213 lines
5.1 KiB
HTML
213 lines
5.1 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>xdr_reference()--Provide Pointer Chasing within Structures</title>
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
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</script>
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<a name="Top_of_Page"></a>
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<h2>xdr_reference()--Provide Pointer Chasing within Structures</h2>
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<div class="box" style="width: 60%;">
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<br>
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Syntax<br>
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<pre>
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#include <rpc/xdr.h>
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bool_t xdr_reference(XDR *<em>xdrs</em>,
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caddr_t *<em>pp</em>,
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u_int <em>size</em>,
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const xdrproc_t <em>proc</em>);
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</pre>
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<br>
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Service Program Name: QZNFTRPC<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: No<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>xdr_reference()</strong> function is a filter primitive that
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provides pointer chasing within structures. This primitive allows the
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serializing, deserializing, and freeing of any pointers within one structure
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that are referenced by another structure.</p>
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<p>The <strong>xdr_reference()</strong> function does not attach special
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meaning to a null pointer during serialization, and passing the address of a
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null pointer may cause a memory error. Therefore, the programmer must describe
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data with a two-sided discriminated union. One side is used when the pointer is
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valid; the other side, when the pointer is null.</p>
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<p><strong>Pointer chasing</strong> is the substitution of the pointer itself
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with the actual structure it points to.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong>xdrs</strong> (Input) </dt>
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<dd>A pointer to the eXternal Data Representation (XDR) stream handle.<br>
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<br>
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</dd>
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<dt><strong>pp</strong> (I/O) </dt>
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<dd>The address of the structure. When you decode data, XDR allocates storage
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if the pointer is NULL.<br>
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<br>
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</dd>
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<dt><strong>size</strong> (Input) </dt>
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<dd>The byte size of the structure pointed to by the <em>pp</em> parameter.<br>
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<br>
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</dd>
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<dt><strong>proc</strong> (Input) </dt>
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<dd>A translation of the structure between its C form and its external
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representation. This parameter is the XDR procedure that describes the
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structure.</dd>
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</dl>
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<br>
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<h3>Authorities</h3>
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<p>No authorization is required.</p>
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<br>
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<h3>Return Value</h3>
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<table cellpadding="5">
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<!-- cols="15 85" -->
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<tr>
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<td valign="top"><em>TRUE (1)</em></td>
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<td valign="top">Successful</td>
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</tr>
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<tr>
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<td valign="top"><em>FALSE (0)</em></td>
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<td valign="top">Unsuccessful</td>
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</tr>
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</table>
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<br>
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<br>
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<h3>Error Conditions</h3>
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<p>None.</p>
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<br>
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<h3>Error Messages</h3>
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<table width="100%" cellpadding="5">
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<!-- cols="15 85" -->
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<tr>
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<th align="left" valign="top">Message ID</th>
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<th align="left" valign="top">Error Message Text</th>
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</tr>
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<tr>
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<td width="15%" valign="top">CPE3418 E</td>
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<td width="85%" valign="top">Possible APAR condition or hardware failure.</td>
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</tr>
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<tr>
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<td valign="top">CPF3CF2 E</td>
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<td valign="top">Error(s) occurred during running of &1 API.</td>
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</tr>
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<tr>
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<td valign="top">CPF9872 E</td>
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<td valign="top">Program or service program &1 in library &2 ended.
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Reason code &3.</td>
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</tr>
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</table>
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<br>
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<br>
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<h3>Example</h3>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<p>The following example shows how <strong>xdr_reference()</strong> is
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used:</p>
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<pre>
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#include <xdr.h>
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typedef struct node
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{
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int value;
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struct node *p;
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} node ;
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/*
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* Do not call it with p_node==NULL, because it will fail.
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*/
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bool_t xdr_list(XDR *xdrs, node **p_node)
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{
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return <strong>xdr_reference</strong>(xdrs,(caddr_t)p_node,
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sizeof(node),(xdrproc_t)xdr_node)
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}
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bool_t xdr_node(XDR *xdrs, node *p_node)
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{
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xdr_int(xdrs,&(p_node->value));
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return <strong>xdr_list</strong>(xdrs,&(p_node->p));
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}
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</pre>
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<br>
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<hr>
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API introduced: V4R2
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<hr>
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<table cellpadding="2" cellspacing="2" align="center">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"rpc1.htm">Remote Procedure Call (RPC) APIs</a> | <a href="aplist.htm">APIs by
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category</a></td>
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</tr>
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</table>
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</body>
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</html>
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