lwres_context.docbook [plain text]
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<refentry>
<refentryinfo>
<date>Jun 30, 2000</date>
</refentryinfo>
<refmeta>
<refentrytitle>lwres_context</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>BIND9</refmiscinfo>
</refmeta>
<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 <lwres/lwres.h></funcsynopsisinfo>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_context_create</function></funcdef>
<paramdef>lwres_context_t **contextp</paramdef>
<paramdef>void *arg</paramdef>
<paramdef>lwres_malloc_t malloc_function</paramdef>
<paramdef>lwres_free_t free_function</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_result_t
<function>lwres_context_destroy</function></funcdef>
<paramdef>lwres_context_t **contextp</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void
<function>lwres_context_initserial</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>lwres_uint32_t serial</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
lwres_uint32_t
<function>lwres_context_nextserial</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void
<function>lwres_context_freemem</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>void *mem</paramdef>
<paramdef>size_t len</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void
<function>lwres_context_allocmem</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>size_t len</paramdef>
</funcprototype>
<funcprototype>
<funcdef>
void *
<function>lwres_context_sendrecv</function></funcdef>
<paramdef>lwres_context_t *ctx</paramdef>
<paramdef>void *sendbase</paramdef>
<paramdef>int sendlen</paramdef>
<paramdef>void *recvbase</paramdef>
<paramdef>int recvlen</paramdef>
<paramdef>int *recvd_len</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>DESCRIPTION</title>
<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 throught
<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
.Xr malloc 3
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>
— typically a lightweight resolver query packet —
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>
</refsect1>
<refsect1>
<title>RETURN VALUES</title>
<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>
</refsect1>
<refsect1>
<title>SEE ALSO</title>
<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>
</refsect1>
</refentry>