contrib/bind-9.3/lib/lwres/man/lwres_buffer.html

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  18 <html>
  19 <head>
  20 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
  21 <title>lwres_buffer</title>
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  23 </head>
  24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
  25 <a name="id2463721"></a><div class="titlepage"></div>
  26 <div class="refnamediv">
  27 <h2>Name</h2>
  28 <p>lwres_buffer_init, lwres_buffer_invalidate, lwres_buffer_add, lwres_buffer_subtract, lwres_buffer_clear, lwres_buffer_first, lwres_buffer_forward, lwres_buffer_back, lwres_buffer_getuint8, lwres_buffer_putuint8, lwres_buffer_getuint16, lwres_buffer_putuint16, lwres_buffer_getuint32, lwres_buffer_putuint32, lwres_buffer_putmem, lwres_buffer_getmem &#8212; lightweight resolver buffer management</p>
  29 </div>
  30 <div class="refsynopsisdiv">
  31 <h2>Synopsis</h2>
  32 <div class="funcsynopsis">
  33 <pre class="funcsynopsisinfo">
  34 #include &lt;lwres/lwbuffer.h&gt;
  35 </pre>
  36 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
  37 <tr>
  38 <td><code class="funcdef">
  39 void
  40 <b class="fsfunc">lwres_buffer_init</b>(</code></td>
  41 <td> </td>
  42 <td>, </td>
  43 </tr>
  44 <tr>
  45 <td> </td>
  46 <td> </td>
  47 <td>, </td>
  48 </tr>
  49 <tr>
  50 <td> </td>
  51 <td> </td>
  52 <td>
  53 <code>)</code>;</td>
  54 </tr>
  55 </table>
  56 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
  57 <td><code class="funcdef">
  58 void
  59 <b class="fsfunc">lwres_buffer_invalidate</b>(</code></td>
  60 <td> </td>
  61 <td>
  62 <code>)</code>;</td>
  63 </tr></table>
  64 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
  65 <tr>
  66 <td><code class="funcdef">
  67 void
  68 <b class="fsfunc">lwres_buffer_add</b>(</code></td>
  69 <td> </td>
  70 <td>, </td>
  71 </tr>
  72 <tr>
  73 <td> </td>
  74 <td> </td>
  75 <td>
  76 <code>)</code>;</td>
  77 </tr>
  78 </table>
  79 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
  80 <tr>
  81 <td><code class="funcdef">
  82 void
  83 <b class="fsfunc">lwres_buffer_subtract</b>(</code></td>
  84 <td> </td>
  85 <td>, </td>
  86 </tr>
  87 <tr>
  88 <td> </td>
  89 <td> </td>
  90 <td>
  91 <code>)</code>;</td>
  92 </tr>
  93 </table>
  94 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
  95 <td><code class="funcdef">
  96 void
  97 <b class="fsfunc">lwres_buffer_clear</b>(</code></td>
  98 <td> </td>
  99 <td>
 100 <code>)</code>;</td>
 101 </tr></table>
 102 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
 103 <td><code class="funcdef">
 104 void
 105 <b class="fsfunc">lwres_buffer_first</b>(</code></td>
 106 <td> </td>
 107 <td>
 108 <code>)</code>;</td>
 109 </tr></table>
 110 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
 111 <tr>
 112 <td><code class="funcdef">
 113 void
 114 <b class="fsfunc">lwres_buffer_forward</b>(</code></td>
 115 <td> </td>
 116 <td>, </td>
 117 </tr>
 118 <tr>
 119 <td> </td>
 120 <td> </td>
 121 <td>
 122 <code>)</code>;</td>
 123 </tr>
 124 </table>
 125 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
 126 <tr>
 127 <td><code class="funcdef">
 128 void
 129 <b class="fsfunc">lwres_buffer_back</b>(</code></td>
 130 <td> </td>
 131 <td>, </td>
 132 </tr>
 133 <tr>
 134 <td> </td>
 135 <td> </td>
 136 <td>
 137 <code>)</code>;</td>
 138 </tr>
 139 </table>
 140 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
 141 <td><code class="funcdef">
 142 lwres_uint8_t
 143 <b class="fsfunc">lwres_buffer_getuint8</b>(</code></td>
 144 <td> </td>
 145 <td>
 146 <code>)</code>;</td>
 147 </tr></table>
 148 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
 149 <tr>
 150 <td><code class="funcdef">
 151 void
 152 <b class="fsfunc">lwres_buffer_putuint8</b>(</code></td>
 153 <td> </td>
 154 <td>, </td>
 155 </tr>
 156 <tr>
 157 <td> </td>
 158 <td> </td>
 159 <td>
 160 <code>)</code>;</td>
 161 </tr>
 162 </table>
 163 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
 164 <td><code class="funcdef">
 165 lwres_uint16_t
 166 <b class="fsfunc">lwres_buffer_getuint16</b>(</code></td>
 167 <td> </td>
 168 <td>
 169 <code>)</code>;</td>
 170 </tr></table>
 171 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
 172 <tr>
 173 <td><code class="funcdef">
 174 void
