82 lines
2.1 KiB
C#
82 lines
2.1 KiB
C#
namespace ZelWiki.Security
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{
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/// <summary>
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///
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/// </summary>
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public class Crc32
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{
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#region
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/// <summary>
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/// 逆CRC32算法的生成多项式（模2）
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/// </summary>
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private const UInt32 s_generator = 0xEDB88320;
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#endregion
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#region
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/// <summary>
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/// 创建Crc32类的新实例
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/// </summary>
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public Crc32()
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{
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m_checksumTable = Enumerable.Range(0, 256).Select(i =>
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{
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var tableEntry = (uint)i;
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for (var j = 0; j < 8; ++j)
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{
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tableEntry = ((tableEntry & 1) != 0)
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? (s_generator ^ (tableEntry >> 1))
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: (tableEntry >> 1);
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}
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return tableEntry;
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}).ToArray();
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}
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#endregion
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#region
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/// <summary>
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/// 计算字节流的校验和
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/// </summary>
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/// <param name="byteStream"></param>
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/// <typeparam name="T"></typeparam>
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/// <returns></returns>
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/// <exception cref="Exception"></exception>
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public UInt32 Get<T>(IEnumerable<T> byteStream)
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{
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try
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{
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return ~byteStream.Aggregate(0xFFFFFFFF, (checksumRegister, currentByte) =>
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(m_checksumTable[(checksumRegister & 0xFF) ^ Convert.ToByte(currentByte)] ^
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(checksumRegister >> 8)));
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}
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catch (FormatException e)
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{
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throw new Exception("无法以字节形式读取流", e);
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}
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catch (InvalidCastException e)
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{
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throw new Exception("无法以字节形式读取流", e);
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}
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catch (OverflowException e)
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{
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throw new Exception("无法以字节形式读取流", e);
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}
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}
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#endregion
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#region
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/// <summary>
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/// 包含计算校验和块的缓存
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/// </summary>
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private readonly UInt32[] m_checksumTable;
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#endregion
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}
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} |