📄 t_rcv.html

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>t_rcv</title></head><body bgcolor=white><center><font size=2>The Single UNIX &reg; Specification, Version 2<br>Copyright &copy; 1997 The Open Group</font></center><hr size=2 noshade><h4>NAME</h4><blockquote>t_rcv - receive data or expedited data sent over a connection</blockquote><h4>SYNOPSIS</h4><blockquote><pre><code>#include &lt;<a href="xti.h.html">xti.h</a>&gt;int t_rcv(    int fd,    void *buf,    unsigned int nbytes,    int *flags)</code></pre></blockquote><h4>DESCRIPTION</h4><blockquote><pre><P><table  bordercolor=#000000 border=1 align=center><tr valign=top><th align=center><b>Parameters</b><th align=center><b>Before call</b><th align=center><b>After call</b><tr valign=top><td align=left>fd<td align=center>x<td align=center>/<tr valign=top><td align=left>buf<td align=center>x<td align=center>(x)<tr valign=top><td align=left>nbytes<td align=center>x<td align=center>/<tr valign=top><td align=left>flags<td align=center>/<td align=center>x</table></pre><p>This function receives either normal or expedited data.The argument<I>fd</I>identifies the local transport endpoint through which data will arrive,<I>buf</I>points to a receive buffer where user data will be placed, and<I>nbytes</I>specifies the size of the receive buffer.The argument<I>flags</I>may be set on return from<i>t_rcv()</i>and specifies optional flags as described below.<p>By default,<i>t_rcv()</i>operates in synchronous mode and willwait for data to arrive if none is currently available.However, ifO_NONBLOCKis set (via<i><a href="t_open.html">t_open()</a></i>or<i><a href="fcntl.html">fcntl()</a></i>),<i>t_rcv()</i>will execute in asynchronous mode and willfail if no data is available.(See [TNODATA] below.)<p>On return from the call,if T_MORE is set in<I>flags</I>,this indicates that there is more data, and the currenttransport service data unit (TSDU) or expedited transportservice data unit (ETSDU)must be received in multiple<i>t_rcv()</i>calls.In the asynchronous mode,or under unusual conditions (for example, thearrival of a signal or T_EXDATA event), the T_MORE flag may be set on return from the<i>t_rcv()</i>call even when the number of bytes received is less than the size of thereceive buffer specified.Each<i>t_rcv()</i>with the T_MORE flag set indicates that another<i>t_rcv()</i>must follow to get more data for the current TSDU.The end of the TSDU is identified by the return of a<i>t_rcv()</i>call with the T_MORE flag not set.If the transport provider does not support the concept of a TSDUas indicated in the<I>info</I>argument on return from<i><a href="t_open.html">t_open()</a></i>or<i><a href="t_getinfo.html">t_getinfo()</a></i>,the T_MORE flag is not meaningful and should be ignored.  If<I>nbytes</I>is greater than zero on the call to<i>t_rcv()</i>,<i>t_rcv()</i>will return 0 only if the end of a TSDU is being returned to the user.<p>On return, the data is expedited if T_EXPEDITED is set inflags.  If T_MORE is also set, it indicates that the number ofexpedited bytes exceeded nbytes, a signal has interrupted the call, or that an entire ETSDU was not available (only for     transport protocols that support fragmentation of ETSDUs).  Therest of the ETSDU will be returned by subsequent calls to       <i>t_rcv()</i>which will return with T_EXPEDITED set in flags. The end ofthe ETSDU is identified by the return of a <i>t_rcv()</i>call with T_EXPEDITED set and T_MORE cleared.  If the entire ETSDU is notavailable it is possible for normal data fragments to be      returned between the initial and final fragments of an ETSDU.<p>If a signal arrives,<i>t_rcv()</i>returns, giving the user any datacurrently available.  If no data is available, <i>t_rcv()</i>returns -1, sets <I>t_errno</I>to [TSYSERR] and <I>errno</I>to [EINTR].  If somedata is available, <i>t_rcv()</i>returns the number of bytes received and T_MORE is set in flags.<p>In synchronous mode, the only way for the user to be notified ofthe arrival of normal or expedited data is to issue this functionor check for the T_DATA or T_EXDATA events using the<i><a href="t_look.html">t_look()</a></i>function.  Additionally, the process can arrange to be notified via the EMinterface.</blockquote><h4>VALID STATES</h4><blockquote>T_DATAXFER, T_OUTREL</blockquote><h4>ERRORS</h4><blockquote>On failure,<I>t_errno</I>is set to one of the following:<dl compact><dt>[TBADF]<dd>The specified file descriptor does not refer to a transport endpoint.<dt>[TLOOK]<dd>An asynchronous event has occurred on this transport endpoint and requiresimmediate attention.<dt>[TNODATA]<dd>O_NONBLOCKwas set, butno data is currently available from the transport provider.<dt>[TNOTSUPPORT]<dd>This function is not supported by the underlying transport provider.<dt>[TPROTO]<dd>This error indicates that a communication problem has been detected betweenXTI and the transport provider for which there is no other suitable XTIerror<I>(t_errno)</I>.<dt>[TSYSERR]<dd>A system error has occurred during execution of this function.</dl></blockquote><h4>RETURN VALUE</h4><blockquote>On successful completion,<i>t_rcv()</i>returns the number of bytes received. Otherwise, itreturns -1 on failure and<I>t_errno</I>is set to indicate the error.</blockquote><h4>SEE ALSO</h4><blockquote><i><a href="fcntl.html">fcntl()</a></i>,<i><a href="t_getinfo.html">t_getinfo()</a></i>,<i><a href="t_look.html">t_look()</a></i>,<i><a href="t_open.html">t_open()</a></i>,<i><a href="t_snd.html">t_snd()</a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX &reg; is a registered Trademark of The Open Group.<br>Copyright &copy; 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>
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