 175 <b class="fsfunc">lwres_buffer_putuint16</b>(</code></td>
 176 <td> </td>
 177 <td>, </td>
 178 </tr>
 179 <tr>
 180 <td> </td>
 181 <td> </td>
 182 <td>
 183 <code>)</code>;</td>
 184 </tr>
 185 </table>
 186 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
 187 <td><code class="funcdef">
 188 lwres_uint32_t
 189 <b class="fsfunc">lwres_buffer_getuint32</b>(</code></td>
 190 <td> </td>
 191 <td>
 192 <code>)</code>;</td>
 193 </tr></table>
 194 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
 195 <tr>
 196 <td><code class="funcdef">
 197 void
 198 <b class="fsfunc">lwres_buffer_putuint32</b>(</code></td>
 199 <td> </td>
 200 <td>, </td>
 201 </tr>
 202 <tr>
 203 <td> </td>
 204 <td> </td>
 205 <td>
 206 <code>)</code>;</td>
 207 </tr>
 208 </table>
 209 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
 210 <tr>
 211 <td><code class="funcdef">
 212 void
 213 <b class="fsfunc">lwres_buffer_putmem</b>(</code></td>
 214 <td> </td>
 215 <td>, </td>
 216 </tr>
 217 <tr>
 218 <td> </td>
 219 <td> </td>
 220 <td>, </td>
 221 </tr>
 222 <tr>
 223 <td> </td>
 224 <td> </td>
 225 <td>
 226 <code>)</code>;</td>
 227 </tr>
 228 </table>
 229 <table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
 230 <tr>
 231 <td><code class="funcdef">
 232 void
 233 <b class="fsfunc">lwres_buffer_getmem</b>(</code></td>
 234 <td> </td>
 235 <td>, </td>
 236 </tr>
 237 <tr>
 238 <td> </td>
 239 <td> </td>
 240 <td>, </td>
 241 </tr>
 242 <tr>
 243 <td> </td>
 244 <td> </td>
 245 <td>
 246 <code>)</code>;</td>
 247 </tr>
 248 </table>
 249 </div>
 250 </div>
 251 <div class="refsect1" lang="en">
 252 <a name="id2526109"></a><h2>DESCRIPTION</h2>
 253 <p>
 254 These functions provide bounds checked access to a region of memory
 255 where data is being read or written.
 256 They are based on, and similar to, the
 257 <code class="literal">isc_buffer_</code>
 258 functions in the ISC library.
 259 </p>
 260 <p>
 261 A buffer is a region of memory, together with a set of related
 262 subregions.
 263 The <span class="emphasis"><em>used region</em></span> and the
 264 <span class="emphasis"><em>available</em></span> region are disjoint, and
 265 their union is the buffer's region.
 266 The used region extends from the beginning of the buffer region to the
 267 last used byte.
 268 The available region extends from one byte greater than the last used
 269 byte to the end of the  buffer's region.
 270 The size of the used region can be changed using various
 271 buffer commands.
 272 Initially, the used region is empty.
 273 </p>
 274 <p>
 275 The used region is further subdivided into two disjoint regions: the
 276 <span class="emphasis"><em>consumed region</em></span> and the <span class="emphasis"><em>remaining region</em></span>.
 277 The union of these two regions is the used region.
 278 The consumed region extends from the beginning of the used region to
 279 the byte before the <span class="emphasis"><em>current</em></span> offset (if any).
 280 The <span class="emphasis"><em>remaining</em></span> region the current pointer to the end of the used
 281 region.
 282 The size of the consumed region can be changed using various
 283 buffer commands.
 284 Initially, the consumed region is empty.
 285 </p>
 286 <p>
 287 The <span class="emphasis"><em>active region</em></span> is an (optional) subregion of the remaining
 288 region.
 289 It extends from the current offset to an offset in the
 290 remaining region.
 291 Initially, the active region is empty.
 292 If the current offset advances beyond the chosen offset,
 293 the active region will also be empty.
 294 </p>
 295 <p>
 296 </p>
 297 <pre class="programlisting">
 298
 299    /------------entire length---------------\\
 300    /----- used region -----\\/-- available --\\
 301    +----------------------------------------+
 302    | consumed  | remaining |                |
 303    +----------------------------------------+
 304    a           b     c     d                e
 305
 306   a == base of buffer.
 307   b == current pointer.  Can be anywhere between a and d.
 308   c == active pointer.  Meaningful between b and d.
 309   d == used pointer.
 310   e == length of buffer.
 311
 312   a-e == entire length of buffer.
 313   a-d == used region.
 314   a-b == consumed region.
 315   b-d == remaining region.
 316   b-c == optional active region.
