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+++ b/Symbian3/SDK/Source/GUID-2AC1C0B6-0405-5F1D-A813-39DA35808182.dita Wed Mar 31 11:11:55 2010 +0100
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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License
+"Eclipse Public License v1.0" which accompanies this distribution,
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+ Nokia Corporation - initial contribution.
+Contributors:
+-->
+<!DOCTYPE concept
+ PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-2AC1C0B6-0405-5F1D-A813-39DA35808182" xml:lang="en"><title>STDLIB
+Console and I/O operations</title><prolog><metadata><keywords/></metadata></prolog><conbody>
+<p>This section explains the console and the asynchronous input/output operations
+of STDLIB. </p>
+<section id="GUID-C5A9CB9B-3ABA-4192-944C-9F16C6033A9A"><title>Console versus terminals</title> <p>The STDLIB console (encapsulated
+by class <codeph>CTtyDesc</codeph>, defined in <filepath>fdesc.h</filepath>)
+is a client of the <codeph>CConsoleBase</codeph> class implemented by <filepath>econs.dll</filepath>.
+It provides very simple text input and output with no support for embedded
+control sequences. When STDLIB receives a character from the console it prints
+it out to the same console, providing a "local echo" facility to make simple
+command-line interfaces possible. </p> <p>STDLIB does not provide any sort
+of terminal driver or line-discipline. In particular there is no support for
+local processing of backspace, nor any line buffering. Neither does it provide
+termio or termcap facilities. The Symbian platform is a graphics-based system
+and it is recommended that C code be ported into a Symbian program which uses
+a graphical user interface. </p> </section>
+<section id="GUID-2F5F2A9F-2FC4-48A1-ADCF-D45BE2AE85A7"><title>Asynchronous I/O vs blocking I/O</title> <p>All STDLIB I/O
+operations are blocking; that is they will suspend the calling thread indefinitely
+until the I/O completes. Hence, in general, STDLIB I/O must not be used in
+a Symbian platform active object because it will cause the entire active scheduler
+to block. A possible way to avoid this problem might be to use <codeph>fcntl()</codeph> for
+individual file descriptors, but STDLIB does not currently implement this
+function. </p> <p>Asynchronous I/O can be achieved using a set of C++ functions
+provided by STDLIB which implement a per-file-descriptor equivalent of the
+POSIX <codeph>select()</codeph> function. These functions provide a form of
+the <codeph>ioctl()</codeph> function which takes a <codeph>TRequestStatus&</codeph> as
+a parameter, together with functions for completing the <codeph>ioctl()</codeph> operation
+once the status has been signaled or canceling the pending <codeph>ioctl</codeph>.
+This scheme can be used within an active object to wait for a socket to become
+ready for reading or writing, so that the subsequent i/o does not block the
+whole active scheduler. See <filepath>estlib.h</filepath> for the interface
+to these functions. For more information on active objects and active
+scheduler, see <xref href="GUID-890F06C6-DE32-5EB1-BF0F-D41794F47AE1.dita">active
+objects</xref>. </p> <p> <b> NOTE</b>: There are no such blocking problems
+with I/O to local files, which is essentially a synchronous operation. </p> </section>
+<section id="GUID-AB42F727-8976-4D44-97C6-99319D32A420"><title>See also</title> <p> <xref href="GUID-890F06C6-DE32-5EB1-BF0F-D41794F47AE1.dita">Active
+Objects</xref> </p> </section>
+</conbody></concept>
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