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415 lines
7.2 KiB
HTML
415 lines
7.2 KiB
HTML
<!--
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- Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC")
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- Copyright (C) 2001 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 ISC DISCLAIMS ALL WARRANTIES WITH
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- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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- AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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- OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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- PERFORMANCE OF THIS SOFTWARE.
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-->
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<!-- $Id: lwres_resutil.html,v 1.8.2.1.4.1 2004/03/06 08:15:42 marka Exp $ -->
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<HTML
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><HEAD
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><TITLE
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>lwres_resutil</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.73
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"></HEAD
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><BODY
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CLASS="REFENTRY"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><H1
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><A
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NAME="AEN1"
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>lwres_resutil</A
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></H1
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><DIV
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CLASS="REFNAMEDIV"
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><A
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NAME="AEN8"
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></A
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><H2
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>Name</H2
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>lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr -- lightweight resolver utility functions</DIV
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><DIV
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CLASS="REFSYNOPSISDIV"
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><A
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NAME="AEN14"
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></A
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><H2
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>Synopsis</H2
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><DIV
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CLASS="FUNCSYNOPSIS"
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><A
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NAME="AEN15"
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></A
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><P
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></P
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><PRE
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CLASS="FUNCSYNOPSISINFO"
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>#include <lwres/lwres.h></PRE
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><P
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><CODE
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><CODE
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CLASS="FUNCDEF"
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>lwres_result_t
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lwres_string_parse</CODE
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>(lwres_buffer_t *b, char **c, lwres_uint16_t *len);</CODE
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></P
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><P
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><CODE
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><CODE
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CLASS="FUNCDEF"
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>lwres_result_t
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lwres_addr_parse</CODE
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>(lwres_buffer_t *b, lwres_addr_t *addr);</CODE
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></P
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><P
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><CODE
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><CODE
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CLASS="FUNCDEF"
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>lwres_result_t
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lwres_getaddrsbyname</CODE
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>(lwres_context_t *ctx, const char *name, lwres_uint32_t addrtypes, lwres_gabnresponse_t **structp);</CODE
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></P
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><P
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><CODE
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><CODE
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CLASS="FUNCDEF"
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>lwres_result_t
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lwres_getnamebyaddr</CODE
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>(lwres_context_t *ctx, lwres_uint32_t addrtype, lwres_uint16_t addrlen, const unsigned char *addr, lwres_gnbaresponse_t **structp);</CODE
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></P
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><P
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></P
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></DIV
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN43"
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></A
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><H2
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>DESCRIPTION</H2
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><P
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><TT
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CLASS="FUNCTION"
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>lwres_string_parse()</TT
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> retrieves a DNS-encoded
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string starting the current pointer of lightweight resolver buffer
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<TT
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CLASS="PARAMETER"
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><I
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>b</I
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></TT
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>: i.e. <TT
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CLASS="CONSTANT"
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>b->current</TT
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>.
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When the function returns, the address of the first byte of the
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encoded string is returned via <TT
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CLASS="PARAMETER"
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><I
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>*c</I
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></TT
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> and the
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length of that string is given by <TT
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CLASS="PARAMETER"
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><I
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>*len</I
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></TT
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>. The
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buffer's current pointer is advanced to point at the character
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following the string length, the encoded string, and the trailing
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<SPAN
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CLASS="TYPE"
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>NULL</SPAN
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> character.</P
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><P
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><TT
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CLASS="FUNCTION"
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>lwres_addr_parse()</TT
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> extracts an address from the
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buffer <TT
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CLASS="PARAMETER"
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><I
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>b</I
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></TT
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>. The buffer's current pointer
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<TT
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CLASS="CONSTANT"
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>b->current</TT
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> is presumed to point at an encoded
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address: the address preceded by a 32-bit protocol family identifier
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and a 16-bit length field. The encoded address is copied to
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<TT
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CLASS="CONSTANT"
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>addr->address</TT
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> and
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<TT
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CLASS="CONSTANT"
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>addr->length</TT
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> indicates the size in bytes of
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the address that was copied. <TT
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CLASS="CONSTANT"
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>b->current</TT
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> is
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advanced to point at the next byte of available data in the buffer
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following the encoded address.</P
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><P
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><TT
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CLASS="FUNCTION"
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>lwres_getaddrsbyname()</TT
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>
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and
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<TT
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CLASS="FUNCTION"
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>lwres_getnamebyaddr()</TT
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>
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use the
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<SPAN
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CLASS="TYPE"
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>lwres_gnbaresponse_t</SPAN
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>
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structure defined below:
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<PRE
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CLASS="PROGRAMLISTING"
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>typedef struct {
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lwres_uint32_t flags;
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lwres_uint16_t naliases;
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lwres_uint16_t naddrs;
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char *realname;
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char **aliases;
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lwres_uint16_t realnamelen;
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lwres_uint16_t *aliaslen;
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lwres_addrlist_t addrs;
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void *base;
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size_t baselen;
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} lwres_gabnresponse_t;</PRE
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>
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The contents of this structure are not manipulated directly but
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they are controlled through the
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<SPAN
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CLASS="CITEREFENTRY"
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><SPAN
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CLASS="REFENTRYTITLE"
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>lwres_gabn</SPAN
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>(3)</SPAN
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>
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functions.</P
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><P
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>The lightweight resolver uses
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<TT
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CLASS="FUNCTION"
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>lwres_getaddrsbyname()</TT
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> to perform foward lookups.
