
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this.forEncryption = forEncryption;
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if (parameters is ParametersWithRandom)
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{
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parameters = ((ParametersWithRandom) parameters).Parameters;
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}
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Reset();
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cipher.Init(forEncryption, parameters);
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}
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/**
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* return the blocksize for the underlying cipher.
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*
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* @return the blocksize for the underlying cipher.
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*/
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public override int GetBlockSize()
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{
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return cipher.GetBlockSize();
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}
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/**
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* return the size of the output buffer required for an update
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* an input of len bytes.
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*
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* @param len the length of the input.
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* @return the space required to accommodate a call to update
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* with len bytes of input.
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*/
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public override int GetUpdateOutputSize(
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int length)
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{
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int total = length + bufOff;
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int leftOver = total % buf.Length;
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return total - leftOver;
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}
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/**
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* return the size of the output buffer required for an update plus a
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* doFinal with an input of len bytes.
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*
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* @param len the length of the input.
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* @return the space required to accommodate a call to update and doFinal
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* with len bytes of input.
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*/
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public override int GetOutputSize(
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int length)
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{
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int total = length + bufOff;
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int leftOver = total % buf.Length;
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if (leftOver == 0)
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{
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return total;
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}
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return total - leftOver + buf.Length;
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}
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/**
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* process a single byte, producing an output block if neccessary.
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*
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* @param in the input byte.
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* @param out the space for any output that might be produced.
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* @param outOff the offset from which the output will be copied.
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* @return the number of output bytes copied to out.
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* @exception DataLengthException if there isn't enough space in out.
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* @exception InvalidOperationException if the cipher isn't initialised.
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*/
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public override int ProcessByte(
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byte input,
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byte[] output,
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int outOff)
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{
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buf[bufOff++] = input;
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if (bufOff == buf.Length)
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{
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if ((outOff + buf.Length) > output.Length)
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throw new DataLengthException("output buffer too short");
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bufOff = 0;
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return cipher.ProcessBlock(buf, 0, output, outOff);
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}
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return 0;
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}
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public override byte[] ProcessByte(
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byte input)
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{
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int outLength = GetUpdateOutputSize(1);
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byte[] outBytes = outLength > 0 ? new byte[outLength] : null;
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int pos = ProcessByte(input, outBytes, 0);
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if (outLength > 0 && pos < outLength)
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{
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byte[] tmp = new byte[pos];
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Array.Copy(outBytes, 0, tmp, 0, pos);
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outBytes = tmp;
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}
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return outBytes;
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}
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public override byte[] ProcessBytes(
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byte[] input,
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int inOff,
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int length)
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{
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if (input == null)
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throw new ArgumentNullException("input");
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if (length < 1)
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return null;
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int outLength = GetUpdateOutputSize(length);
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byte[] outBytes = outLength > 0 ? new byte[outLength] : null;
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int pos = ProcessBytes(input, inOff, length, outBytes, 0);
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if (outLength > 0 && pos < outLength)
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{
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byte[] tmp = new byte[pos];
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Array.Copy(outBytes, 0, tmp, 0, pos);
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outBytes = tmp;
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}
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return outBytes;
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}
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/**
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* process an array of bytes, producing output if necessary.
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*
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* @param in the input byte array.
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* @param inOff the offset at which the input data starts.
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* @param len the number of bytes to be copied out of the input array.
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* @param out the space for any output that might be produced.
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* @param outOff the offset from which the output will be copied.
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* @return the number of output bytes copied to out.
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* @exception DataLengthException if there isn't enough space in out.
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* @exception InvalidOperationException if the cipher isn't initialised.
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*/
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public override int ProcessBytes(
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byte[] input,
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int inOff,
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int length,
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byte[] output,
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int outOff)
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{
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if (length < 1)
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{
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if (length < 0)
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throw new ArgumentException("Can't have a negative input length!");
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return 0;
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}
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int blockSize = GetBlockSize();
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int outLength = GetUpdateOutputSize(length);
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if (outLength > 0)
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{
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if ((outOff + outLength) > output.Length)
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{
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throw new DataLengthException("output buffer too short");
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}
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}
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int resultLen = 0;
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int gapLen = buf.Length - bufOff;
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if (length > gapLen)
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{
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Array.Copy(input, inOff, buf, bufOff, gapLen);
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resultLen += cipher.ProcessBlock(buf, 0, output, outOff);
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bufOff = 0;
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length -= gapLen;
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inOff += gapLen;
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while (length > buf.Length)
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{
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resultLen += cipher.ProcessBlock(input, inOff, output, outOff + resultLen);
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length -= blockSize;
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inOff += blockSize;
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}
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}
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Array.Copy(input, inOff, buf, bufOff, length);
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bufOff += length;
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if (bufOff == buf.Length)
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{
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resultLen += cipher.ProcessBlock(buf, 0, output, outOff + resultLen);
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bufOff = 0;
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}
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return resultLen;
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}
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public override byte[] DoFinal()
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{
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byte[] outBytes = EmptyBuffer;
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int length = GetOutputSize(0);
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if (length > 0)
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{
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outBytes = new byte[length];
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int pos = DoFinal(outBytes, 0);
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if (pos < outBytes.Length)
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{
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byte[] tmp = new byte[pos];
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Array.Copy(outBytes, 0, tmp, 0, pos);
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outBytes = tmp;
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}
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}
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return outBytes;
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}
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public override byte[] DoFinal(
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byte[] input,
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int inOff,
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int inLen)
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{
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if (input == null)
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throw new ArgumentNullException("input");
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int length = GetOutputSize(inLen);
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byte[] outBytes = EmptyBuffer;
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if (length > 0)
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{
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outBytes = new byte[length];
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int pos = (inLen > 0)
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? ProcessBytes(input, inOff, inLen, outBytes, 0)
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: 0;
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pos += DoFinal(outBytes, pos);
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if (pos < outBytes.Length)
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{
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byte[] tmp = new byte[pos];
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Array.Copy(outBytes, 0, tmp, 0, pos);
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outBytes = tmp;
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}
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}
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return outBytes;
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}
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/**
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* Process the last block in the buffer.
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*
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* @param out the array the block currently being held is copied into.
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* @param outOff the offset at which the copying starts.
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* @return the number of output bytes copied to out.
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* @exception DataLengthException if there is insufficient space in out for
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* the output, or the input is not block size aligned and should be.
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* @exception InvalidOperationException if the underlying cipher is not
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* initialised.
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* @exception InvalidCipherTextException if padding is expected and not found.
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* @exception DataLengthException if the input is not block size
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* aligned.
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*/
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public override int DoFinal(
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byte[] output,
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int outOff)
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{
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if (bufOff != 0)
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{
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if (!cipher.IsPartialBlockOkay)
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{
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throw new DataLengthException("data not block size aligned");
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}
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if (outOff + bufOff > output.Length)
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{
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throw new DataLengthException("output buffer too short for DoFinal()");
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}
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// NB: Can't copy directly, or we may write too much output
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cipher.ProcessBlock(buf, 0, buf, 0);
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Array.Copy(buf, 0, output, outOff, bufOff);
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}
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int resultLen = bufOff;
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Reset();
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return resultLen;
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}
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/**
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* Reset the buffer and cipher. After resetting the object is in the same
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* state as it was after the last init (if there was one).
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*/
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public override void Reset()
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{
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Array.Clear(buf, 0, buf.Length);
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bufOff = 0;
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cipher.Reset();
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}
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}
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}
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