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<a href="" class="back" onclick="history.back();return false;">⬅</a>
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<div class="headertitle"><div class="title">/Users/hauk/src/libzdb/zdb/zdb.h</div></div>
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<p>Provides a default value if the expression is NULL, 0, or negative.</p>
<p>Provides a default value if the expression is NULL, 0, or negative.The valueOr macro is a convenient way to handle potentially unset or error values returned by libzdb functions. It works with pointers, integers, and floating-point types.</p>
<p>This macro evaluates the expression only once, making it safe to use with function calls or expressions that may have side effects.</p>
<p>For pointers:</p><ul>
<li>Returns the default value if the expression evaluates to NULL.</li>
<li>Otherwise, returns the original pointer value.</li>
</ul>
<p>For integers and floating-point types:</p><ul>
<li>Returns the default value if the expression evaluates to 0 or any negative value.</li>
<li>Otherwise, returns the original numeric value.</li>
</ul>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">expr</td><td>The expression to evaluate (typically a libzdb function call) </td></tr>
<tr><td class="paramname">default_value</td><td>The value to return if expr is NULL, 0, or negative</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>If expr is not NULL, 0, or negative, returns expr. Otherwise, returns default_value.</dd></dl>
<dl class="section note"><dt>Note</dt><dd>This macro uses a GNU C extension and is compatible with GCC and Clang. It may not work with other C compilers.</dd></dl>
<p>// Usage with string (pointer) return type const char* host = valueOr(URL_getHost(url), "localhost"); printf("Host: %s\n", host);</p>
<p>// Usage with integer return type int port = <a class="el" href="zdb_8h.html#a297ccf9a42e722258e3b51f9dabeab0a">valueOr(ResultSet_getInt(r, 1), 5432)</a>; printf("Port: %d\n", port);</p>
<p>// Usage with floating-point return type double percent = valueOr(ResultSet_getDouble(r, 1), 1.0); printf("Percent: %.1f\n", percent);</p>
<div class="fragment"><div class="line"><span class="comment">/*</span></div>
<div class="line"><span class="comment"> * Copyright (C) Tildeslash Ltd. All rights reserved.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * This program is free software: you can redistribute it and/or modify</span></div>
<div class="line"><span class="comment"> * it under the terms of the GNU General Public License version 3.</span></div>
<div class="line"><span class="comment"> * </span></div>
<div class="line"><span class="comment"> * This program is distributed in the hope that it will be useful,</span></div>
<div class="line"><span class="comment"> * but WITHOUT ANY WARRANTY; without even the implied warranty of</span></div>
<div class="line"><span class="comment"> * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span></div>
<div class="line"><span class="comment"> * GNU General Public License for more details.</span></div>
<div class="line"><span class="comment"> * </span></div>
<div class="line"><span class="comment"> * You should have received a copy of the GNU General Public License</span></div>
<div class="line"><span class="comment"> * along with this program. If not, see <http://www.gnu.org/licenses/>.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * In addition, as a special exception, the copyright holders give</span></div>
<div class="line"><span class="comment"> * permission to link the code of portions of this program with the</span></div>
<div class="line"><span class="comment"> * OpenSSL library under certain conditions as described in each</span></div>
<div class="line"><span class="comment"> * individual source file, and distribute linked combinations</span></div>
<div class="line"><span class="comment"> * including the two.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * You must obey the GNU General Public License in all respects</span></div>
<div class="line"><span class="comment"> * for all of the code used other than OpenSSL.</span></div>
<div class="line"><span class="comment"> */</span></div>
<div class="line"> </div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#ifndef ZDB_INCLUDED</span></div>
<div class="line"><span class="preprocessor">#define ZDB_INCLUDED</span></div>
<div class="line"><span class="preprocessor">#ifdef __cplusplus</span></div>
<div class="line"><span class="keyword">extern</span> <span class="stringliteral">"C"</span> {</div>
<div class="line"><span class="preprocessor">#endif</span></div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#include <stdbool.h></span></div>
<div class="line"><span class="comment"></span> </div>
<div class="line"><span class="comment">/**</span></div>
<div class="line"><span class="comment"> * Include this interface in your C code to import the libzdb API.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * @file</span></div>
<div class="line"><span class="comment"> */</span></div>
<div class="line"> </div>
<div class="line"><span class="comment">/* --------------------------------------------------------------- Version */</span></div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#define LIBZDB_MAJOR 3</span></div>
<div class="line"><span class="preprocessor">#define LIBZDB_MINOR 4</span></div>
<div class="line"><span class="preprocessor">#define LIBZDB_REVISION 0</span></div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#define LIBZDB_VERSION "3.4.0"</span></div>
<div class="line"><span class="preprocessor">#define LIBZDB_VERSION_NUMBER ((LIBZDB_MAJOR * 1000000) + (LIBZDB_MINOR * 1000) + LIBZDB_REVISION)</span></div>
<div class="line"> </div>
<div class="line"><span class="comment">/* ------------------------------------------------- libzdb API interfaces */</span></div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#include <<a class="code" href="SQLException_8h.html">SQLException.h</a>></span></div>
<div class="line"><span class="preprocessor">#include <<a class="code" href="URL_8h.html">URL.h</a>></span></div>