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Hostname <TT
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CLASS="PARAMETER"
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><I
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>name</I
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></TT
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> is looked up using the resolver
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context <TT
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CLASS="PARAMETER"
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><I
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>ctx</I
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></TT
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> for memory allocation.
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<TT
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CLASS="PARAMETER"
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><I
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>addrtypes</I
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></TT
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> is a bitmask indicating which type of
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addresses are to be looked up. Current values for this bitmask are
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<SPAN
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CLASS="TYPE"
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>LWRES_ADDRTYPE_V4</SPAN
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> for IPv4 addresses and
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<SPAN
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CLASS="TYPE"
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>LWRES_ADDRTYPE_V6</SPAN
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> for IPv6 addresses. Results of the
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lookup are returned in <TT
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CLASS="PARAMETER"
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><I
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>*structp</I
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></TT
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>.</P
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><P
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><TT
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CLASS="FUNCTION"
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>lwres_getnamebyaddr()</TT
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> performs reverse lookups.
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Resolver context <TT
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CLASS="PARAMETER"
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><I
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>ctx</I
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></TT
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> is used for memory
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allocation. The address type is indicated by
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<TT
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CLASS="PARAMETER"
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><I
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>addrtype</I
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></TT
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>: <SPAN
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CLASS="TYPE"
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>LWRES_ADDRTYPE_V4</SPAN
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> or
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<SPAN
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CLASS="TYPE"
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>LWRES_ADDRTYPE_V6</SPAN
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>. The address to be looked up is given
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by <TT
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CLASS="PARAMETER"
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><I
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>addr</I
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></TT
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> and its length is
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<TT
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CLASS="PARAMETER"
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><I
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>addrlen</I
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></TT
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> bytes. The result of the function call
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is made available through <TT
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CLASS="PARAMETER"
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><I
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>*structp</I
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></TT
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>.</P
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN84"
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></A
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><H2
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>RETURN VALUES</H2
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><P
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>Successful calls to
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<TT
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CLASS="FUNCTION"
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>lwres_string_parse()</TT
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>
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and
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<TT
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CLASS="FUNCTION"
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>lwres_addr_parse()</TT
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>
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return
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<SPAN
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CLASS="ERRORCODE"
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>LWRES_R_SUCCESS.</SPAN
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>
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Both functions return
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<SPAN
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CLASS="ERRORCODE"
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>LWRES_R_FAILURE</SPAN
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>
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if the buffer is corrupt or
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<SPAN
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CLASS="ERRORCODE"
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>LWRES_R_UNEXPECTEDEND</SPAN
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>
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if the buffer has less space than expected for the components of the
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encoded string or address.</P
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><P
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><TT
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CLASS="FUNCTION"
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>lwres_getaddrsbyname()</TT
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>
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returns
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<SPAN
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CLASS="ERRORCODE"
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>LWRES_R_SUCCESS</SPAN
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>
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on success and it returns
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<SPAN
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CLASS="ERRORCODE"
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>LWRES_R_NOTFOUND</SPAN
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>
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if the hostname
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<TT
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CLASS="PARAMETER"
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><I
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>name</I
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></TT
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>
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could not be found.</P
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><P
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><SPAN
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CLASS="ERRORCODE"
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>LWRES_R_SUCCESS</SPAN
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>
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is returned by a successful call to
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<TT
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CLASS="FUNCTION"
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>lwres_getnamebyaddr()</TT
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>.</P
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><P
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>Both
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<TT
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CLASS="FUNCTION"
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>lwres_getaddrsbyname()</TT
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>
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and
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<TT
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CLASS="FUNCTION"
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>lwres_getnamebyaddr()</TT
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>
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return
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<SPAN
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CLASS="ERRORCODE"
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>LWRES_R_NOMEMORY</SPAN
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>
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when memory allocation requests fail and
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<SPAN
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CLASS="ERRORCODE"
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>LWRES_R_UNEXPECTEDEND</SPAN
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>
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if the buffers used for sending queries and receiving replies are too
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small.</P
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN105"
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></A
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><H2
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>SEE ALSO</H2
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><P
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><SPAN
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CLASS="CITEREFENTRY"
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><SPAN
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CLASS="REFENTRYTITLE"
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>lwres_buffer</SPAN
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>(3)</SPAN
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>,
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<SPAN
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CLASS="CITEREFENTRY"
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><SPAN
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CLASS="REFENTRYTITLE"
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>lwres_gabn</SPAN
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>(3)</SPAN
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>.</P
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></DIV
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></BODY
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></HTML
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>
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