contrib/bind9/lib/lwres/man/lwres_context.docbook

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  22
  23 <refentry>
  24 <refentryinfo>
  25
  26
  27 <date>Jun 30, 2000</date>
  28 </refentryinfo>
  29 <refmeta>
  30 <refentrytitle>lwres_context</refentrytitle>
  31 <manvolnum>3</manvolnum>
  32 <refmiscinfo>BIND9</refmiscinfo>
  33 </refmeta>
  34
  35   <docinfo>
  36     <copyright>
  37       <year>2004</year>
  38       <year>2005</year>
  39       <year>2007</year>
  40       <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
  41     </copyright>
  42     <copyright>
  43       <year>2000</year>
  44       <year>2001</year>
  45       <year>2003</year>
  46       <holder>Internet Software Consortium.</holder>
  47     </copyright>
  48   </docinfo>
  49
  50 <refnamediv>
  51 <refname>lwres_context_create</refname>
  52 <refname>lwres_context_destroy</refname>
  53 <refname>lwres_context_nextserial</refname>
  54 <refname>lwres_context_initserial</refname>
  55 <refname>lwres_context_freemem</refname>
  56 <refname>lwres_context_allocmem</refname>
  57 <refname>lwres_context_sendrecv</refname>
  58 <refpurpose>lightweight resolver context management</refpurpose>
  59 </refnamediv>
  60 <refsynopsisdiv>
  61 <funcsynopsis>
  62 <funcsynopsisinfo>#include &lt;lwres/lwres.h&gt;</funcsynopsisinfo>
  63 <funcprototype>
  64 <funcdef>
  65 lwres_result_t
  66 <function>lwres_context_create</function></funcdef>
  67 <paramdef>lwres_context_t **contextp</paramdef>
  68 <paramdef>void *arg</paramdef>
  69 <paramdef>lwres_malloc_t malloc_function</paramdef>
  70 <paramdef>lwres_free_t free_function</paramdef>
  71 </funcprototype>
  72 <funcprototype>
  73 <funcdef>
  74 lwres_result_t
  75 <function>lwres_context_destroy</function></funcdef>
  76 <paramdef>lwres_context_t **contextp</paramdef>
  77 </funcprototype>
  78 <funcprototype>
  79 <funcdef>
  80 void
  81 <function>lwres_context_initserial</function></funcdef>
  82 <paramdef>lwres_context_t *ctx</paramdef>
  83 <paramdef>lwres_uint32_t serial</paramdef>
  84 </funcprototype>
  85 <funcprototype>
  86 <funcdef>
  87 lwres_uint32_t
  88 <function>lwres_context_nextserial</function></funcdef>
  89 <paramdef>lwres_context_t *ctx</paramdef>
  90 </funcprototype>
  91 <funcprototype>
  92 <funcdef>
  93 void
  94 <function>lwres_context_freemem</function></funcdef>
  95 <paramdef>lwres_context_t *ctx</paramdef>
  96 <paramdef>void *mem</paramdef>
  97 <paramdef>size_t len</paramdef>
  98 </funcprototype>
  99 <funcprototype>
 100 <funcdef>
 101 void
 102 <function>lwres_context_allocmem</function></funcdef>
 103 <paramdef>lwres_context_t *ctx</paramdef>
 104 <paramdef>size_t len</paramdef>
 105 </funcprototype>
 106 <funcprototype>
 107 <funcdef>
 108 void *
 109 <function>lwres_context_sendrecv</function></funcdef>
 110 <paramdef>lwres_context_t *ctx</paramdef>
 111 <paramdef>void *sendbase</paramdef>
 112 <paramdef>int sendlen</paramdef>
 113 <paramdef>void *recvbase</paramdef>
 114 <paramdef>int recvlen</paramdef>
 115 <paramdef>int *recvd_len</paramdef>
 116 </funcprototype>
 117 </funcsynopsis>
 118 </refsynopsisdiv>
 119 <refsect1>
 120 <title>DESCRIPTION</title>
 121 <para>
 122 <function>lwres_context_create()</function>
 123 creates a
 124 <type>lwres_context_t</type>
 125 structure for use in lightweight resolver operations.
 126 It holds a socket and other data needed for communicating
 127 with a resolver daemon.
 128 The new
 129 <type>lwres_context_t</type>
 130 is returned through
 131 <parameter>contextp</parameter>,
 132
 133 a pointer to a
 134 <type>lwres_context_t</type>
 135 pointer.  This
 136 <type>lwres_context_t</type>
 137 pointer must initially be NULL, and is modified
 138 to point to the newly created
 139 <type>lwres_context_t</type>.
 140
 141 </para>
 142 <para>
 143 When the lightweight resolver needs to perform dynamic memory
 144 allocation, it will call
 145 <parameter>malloc_function</parameter>
 146 to allocate memory and
 147 <parameter>free_function</parameter>
 148
 149 to free it.  If
 150 <parameter>malloc_function</parameter>
 151 and
 152 <parameter>free_function</parameter>
 153
 154 are NULL, memory is allocated using
 155 .Xr malloc 3
 156 and
 157 <citerefentry>
 158 <refentrytitle>free</refentrytitle><manvolnum>3</manvolnum>
 159 </citerefentry>.
