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24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
25 <a name="id2476275"></a><div class="titlepage"></div>
26 <div class="refnamediv">
28 <p>lwres_context_create, lwres_context_destroy, lwres_context_nextserial, lwres_context_initserial, lwres_context_freemem, lwres_context_allocmem, lwres_context_sendrecv — lightweight resolver context management</p>
30 <div class="refsynopsisdiv">
32 <div class="funcsynopsis">
33 <pre class="funcsynopsisinfo">#include <lwres/lwres.h></pre>
34 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
36 <td><code class="funcdef">
38 <b class="fsfunc">lwres_context_create</b>(</code></td>
39 <td>lwres_context_t ** </td>
41 <var class="pdparam">contextp</var>, </td>
47 <var class="pdparam">arg</var>, </td>
51 <td>lwres_malloc_t </td>
53 <var class="pdparam">malloc_function</var>, </td>
57 <td>lwres_free_t </td>
59 <var class="pdparam">free_function</var><code>)</code>;</td>
62 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
63 <td><code class="funcdef">
65 <b class="fsfunc">lwres_context_destroy</b>(</code></td>
66 <td>lwres_context_t ** </td>
68 <var class="pdparam">contextp</var><code>)</code>;</td>
70 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
72 <td><code class="funcdef">
74 <b class="fsfunc">lwres_context_initserial</b>(</code></td>
75 <td>lwres_context_t * </td>
77 <var class="pdparam">ctx</var>, </td>
81 <td>lwres_uint32_t </td>
83 <var class="pdparam">serial</var><code>)</code>;</td>
86 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
87 <td><code class="funcdef">
89 <b class="fsfunc">lwres_context_nextserial</b>(</code></td>
90 <td>lwres_context_t * </td>
92 <var class="pdparam">ctx</var><code>)</code>;</td>
94 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
96 <td><code class="funcdef">
98 <b class="fsfunc">lwres_context_freemem</b>(</code></td>
99 <td>lwres_context_t * </td>
101 <var class="pdparam">ctx</var>, </td>
107 <var class="pdparam">mem</var>, </td>
113 <var class="pdparam">len</var><code>)</code>;</td>
116 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
118 <td><code class="funcdef">
120 <b class="fsfunc">lwres_context_allocmem</b>(</code></td>
121 <td>lwres_context_t * </td>
123 <var class="pdparam">ctx</var>, </td>
129 <var class="pdparam">len</var><code>)</code>;</td>
132 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
134 <td><code class="funcdef">
136 <b class="fsfunc">lwres_context_sendrecv</b>(</code></td>
137 <td>lwres_context_t * </td>
139 <var class="pdparam">ctx</var>, </td>
145 <var class="pdparam">sendbase</var>, </td>
151 <var class="pdparam">sendlen</var>, </td>
157 <var class="pdparam">recvbase</var>, </td>
163 <var class="pdparam">recvlen</var>, </td>
169 <var class="pdparam">recvd_len</var><code>)</code>;</td>
174 <div class="refsect1" lang="en">
175 <a name="id2543531"></a><h2>DESCRIPTION</h2>
176 <p><code class="function">lwres_context_create()</code>
177 creates a <span class="type">lwres_context_t</span> structure for use in
178 lightweight resolver operations. It holds a socket and other
179 data needed for communicating with a resolver daemon. The new
180 <span class="type">lwres_context_t</span> is returned through
181 <em class="parameter"><code>contextp</code></em>, a pointer to a
182 <span class="type">lwres_context_t</span> pointer. This
183 <span class="type">lwres_context_t</span> pointer must initially be NULL, and
184 is modified to point to the newly created
185 <span class="type">lwres_context_t</span>.
188 When the lightweight resolver needs to perform dynamic memory
189 allocation, it will call
190 <em class="parameter"><code>malloc_function</code></em>
191 to allocate memory and
192 <em class="parameter"><code>free_function</code></em>
194 <em class="parameter"><code>malloc_function</code></em>
196 <em class="parameter"><code>free_function</code></em>
197 are NULL, memory is allocated using
198 <span class="citerefentry"><span class="refentrytitle">malloc</span>(3)</span>.
200 <span class="citerefentry"><span class="refentrytitle">free</span>(3)</span>.
