347 lines
11 KiB
HTML
347 lines
11 KiB
HTML
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<!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>sqludf_length()--SQL LOB Locator Length</title>
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Begin Header Records ============================================== -->
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<!-- Change History: -->
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<!-- sqludf_length.htm created by Paul Hospers on Tue Aug 6 2002 -->
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<!-- 0300507 JETAYLOR html cleanup -->
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<!--End Header Records ============================================== -->
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<!-- end header records -->
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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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<a name="Top_Of_Page"></a>
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<!-- Java sync-link -->
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<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
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</script>
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<h2>sqludf_length()--SQL LOB locator length</h2>
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<div class="box" style="width: 60%;">
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<br>
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Syntax
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<pre>
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#include <sqludf.h>
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extern int SQL_API_FN sqludf_length(
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udf_locator * <em>udfloc_p</em>,
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long * <em>return_len_p</em>)
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</pre>
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Service Program Name: QSYS/QSQAPIS<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: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>sqludf_length()</strong> function returns the length of the LOB data represented by a LOB locator.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong>udfloc_p</strong></dt>
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<dd>(Input) Pointer to the LOB locator value.<br>
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<br>
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</dd>
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<dt><strong>return_len_p</strong></dt>
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<dd>(Input/Output) Pointer to the length of the LOB data represented by the LOB locator.<br>
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<br>
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</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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<strong>sqludf_length()</strong>
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<p>returns an integer. Possible values are:</p>
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<dl compact>
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<dt>0</dt>
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<dd><strong>sqludf_length()</strong> was successful. The
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information is returned in the buffer pointed to by <em>return_len_p</em>.<br>
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<br>
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</dd>
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<dt>-3</dt>
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<dd><strong>squdf_length()</strong> was not successful. An invalid parameter was passed into the function.<br>
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<br>
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</dd>
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<dt>-423</dt>
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<dd><strong>squdf_length()</strong> was not successful. The <em>udfloc_p</em> parameter
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points to an invalid locator value.<br>
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<br>
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</dd>
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<dt>-901</dt>
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<dd><strong>sqludf_length()</strong> was not successful. An SQL system error has occurred.<br>
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<br>
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</dd>
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<dt>-7034</dt>
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<dd><strong>sqludf_length()</strong> was not successful. LOB locators are not allowed with COMMIT(*NONE).<br>
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<br>
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</dd>
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</dl>
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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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<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">SQL7034 D</td>
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<td width="85%" valign="top">LOB locators are not allowed with COMMIT(*NONE).</td>
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</tr>
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<tr>
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<td width="15%" valign="top">SQL0901 D</td>
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<td width="85%" valign="top">SQL system error.</td>
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</tr>
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<tr>
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<td width="15%" valign="top">SQL0952 D</td>
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<td width="85%" valign="top">Processing of the SQL statement ended. </td>
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</tr>
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<tr>
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<td width="15%" valign="top">CPF9872 E</td>
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<td width="85%" valign="top">Program or service program &1 in library &2 ended. Reason code &3.</td>
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</tr>
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</table>
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<br>
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<h3>Usage Notes</h3>
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<ol>
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<li>This API is used to find out the length of a LOB value when it receives a locator.</li>
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</ol>
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<br>
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<h3>Related Information</h3>
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<ul>
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<li><a href="sqludf_append.htm">sqludf_append()</a>--SQL LOB append locator</li>
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<li><a href="sqludf_create_locator.htm">sqludf_create_locator()</a>--SQL LOB create locator</li>
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<li><a href="sqludf_create_locator_with_ccsid.htm">sqludf_create_locator_with_ccsid()</a>--SQL LOB create locator with ccsid</li>
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<li><a href="sqludf_free_locator.htm">sqludf_free_locator()</a>--SQL LOB free locator</li>
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<li><a href="sqludf_substr.htm">sqludf_substr()</a>--SQL LOB substring locator</li>
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</ul>
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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>This UDF takes a locator for an input LOB, and returns a locator for another LOB which is a subset of the input LOB. There are some criteria passed as a second input value, which tell the UDF how exactly to break up the input LOB.</p>
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<pre>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <sql.h>
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#include <sqludf.h>
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void SQL_API_FN lob_subsetter(
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udf_locator * lob_input, /* locator of LOB value to carve up */
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char * criteria, /* criteria for carving */
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udf_locator * lob_output, /* locator of result LOB value */
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sqlint16 * inp_nul,
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sqlint16 * cri_nul,
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sqlint16 * out_nul,
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char * sqlstate,
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char * funcname,
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char * specname,
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char * msgtext ) {
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/* local vars */
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short j; /* local indexing var */
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int rc; /* return code variable for API calls */
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sqlint32 input_len; /* receiver for input LOB length */
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sqlint32 input_pos; /* current position for scanning input LOB */
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char lob_buf[100]; /* data buffer */
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sqlint32 input_rec; /* number of bytes read by sqludf_substr */
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sqlint32 output_rec; /* number of bytes written by sqludf_append */
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/*---------------------------------------------
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* UDF Program Logic Starts Here
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*---------------------------------------------
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* What we do is create an output handle, and then
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* loop over the input, 50 bytes at a time.
