Initial commit - WPinternals 2.6

DiscUtils/Compression/Adler32.cs

@@ -0,0 +1,93 @@
+//
+// Copyright (c) 2008-2011, Kenneth Bell
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+//
+
+namespace DiscUtils.Compression
+{
+    using System;
+
+    /// <summary>
+    /// Implementation of the Adler-32 checksum algorithm.
+    /// </summary>
+    public class Adler32
+    {
+        private uint _a;
+        private uint _b;
+
+        /// <summary>
+        /// Initializes a new instance of the Adler32 class.
+        /// </summary>
+        public Adler32()
+        {
+            _a = 1;
+        }
+
+        /// <summary>
+        /// Gets the checksum of all data processed so far.
+        /// </summary>
+        public int Value
+        {
+            get { return (int)(_b << 16 | _a); }
+        }
+
+        /// <summary>
+        /// Provides data that should be checksummed.
+        /// </summary>
+        /// <param name="buffer">Buffer containing the data to checksum.</param>
+        /// <param name="offset">Offset of the first byte to checksum.</param>
+        /// <param name="count">The number of bytes to checksum.</param>
+        /// <remarks>
+        /// Call this method repeatedly until all checksummed
+        /// data has been processed.
+        /// </remarks>
+        public void Process(byte[] buffer, int offset, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException("buffer");
+            }
+
+            if (offset < 0 || offset > buffer.Length)
+            {
+                throw new ArgumentException("Offset outside of array bounds", "offset");
+            }
+
+            if (count < 0 || offset + count > buffer.Length)
+            {
+                throw new ArgumentException("Array index out of bounds", "count");
+            }
+
+            int processed = 0;
+            while (processed < count)
+            {
+                int innerEnd = Math.Min(count, processed + 2000);
+                while (processed < innerEnd)
+                {
+                    _a += buffer[processed++];
+                    _b += _a;
+                }
+
+                _a %= 65521;
+                _b %= 65521;
+            }
+        }
+    }
+}