Initial commit - WPinternals 2.6

DiscUtils/BlockCache.cs

@@ -0,0 +1,138 @@
+//
+// 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
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Text;
+
+    internal class BlockCache<T>
+        where T : Block, new()
+    {
+        private int _blockSize;
+        private Dictionary<long, T> _blocks;
+        private LinkedList<T> _lru;
+        private List<T> _freeBlocks;
+        private int _blocksCreated;
+        private int _totalBlocks;
+
+        private int _freeBlockCount;
+
+        public BlockCache(int blockSize, int blockCount)
+        {
+            _blockSize = blockSize;
+            _totalBlocks = blockCount;
+
+            _blocks = new Dictionary<long, T>();
+            _lru = new LinkedList<T>();
+            _freeBlocks = new List<T>(_totalBlocks);
+
+            _freeBlockCount = _totalBlocks;
+        }
+
+        public int FreeBlockCount
+        {
+            get { return _freeBlockCount; }
+        }
+
+        public bool ContainsBlock(long position)
+        {
+            return _blocks.ContainsKey(position);
+        }
+
+        public bool TryGetBlock(long position, out T block)
+        {
+            if (_blocks.TryGetValue(position, out block))
+            {
+                _lru.Remove(block);
+                _lru.AddFirst(block);
+                return true;
+            }
+
+            return false;
+        }
+
+        public T GetBlock(long position)
+        {
+            T result;
+
+            if (TryGetBlock(position, out result))
+            {
+                return result;
+            }
+
+            result = GetFreeBlock();
+            result.Position = position;
+            result.Available = -1;
+            StoreBlock(result);
+
+            return result;
+        }
+
+        public void ReleaseBlock(long position)
+        {
+            T block;
+            if (_blocks.TryGetValue(position, out block))
+            {
+                _blocks.Remove(position);
+                _lru.Remove(block);
+                _freeBlocks.Add(block);
+                _freeBlockCount++;
+            }
+        }
+
+        private void StoreBlock(T block)
+        {
+            _blocks[block.Position] = block;
+            _lru.AddFirst(block);
+        }
+
+        private T GetFreeBlock()
+        {
+            T block;
+
+            if (_freeBlocks.Count > 0)
+            {
+                int idx = _freeBlocks.Count - 1;
+                block = _freeBlocks[idx];
+                _freeBlocks.RemoveAt(idx);
+                _freeBlockCount--;
+            }
+            else if (_blocksCreated < _totalBlocks)
+            {
+                block = new T();
+                block.Data = new byte[_blockSize];
+                _blocksCreated++;
+                _freeBlockCount--;
+            }
+            else
+            {
+                block = _lru.Last.Value;
+                _lru.RemoveLast();
+                _blocks.Remove(block.Position);
+            }
+
+            return block;
+        }
+    }
+}