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* Depending on the "criteria" passed in, we may decide
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* to append the 50 byte input lob segment to the output, or not.
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*---------------------------------------------
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* Create the output locator, right in the return buffer.
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*/
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rc = sqludf_create_locator(SQL_TYP_CLOB, &lob_output);
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/* Error and exit if unable to create locator */
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if (rc) {
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memcpy (sqlstate, "38901", 5);
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/* special sqlstate for this condition */
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goto exit;
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}
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/* Find out the size of the input LOB value */
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rc = sqludf_length(lob_input, &input_len) ;
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/* Error and exit if unable to find out length */
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if (rc) {
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memcpy (sqlstate, "38902", 5);
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/* special sqlstate for this condition */
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goto exit;
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}
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/* Loop to read next 50 bytes, and append to result if it meets
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* the criteria.
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*/
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for (input_pos = 1; (input_pos < input_len); input_pos += 50) {
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/* Read the next 50 (or less) bytes of the input LOB value */
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rc = sqludf_substr(lob_input, input_pos, 50,
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(unsigned char *) lob_buf, &input_rec) ;
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/* Error and exit if unable to read the segment */
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if (rc) {
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memcpy (sqlstate, "38903", 5);
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/* special sqlstate for this condition */
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goto exit;
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}
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/* apply the criteria for appending this segment to result
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* if (...predicate involving buffer and criteria...) {
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* The example shows if the segment matches the first 6
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* characters with the criteria it is appended.
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*/
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if (memcmp(lob_buf,criteria,6) == 0) {
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rc = sqludf_append(lob_output,
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(unsigned char *) lob_buf, input_rec, &output_rec) ;
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/* Error and exit if unable to read the 50 byte segment */
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if (rc) {
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memcpy (sqlstate, "38904", 5);
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/* special sqlstate for this condition */
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goto exit;
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}
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}
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/* } end if criteria for inclusion met */
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} /* end of for loop, processing 50-byte chunks of input LOB
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* if we fall out of for loop, we are successful, and done.
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*/
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*out_nul = 0;
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exit: /* used for errors, which will override null-ness of output. */
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return;
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}
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</pre>
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<p>Referring to this UDF code, observe that: </p>
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<ul>
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<li>There are includes for <em>sql.h</em>, where the type
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<tt>SQL_TYP_CLOB</tt> used in the <tt>sqludf_create_locator()</tt> call is
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defined, and <tt>sqludf.h</tt>, where the type <tt>udf_locator</tt>
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is defined.</li>
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<li>The first input argument, and the third input argument (which represents
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the function output) are defined as pointers to <tt>sqludf_locator</tt>,
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that is, they represent CREATE FUNCTION specifications of AS LOCATOR.
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</li>
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<li>The UDF does not test whether either input argument is null, as NOT NULL
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CALL is specified in the CREATE FUNCTION statement.</li>
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<li>In the event of error, the UDF exits with <tt>sqlstate</tt> set to
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38<i>xxx</i>. This is sufficient to stop the execution of the
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statement referencing the UDF. The actual 38<i>xxx</i> SQLSTATE
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values you choose are not important to DB2, but can serve to differentiate the
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exception conditions which your UDF may encounter.</li>
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<li>By using the <tt>input_rec</tt> variable as the length of the data
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appended, the UDF takes care of any partial buffer condition.</li>
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</ul>
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<p>Following is the CREATE FUNCTION statement for this UDF:</p>
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<pre> CREATE FUNCTION carve(CLOB(50M) AS LOCATOR, VARCHAR(255) )
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RETURNS CLOB(50M) AS LOCATOR
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NOT NULL CALL
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DETERMINISTIC
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NO SQL
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NO EXTERNAL ACTION
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LANGUAGE C
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PARAMETER STYLE DB2SQL
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EXTERNAL NAME 'MYLIB/LOBUDFS(lob_subsetter)' ;
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</pre>
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<p>Referring to this statement, observe that:</p>
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<ul>
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<li>NOT NULL CALL is specified, so the UDF will not be called if any of its
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input SQL arguments are NULL, and does not have to check for this
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condition.</li>
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<li>The function is specified as DETERMINISTIC, meaning that with a given
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input CLOB value and a given set of criteria, the result will be the same
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every time.</li>
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</ul>
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<p>Now you can successfully run the following statement:
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<pre>
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strcpy(hvchar,"return this text 1 "
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"remove 1 "
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"return this text 2 "
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"remove 2 ");
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exec sql set :hvloc = clob(:hvchar);
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exec sql set :hvloc2 = carve(:hvloc,'return');
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strcpy(hvchar,"");
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exec sql set :hvchar = char(:hvloc2);
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</pre>
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<p>The UDF is used to subset the value represented by the host variable
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:hvchar. The first and third 50 byte character segments are returned from the UDF. </p>
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<br>
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<hr>
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API introduced: V5R3
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> |
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<a href= "file1.htm">Database and File APIs</a> |<a href=
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"aplist.htm">APIs by category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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