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- /* Copyright (C) 2016 Tal Aloni <tal.aloni.il@gmail.com>. All rights reserved.
- *
- * You can redistribute this program and/or modify it under the terms of
- * the GNU Lesser Public License as published by the Free Software Foundation,
- * either version 3 of the License, or (at your option) any later version.
- */
- using System;
- using System.Collections.Generic;
- using System.IO;
- using System.Text;
- using System.Threading;
- namespace Utilities
- {
- public class PrefetchedStream : Stream
- {
- public const int CacheSize = 1048576; // 1 MB
- private long m_cacheOffset;
- private byte[] m_cache = new byte[0];
- private Stream m_stream;
- private object m_syncLock = new object();
- public PrefetchedStream(Stream stream)
- {
- m_stream = stream;
- if (m_stream.CanRead)
- {
- new Thread(delegate()
- {
- lock (m_syncLock)
- {
- m_cacheOffset = 0;
- m_cache = new byte[CacheSize];
- int bytesRead = m_stream.Read(m_cache, 0, CacheSize);
- System.Diagnostics.Debug.Print("[{0}] {1} bytes have been prefetched.", DateTime.Now.ToString("HH:mm:ss:ffff"), bytesRead);
- this.Position = 0;
- if (bytesRead < CacheSize)
- {
- // EOF, we must trim the response data array
- m_cache = ByteReader.ReadBytes(m_cache, 0, bytesRead);
- }
- }
- }).Start();
- }
- }
- public override int Read(byte[] buffer, int offset, int count)
- {
- long position;
- lock (m_syncLock)
- {
- position = this.Position;
- bool isInCache = (position >= m_cacheOffset) && (position + count <= m_cacheOffset + m_cache.Length);
- if (!isInCache)
- {
- m_cacheOffset = position;
- int cacheSize = Math.Max(CacheSize, count);
- m_cache = new byte[cacheSize];
- int bytesRead = m_stream.Read(m_cache, 0, cacheSize);
-
- if (bytesRead < cacheSize)
- {
- // EOF, we must trim the response data array
- m_cache = ByteReader.ReadBytes(m_cache, 0, bytesRead);
- }
- }
- }
- int offsetInCache = (int)(position - m_cacheOffset);
- int bytesRemained = m_cache.Length - offsetInCache;
- int dataLength = Math.Min(count, bytesRemained);
- Array.Copy(m_cache, offsetInCache, buffer, offset, dataLength);
- lock (m_syncLock)
- {
- this.Position = position + dataLength;
- }
- return dataLength;
- }
- public override void Write(byte[] buffer, int offset, int count)
- {
- m_cache = new byte[0];
- m_stream.Write(buffer, offset, count);
- }
- public override void Close()
- {
- m_stream.Close();
- base.Close();
- }
- public override bool CanRead
- {
- get
- {
- return m_stream.CanRead;
- }
- }
- public override bool CanSeek
- {
- get
- {
- return m_stream.CanSeek;
- }
- }
- public override bool CanWrite
- {
- get
- {
- return m_stream.CanWrite;
- }
- }
- public override long Length
- {
- get
- {
- return m_stream.Length;
- }
- }
- public override long Position
- {
- get
- {
- return m_stream.Position;
- }
- set
- {
- m_stream.Position = value;
- }
- }
- public override void Flush()
- {
- m_stream.Flush();
- }
- public override long Seek(long offset, SeekOrigin origin)
- {
- return m_stream.Seek(offset, origin);
- }
- public override void SetLength(long value)
- {
- m_stream.SetLength(value);
- }
- }
- }
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