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
|
.\"-
.\" Copyright (c) 2000 Poul-Henning Kamp and Dag-Erling Coïdan Smørgrav
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd January 25, 2011
.Dt SBUF 9
.Os
.Sh NAME
.Nm sbuf ,
.Nm sbuf_new ,
.Nm sbuf_new_auto ,
.Nm sbuf_new_for_sysctl ,
.Nm sbuf_clear ,
.Nm sbuf_setpos ,
.Nm sbuf_bcat ,
.Nm sbuf_bcopyin ,
.Nm sbuf_bcpy ,
.Nm sbuf_cat ,
.Nm sbuf_copyin ,
.Nm sbuf_cpy ,
.Nm sbuf_printf ,
.Nm sbuf_vprintf ,
.Nm sbuf_putc ,
.Nm sbuf_set_drain ,
.Nm sbuf_trim ,
.Nm sbuf_error ,
.Nm sbuf_finish ,
.Nm sbuf_data ,
.Nm sbuf_len ,
.Nm sbuf_done ,
.Nm sbuf_delete
.Nd safe string composition
.Sh SYNOPSIS
.In sys/types.h
.In sys/sbuf.h
.Ft typedef\ int ( sbuf_drain_func ) ( void\ *arg, const\ char\ *data, int\ len ) ;
.Pp
.Ft struct sbuf *
.Fn sbuf_new "struct sbuf *s" "char *buf" "int length" "int flags"
.Ft struct sbuf *
.Fn sbuf_new_auto
.Ft void
.Fn sbuf_clear "struct sbuf *s"
.Ft int
.Fn sbuf_setpos "struct sbuf *s" "int pos"
.Ft int
.Fn sbuf_bcat "struct sbuf *s" "const void *buf" "size_t len"
.Ft int
.Fn sbuf_bcopyin "struct sbuf *s" "const void *uaddr" "size_t len"
.Ft int
.Fn sbuf_bcpy "struct sbuf *s" "const void *buf" "size_t len"
.Ft int
.Fn sbuf_cat "struct sbuf *s" "const char *str"
.Ft int
.Fn sbuf_copyin "struct sbuf *s" "const void *uaddr" "size_t len"
.Ft int
.Fn sbuf_cpy "struct sbuf *s" "const char *str"
.Ft int
.Fn sbuf_printf "struct sbuf *s" "const char *fmt" "..."
.Ft int
.Fn sbuf_vprintf "struct sbuf *s" "const char *fmt" "va_list ap"
.Ft int
.Fn sbuf_putc "struct sbuf *s" "int c"
.Ft void
.Fn sbuf_set_drain "struct sbuf *s" "sbuf_drain_func *func" "void *arg"
.Ft int
.Fn sbuf_trim "struct sbuf *s"
.Ft int
.Fn sbuf_error "struct sbuf *s"
.Ft int
.Fn sbuf_finish "struct sbuf *s"
.Ft char *
.Fn sbuf_data "struct sbuf *s"
.Ft int
.Fn sbuf_len "struct sbuf *s"
.Ft int
.Fn sbuf_done "struct sbuf *s"
.Ft void
.Fn sbuf_delete "struct sbuf *s"
.In sys/sysctl.h
.Ft struct sbuf *
.Fn sbuf_new_for_sysctl "struct sbuf *s" "char *buf" "int length" "struct sysctl_req *req"
.Sh DESCRIPTION
The
.Nm
family of functions allows one to safely allocate, compose and
release strings in kernel or user space.
.Pp
Instead of arrays of characters, these functions operate on structures
called
.Fa sbufs ,
defined in
.In sys/sbuf.h .
.Pp
Any errors encountered during the allocation or composition of the
string will be latched in the data structure,
making a single error test at the end of the composition
sufficient to determine success or failure of the entire process.
.Pp
The
.Fn sbuf_new
function initializes the
.Fa sbuf
pointed to by its first argument.
If that pointer is
.Dv NULL ,
.Fn sbuf_new
allocates a
.Vt struct sbuf
using
.Xr malloc 9 .
The
.Fa buf
argument is a pointer to a buffer in which to store the actual string;
if it is
.Dv NULL ,
.Fn sbuf_new
will allocate one using
.Xr malloc 9 .
The
.Fa length
is the initial size of the storage buffer.
The fourth argument,
.Fa flags ,
may be comprised of the following flags:
.Bl -tag -width ".Dv SBUF_AUTOEXTEND"
.It Dv SBUF_FIXEDLEN
The storage buffer is fixed at its initial size.
Attempting to extend the sbuf beyond this size results in an overflow condition.
.It Dv SBUF_AUTOEXTEND
This indicates that the storage buffer may be extended as necessary, so long
as resources allow, to hold additional data.
