mirror of
https://github.com/boostorg/iostreams.git
synced 2026-02-26 04:42:19 +00:00
69 lines
2.6 KiB
HTML
Executable File
69 lines
2.6 KiB
HTML
Executable File
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
<HTML>
|
|
<HEAD>
|
|
<TITLE>Blocking</TITLE>
|
|
<LINK REL="stylesheet" HREF="../../../../boost.css">
|
|
<LINK REL="stylesheet" HREF="../theme/iostreams.css">
|
|
</HEAD>
|
|
<BODY>
|
|
|
|
<!-- Begin Banner -->
|
|
|
|
<H1 CLASS="title">Blocking</H1>
|
|
<HR CLASS="banner">
|
|
|
|
<!-- End Banner -->
|
|
|
|
<H2>Description</H2>
|
|
|
|
<P>
|
|
A Device is Blocking if a <CODE>read</CODE> request never produces fewer characters than requested except at end-of-stream, and if a <CODE>write</CODE> request never consumes fewer characters than requested under any circumstances. All Devices currently provided with the Iostreams library are Blocking. Limited support for non-Blocking Devices has been provided as a foundation for future more comprehensive support of non-blocking and asynchronous i/o. See <A HREF='../non_blocking.html'>Non-Blocking and Asynchronous I/o</A>.
|
|
</P>
|
|
|
|
<P>
|
|
The Blocking concept does not apply to filters. Instead, filters are required to be <SPAN CLASS='term'>blocking-preserving</SPAN>, which means that
|
|
</P>
|
|
<UL>
|
|
<LI>
|
|
a <CODE>read</CODE> request never produces fewer characters than requested unless end-of-stream has been reached or unless a <CODE>read</CODE> request to a downsteam Source produces fewer characters than requested, and
|
|
</LI>
|
|
<LI>
|
|
a <CODE>write</CODE> request never consumes fewer characters than requested unless a <CODE>write</CODE> request to a downsteam Sink consumes fewer characters than requested.
|
|
</LI>
|
|
</UL>
|
|
|
|
<P>
|
|
Unlike other Iostreams library concepts, Blocking is not associated with any <A HREF='../guide/traits.html#category_tags'>category tag</A>. In the future, a <CODE>non_blocking_tag</CODE> may be introduced.
|
|
</P>
|
|
|
|
<H2>Refinement of</H2>
|
|
|
|
<P><A HREF="device.html">Device</A>.</P>
|
|
|
|
<A NAME="types"></A>
|
|
<H2>Associated Types</H2>
|
|
|
|
<P>Same as <A HREF="device.html">Device</A>.</P>
|
|
|
|
<A NAME="expressions"></A>
|
|
<H2>Valid Expressions / Semantics</H2>
|
|
|
|
<P>Valid expressions are the same as <A HREF="device.html">Device</A>. The additional semantic requirements are described informally above.</P>
|
|
|
|
<!-- Begin Footer -->
|
|
|
|
<HR>
|
|
<P CLASS="copyright">Revised
|
|
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
|
20 May, 2004
|
|
<!--webbot bot="Timestamp" endspan i-checksum="38504" -->
|
|
</P>
|
|
|
|
<P CLASS="copyright">© Copyright Jonathan Turkanis, 2004</P>
|
|
<P CLASS="copyright">
|
|
Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)
|
|
</P>
|
|
|
|
<!-- End Footer -->
|
|
|
|
</BODY> |