 160
 161 It is not permitted to have a NULL
 162 <parameter>malloc_function</parameter>
 163 and a non-NULL
 164 <parameter>free_function</parameter>
 165 or vice versa.
 166 <parameter>arg</parameter>
 167 is passed as the first parameter to the memory
 168 allocation functions.
 169 If
 170 <parameter>malloc_function</parameter>
 171 and
 172 <parameter>free_function</parameter>
 173 are NULL,
 174 <parameter>arg</parameter>
 175
 176 is unused and should be passed as NULL.
 177 </para>
 178 <para>
 179 Once memory for the structure has been allocated,
 180 it is initialized using
 181 <citerefentry>
 182 <refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>
 183 </citerefentry>
 184
 185 and returned via
 186 <parameter>*contextp</parameter>.
 187
 188 </para>
 189 <para>
 190 <function>lwres_context_destroy()</function>
 191 destroys a
 192 <type>lwres_context_t</type>,
 193
 194 closing its socket.
 195 <parameter>contextp</parameter>
 196 is a pointer to a pointer to the context that is to be destroyed.
 197 The pointer will be set to NULL when the context has been destroyed.
 198 </para>
 199 <para>
 200 The context holds a serial number that is used to identify resolver
 201 request packets and associate responses with the corresponding requests.
 202 This serial number is controlled using
 203 <function>lwres_context_initserial()</function>
 204 and
 205 <function>lwres_context_nextserial()</function>.
 206 <function>lwres_context_initserial()</function>
 207 sets the serial number for context
 208 <parameter>*ctx</parameter>
 209 to
 210 <parameter>serial</parameter>.
 211
 212 <function>lwres_context_nextserial()</function>
 213 increments the serial number and returns the previous value.
 214 </para>
 215 <para>
 216 Memory for a lightweight resolver context is allocated and freed using
 217 <function>lwres_context_allocmem()</function>
 218 and
 219 <function>lwres_context_freemem()</function>.
 220 These use whatever allocations were defined when the context was
 221 created with
 222 <function>lwres_context_create()</function>.
 223 <function>lwres_context_allocmem()</function>
 224 allocates
 225 <parameter>len</parameter>
 226 bytes of memory and if successful returns a pointer to the allocated
 227 storage.
 228 <function>lwres_context_freemem()</function>
 229 frees
 230 <parameter>len</parameter>
 231 bytes of space starting at location
 232 <parameter>mem</parameter>.
 233
 234 </para>
 235 <para>
 236 <function>lwres_context_sendrecv()</function>
 237 performs I/O for the context
 238 <parameter>ctx</parameter>.
 239
 240 Data are read and written from the context's socket.
 241 It writes data from
 242 <parameter>sendbase</parameter>
 243 &mdash; typically a lightweight resolver query packet &mdash;
 244 and waits for a reply which is copied to the receive buffer at
 245 <parameter>recvbase</parameter>.
 246
 247 The number of bytes that were written to this receive buffer is
 248 returned in
 249 <parameter>*recvd_len</parameter>.
 250
 251 </para>
 252 </refsect1>
 253 <refsect1>
 254 <title>RETURN VALUES</title>
 255 <para>
 256 <function>lwres_context_create()</function>
 257 returns
 258 <errorcode>LWRES_R_NOMEMORY</errorcode>
 259 if memory for the
 260 <type>struct lwres_context</type>
 261 could not be allocated,
 262 <errorcode>LWRES_R_SUCCESS</errorcode>
 263 otherwise.
 264 </para>
 265 <para>
 266 Successful calls to the memory allocator
 267 <function>lwres_context_allocmem()</function>
 268 return a pointer to the start of the allocated space.
 269 It returns NULL if memory could not be allocated.
 270 </para>
 271 <para>
 272 <errorcode>LWRES_R_SUCCESS</errorcode>
 273 is returned when
 274 <function>lwres_context_sendrecv()</function>
 275 completes successfully.
 276 <errorcode>LWRES_R_IOERROR</errorcode>
 277 is returned if an I/O error occurs and
 278 <errorcode>LWRES_R_TIMEOUT</errorcode>
 279 is returned if
 280 <function>lwres_context_sendrecv()</function>
 281 times out waiting for a response.
 282 </para>
 283 </refsect1>
 284 <refsect1>
 285 <title>SEE ALSO</title>
 286 <para>
 287 <citerefentry>
 288 <refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>
 289 </citerefentry>,
 290
 291 <citerefentry>
 292 <refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum>
 293 </citerefentry>,
 294
 295 <citerefentry>
 296 <refentrytitle>free</refentrytitle><manvolnum>3
 297 </manvolnum>
 298 </citerefentry>.
 299 </para>
 300 </refsect1>
 301 </refentry>