.El
.Pp
Note that if
.Fa buf
is not
.Dv NULL ,
it must point to an array of at least
.Fa length
characters.
The result of accessing that array directly while it is in use by the
sbuf is undefined.
.Pp
The
.Fn sbuf_new_auto
function is a shortcut for creating a completely dynamic
.Nm .
It is the equivalent of calling
.Fn sbuf_new
with values
.Dv NULL ,
.Dv NULL ,
.Dv 0 ,
and
.Dv SBUF_AUTOEXTEND .
.Pp
The
.Fn sbuf_new_for_sysctl
function will set up an sbuf with a drain function to use
.Fn SYSCTL_OUT
when the internal buffer fills.
Note that if the various functions which append to an sbuf are used while
a non-sleepable lock is held, the user buffer should be wired using
.Fn sysctl_wire_old_buffer .
.Pp
The
.Fn sbuf_delete
function clears the
.Fa sbuf
and frees any memory allocated for it.
There must be a call to
.Fn sbuf_delete
for every call to
.Fn sbuf_new .
Any attempt to access the sbuf after it has been deleted will fail.
.Pp
The
.Fn sbuf_clear
function invalidates the contents of the
.Fa sbuf
and resets its position to zero.
.Pp
The
.Fn sbuf_setpos
function sets the
.Fa sbuf Ns 's
end position to
.Fa pos ,
which is a value between zero and one less than the size of the
storage buffer.
This effectively truncates the sbuf at the new position.
.Pp
The
.Fn sbuf_bcat
function appends the first
.Fa len
bytes from the buffer
.Fa buf
to the
.Fa sbuf .
.Pp
The
.Fn sbuf_bcopyin
function copies
.Fa len
bytes from the specified userland address into the
.Fa sbuf .
.Pp
The
.Fn sbuf_bcpy
function replaces the contents of the
.Fa sbuf
with the first
.Fa len
bytes from the buffer
.Fa buf .
.Pp
The
.Fn sbuf_cat
function appends the NUL-terminated string
.Fa str
to the
.Fa sbuf
at the current position.
.Pp
The
.Fn sbuf_set_drain
function sets a drain function
.Fa func
for the
.Fa sbuf ,
and records a pointer
.Fa arg
to be passed to the drain on callback.
The drain function cannot be changed while
.Fa sbuf_len
is non-zero.
.Pp
The registered drain function
.Vt sbuf_drain_func
will be called with the argument
.Fa arg
provided to
.Fn sbuf_set_drain ,
a pointer
.Fa data
to a byte string that is the contents of the sbuf, and the length
.Fa len
of the data.
If the drain function exists, it will be called when the sbuf internal
buffer is full, or on behalf of
.Fn sbuf_finish .
The drain function may drain some or all of the data, but must drain
at least 1 byte.
The return value from the drain function, if positive, indicates how
many bytes were drained.
If negative, the return value indicates the negative error code which
will be returned from this or a later call to
.Fn sbuf_finish .
The returned drained length cannot be zero.
To do unbuffered draining, initialize the sbuf with a two-byte buffer.
The drain will be called for every byte added to the sbuf.
The
.Fn sbuf_bcopyin ,
.Fn sbuf_copyin ,
.Fn sbuf_trim ,
and
.Fn sbuf_data
functions cannot be used on an sbuf with a drain.
.Pp
The
.Fn sbuf_copyin
function copies a NUL-terminated string from the specified userland
address into the
.Fa sbuf .
If the
.Fa len
argument is non-zero, no more than
.Fa len
characters (not counting the terminating NUL) are copied; otherwise
the entire string, or as much of it as can fit in the
.Fa sbuf ,
is copied.
.Pp
The
.Fn sbuf_cpy
function replaces the contents of the
.Fa sbuf
with those of the NUL-terminated string
.Fa str .
This is equivalent to calling
.Fn sbuf_cat
with a fresh
.Fa sbuf
or one which position has been reset to zero with
.Fn sbuf_clear
or
.Fn sbuf_setpos .
.Pp
The
.Fn sbuf_printf
function formats its arguments according to the format string pointed
to by
.Fa fmt
and appends the resulting string to the
.Fa sbuf
at the current position.
.Pp
The
.Fn sbuf_vprintf
function behaves the same as
.Fn sbuf_printf
except that the arguments are obtained from the variable-length argument list
.Fa ap .
.Pp
The
.Fn sbuf_putc
function appends the character
.Fa c
to the
.Fa sbuf
at the current position.
.Pp
The
.Fn sbuf_trim
function removes trailing whitespace from the
.Fa sbuf .
.Pp
The
.Fn sbuf_error
function returns any error value that the
.Fa sbuf
may have accumulated, either from the drain function, or ENOMEM if the
.Fa sbuf
overflowed.
This function is generally not needed and instead the error code from
.Fn sbuf_finish
is the preferred way to discover whether an sbuf had an error.
