<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>hsearch</title> <link rel="stylesheet" href="apiReference.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Berkeley DB C API Reference" /> <link rel="up" href="historic.html" title="Appendix B. Historic Interfaces" /> <link rel="prev" href="dbm.html" title="dbm/ndbm" /> <link rel="next" href="setfunc.html" title="Appendix C. Berkeley DB Application Space Static Functions" /> </head> <body> <div xmlns="" class="navheader"> <div class="libver"> <p>Library Version 11.2.5.3</p> </div> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">hsearch</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="dbm.html">Prev</a> </td> <th width="60%" align="center">Appendix B. Historic Interfaces </th> <td width="20%" align="right"> <a accesskey="n" href="setfunc.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="hsearch"></a>hsearch</h2> </div> </div> </div> <pre class="programlisting">#define DB_DBM_HSEARCH 1 #include <db.h> typedef enum { FIND, ENTER } ACTION; typedef struct entry { char *key; void *data; } ENTRY; ENTRY * hsearch(ENTRY item, ACTION action); int hcreate(size_t nelem); void hdestroy(void); </pre> <p> The hsearch functions are intended to provide a high-performance implementation and source code compatibility for applications written to the historic hsearch interface. It is not recommended for any other purpose. </p> <p> To compile hsearch applications, replace the application's <span class="bold"><strong>#include</strong></span> of the hsearch include file (for example, <span class="bold"><strong>#include <search.h></strong></span>) with the following two lines: </p> <pre class="programlisting">#define DB_DBM_HSEARCH 1 #include <db.h></pre> <p> and recompile. </p> <p> The hcreate function creates an in-memory database. The <span class="bold"><strong>nelem</strong></span> parameter is an estimation of the maximum number of key/data pairs that will be stored in the database. </p> <p> The <span class="bold"><strong>hdestroy</strong></span> function discards the database. </p> <p> Database elements are structures of type <span class="bold"><strong>ENTRY</strong></span>, which contain at least two fields: <span class="bold"><strong>key</strong></span> and <span class="bold"><strong>data</strong></span>. The field <span class="bold"><strong>key</strong></span> is declared to be of type <span class="bold"><strong>char *</strong></span>, and is the key used for storage and retrieval. The field <span class="bold"><strong>data</strong></span> is declared to be of type <span class="bold"><strong>void *</strong></span>, and is its associated data. </p> <p> The hsearch function retrieves key/data pairs from, and stores key/data pairs into the database. </p> <p> The <span class="bold"><strong>action</strong></span> parameter must be set to one of two values: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p> <span class="bold"><strong>ENTER</strong></span> </p> <p> If the key does not already appear in the database, insert the key/data pair into the database. If the key already appears in the database, return a reference to an <span class="bold"><strong>ENTRY</strong></span> structure which refers to the existing key and its associated data element. </p> </li> <li> <p> <span class="bold"><strong>FIND</strong></span> </p> <p> Retrieve the specified key/data pair from the database. </p> </li> </ul> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="hsearch_compatnotes"></a>Compatibility Notes</h3> </div> </div> </div> <p> Historically, hsearch required applications to maintain the keys and data in the application's memory for as long as the <span class="bold"><strong>hsearch</strong></span> database existed. Because Berkeley DB handles key and data management internally, there is no requirement that applications maintain local copies of key and data items, although the only effect of doing so should be the allocation of additional memory. </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="hsearch_diagnostics"></a>Hsearch Diagnostics</h3> </div> </div> </div> <p> The <span class="bold"><strong>hcreate</strong></span> function returns 0 on failure, setting <span class="bold"><strong>errno</strong></span>, and non-zero on success. </p> <p> The <span class="bold"><strong>hsearch</strong></span> function returns a pointer to an ENTRY structure on success, and NULL, setting <span class="bold"><strong>errno</strong></span>, if the <span class="bold"><strong>action</strong></span> specified was FIND and the item did not appear in the database. </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="hsearch_errors"></a>Hsearch Errors</h3> </div> </div> </div> <p> The <span class="bold"><strong>hsearch</strong></span> function will fail, setting <span class="bold"><strong>errno</strong></span> to 0, if the <span class="bold"><strong>action</strong></span> specified was FIND and the item did not appear in the database. </p> <p> In addition, the hcreate, hsearch and hdestroy functions may fail and return an error for errors specified for other Berkeley DB and C library or system functions. </p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="dbm.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="historic.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="setfunc.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">dbm/ndbm </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> Appendix C. Berkeley DB Application Space Static Functions </td> </tr> </table> </div> </body> </html>