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Copy pathCrc32Algorithm.cs
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192 lines (175 loc) · 7.27 KB
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using System;
using System.Security.Cryptography;
namespace Force.Crc32
{
/// <summary>
/// Implementation of CRC-32.
/// This class supports several convenient static methods returning the CRC as UInt32.
/// </summary>
public class Crc32Algorithm : HashAlgorithm
{
private uint _currentCrc;
private readonly bool _isBigEndian = true;
/// <summary>
/// Initializes a new instance of the <see cref="Crc32Algorithm"/> class.
/// </summary>
public Crc32Algorithm()
{
#if !NETCORE13
HashSizeValue = 32;
#endif
}
/// <summary>
/// Initializes a new instance of the <see cref="Crc32Algorithm"/> class.
/// </summary>
/// <param name="isBigEndian">Should return bytes result as big endian or little endian</param>
// Crc32 by dariogriffo uses big endian, so, we need to be compatible and return big endian as default
public Crc32Algorithm(bool isBigEndian = true)
: this()
{
_isBigEndian = isBigEndian;
}
/// <summary>
/// Computes CRC-32 from multiple buffers.
/// Call this method multiple times to chain multiple buffers.
/// </summary>
/// <param name="initial">
/// Initial CRC value for the algorithm. It is zero for the first buffer.
/// Subsequent buffers should have their initial value set to CRC value returned by previous call to this method.
/// </param>
/// <param name="input">Input buffer with data to be checksummed.</param>
/// <param name="offset">Offset of the input data within the buffer.</param>
/// <param name="length">Length of the input data in the buffer.</param>
/// <returns>Accumulated CRC-32 of all buffers processed so far.</returns>
public static uint Append(uint initial, byte[] input, int offset, int length)
{
if (input == null)
throw new ArgumentNullException("input");
if (offset < 0 || length < 0 || offset + length > input.Length)
throw new ArgumentOutOfRangeException("length");
return AppendInternal(initial, input, offset, length);
}
/// <summary>
/// Computes CRC-32 from multiple buffers.
/// Call this method multiple times to chain multiple buffers.
/// </summary>
/// <param name="initial">
/// Initial CRC value for the algorithm. It is zero for the first buffer.
/// Subsequent buffers should have their initial value set to CRC value returned by previous call to this method.
/// </param>
/// <param name="input">Input buffer containing data to be checksummed.</param>
/// <returns>Accumulated CRC-32 of all buffers processed so far.</returns>
public static uint Append(uint initial, byte[] input)
{
if (input == null)
throw new ArgumentNullException();
return AppendInternal(initial, input, 0, input.Length);
}
/// <summary>
/// Computes CRC-32 from input buffer.
/// </summary>
/// <param name="input">Input buffer with data to be checksummed.</param>
/// <param name="offset">Offset of the input data within the buffer.</param>
/// <param name="length">Length of the input data in the buffer.</param>
/// <returns>CRC-32 of the data in the buffer.</returns>
public static uint Compute(byte[] input, int offset, int length)
{
return Append(0, input, offset, length);
}
/// <summary>
/// Computes CRC-32 from input buffer.
/// </summary>
/// <param name="input">Input buffer containing data to be checksummed.</param>
/// <returns>CRC-32 of the buffer.</returns>
public static uint Compute(byte[] input)
{
return Append(0, input);
}
/// <summary>
/// Computes CRC-32 from input buffer and writes it after end of data (buffer should have 4 bytes reserved space for it). Can be used in conjunction with <see cref="IsValidWithCrcAtEnd(byte[],int,int)"/>
/// </summary>
/// <param name="input">Input buffer with data to be checksummed.</param>
/// <param name="offset">Offset of the input data within the buffer.</param>
/// <param name="length">Length of the input data in the buffer.</param>
/// <returns>CRC-32 of the data in the buffer.</returns>
public static uint ComputeAndWriteToEnd(byte[] input, int offset, int length)
{
if (length + 4 > input.Length)
throw new ArgumentOutOfRangeException("length", "Length of data should be less than array length - 4 bytes of CRC data");
var crc = Append(0, input, offset, length);
var r = offset + length;
input[r] = (byte)crc;
input[r + 1] = (byte)(crc >> 8);
input[r + 2] = (byte)(crc >> 16);
input[r + 3] = (byte)(crc >> 24);
return crc;
}
/// <summary>
/// Computes CRC-32 from input buffer - 4 bytes and writes it as last 4 bytes of buffer. Can be used in conjunction with <see cref="IsValidWithCrcAtEnd(byte[])"/>
/// </summary>
/// <param name="input">Input buffer with data to be checksummed.</param>
/// <returns>CRC-32 of the data in the buffer.</returns>
public static uint ComputeAndWriteToEnd(byte[] input)
{
if (input.Length < 4)
throw new ArgumentOutOfRangeException("input", "Input array should be 4 bytes at least");
return ComputeAndWriteToEnd(input, 0, input.Length - 4);
}
/// <summary>
/// Validates correctness of CRC-32 data in source buffer with assumption that CRC-32 data located at end of buffer in reverse bytes order. Can be used in conjunction with <see cref="ComputeAndWriteToEnd(byte[],int,int)"/>
/// </summary>
/// <param name="input">Input buffer with data to be checksummed.</param>
/// <param name="offset">Offset of the input data within the buffer.</param>
/// <param name="lengthWithCrc">Length of the input data in the buffer with CRC-32 bytes.</param>
/// <returns>Is checksum valid.</returns>
public static bool IsValidWithCrcAtEnd(byte[] input, int offset, int lengthWithCrc)
{
return Append(0, input, offset, lengthWithCrc) == 0x2144DF1C;
}
/// <summary>
/// Validates correctness of CRC-32 data in source buffer with assumption that CRC-32 data located at end of buffer in reverse bytes order. Can be used in conjunction with <see cref="ComputeAndWriteToEnd(byte[],int,int)"/>
/// </summary>
/// <param name="input">Input buffer with data to be checksummed.</param>
/// <returns>Is checksum valid.</returns>
public static bool IsValidWithCrcAtEnd(byte[] input)
{
if (input.Length < 4)
throw new ArgumentOutOfRangeException("input", "Input array should be 4 bytes at least");
return Append(0, input, 0, input.Length) == 0x2144DF1C;
}
/// <summary>
/// Resets internal state of the algorithm. Used internally.
/// </summary>
public override void Initialize()
{
_currentCrc = 0;
}
/// <summary>
/// Appends CRC-32 from given buffer
/// </summary>
protected override void HashCore(byte[] input, int offset, int length)
{
_currentCrc = AppendInternal(_currentCrc, input, offset, length);
}
/// <summary>
/// Computes CRC-32 from <see cref="HashCore"/>
/// </summary>
protected override byte[] HashFinal()
{
if (_isBigEndian)
return new[] { (byte)(_currentCrc >> 24), (byte)(_currentCrc >> 16), (byte)(_currentCrc >> 8), (byte)_currentCrc };
else
return new[] { (byte)_currentCrc, (byte)(_currentCrc >> 8), (byte)(_currentCrc >> 16), (byte)(_currentCrc >> 24) };
}
private static readonly SafeProxy _proxy = new SafeProxy();
private static uint AppendInternal(uint initial, byte[] input, int offset, int length)
{
if (length > 0)
{
return _proxy.Append(initial, input, offset, length);
}
else
return initial;
}
}
}