.Pp
The
.Fn sbuf_finish
function will call the attached drain function if one exists until all
the data in the
.Fa sbuf
is flushed.
If there is no attached drain,
.Fn sbuf_finish
NUL-terminates the
.Fa sbuf .
In either case it marks the
.Fa sbuf
as finished, which means that it may no longer be modified using
.Fn sbuf_setpos ,
.Fn sbuf_cat ,
.Fn sbuf_cpy ,
.Fn sbuf_printf
or
.Fn sbuf_putc ,
until
.Fn sbuf_clear
is used to reset the sbuf.
.Pp
The
.Fn sbuf_data
function returns the actual string;
.Fn sbuf_data
only works on a finished
.Fa sbuf .
The
.Fn sbuf_len function returns the length of the string.
For an
.Fa sbuf
with an attached drain,
.Fn sbuf_len
returns the length of the un-drained data.
.Fn sbuf_done
returns non-zero if the
.Fa sbuf
is finished.
.Sh NOTES
If an operation caused an
.Fa sbuf
to overflow, most subsequent operations on it will fail until the
.Fa sbuf
is finished using
.Fn sbuf_finish
or reset using
.Fn sbuf_clear ,
or its position is reset to a value between 0 and one less than the
size of its storage buffer using
.Fn sbuf_setpos ,
or it is reinitialized to a sufficiently short string using
.Fn sbuf_cpy .
.Pp
Drains in user-space will not always function as indicated.
While the drain function will be called immediately on overflow from
the
.Fa sbuf_putc ,
.Fa sbuf_bcat ,
.Fa sbuf_cat
functions,
.Fa sbuf_printf
and
.Fa sbuf_vprintf
currently have no way to determine whether there will be an overflow
until after it occurs, and cannot do a partial expansion of the format
string.
Thus when using libsbuf the buffer may be extended to allow completion
of a single printf call, even though a drain is attached.
.Sh RETURN VALUES
The
.Fn sbuf_new
function returns
.Dv NULL
if it failed to allocate a storage buffer, and a pointer to the new
.Fa sbuf
otherwise.
.Pp
The
.Fn sbuf_setpos
function returns \-1 if
.Fa pos
was invalid, and zero otherwise.
.Pp
The
.Fn sbuf_cat ,
.Fn sbuf_cpy ,
.Fn sbuf_printf ,
.Fn sbuf_putc ,
and
.Fn sbuf_trim
functions
all return \-1 if the buffer overflowed, and zero otherwise.
.Pp
The
.Fn sbuf_error
function returns a non-zero value if the buffer has an overflow or
drain error, and zero otherwise.
.Pp
The
.Fn sbuf_data
and
.Fn sbuf_len
functions return
.Dv NULL
and \-1, respectively, if the buffer overflowed.
.Pp
The
.Fn sbuf_copyin
function
returns \-1 if copying string from userland failed, and number of bytes
copied otherwise.
.Pp
The
.Fn sbuf_finish 9
function (the kernel version) returns ENOMEM if the sbuf overflowed before
being finished,
or returns the error code from the drain if one is attached.
.Pp
The
.Fn sbuf_finish 3
function (the userland version)
will return zero for success and \-1 and set errno on error.
.Sh EXAMPLES
.Bd -literal -compact
#include <sys/sbuf.h>
struct sbuf *sb;
sb = sbuf_new_auto();
sbuf_cat(sb, "Customers found:\en");
TAILQ_FOREACH(foo, &foolist, list) {
sbuf_printf(sb, " %4d %s\en", foo->index, foo->name);
sbuf_printf(sb, " Address: %s\en", foo->address);
sbuf_printf(sb, " Zip: %s\en", foo->zipcode);
}
if (sbuf_finish(sb)) /* Check for any and all errors */
err(1,"Could not generate message");
transmit_msg(sbuf_data(sb), sbuf_len(sb));
sbuf_delete(sb);
.Ed
.Sh SEE ALSO
.Xr printf 3 ,
.Xr strcat 3 ,
.Xr strcpy 3 ,
.Xr copyin 9 ,
.Xr copyinstr 9 ,
.Xr printf 9
.Sh HISTORY
The
.Nm
family of functions first appeared in
.Fx 4.4 .
.Sh AUTHORS
.An -nosplit
The
.Nm
family of functions was designed by
.An Poul-Henning Kamp Aq phk@FreeBSD.org
and implemented by
.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
Additional improvements were suggested by
.An Justin T. Gibbs Aq gibbs@FreeBSD.org .
Auto-extend support added by
.An Kelly Yancey Aq kbyanc@FreeBSD.org .
Drain functionality added by
.An Matthew Fleming Aq mdf@FreeBSD.org .
.Pp
This manual page was written by
.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
|