202 It is not permitted to have a NULL
203 <em class="parameter"><code>malloc_function</code></em> and a non-NULL
204 <em class="parameter"><code>free_function</code></em> or vice versa.
205 <em class="parameter"><code>arg</code></em> is passed as the first parameter to
206 the memory allocation functions. If
207 <em class="parameter"><code>malloc_function</code></em> and
208 <em class="parameter"><code>free_function</code></em> are NULL,
209 <em class="parameter"><code>arg</code></em> is unused and should be passed as
213 Once memory for the structure has been allocated,
214 it is initialized using
215 <span class="citerefentry"><span class="refentrytitle">lwres_conf_init</span>(3)</span>
216 and returned via <em class="parameter"><code>*contextp</code></em>.
218 <p><code class="function">lwres_context_destroy()</code>
219 destroys a <span class="type">lwres_context_t</span>, closing its socket.
220 <em class="parameter"><code>contextp</code></em> is a pointer to a pointer to the
221 context that is to be destroyed. The pointer will be set to
222 NULL when the context has been destroyed.
225 The context holds a serial number that is used to identify
226 resolver request packets and associate responses with the
227 corresponding requests. This serial number is controlled using
228 <code class="function">lwres_context_initserial()</code> and
229 <code class="function">lwres_context_nextserial()</code>.
230 <code class="function">lwres_context_initserial()</code> sets the serial
231 number for context <em class="parameter"><code>*ctx</code></em> to
232 <em class="parameter"><code>serial</code></em>.
233 <code class="function">lwres_context_nextserial()</code> increments the
234 serial number and returns the previous value.
237 Memory for a lightweight resolver context is allocated and freed
238 using <code class="function">lwres_context_allocmem()</code> and
239 <code class="function">lwres_context_freemem()</code>. These use
240 whatever allocations were defined when the context was created
241 with <code class="function">lwres_context_create()</code>.
242 <code class="function">lwres_context_allocmem()</code> allocates
243 <em class="parameter"><code>len</code></em> bytes of memory and if successful
244 returns a pointer to the allocated storage.
245 <code class="function">lwres_context_freemem()</code> frees
246 <em class="parameter"><code>len</code></em> bytes of space starting at location
247 <em class="parameter"><code>mem</code></em>.
249 <p><code class="function">lwres_context_sendrecv()</code>
250 performs I/O for the context <em class="parameter"><code>ctx</code></em>. Data
251 are read and written from the context's socket. It writes data
252 from <em class="parameter"><code>sendbase</code></em> — typically a
253 lightweight resolver query packet — and waits for a reply
254 which is copied to the receive buffer at
255 <em class="parameter"><code>recvbase</code></em>. The number of bytes that were
256 written to this receive buffer is returned in
257 <em class="parameter"><code>*recvd_len</code></em>.
260 <div class="refsect1" lang="en">
261 <a name="id2543719"></a><h2>RETURN VALUES</h2>
262 <p><code class="function">lwres_context_create()</code>
263 returns <span class="errorcode">LWRES_R_NOMEMORY</span> if memory for
264 the <span class="type">struct lwres_context</span> could not be allocated,
265 <span class="errorcode">LWRES_R_SUCCESS</span> otherwise.
268 Successful calls to the memory allocator
269 <code class="function">lwres_context_allocmem()</code>
270 return a pointer to the start of the allocated space.
271 It returns NULL if memory could not be allocated.
273 <p><span class="errorcode">LWRES_R_SUCCESS</span>
275 <code class="function">lwres_context_sendrecv()</code>
276 completes successfully.
277 <span class="errorcode">LWRES_R_IOERROR</span>
278 is returned if an I/O error occurs and
279 <span class="errorcode">LWRES_R_TIMEOUT</span>
281 <code class="function">lwres_context_sendrecv()</code>
282 times out waiting for a response.
285 <div class="refsect1" lang="en">
286 <a name="id2543769"></a><h2>SEE ALSO</h2>
287 <p><span class="citerefentry"><span class="refentrytitle">lwres_conf_init</span>(3)</span>,
289 <span class="citerefentry"><span class="refentrytitle">malloc</span>(3)</span>,
291 <span class="citerefentry"><span class="refentrytitle">free</span>(3)</span>.