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+<!DOCTYPE book [
+<!ENTITY mdash "&#8212;">]>
+<!--
+ - Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ -
+ - This Source Code Form is subject to the terms of the Mozilla Public
+ - License, v. 2.0. If a copy of the MPL was not distributed with this
+ - file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ -
+ - See the COPYRIGHT file distributed with this work for additional
+ - information regarding copyright ownership.
+-->
+
+<!-- Converted by db4-upgrade version 1.0 -->
+<refentry xmlns:db="http://docbook.org/ns/docbook" version="5.0">
+ <info>
+ <date>2007-06-18</date>
+ </info>
+ <refentryinfo>
+ <corpname>ISC</corpname>
+ <corpauthor>Internet Systems Consortium, Inc.</corpauthor>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>lwres_context</refentrytitle>
+ <manvolnum>3</manvolnum>
+ <refmiscinfo>BIND9</refmiscinfo>
+ </refmeta>
+
+ <docinfo>
+ <copyright>
+ <year>2000</year>
+ <year>2001</year>
+ <year>2003</year>
+ <year>2004</year>
+ <year>2005</year>
+ <year>2007</year>
+ <year>2014</year>
+ <year>2015</year>
+ <year>2016</year>
+ <year>2018</year>
+ <year>2019</year>
+ <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
+ </copyright>
+ </docinfo>
+
+ <refnamediv>
+ <refname>lwres_context_create</refname>
+ <refname>lwres_context_destroy</refname>
+ <refname>lwres_context_nextserial</refname>
+ <refname>lwres_context_initserial</refname>
+ <refname>lwres_context_freemem</refname>
+ <refname>lwres_context_allocmem</refname>
+ <refname>lwres_context_sendrecv</refname>
+ <refpurpose>lightweight resolver context management</refpurpose>
+ </refnamediv>
+ <refsynopsisdiv>
+ <funcsynopsis>
+<funcsynopsisinfo>#include &lt;lwres/lwres.h&gt;</funcsynopsisinfo>
+<funcprototype>
+ <funcdef>
+lwres_result_t
+<function>lwres_context_create</function></funcdef>
+ <paramdef>lwres_context_t **<parameter>contextp</parameter></paramdef>
+ <paramdef>void *<parameter>arg</parameter></paramdef>
+ <paramdef>lwres_malloc_t <parameter>malloc_function</parameter></paramdef>
+ <paramdef>lwres_free_t <parameter>free_function</parameter></paramdef>
+ </funcprototype>
+<funcprototype>
+ <funcdef>
+lwres_result_t
+<function>lwres_context_destroy</function></funcdef>
+ <paramdef>lwres_context_t **<parameter>contextp</parameter></paramdef>
+ </funcprototype>
+<funcprototype>
+ <funcdef>
+void
+<function>lwres_context_initserial</function></funcdef>
+ <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
+ <paramdef>uint32_t <parameter>serial</parameter></paramdef>
+ </funcprototype>
+<funcprototype>
+ <funcdef>
+uint32_t
+<function>lwres_context_nextserial</function></funcdef>
+ <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
+ </funcprototype>
+<funcprototype>
+ <funcdef>
+void
+<function>lwres_context_freemem</function></funcdef>
+ <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
+ <paramdef>void *<parameter>mem</parameter></paramdef>
+ <paramdef>size_t <parameter>len</parameter></paramdef>
+ </funcprototype>
+<funcprototype>
+ <funcdef>
+void
+<function>lwres_context_allocmem</function></funcdef>
+ <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
+ <paramdef>size_t <parameter>len</parameter></paramdef>
+ </funcprototype>
+<funcprototype>
+ <funcdef>
+void *
+<function>lwres_context_sendrecv</function></funcdef>
+ <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
+ <paramdef>void *<parameter>sendbase</parameter></paramdef>
+ <paramdef>int <parameter>sendlen</parameter></paramdef>
+ <paramdef>void *<parameter>recvbase</parameter></paramdef>
+ <paramdef>int <parameter>recvlen</parameter></paramdef>
+ <paramdef>int *<parameter>recvd_len</parameter></paramdef>
+ </funcprototype>
+</funcsynopsis>
+ </refsynopsisdiv>
+ <refsection><info><title>DESCRIPTION</title></info>
+
+
+ <para><function>lwres_context_create()</function>
+ creates a <type>lwres_context_t</type> structure for use in
+ lightweight resolver operations. It holds a socket and other
+ data needed for communicating with a resolver daemon. The new
+ <type>lwres_context_t</type> is returned through
+ <parameter>contextp</parameter>, a pointer to a
+ <type>lwres_context_t</type> pointer. This
+ <type>lwres_context_t</type> pointer must initially be NULL, and
+ is modified to point to the newly created
+ <type>lwres_context_t</type>.
