1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
|
<!--
- Copyright (C) 2000, 2001 Internet Software Consortium.
-
- Permission to use, copy, modify, and distribute this software for any
- purpose with or without fee is hereby granted, provided that the above
- copyright notice and this permission notice appear in all copies.
-
- THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
- DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
- IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
- INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
- FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
- NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
- WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-->
<HTML
><HEAD
><TITLE
>lwres_buffer</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.61
"></HEAD
><BODY
CLASS="REFENTRY"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><H1
><A
NAME="AEN1"
>lwres_buffer</A
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN8"
></A
><H2
>Name</H2
>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 -- lightweight resolver buffer management</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN26"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN27"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include <lwres/lwbuffer.h></PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_init</CODE
>(lwres_buffer_t *b, void *base, unsigned int length);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_invalidate</CODE
>(lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_add</CODE
>(lwres_buffer_t *b, unsigned int n);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_subtract</CODE
>(lwres_buffer_t *b, unsigned int n);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_clear</CODE
>(lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_first</CODE
>(lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_forward</CODE
>(lwres_buffer_t *b, unsigned int n);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_back</CODE
>(lwres_buffer_t *b, unsigned int n);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_uint8_t
lwres_buffer_getuint8</CODE
>(lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_putuint8</CODE
>(lwres_buffer_t *b, lwres_uint8_t val);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_uint16_t
lwres_buffer_getuint16</CODE
>(lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_putuint16</CODE
>(lwres_buffer_t *b, lwres_uint16_t val);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>lwres_uint32_t
lwres_buffer_getuint32</CODE
>(lwres_buffer_t *b);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_putuint32</CODE
>(lwres_buffer_t *b, lwres_uint32_t val);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_putmem</CODE
>(lwres_buffer_t *b, const unsigned char *base, unsigned int length);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void
lwres_buffer_getmem</CODE
>(lwres_buffer_t *b, unsigned char *base, unsigned int length);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN106"
></A
><H2
>DESCRIPTION</H2
><P
>These functions provide bounds checked access to a region of memory
where data is being read or written.
They are based on, and similar to, the
<TT
CLASS="LITERAL"
>isc_buffer_</TT
>
functions in the ISC library.</P
><P
>A buffer is a region of memory, together with a set of related
subregions.
The <I
CLASS="EMPHASIS"
>used region</I
> and the
<I
CLASS="EMPHASIS"
>available</I
> region are disjoint, and
their union is the buffer's region.
The used region extends from the beginning of the buffer region to the
last used byte.
The available region extends from one byte greater than the last used
byte to the end of the buffer's region.
The size of the used region can be changed using various
buffer commands.
Initially, the used region is empty.</P
><P
>The used region is further subdivided into two disjoint regions: the
<I
CLASS="EMPHASIS"
>consumed region</I
> and the <I
CLASS="EMPHASIS"
>remaining region</I
>.
The union of these two regions is the used region.
The consumed region extends from the beginning of the used region to
the byte before the <I
CLASS="EMPHASIS"
>current</I
> offset (if any).
The <I
CLASS="EMPHASIS"
>remaining</I
> region the current pointer to the end of the used
region.
The size of the consumed region can be changed using various
buffer commands.
Initially, the consumed region is empty.</P
><P
>The <I
CLASS="EMPHASIS"
>active region</I
> is an (optional) subregion of the remaining
region.
It extends from the current offset to an offset in the
remaining region.
Initially, the active region is empty.
If the current offset advances beyond the chosen offset,
the active region will also be empty.</P
><P
><PRE
CLASS="PROGRAMLISTING"
>
/------------entire length---------------\\
/----- used region -----\\/-- available --\\
+----------------------------------------+
| consumed | remaining | |
+----------------------------------------+
a b c d e
a == base of buffer.
b == current pointer. Can be anywhere between a and d.
c == active pointer. Meaningful between b and d.
d == used pointer.
e == length of buffer.
a-e == entire length of buffer.
a-d == used region.
a-b == consumed region.
b-d == remaining region.
b-c == optional active region.</PRE
></P
><P
><TT
CLASS="FUNCTION"
>lwres_buffer_init()</TT
>
initializes the
<SPAN
CLASS="TYPE"
>lwres_buffer_t</SPAN
>
<TT
CLASS="PARAMETER"
><I
>*b</I
></TT
>
and assocates it with the memory region of size
<TT
CLASS="PARAMETER"
><I
>length</I
></TT
>
bytes starting at location
<TT
CLASS="PARAMETER"
><I
>base.</I
></TT
></P
><P
><TT
CLASS="FUNCTION"
>lwres_buffer_invalidate()</TT
>
marks the buffer
<TT
CLASS="PARAMETER"
><I
>*b</I
></TT
>
as invalid. Invalidating a buffer after use is not required,
but makes it possible to catch its possible accidental use.</P
><P
>The functions
<TT
CLASS="FUNCTION"
>lwres_buffer_add()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_buffer_subtract()</TT
>
respectively increase and decrease the used space in
buffer
<TT
CLASS="PARAMETER"
><I
>*b</I
></TT
>
by
<TT
CLASS="PARAMETER"
><I
>n</I
></TT
>
bytes.
