132 lines
3.8 KiB
C#
132 lines
3.8 KiB
C#
//
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// Copyright (c) 2008-2011, Kenneth Bell
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//
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// Permission is hereby granted, free of charge, to any person obtaining a
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// copy of this software and associated documentation files (the "Software"),
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// to deal in the Software without restriction, including without limitation
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// the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// and/or sell copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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//
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using System.Collections.Generic;
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namespace DiscUtils.Streams
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{
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public class BlockCache<T>
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where T : Block, new()
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{
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private readonly Dictionary<long, T> _blocks;
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private int _blocksCreated;
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private readonly int _blockSize;
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private readonly List<T> _freeBlocks;
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private readonly LinkedList<T> _lru;
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private readonly int _totalBlocks;
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public BlockCache(int blockSize, int blockCount)
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{
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_blockSize = blockSize;
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_totalBlocks = blockCount;
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_blocks = new Dictionary<long, T>();
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_lru = new LinkedList<T>();
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_freeBlocks = new List<T>(_totalBlocks);
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FreeBlockCount = _totalBlocks;
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}
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public int FreeBlockCount { get; private set; }
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public bool ContainsBlock(long position)
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{
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return _blocks.ContainsKey(position);
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}
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public bool TryGetBlock(long position, out T block)
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{
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if (_blocks.TryGetValue(position, out block))
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{
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_lru.Remove(block);
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_lru.AddFirst(block);
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return true;
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}
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return false;
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}
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public T GetBlock(long position)
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{
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T result;
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if (TryGetBlock(position, out result))
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{
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return result;
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}
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result = GetFreeBlock();
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result.Position = position;
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result.Available = -1;
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StoreBlock(result);
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return result;
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}
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public void ReleaseBlock(long position)
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{
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T block;
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if (_blocks.TryGetValue(position, out block))
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{
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_blocks.Remove(position);
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_lru.Remove(block);
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_freeBlocks.Add(block);
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FreeBlockCount++;
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}
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}
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private void StoreBlock(T block)
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{
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_blocks[block.Position] = block;
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_lru.AddFirst(block);
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}
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private T GetFreeBlock()
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{
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T block;
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if (_freeBlocks.Count > 0)
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{
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int idx = _freeBlocks.Count - 1;
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block = _freeBlocks[idx];
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_freeBlocks.RemoveAt(idx);
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FreeBlockCount--;
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}
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else if (_blocksCreated < _totalBlocks)
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{
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block = new T();
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block.Data = new byte[_blockSize];
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_blocksCreated++;
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FreeBlockCount--;
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}
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else
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{
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block = _lru.Last.Value;
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_lru.RemoveLast();
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_blocks.Remove(block.Position);
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}
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return block;
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}
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}
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} |