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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.sodium-memcmp" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>sodium_memcmp</refname>
<refpurpose>Test for equality in constant-time</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>int</type><methodname>sodium_memcmp</methodname>
<methodparam><modifier role="attribute">#[\SensitiveParameter]</modifier><type>string</type><parameter>string1</parameter></methodparam>
<methodparam><modifier role="attribute">#[\SensitiveParameter]</modifier><type>string</type><parameter>string2</parameter></methodparam>
</methodsynopsis>
<para>
Compare two strings in constant-time.
</para>
<para>
In practice, you almost always want to use <function>hash_equals</function> instead,
since it provides the same logic but returns a <type>bool</type> instead of an
<type>int</type>. However, if you're using the return value of a comparison in a
calculation that's timing-sensitive, and worried about timing leaks with bool-to-int
conversions, <function>sodium_memcmp</function> is an ideal replacement.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<variablelist>
<varlistentry>
<term><parameter>string1</parameter></term>
<listitem>
<para>
String to compare
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>string2</parameter></term>
<listitem>
<para>
Other string to compare
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns <literal>0</literal> if both strings are equal; <literal>-1</literal> otherwise.
</para>
</refsect1>
</refentry>
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