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304N/A>lwres_noop</TITLE
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304N/A><H1
304N/A><A
304N/ANAME="AEN1"
304N/A>lwres_noop</A
304N/A></H1
304N/A><DIV
304N/ACLASS="REFNAMEDIV"
304N/A><A
304N/ANAME="AEN8"
304N/A></A
304N/A><H2
304N/A>Name</H2
304N/A>lwres_nooprequest_render, lwres_noopresponse_render, lwres_nooprequest_parse, lwres_noopresponse_parse, lwres_noopresponse_free, lwres_nooprequest_free&nbsp;--&nbsp;lightweight resolver no-op message handling</DIV
304N/A><DIV
304N/ACLASS="REFSYNOPSISDIV"
304N/A><A
304N/ANAME="AEN16"
304N/A></A
304N/A><H2
304N/A>Synopsis</H2
304N/A><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN17"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include &lt;lwres/lwres.h&gt;</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_nooprequest_render</CODE
>(lwres_context_t *ctx, lwres_nooprequest_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_noopresponse_render</CODE
>(lwres_context_t *ctx, lwres_noopresponse_t *req, lwres_lwpacket_t *pkt, lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_nooprequest_parse</CODE
>(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_nooprequest_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_result_t
lwres_noopresponse_parse</CODE
>(lwres_context_t *ctx, lwres_buffer_t *b, lwres_lwpacket_t *pkt, lwres_noopresponse_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_noopresponse_free</CODE
>(lwres_context_t *ctx, lwres_noopresponse_t **structp);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_nooprequest_free</CODE
>(lwres_context_t *ctx, lwres_nooprequest_t **structp);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN57"
></A
><H2
>DESCRIPTION</H2
><P
>These are low-level routines for creating and parsing
lightweight resolver no-op request and response messages.</P
><P
>The no-op message is analogous to a <B
CLASS="COMMAND"
>ping</B
> packet:
a packet is sent to the resolver daemon and is simply echoed back.
The opcode is intended to allow a client to determine if the server is
operational or not.</P
><P
>There are four main functions for the no-op opcode.
One render function converts a no-op request structure &mdash;
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
> &mdash;
to the lighweight resolver's canonical format.
It is complemented by a parse function that converts a packet in this
canonical format to a no-op request structure.
Another render function converts the no-op response structure &mdash;
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
to the canonical format.
This is complemented by a parse function which converts a packet in
canonical format to a no-op response structure.</P
><P
>These structures are defined in
<TT
CLASS="FILENAME"
>lwres/lwres.h</TT
>.
They are shown below.
<PRE
CLASS="PROGRAMLISTING"
>#define LWRES_OPCODE_NOOP 0x00000000U
typedef struct {
lwres_uint16_t datalength;
unsigned char *data;
} lwres_nooprequest_t;
typedef struct {
lwres_uint16_t datalength;
unsigned char *data;
} lwres_noopresponse_t;</PRE
>
Although the structures have different types, they are identical.
This is because the no-op opcode simply echos whatever data was sent:
the response is therefore identical to the request.</P
><P
><TT
CLASS="FUNCTION"
>lwres_nooprequest_render()</TT
>
uses resolver context
<TT
CLASS="PARAMETER"
><I
>ctx</I
></TT
>
to convert no-op request structure
<TT
CLASS="PARAMETER"
><I
>req</I
></TT
>
to canonical format.
The packet header structure
<TT
CLASS="PARAMETER"
><I
>pkt</I
></TT
>
is initialised and transferred to
buffer
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>.
The contents of
<TT
CLASS="PARAMETER"
><I
>*req</I
></TT
>
are then appended to the buffer in canonical format.
<TT
CLASS="FUNCTION"
>lwres_noopresponse_render()</TT
>
performs the same task, except it converts a no-op response structure
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
to the lightweight resolver's canonical format.</P
><P
><TT
CLASS="FUNCTION"
>lwres_nooprequest_parse()</TT
>
uses context
<TT
CLASS="PARAMETER"
><I
>ctx</I
></TT
>
to convert the contents of packet
<TT
CLASS="PARAMETER"
><I
>pkt</I
></TT
>
to a
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
>
structure.
Buffer
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>
provides space to be used for storing this structure.
When the function succeeds, the resulting
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
>
is made available through
<TT
CLASS="PARAMETER"
><I
>*structp</I
></TT
>.
<TT
CLASS="FUNCTION"
>lwres_noopresponse_parse()</TT
>
offers the same semantics as
<TT
CLASS="FUNCTION"
>lwres_nooprequest_parse()</TT
>
except it yields a
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
structure.</P
><P
><TT
CLASS="FUNCTION"
>lwres_noopresponse_free()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_nooprequest_free()</TT
>
release the memory in resolver context
<TT
CLASS="PARAMETER"
><I
>ctx</I
></TT
>
that was allocated to the
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
or
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
>
structures referenced via
<TT
CLASS="PARAMETER"
><I
>structp</I
></TT
>.&#13;</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN95"
></A
><H2
>RETURN VALUES</H2
><P
>The no-op opcode functions
<TT
CLASS="FUNCTION"
>lwres_nooprequest_render()</TT
>,
<TT
CLASS="FUNCTION"
>lwres_noopresponse_render()</TT
>
<TT
CLASS="FUNCTION"
>lwres_nooprequest_parse()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_noopresponse_parse()</TT
>
all return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_SUCCESS</SPAN
>
on success.
They return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_NOMEMORY</SPAN
>
if memory allocation fails.
<SPAN
CLASS="ERRORCODE"
>LWRES_R_UNEXPECTEDEND</SPAN
>
is returned if the available space in the buffer
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>
is too small to accommodate the packet header or the
<SPAN
CLASS="TYPE"
>lwres_nooprequest_t</SPAN
>
and
<SPAN
CLASS="TYPE"
>lwres_noopresponse_t</SPAN
>
structures.
<TT
CLASS="FUNCTION"
>lwres_nooprequest_parse()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_noopresponse_parse()</TT
>
will return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_UNEXPECTEDEND</SPAN
>
if the buffer is not empty after decoding the received packet.
These functions will return
<SPAN
CLASS="ERRORCODE"
>LWRES_R_FAILURE</SPAN
>
if
<TT
CLASS="CONSTANT"
>pktflags</TT
>
in the packet header structure
<SPAN
CLASS="TYPE"
>lwres_lwpacket_t</SPAN
>
indicate that the packet is not a response to an earlier query.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN114"
></A
><H2
>SEE ALSO</H2
><P
><SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>lwres_packet</SPAN
>(3)</SPAN
></P
></DIV
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>