+ </para>
+ <para>
+ When the lightweight resolver needs to perform dynamic memory
+ allocation, it will call
+ <parameter>malloc_function</parameter>
+ to allocate memory and
+ <parameter>free_function</parameter>
+ to free it. If
+ <parameter>malloc_function</parameter>
+ and
+ <parameter>free_function</parameter>
+ are NULL, memory is allocated using
+ <citerefentry>
+ <refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum>
+ </citerefentry>.
+ and
+ <citerefentry>
+ <refentrytitle>free</refentrytitle><manvolnum>3</manvolnum>
+ </citerefentry>.
+
+ It is not permitted to have a NULL
+ <parameter>malloc_function</parameter> and a non-NULL
+ <parameter>free_function</parameter> or vice versa.
+ <parameter>arg</parameter> is passed as the first parameter to
+ the memory allocation functions. If
+ <parameter>malloc_function</parameter> and
+ <parameter>free_function</parameter> are NULL,
+ <parameter>arg</parameter> is unused and should be passed as
+ NULL.
+ </para>
+
+ <para>
+ Once memory for the structure has been allocated,
+ it is initialized using
+ <citerefentry>
+ <refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>
+ </citerefentry>
+ and returned via <parameter>*contextp</parameter>.
+ </para>
+
+ <para><function>lwres_context_destroy()</function>
+ destroys a <type>lwres_context_t</type>, closing its socket.
+ <parameter>contextp</parameter> 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.
+ </para>
+
+ <para>
+ 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
+ <function>lwres_context_initserial()</function> and
+ <function>lwres_context_nextserial()</function>.
+ <function>lwres_context_initserial()</function> sets the serial
+ number for context <parameter>*ctx</parameter> to
+ <parameter>serial</parameter>.
+ <function>lwres_context_nextserial()</function> increments the
+ serial number and returns the previous value.
+ </para>
+
+ <para>
+ Memory for a lightweight resolver context is allocated and freed
+ using <function>lwres_context_allocmem()</function> and
+ <function>lwres_context_freemem()</function>. These use
+ whatever allocations were defined when the context was created
+ with <function>lwres_context_create()</function>.
+ <function>lwres_context_allocmem()</function> allocates
+ <parameter>len</parameter> bytes of memory and if successful
+ returns a pointer to the allocated storage.
+ <function>lwres_context_freemem()</function> frees
+ <parameter>len</parameter> bytes of space starting at location
+ <parameter>mem</parameter>.
+ </para>
+
+ <para><function>lwres_context_sendrecv()</function>
+ performs I/O for the context <parameter>ctx</parameter>. Data
+ are read and written from the context's socket. It writes data
+ from <parameter>sendbase</parameter> &mdash; typically a
+ lightweight resolver query packet &mdash; and waits for a reply
+ which is copied to the receive buffer at
+ <parameter>recvbase</parameter>. The number of bytes that were
+ written to this receive buffer is returned in
+ <parameter>*recvd_len</parameter>.
+ </para>
+ </refsection>
+
+ <refsection><info><title>RETURN VALUES</title></info>
+
+
+ <para><function>lwres_context_create()</function>
+ returns <errorcode>LWRES_R_NOMEMORY</errorcode> if memory for
+ the <type>struct lwres_context</type> could not be allocated,
+ <errorcode>LWRES_R_SUCCESS</errorcode> otherwise.
+ </para>
+ <para>
+ Successful calls to the memory allocator
+ <function>lwres_context_allocmem()</function>
+ return a pointer to the start of the allocated space.
+ It returns NULL if memory could not be allocated.
+ </para>
+ <para><errorcode>LWRES_R_SUCCESS</errorcode>
+ is returned when
+ <function>lwres_context_sendrecv()</function>
+ completes successfully.
+ <errorcode>LWRES_R_IOERROR</errorcode>
+ is returned if an I/O error occurs and
+ <errorcode>LWRES_R_TIMEOUT</errorcode>
+ is returned if
+ <function>lwres_context_sendrecv()</function>
+ times out waiting for a response.
+ </para>
+ </refsection>
+ <refsection><info><title>SEE ALSO</title></info>
+
+ <para><citerefentry>
+ <refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>
+ </citerefentry>,
+
+ <citerefentry>
+ <refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum>
+ </citerefentry>,
+
+ <citerefentry>
+ <refentrytitle>free</refentrytitle><manvolnum>3</manvolnum>
+ </citerefentry>.
+ </para>
+ </refsection>
+</refentry>