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<title>lwres_context</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
<a name="id2482688"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>lwres_context_create, lwres_context_destroy, lwres_context_nextserial, lwres_context_initserial, lwres_context_freemem, lwres_context_allocmem, lwres_context_sendrecv — lightweight resolver context management</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="funcsynopsis">
<pre class="funcsynopsisinfo">#include <lwres/lwres.h></pre>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_context_create</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_context_destroy</b>(</code></td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_context_initserial</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_uint32_t
<b class="fsfunc">lwres_context_nextserial</b>(</code></td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_context_freemem</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_context_allocmem</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
<tr>
<td><code class="funcdef">
void *
<b class="fsfunc">lwres_context_sendrecv</b>(</code></td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>, </td>
</tr>
<tr>
<td> </td>
<td> </td>
<td>
<code>)</code>;</td>
</tr>
</table>
</div>
</div>
<div class="refsect1" lang="en">
<a name="id2549540"></a><h2>DESCRIPTION</h2>
<p>
<code class="function">lwres_context_create()</code>
creates a
<span class="type">lwres_context_t</span>
structure for use in lightweight resolver operations.
It holds a socket and other data needed for communicating
with a resolver daemon.
The new
<span class="type">lwres_context_t</span>
is returned through
<em class="parameter"><code>contextp</code></em>,
a pointer to a
<span class="type">lwres_context_t</span>
pointer. This
<span class="type">lwres_context_t</span>
pointer must initially be NULL, and is modified
to point to the newly created
<span class="type">lwres_context_t</span>.
</p>
<p>
When the lightweight resolver needs to perform dynamic memory
allocation, it will call
<em class="parameter"><code>malloc_function</code></em>
to allocate memory and
<em class="parameter"><code>free_function</code></em>
to free it. If
<em class="parameter"><code>malloc_function</code></em>
and
<em class="parameter"><code>free_function</code></em>
are NULL, memory is allocated using
.Xr malloc 3
and
<span class="citerefentry"><span class="refentrytitle">free</span>(3)</span>.
It is not permitted to have a NULL
<em class="parameter"><code>malloc_function</code></em>
and a non-NULL
<em class="parameter"><code>free_function</code></em>
or vice versa.
<em class="parameter"><code>arg</code></em>
is passed as the first parameter to the memory
allocation functions.
If
<em class="parameter"><code>malloc_function</code></em>
and
<em class="parameter"><code>free_function</code></em>
are NULL,
<em class="parameter"><code>arg</code></em>
is unused and should be passed as NULL.
</p>
<p>
Once memory for the structure has been allocated,
it is initialized using
<span class="citerefentry"><span class="refentrytitle">lwres_conf_init</span>(3)</span>
and returned via
<em class="parameter"><code>*contextp</code></em>.
</p>
<p>
<code class="function">lwres_context_destroy()</code>
destroys a
<span class="type">lwres_context_t</span>,
closing its socket.
<em class="parameter"><code>contextp</code></em>
is a pointer to a pointer to the context that is to be destroyed.
The pointer will be set to NULL when the context has been destroyed.
</p>
<p>
The context holds a serial number that is used to identify resolver
request packets and associate responses with the corresponding requests.
This serial number is controlled using
<code class="function">lwres_context_initserial()</code>
and
<code class="function">lwres_context_nextserial()</code>.
<code class="function">lwres_context_initserial()</code>
sets the serial number for context
<em class="parameter"><code>*ctx</code></em>
to
<em class="parameter"><code>serial</code></em>.
<code class="function">lwres_context_nextserial()</code>
increments the serial number and returns the previous value.
</p>
<p>
Memory for a lightweight resolver context is allocated and freed using
<code class="function">lwres_context_allocmem()</code>
and
<code class="function">lwres_context_freemem()</code>.
These use whatever allocations were defined when the context was
created with
<code class="function">lwres_context_create()</code>.
<code class="function">lwres_context_allocmem()</code>
allocates
<em class="parameter"><code>len</code></em>
bytes of memory and if successful returns a pointer to the allocated
storage.
<code class="function">lwres_context_freemem()</code>
frees
<em class="parameter"><code>len</code></em>
bytes of space starting at location
<em class="parameter"><code>mem</code></em>.
</p>
<p>
<code class="function">lwres_context_sendrecv()</code>
performs I/O for the context
<em class="parameter"><code>ctx</code></em>.
Data are read and written from the context's socket.
It writes data from
<em class="parameter"><code>sendbase</code></em>
— typically a lightweight resolver query packet —
and waits for a reply which is copied to the receive buffer at
<em class="parameter"><code>recvbase</code></em>.
The number of bytes that were written to this receive buffer is
returned in
<em class="parameter"><code>*recvd_len</code></em>.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2549789"></a><h2>RETURN VALUES</h2>
<p>
<code class="function">lwres_context_create()</code>
returns
<span class="errorcode">LWRES_R_NOMEMORY</span>
if memory for the
<span class="type">struct lwres_context</span>
could not be allocated,
<span class="errorcode">LWRES_R_SUCCESS</span>
otherwise.
</p>
<p>
Successful calls to the memory allocator
<code class="function">lwres_context_allocmem()</code>
return a pointer to the start of the allocated space.
It returns NULL if memory could not be allocated.
</p>
<p>
<span class="errorcode">LWRES_R_SUCCESS</span>
is returned when
<code class="function">lwres_context_sendrecv()</code>
completes successfully.
<span class="errorcode">LWRES_R_IOERROR</span>
is returned if an I/O error occurs and
<span class="errorcode">LWRES_R_TIMEOUT</span>
is returned if
<code class="function">lwres_context_sendrecv()</code>
times out waiting for a response.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2549841"></a><h2>SEE ALSO</h2>
<p>
<span class="citerefentry"><span class="refentrytitle">lwres_conf_init</span>(3)</span>,
<span class="citerefentry"><span class="refentrytitle">malloc</span>(3)</span>,
<span class="citerefentry"><span class="refentrytitle">free</span>(3
)</span>.
</p>
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