<TT
CLASS="FUNCTION"
>lwres_buffer_add()</TT
>
checks for buffer overflow and
<TT
CLASS="FUNCTION"
>lwres_buffer_subtract()</TT
>
checks for underflow.
These functions do not allocate or deallocate memory.
They just change the value of
<TT
CLASS="STRUCTFIELD"
><I
>used</I
></TT
>.</P
><P
>A buffer is re-initialised by
<TT
CLASS="FUNCTION"
>lwres_buffer_clear()</TT
>.
The function sets
<TT
CLASS="STRUCTFIELD"
><I
>used</I
></TT
> ,
<TT
CLASS="STRUCTFIELD"
><I
>current</I
></TT
>
and
<TT
CLASS="STRUCTFIELD"
><I
>active</I
></TT
>
to zero.</P
><P
><TT
CLASS="FUNCTION"
>lwres_buffer_first</TT
>
makes the consumed region of buffer
<TT
CLASS="PARAMETER"
><I
>*p</I
></TT
>
empty by setting
<TT
CLASS="STRUCTFIELD"
><I
>current</I
></TT
>
to zero (the start of the buffer).</P
><P
><TT
CLASS="FUNCTION"
>lwres_buffer_forward()</TT
>
increases the consumed region of buffer
<TT
CLASS="PARAMETER"
><I
>*b</I
></TT
>
by
<TT
CLASS="PARAMETER"
><I
>n</I
></TT
>
bytes, checking for overflow.
Similarly,
<TT
CLASS="FUNCTION"
>lwres_buffer_back()</TT
>
decreases buffer
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>'s
consumed region by
<TT
CLASS="PARAMETER"
><I
>n</I
></TT
>
bytes and checks for underflow.</P
><P
><TT
CLASS="FUNCTION"
>lwres_buffer_getuint8()</TT
>
reads an unsigned 8-bit integer from
<TT
CLASS="PARAMETER"
><I
>*b</I
></TT
>
and returns it.
<TT
CLASS="FUNCTION"
>lwres_buffer_putuint8()</TT
>
writes the unsigned 8-bit integer
<TT
CLASS="PARAMETER"
><I
>val</I
></TT
>
to buffer
<TT
CLASS="PARAMETER"
><I
>*b</I
></TT
>.</P
><P
><TT
CLASS="FUNCTION"
>lwres_buffer_getuint16()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_buffer_getuint32()</TT
>
are identical to
<TT
CLASS="FUNCTION"
>lwres_buffer_putuint8()</TT
>
except that they respectively read an unsigned 16-bit or 32-bit integer
in network byte order from
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>.
Similarly,
<TT
CLASS="FUNCTION"
>lwres_buffer_putuint16()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_buffer_putuint32()</TT
>
writes the unsigned 16-bit or 32-bit integer
<TT
CLASS="PARAMETER"
><I
>val</I
></TT
>
to buffer
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>,
in network byte order.</P
><P
>Arbitrary amounts of data are read or written from a lightweight
resolver buffer with
<TT
CLASS="FUNCTION"
>lwres_buffer_getmem()</TT
>
and
<TT
CLASS="FUNCTION"
>lwres_buffer_putmem()</TT
>
respectively.
<TT
CLASS="FUNCTION"
>lwres_buffer_putmem()</TT
>
copies
<TT
CLASS="PARAMETER"
><I
>length</I
></TT
>
bytes of memory at
<TT
CLASS="PARAMETER"
><I
>base</I
></TT
>
to
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>.
Conversely,
<TT
CLASS="FUNCTION"
>lwres_buffer_getmem()</TT
>
copies
<TT
CLASS="PARAMETER"
><I
>length</I
></TT
>
bytes of memory from
<TT
CLASS="PARAMETER"
><I
>b</I
></TT
>
to
<TT
CLASS="PARAMETER"
><I
>base</I
></TT
>.</P
></DIV
></BODY
></HTML
>
|