<div class="line"><span class="preprocessor">#include <<a class="code" href="ResultSet_8h.html">ResultSet.h</a>></span></div>
<div class="line"><span class="preprocessor">#include <<a class="code" href="PreparedStatement_8h.html">PreparedStatement.h</a>></span></div>
<div class="line"><span class="preprocessor">#include <<a class="code" href="Connection_8h.html">Connection.h</a>></span></div>
<div class="line"><span class="preprocessor">#include <<a class="code" href="ConnectionPool_8h.html">ConnectionPool.h</a>></span></div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#ifdef __cplusplus</span></div>
<div class="line">}</div>
<div class="line"><span class="preprocessor">#endif</span></div>
<div class="line"> </div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#ifndef __cplusplus</span></div>
<div class="line"><span class="comment">/* --------------------------------------------------------- Utility Macro */</span></div>
<div class="line"> </div>
<div class="line"><span class="comment"></span> </div>
<div class="line"><span class="comment">/**</span></div>
<div class="line"><span class="comment"> * @brief Provides a default value if the expression is NULL, 0, or negative.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * The valueOr macro is a convenient way to handle potentially unset or error</span></div>
<div class="line"><span class="comment"> * values returned by libzdb functions. It works with pointers, integers, and</span></div>
<div class="line"><span class="comment"> * floating-point types.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * This macro evaluates the expression only once, making it safe to use with</span></div>
<div class="line"><span class="comment"> * function calls or expressions that may have side effects.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * For pointers:</span></div>
<div class="line"><span class="comment"> * - Returns the default value if the expression evaluates to NULL.</span></div>
<div class="line"><span class="comment"> * - Otherwise, returns the original pointer value.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * For integers and floating-point types:</span></div>
<div class="line"><span class="comment"> * - Returns the default value if the expression evaluates to 0 or any negative value.</span></div>
<div class="line"><span class="comment"> * - Otherwise, returns the original numeric value.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * @param expr The expression to evaluate (typically a libzdb function call)</span></div>
<div class="line"><span class="comment"> * @param default_value The value to return if expr is NULL, 0, or negative</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * @return If expr is not NULL, 0, or negative, returns expr.</span></div>
<div class="line"><span class="comment"> * Otherwise, returns default_value.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * @note This macro uses a GNU C extension and is compatible with GCC and Clang.</span></div>
<div class="line"><span class="comment"> * It may not work with other C compilers.</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * @example</span></div>
<div class="line"><span class="comment"> * // Usage with string (pointer) return type</span></div>
<div class="line"><span class="comment"> * const char* host = valueOr(URL_getHost(url), "localhost");</span></div>
<div class="line"><span class="comment"> * printf("Host: %s\n", host);</span></div>
<div class="line"><span class="comment"> * </span></div>
<div class="line"><span class="comment"> * // Usage with integer return type</span></div>
<div class="line"><span class="comment"> * int port = valueOr(ResultSet_getInt(r, 1), 5432);</span></div>
<div class="line"><span class="comment"> * printf("Port: %d\n", port);</span></div>
<div class="line"><span class="comment"> *</span></div>
<div class="line"><span class="comment"> * // Usage with floating-point return type</span></div>
<div class="line"><span class="comment"> * double percent = valueOr(ResultSet_getDouble(r, 1), 1.0);</span></div>
<div class="line"><span class="comment"> * printf("Percent: %.1f\n", percent);</span></div>
<div class="line"><span class="comment"> */</span></div>
<div class="line"><span class="preprocessor">#define valueOr(expr, default_value) \</span></div>
<div class="line"><span class="preprocessor"> ({ \</span></div>
<div class="line"><span class="preprocessor"> __typeof__(expr) _t = (expr); \</span></div>
<div class="line"><span class="preprocessor"> (_t < 0 || _t == 0) ? (default_value) : _t; \</span></div>
<div class="line"><span class="preprocessor"> })</span></div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#endif </span><span class="comment">/* not __cplusplus */</span><span class="preprocessor"></span></div>
<div class="line"><span class="preprocessor">#endif</span></div>
<div class="ttc" id="aConnectionPool_8h_html"><div class="ttname"><a href="ConnectionPool_8h.html">ConnectionPool.h</a></div><div class="ttdoc">A ConnectionPool represents a database connection pool.</div></div>
<div class="ttc" id="aConnection_8h_html"><div class="ttname"><a href="Connection_8h.html">Connection.h</a></div><div class="ttdoc">A Connection represents a connection to a SQL database system.</div></div>
<div class="ttc" id="aPreparedStatement_8h_html"><div class="ttname"><a href="PreparedStatement_8h.html">PreparedStatement.h</a></div><div class="ttdoc">A PreparedStatement represents a single SQL statement pre-compiled into byte code for later execution...</div></div>
<div class="ttc" id="aResultSet_8h_html"><div class="ttname"><a href="ResultSet_8h.html">ResultSet.h</a></div><div class="ttdoc">A ResultSet represents a database result set.</div></div>
<div class="ttc" id="aSQLException_8h_html"><div class="ttname"><a href="SQLException_8h.html">SQLException.h</a></div><div class="ttdoc">Signals that an SQL specific exception has occurred.</div></div>
<div class="ttc" id="aURL_8h_html"><div class="ttname"><a href="URL_8h.html">URL.h</a></div><div class="ttdoc">URL represents an immutable Uniform Resource Locator.</div></div>
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