Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / Net / System / Net / SecureProtocols / _FixedSizeReader.cs / 1 / _FixedSizeReader.cs
/*++ Copyright (c) 2000 Microsoft Corporation Module Name: _FixedSizeReader.cs Abstract: The class is a simple wrapper on top of a read stream. It will read the exact number of bytes requested. It operates either sync or async. Author: Alexei Vopilov Aug 18 2003 Revision History: --*/ namespace System.Net { using System; using System.IO; using System.Threading; // // Reads a fixed size packet from a stream, can disover EOF as 0 bytes read from stream // internal class FixedSizeReader { private static readonly AsyncCallback _ReadCallback = new AsyncCallback(ReadCallback); private readonly Stream _Transport; private AsyncProtocolRequest _Request; private int _TotalRead; public FixedSizeReader(Stream transport) { _Transport = transport; } // // Returns 0 on legitimate EOF or if 0 bytes was requested, otheriwse reads as directed or throws // Returns count on success // public int ReadPacket(byte[] buffer, int offset, int count) { int tempCount = count; do { int bytes = _Transport.Read(buffer, offset, tempCount); if (bytes == 0) { if (tempCount != count) { throw new IOException(SR.GetString(SR.net_io_eof)); } return 0; } tempCount -= bytes; offset += bytes; }while (tempCount != 0); return count; } // // Completes "_Request" with 0 if 0 bytes was requested or legitimate EOF received // Otheriwse, reads as directed or completes "_Request" with an Exception or throws right here // public void AsyncReadPacket(AsyncProtocolRequest request) { _Request = request; _TotalRead = 0; StartReading(); } // // Loops while subsequest completions are sync // private void StartReading() { while (true) { IAsyncResult ar = _Transport.BeginRead(_Request.Buffer, _Request.Offset+_TotalRead, _Request.Count-_TotalRead, _ReadCallback, this); if (!ar.CompletedSynchronously) { #if DEBUG _Request._DebugAsyncChain = ar; #endif break; } int bytes = _Transport.EndRead(ar); if (CheckCompletionBeforeNextRead(bytes)) { break; } } } // // // private bool CheckCompletionBeforeNextRead(int bytes) { if (bytes == 0) { // 0 bytes was requested or EOF in the beginning of a frame, the caller should decide whether it's OK if(_TotalRead == 0) { _Request.CompleteRequest(0); return true; } // EOF in the middle of a frame, bummer! throw new IOException(SR.GetString(SR.net_io_eof)); } GlobalLog.Assert(_TotalRead + bytes <= _Request.Count, "FixedSizeReader::CheckCompletion()|State got out of range. Total:{0} Count:{1}", _TotalRead + bytes, _Request.Count); if ((_TotalRead+=bytes) == _Request.Count) { _Request.CompleteRequest(_Request.Count); return true; } return false; } // // // private static void ReadCallback(IAsyncResult transportResult) { GlobalLog.Assert(transportResult.AsyncState is FixedSizeReader, "ReadCallback|State type is wrong, expected FixedSizeReader."); if (transportResult.CompletedSynchronously) { return; } FixedSizeReader reader = (FixedSizeReader)transportResult.AsyncState; // Async completion try { int bytes = reader._Transport.EndRead(transportResult); if (reader.CheckCompletionBeforeNextRead(bytes)) { return; } reader.StartReading(); } catch (Exception e) { if (reader._Request.IsUserCompleted) throw; reader._Request.CompleteWithError(e); } catch { if (reader._Request.IsUserCompleted) throw; reader._Request.CompleteWithError(new Exception(SR.GetString(SR.net_nonClsCompliantException))); } } } }
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