Add initial cut of LZW. Not yet included in repository projects as the code is not well tested...

Author: jfreilly

src/Lzw/LzwConstants.cs

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+// LzwConstants.cs
+//
+// Copyright (C) 2009 Gabriel Burca
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+//
+// Linking this library statically or dynamically with other modules is
+// making a combined work based on this library.  Thus, the terms and
+// conditions of the GNU General Public License cover the whole
+// combination.
+// 
+// As a special exception, the copyright holders of this library give you
+// permission to link this library with independent modules to produce an
+// executable, regardless of the license terms of these independent
+// modules, and to copy and distribute the resulting executable under
+// terms of your choice, provided that you also meet, for each linked
+// independent module, the terms and conditions of the license of that
+// module.  An independent module is a module which is not derived from
+// or based on this library.  If you modify this library, you may extend
+// this exception to your version of the library, but you are not
+// obligated to do so.  If you do not wish to do so, delete this
+// exception statement from your version.
+
+namespace ICSharpCode.SharpZipLib.LZW {
+
+    /// <summary>
+    /// This class contains constants used for LZW
+    /// </summary>
+    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;
+
+        LzwConstants() {
+        }
+    }
+}

src/Lzw/LzwException.cs

@@ -0,0 +1,88 @@
+// LzwException.cs
+//
+// Copyright (C) 2009 Gabriel Burca
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+//
+// Linking this library statically or dynamically with other modules is
+// making a combined work based on this library.  Thus, the terms and
+// conditions of the GNU General Public License cover the whole
+// combination.
+// 
+// As a special exception, the copyright holders of this library give you
+// permission to link this library with independent modules to produce an
+// executable, regardless of the license terms of these independent
+// modules, and to copy and distribute the resulting executable under
+// terms of your choice, provided that you also meet, for each linked
+// independent module, the terms and conditions of the license of that
+// module.  An independent module is a module which is not derived from
+// or based on this library.  If you modify this library, you may extend
+// this exception to your version of the library, but you are not
+// obligated to do so.  If you do not wish to do so, delete this
+// exception statement from your version.
+
+using System;
+
+#if !NETCF_1_0 && !NETCF_2_0
+using System.Runtime.Serialization;
+#endif
+
+namespace ICSharpCode.SharpZipLib.LZW
+{
+
+    /// <summary>
+    /// LzwException represents a LZW specific exception
+    /// </summary>
+#if !NETCF_1_0 && !NETCF_2_0
+    [Serializable]
+#endif
+    public class LzwException : SharpZipBaseException
+    {
+
+#if !NETCF_1_0 && !NETCF_2_0
+        /// <summary>
+        /// Deserialization constructor 
+        /// </summary>
+        /// <param name="info"><see cref="SerializationInfo"/> for this constructor</param>
+        /// <param name="context"><see cref="StreamingContext"/> for this constructor</param>
+        protected LzwException(SerializationInfo info, StreamingContext context)
+            : base(info, context) {
+        }
+#endif
+
+        /// <summary>
+        /// Initialise a new instance of LzwException
+        /// </summary>
+        public LzwException() {
+        }
+
+        /// <summary>
+        /// Initialise a new instance of LzwException with its message string.
+        /// </summary>
+        /// <param name="message">A <see cref="string"/> that describes the error.</param>
+        public LzwException(string message)
+            : base(message) {
+        }
+
+        /// <summary>
+        /// Initialise a new instance of <see cref="LzwException"></see>.
+        /// </summary>
+        /// <param name="message">A <see cref="string"/> that describes the error.</param>
+        /// <param name="innerException">The <see cref="Exception"/> that caused this exception.</param>
+        public LzwException(string message, Exception innerException)
+            : base(message, innerException) {
+        }
+    }
+}