Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / ManagedLibraries / Remoting / Channels / CORE / ByteBufferPool.cs / 1305376 / ByteBufferPool.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== //========================================================================== // File: ByteBufferPool.cs // // Summary: Stream used for reading from a socket by remoting channels. // //========================================================================= using System; using System.Threading; namespace System.IO { internal interface IByteBufferPool { byte[] GetBuffer(); void ReturnBuffer(byte[] buffer); } // This isn't actually a buffer pool. It always creates a new byte buffer. internal class ByteBufferAllocator : IByteBufferPool { private int _bufferSize; public ByteBufferAllocator(int bufferSize) { _bufferSize = bufferSize; } public byte[] GetBuffer() { return new byte[_bufferSize]; } public void ReturnBuffer(byte[] buffer) { } } // ByteBufferAllocator internal class ByteBufferPool : IByteBufferPool { private byte[][] _bufferPool = null; private int _current; // -1 for none private int _last; private int _max; // maximum number of buffers to pool private int _bufferSize; private Object _controlCookie = "cookie object"; public ByteBufferPool(int maxBuffers, int bufferSize) { _max = maxBuffers; _bufferPool = new byte[_max][]; _bufferSize = bufferSize; _current = -1; _last = -1; } // ByteBufferPool public byte[] GetBuffer() { Object cookie = null; try { // If a ThreadAbortException gets thrown after the exchange, // but before the result is assigned to cookie, then the // control cookie is lost forever. However, the buffer pool // will still function normally and return everybody a new // buffer each time (that isn't very likely to happen, // so we don't really care). cookie = Interlocked.Exchange(ref _controlCookie, null); if (cookie != null) { // we have the control cookie, so take a buffer if (_current == -1) { _controlCookie = cookie; // no pooled buffers available return new byte[_bufferSize]; } else { // grab next available buffer byte[] buffer = _bufferPool[_current]; _bufferPool[_current] = null; // update "current" index if (_current == _last) { // this is the last free buffer _current = -1; } else { _current = (_current + 1) % _max; } _controlCookie = cookie; return buffer; } } else { // we don't have the control cookie, so just create a new buffer since // there will probably be a lot of contention anyway. return new byte[_bufferSize]; } } catch (ThreadAbortException) { if (cookie != null) { // This should be rare, so just reset // everything to the initial state. _current = -1; _last = -1; // restore cookie _controlCookie = cookie; } throw; } } // GetBuffer public void ReturnBuffer(byte[] buffer) { if (buffer == null) throw new ArgumentNullException("buffer"); // The purpose of the buffer pool is to try to reduce the // amount of garbage generated, so it doesn't matter if // the buffer gets tossed out. Since we don't want to // take the perf hit of taking a lock, we only return // the buffer if we can grab the control cookie. Object cookie = null; try { // If a ThreadAbortException gets thrown after the exchange, // but before the result is assigned to cookie, then the // control cookie is lost forever. However, the buffer pool // will still function normally and return everybody a new // buffer each time (that isn't very likely to happen, // so we don't really care). cookie = Interlocked.Exchange(ref _controlCookie, null); if (cookie != null) { if (_current == -1) { _bufferPool[0] = buffer; _current = 0; _last = 0; } else { int newLast = (_last + 1) % _max; if (newLast != _current) { // the pool isn't full so store this buffer _last = newLast; _bufferPool[_last] = buffer; } } _controlCookie = cookie; } } catch (ThreadAbortException) { if (cookie != null) { // This should be rare, so just reset // everything to the initial state. _current = -1; _last = -1; // restore cookie _controlCookie = cookie; } throw; } } // ReturnBuffer } // ByteBufferPool } // namespace System.IO // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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