 317 </pre>
 318 <p>
 319 </p>
 320 <p>
 321 <code class="function">lwres_buffer_init()</code>
 322 initializes the
 323 <span class="type">lwres_buffer_t</span>
 324 <em class="parameter"><code>*b</code></em>
 325 and assocates it with the memory region of size
 326 <em class="parameter"><code>length</code></em>
 327 bytes starting at location
 328 <em class="parameter"><code>base.</code></em>
 329 </p>
 330 <p>
 331 <code class="function">lwres_buffer_invalidate()</code>
 332 marks the buffer
 333 <em class="parameter"><code>*b</code></em>
 334 as invalid.  Invalidating a buffer after use is not required,
 335 but makes it possible to catch its possible accidental use.
 336 </p>
 337 <p>
 338 The functions
 339 <code class="function">lwres_buffer_add()</code>
 340 and
 341 <code class="function">lwres_buffer_subtract()</code>
 342 respectively increase and decrease the used space in
 343 buffer
 344 <em class="parameter"><code>*b</code></em>
 345 by
 346 <em class="parameter"><code>n</code></em>
 347 bytes.
 348 <code class="function">lwres_buffer_add()</code>
 349 checks for buffer overflow and
 350 <code class="function">lwres_buffer_subtract()</code>
 351 checks for underflow.
 352 These functions do not allocate or deallocate memory.
 353 They just change the value of
 354 <em class="structfield"><code>used</code></em>.
 355 </p>
 356 <p>
 357 A buffer is re-initialised by
 358 <code class="function">lwres_buffer_clear()</code>.
 359 The function sets
 360 <em class="structfield"><code>used</code></em> ,
 361 <em class="structfield"><code>current</code></em>
 362 and
 363 <em class="structfield"><code>active</code></em>
 364 to zero.
 365 </p>
 366 <p>
 367 <code class="function">lwres_buffer_first</code>
 368 makes the consumed region of buffer
 369 <em class="parameter"><code>*p</code></em>
 370 empty by setting
 371 <em class="structfield"><code>current</code></em>
 372 to zero (the start of the buffer).
 373 </p>
 374 <p>
 375 <code class="function">lwres_buffer_forward()</code>
 376 increases the consumed region of buffer
 377 <em class="parameter"><code>*b</code></em>
 378 by
 379 <em class="parameter"><code>n</code></em>
 380 bytes, checking for overflow.
 381 Similarly,
 382 <code class="function">lwres_buffer_back()</code>
 383 decreases buffer
 384 <em class="parameter"><code>b</code></em>'s
 385 consumed region by
 386 <em class="parameter"><code>n</code></em>
 387 bytes and checks for underflow.
 388 </p>
 389 <p>
 390 <code class="function">lwres_buffer_getuint8()</code>
 391 reads an unsigned 8-bit integer from
 392 <em class="parameter"><code>*b</code></em>
 393 and returns it.
 394 <code class="function">lwres_buffer_putuint8()</code>
 395 writes the unsigned 8-bit integer
 396 <em class="parameter"><code>val</code></em>
 397 to buffer
 398 <em class="parameter"><code>*b</code></em>.
 399 </p>
 400 <p>
 401 <code class="function">lwres_buffer_getuint16()</code>
 402 and
 403 <code class="function">lwres_buffer_getuint32()</code>
 404 are identical to
 405 <code class="function">lwres_buffer_putuint8()</code>
 406 except that they respectively read an unsigned 16-bit or 32-bit integer
 407 in network byte order from
 408 <em class="parameter"><code>b</code></em>.
 409 Similarly,
 410 <code class="function">lwres_buffer_putuint16()</code>
 411 and
 412 <code class="function">lwres_buffer_putuint32()</code>
 413 writes the unsigned 16-bit or 32-bit integer
 414 <em class="parameter"><code>val</code></em>
 415 to buffer
 416 <em class="parameter"><code>b</code></em>,
 417 in network byte order.
 418 </p>
 419 <p>
 420 Arbitrary amounts of data are read or written from a lightweight
 421 resolver buffer with
 422 <code class="function">lwres_buffer_getmem()</code>
 423 and
 424 <code class="function">lwres_buffer_putmem()</code>
 425 respectively.
 426 <code class="function">lwres_buffer_putmem()</code>
 427 copies
 428 <em class="parameter"><code>length</code></em>
 429 bytes of memory at
 430 <em class="parameter"><code>base</code></em>
 431 to
 432 <em class="parameter"><code>b</code></em>.
 433 Conversely,
 434 <code class="function">lwres_buffer_getmem()</code>
 435 copies
 436 <em class="parameter"><code>length</code></em>
 437 bytes of memory from
 438 <em class="parameter"><code>b</code></em>
 439 to
 440 <em class="parameter"><code>base</code></em>.
 441 </p>
 442 </div>
 443 </div></body>
 444 </html>