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283 lines
7.8 KiB
Text
283 lines
7.8 KiB
Text
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN">
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<!--
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- Copyright (C) 2001, 2003 Internet Software Consortium.
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-
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- Permission to use, copy, modify, and distribute this software for any
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- purpose with or without fee is hereby granted, provided that the above
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- copyright notice and this permission notice appear in all copies.
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-
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- THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
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- DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
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- IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
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- INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
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- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
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- FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
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- NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
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- WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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-->
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<!-- $Id: lwres_context.docbook,v 1.3.2.2 2003/07/22 04:03:54 marka Exp $ -->
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<refentry>
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<refentryinfo>
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<date>Jun 30, 2000</date>
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</refentryinfo>
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<refmeta>
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<refentrytitle>lwres_context</refentrytitle>
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<manvolnum>3</manvolnum>
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<refmiscinfo>BIND9</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>lwres_context_create</refname>
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<refname>lwres_context_destroy</refname>
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<refname>lwres_context_nextserial</refname>
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<refname>lwres_context_initserial</refname>
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<refname>lwres_context_freemem</refname>
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<refname>lwres_context_allocmem</refname>
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<refname>lwres_context_sendrecv</refname>
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<refpurpose>lightweight resolver context management</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <lwres/lwres.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>
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lwres_result_t
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<function>lwres_context_create</function></funcdef>
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<paramdef>lwres_context_t **contextp</paramdef>
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<paramdef>void *arg</paramdef>
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<paramdef>lwres_malloc_t malloc_function</paramdef>
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<paramdef>lwres_free_t free_function</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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lwres_result_t
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<function>lwres_context_destroy</function></funcdef>
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<paramdef>lwres_context_t **contextp</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void
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<function>lwres_context_initserial</function></funcdef>
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<paramdef>lwres_context_t *ctx</paramdef>
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<paramdef>lwres_uint32_t serial</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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lwres_uint32_t
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<function>lwres_context_nextserial</function></funcdef>
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<paramdef>lwres_context_t *ctx</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void
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<function>lwres_context_freemem</function></funcdef>
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<paramdef>lwres_context_t *ctx</paramdef>
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<paramdef>void *mem</paramdef>
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<paramdef>size_t len</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void
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<function>lwres_context_allocmem</function></funcdef>
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<paramdef>lwres_context_t *ctx</paramdef>
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<paramdef>size_t len</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void *
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<function>lwres_context_sendrecv</function></funcdef>
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<paramdef>lwres_context_t *ctx</paramdef>
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<paramdef>void *sendbase</paramdef>
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<paramdef>int sendlen</paramdef>
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<paramdef>void *recvbase</paramdef>
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<paramdef>int recvlen</paramdef>
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<paramdef>int *recvd_len</paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>DESCRIPTION</title>
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<para>
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<function>lwres_context_create()</function>
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creates a
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<type>lwres_context_t</type>
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structure for use in lightweight resolver operations.
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It holds a socket and other data needed for communicating
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with a resolver daemon.
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The new
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<type>lwres_context_t</type>
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is returned through
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<parameter>contextp</parameter>,
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a pointer to a
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<type>lwres_context_t</type>
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pointer. This
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<type>lwres_context_t</type>
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pointer must initially be NULL, and is modified
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to point to the newly created
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<type>lwres_context_t</type>.
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</para>
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<para>
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When the lightweight resolver needs to perform dynamic memory
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allocation, it will call
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<parameter>malloc_function</parameter>
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to allocate memory and
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<parameter>free_function</parameter>
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to free it. If
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<parameter>malloc_function</parameter>
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and
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<parameter>free_function</parameter>
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are NULL, memory is allocated using
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.Xr malloc 3
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and
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<citerefentry>
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<refentrytitle>free</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>.
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It is not permitted to have a NULL
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<parameter>malloc_function</parameter>
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and a non-NULL
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<parameter>free_function</parameter>
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or vice versa.
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<parameter>arg</parameter>
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is passed as the first parameter to the memory
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allocation functions.
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If
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<parameter>malloc_function</parameter>
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and
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<parameter>free_function</parameter>
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are NULL,
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<parameter>arg</parameter>
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is unused and should be passed as NULL.
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</para>
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<para>
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Once memory for the structure has been allocated,
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it is initialized using
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<citerefentry>
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<refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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and returned via
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<parameter>*contextp</parameter>.
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</para>
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<para>
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<function>lwres_context_destroy()</function>
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destroys a
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<type>lwres_context_t</type>,
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closing its socket.
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<parameter>contextp</parameter>
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is a pointer to a pointer to the context that is to be destroyed.
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The pointer will be set to NULL when the context has been destroyed.
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</para>
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<para>
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The context holds a serial number that is used to identify resolver
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request packets and associate responses with the corresponding requests.
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This serial number is controlled using
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<function>lwres_context_initserial()</function>
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and
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<function>lwres_context_nextserial()</function>.
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<function>lwres_context_initserial()</function>
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sets the serial number for context
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<parameter>*ctx</parameter>
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to
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<parameter>serial</parameter>.
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<function>lwres_context_nextserial()</function>
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increments the serial number and returns the previous value.
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</para>
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<para>
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Memory for a lightweight resolver context is allocated and freed using
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<function>lwres_context_allocmem()</function>
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and
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<function>lwres_context_freemem()</function>.
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These use whatever allocations were defined when the context was
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created with
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<function>lwres_context_create()</function>.
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<function>lwres_context_allocmem()</function>
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allocates
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<parameter>len</parameter>
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bytes of memory and if successful returns a pointer to the allocated
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storage.
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<function>lwres_context_freemem()</function>
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frees
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<parameter>len</parameter>
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bytes of space starting at location
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<parameter>mem</parameter>.
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</para>
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<para>
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<function>lwres_context_sendrecv()</function>
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performs I/O for the context
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<parameter>ctx</parameter>.
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Data are read and written from the context's socket.
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It writes data from
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<parameter>sendbase</parameter>
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— typically a lightweight resolver query packet —
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and waits for a reply which is copied to the receive buffer at
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<parameter>recvbase</parameter>.
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The number of bytes that were written to this receive buffer is
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returned in
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<parameter>*recvd_len</parameter>.
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</para>
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</refsect1>
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<refsect1>
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<title>RETURN VALUES</title>
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<para>
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<function>lwres_context_create()</function>
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returns
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<errorcode>LWRES_R_NOMEMORY</errorcode>
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if memory for the
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<type>struct lwres_context</type>
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could not be allocated,
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<errorcode>LWRES_R_SUCCESS</errorcode>
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otherwise.
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</para>
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<para>
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Successful calls to the memory allocator
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<function>lwres_context_allocmem()</function>
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return a pointer to the start of the allocated space.
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It returns NULL if memory could not be allocated.
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</para>
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<para>
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<errorcode>LWRES_R_SUCCESS</errorcode>
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is returned when
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<function>lwres_context_sendrecv()</function>
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completes successfully.
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<errorcode>LWRES_R_IOERROR</errorcode>
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is returned if an I/O error occurs and
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<errorcode>LWRES_R_TIMEOUT</errorcode>
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is returned if
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<function>lwres_context_sendrecv()</function>
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times out waiting for a response.
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</para>
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</refsect1>
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<refsect1>
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<title>SEE ALSO</title>
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<para>
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<citerefentry>
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<refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>free</refentrytitle><manvolnum>3
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</manvolnum>
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</citerefentry>.
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</para>
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</refsect1>
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</refentry>
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