/
ChecksumImpl.cs
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/
ChecksumImpl.cs
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//
// © Copyright Henrik Ravn 2004
//
// Use, modification and distribution are subject to the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
using System;
using System.Runtime.InteropServices;
using System.Text;
namespace DotZLib
{
#region ChecksumGeneratorBase
/// <summary>
/// Implements the common functionality needed for all <see cref="ChecksumGenerator"/>s
/// </summary>
/// <example></example>
public abstract class ChecksumGeneratorBase : ChecksumGenerator
{
/// <summary>
/// The value of the current checksum
/// </summary>
protected uint _current;
/// <summary>
/// Initializes a new instance of the checksum generator base - the current checksum is
/// set to zero
/// </summary>
public ChecksumGeneratorBase()
{
_current = 0;
}
/// <summary>
/// Initializes a new instance of the checksum generator basewith a specified value
/// </summary>
/// <param name="initialValue">The value to set the current checksum to</param>
public ChecksumGeneratorBase(uint initialValue)
{
_current = initialValue;
}
/// <summary>
/// Resets the current checksum to zero
/// </summary>
public void Reset() { _current = 0; }
/// <summary>
/// Gets the current checksum value
/// </summary>
public uint Value { get { return _current; } }
/// <summary>
/// Updates the current checksum with part of an array of bytes
/// </summary>
/// <param name="data">The data to update the checksum with</param>
/// <param name="offset">Where in <c>data</c> to start updating</param>
/// <param name="count">The number of bytes from <c>data</c> to use</param>
/// <exception cref="ArgumentException">The sum of offset and count is larger than the length of <c>data</c></exception>
/// <exception cref="NullReferenceException"><c>data</c> is a null reference</exception>
/// <exception cref="ArgumentOutOfRangeException">Offset or count is negative.</exception>
/// <remarks>All the other <c>Update</c> methods are implmeneted in terms of this one.
/// This is therefore the only method a derived class has to implement</remarks>
public abstract void Update(byte[] data, int offset, int count);
/// <summary>
/// Updates the current checksum with an array of bytes.
/// </summary>
/// <param name="data">The data to update the checksum with</param>
public void Update(byte[] data)
{
Update(data, 0, data.Length);
}
/// <summary>
/// Updates the current checksum with the data from a string
/// </summary>
/// <param name="data">The string to update the checksum with</param>
/// <remarks>The characters in the string are converted by the UTF-8 encoding</remarks>
public void Update(string data)
{
Update(Encoding.UTF8.GetBytes(data));
}
/// <summary>
/// Updates the current checksum with the data from a string, using a specific encoding
/// </summary>
/// <param name="data">The string to update the checksum with</param>
/// <param name="encoding">The encoding to use</param>
public void Update(string data, Encoding encoding)
{
Update(encoding.GetBytes(data));
}
}
#endregion
#region CRC32
/// <summary>
/// Implements a CRC32 checksum generator
/// </summary>
public sealed class CRC32Checksum : ChecksumGeneratorBase
{
#region DLL imports
[DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
private static extern uint crc32(uint crc, int data, uint length);
#endregion
/// <summary>
/// Initializes a new instance of the CRC32 checksum generator
/// </summary>
public CRC32Checksum() : base() {}
/// <summary>
/// Initializes a new instance of the CRC32 checksum generator with a specified value
/// </summary>
/// <param name="initialValue">The value to set the current checksum to</param>
public CRC32Checksum(uint initialValue) : base(initialValue) {}
/// <summary>
/// Updates the current checksum with part of an array of bytes
/// </summary>
/// <param name="data">The data to update the checksum with</param>
/// <param name="offset">Where in <c>data</c> to start updating</param>
/// <param name="count">The number of bytes from <c>data</c> to use</param>
/// <exception cref="ArgumentException">The sum of offset and count is larger than the length of <c>data</c></exception>
/// <exception cref="NullReferenceException"><c>data</c> is a null reference</exception>
/// <exception cref="ArgumentOutOfRangeException">Offset or count is negative.</exception>
public override void Update(byte[] data, int offset, int count)
{
if (offset < 0 || count < 0) throw new ArgumentOutOfRangeException();
if ((offset+count) > data.Length) throw new ArgumentException();
GCHandle hData = GCHandle.Alloc(data, GCHandleType.Pinned);
try
{
_current = crc32(_current, hData.AddrOfPinnedObject().ToInt32()+offset, (uint)count);
}
finally
{
hData.Free();
}
}
}
#endregion
#region Adler
/// <summary>
/// Implements a checksum generator that computes the Adler checksum on data
/// </summary>
public sealed class AdlerChecksum : ChecksumGeneratorBase
{
#region DLL imports
[DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
private static extern uint adler32(uint adler, int data, uint length);
#endregion
/// <summary>
/// Initializes a new instance of the Adler checksum generator
/// </summary>
public AdlerChecksum() : base() {}
/// <summary>
/// Initializes a new instance of the Adler checksum generator with a specified value
/// </summary>
/// <param name="initialValue">The value to set the current checksum to</param>
public AdlerChecksum(uint initialValue) : base(initialValue) {}
/// <summary>
/// Updates the current checksum with part of an array of bytes
/// </summary>
/// <param name="data">The data to update the checksum with</param>
/// <param name="offset">Where in <c>data</c> to start updating</param>
/// <param name="count">The number of bytes from <c>data</c> to use</param>
/// <exception cref="ArgumentException">The sum of offset and count is larger than the length of <c>data</c></exception>
/// <exception cref="NullReferenceException"><c>data</c> is a null reference</exception>
/// <exception cref="ArgumentOutOfRangeException">Offset or count is negative.</exception>
public override void Update(byte[] data, int offset, int count)
{
if (offset < 0 || count < 0) throw new ArgumentOutOfRangeException();
if ((offset+count) > data.Length) throw new ArgumentException();
GCHandle hData = GCHandle.Alloc(data, GCHandleType.Pinned);
try
{
_current = adler32(_current, hData.AddrOfPinnedObject().ToInt32()+offset, (uint)count);
}
finally
{
hData.Free();
}
}
}
#endregion
}