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常用工具集/Utility/ICSharpCode.SharpZipLib/Lzw/LzwConstants.cs

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+namespace ICSharpCode.SharpZipLib.Lzw
+{
+	/// <summary>
+	/// This class contains constants used for LZW
+	/// </summary>
+	[System.Diagnostics.CodeAnalysis.SuppressMessage("Naming", "CA1707:Identifiers should not contain underscores", Justification = "kept for backwards compatibility")]
+	sealed public class LzwConstants
+	{
+		/// <summary>
+		/// Magic number found at start of LZW header: 0x1f 0x9d
+		/// </summary>
+		public const int MAGIC = 0x1f9d;
+
+		/// <summary>
+		/// Maximum number of bits per code
+		/// </summary>
+		public const int MAX_BITS = 16;
+
+		/* 3rd header byte:
+         * bit 0..4 Number of compression bits
+         * bit 5    Extended header
+         * bit 6    Free
+         * bit 7    Block mode
+         */
+
+		/// <summary>
+		/// Mask for 'number of compression bits'
+		/// </summary>
+		public const int BIT_MASK = 0x1f;
+
+		/// <summary>
+		/// Indicates the presence of a fourth header byte
+		/// </summary>
+		public const int EXTENDED_MASK = 0x20;
+
+		//public const int FREE_MASK      = 0x40;
+
+		/// <summary>
+		/// Reserved bits
+		/// </summary>
+		public const int RESERVED_MASK = 0x60;
+
+		/// <summary>
+		/// Block compression: if table is full and compression rate is dropping,
+		/// clear the dictionary.
+		/// </summary>
+		public const int BLOCK_MODE_MASK = 0x80;
+
+		/// <summary>
+		/// LZW file header size (in bytes)
+		/// </summary>
+		public const int HDR_SIZE = 3;
+
+		/// <summary>
+		/// Initial number of bits per code
+		/// </summary>
+		public const int INIT_BITS = 9;
+
+		private LzwConstants()
+		{
+		}
+	}
+}