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<html><head><meta charset="ISO-8859-1"><title>3.Nibble Memory</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot"><link rel="home" href="index.html" title="YAZ User's Guide and Reference"><link rel="up" href="tools.html" title="Chapter7.Supporting Tools"><link rel="prev" href="tools.oid.html" title="2.Object Identifiers"><link rel="next" href="tools.log.html" title="4.Log"></head><body><link rel="stylesheet" type="text/css" href="common/style1.css"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">3.Nibble Memory</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="tools.oid.html">Prev</a></td><th width="60%" align="center">Chapter7.Supporting Tools</th><td width="20%" align="right"><a accesskey="n" href="tools.log.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="tools.nmem"></a>3.Nibble Memory</h2></div></div></div><p>
Sometimes when you need to allocate and construct a large,
interconnected complex of structures, it can be a bit of a pain to
release the associated memory again. For the structures describing the
Z39.50 PDUs and related structures, it is convenient to use the
memory-management system of the <acronym class="acronym">ODR</acronym> subsystem (see
<a class="xref" href="odr.use.html" title="2.Using ODR">Section2, “Using ODR”</a>). However, in some circumstances
where you might otherwise benefit from using a simple nibble-memory
management system, it may be impractical to use
<code class="function">odr_malloc()</code> and <code class="function">odr_reset()</code>.
For this purpose, the memory manager which also supports the <acronym class="acronym">ODR</acronym>
streams is made available in the NMEM module. The external interface
to this module is given in the <code class="filename">nmem.h</code> file.
</p><p>
The following prototypes are given:
</p><pre class="screen">
NMEM nmem_create(void);
void nmem_destroy(NMEM n);
void *nmem_malloc(NMEM n, size_t size);
void nmem_reset(NMEM n);
size_t nmem_total(NMEM n);
void nmem_init(void);
void nmem_exit(void);
</pre><p>
The <code class="function">nmem_create()</code> function returns a pointer to a
memory control handle, which can be released again by
<code class="function">nmem_destroy()</code> when no longer needed.
The function <code class="function">nmem_malloc()</code> allocates a block of
memory of the requested size. A call to <code class="function">nmem_reset()</code>
or <code class="function">nmem_destroy()</code> will release all memory allocated
on the handle since it was created (or since the last call to
<code class="function">nmem_reset()</code>. The function
<code class="function">nmem_total()</code> returns the number of bytes currently
allocated on the handle.
</p><p>
The nibble-memory pool is shared amongst threads. POSIX
mutexes and WIN32 Critical sections are introduced to keep the
module thread safe. Function <code class="function">nmem_init()</code>
initializes the nibble-memory library and it is called automatically
the first time the <code class="literal">YAZ.DLL</code> is loaded. YAZ uses
function <code class="function">DllMain</code> to achieve this. You should
<span class="emphasis"><em>not</em></span> call <code class="function">nmem_init</code> or
<code class="function">nmem_exit</code> unless you're absolute sure what
you're doing. Note that in previous YAZ versions you'd have to call
<code class="function">nmem_init</code> yourself.
</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="tools.oid.html">Prev</a></td><td width="20%" align="center"><a accesskey="u" href="tools.html">Up</a></td><td width="40%" align="right"><a accesskey="n" href="tools.log.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">2.Object Identifiers</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">4.Log</td></tr></table></div></body></html>
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