Initial commit - WPinternals 2.6

DiscUtils/Compression/InverseBurrowsWheeler.cs

@@ -0,0 +1,97 @@
+//
+// 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;
+
+    internal sealed class InverseBurrowsWheeler : DataBlockTransform
+    {
+        private int[] _pointers;
+        private int[] _nextPos;
+
+        public InverseBurrowsWheeler(int bufferSize)
+        {
+            _pointers = new int[bufferSize];
+            _nextPos = new int[256];
+        }
+
+        public int OriginalIndex { get; set; }
+
+        protected override bool BuffersMustNotOverlap
+        {
+            get { return true; }
+        }
+
+        protected override int DoProcess(byte[] input, int inputOffset, int inputCount, byte[] output, int outputOffset)
+        {
+            int outputCount = inputCount;
+
+            // First find the frequency of each value
+            Array.Clear(_nextPos, 0, _nextPos.Length);
+            for (int i = inputOffset; i < inputOffset + inputCount; ++i)
+            {
+                _nextPos[input[i]]++;
+            }
+
+            // We know they're 'sorted' in the first column, so now can figure
+            // out the position of the first instance of each.
+            int sum = 0;
+            for (int i = 0; i < 256; ++i)
+            {
+                int tempSum = sum;
+                sum += _nextPos[i];
+                _nextPos[i] = tempSum;
+            }
+
+            // For each value in the final column, put a pointer to to the
+            // 'next' character in the first (sorted) column.
+            for (int i = 0; i < inputCount; ++i)
+            {
+                _pointers[_nextPos[input[inputOffset + i]]++] = i;
+            }
+
+            // The 'next' character after the end of the original string is the
+            // first character of the original string.
+            int focus = _pointers[OriginalIndex];
+
+            // We can now just walk the pointers to reconstruct the original string
+            for (int i = 0; i < outputCount; ++i)
+            {
+                output[outputOffset + i] = input[inputOffset + focus];
+                focus = _pointers[focus];
+            }
+
+            return outputCount;
+        }
+
+        protected override int MaxOutputCount(int inputCount)
+        {
+            return inputCount;
+        }
+
+        protected override int MinOutputCount(int inputCount)
+        {
+            return inputCount;
+        }
+    }
+}