2 .\" Copyright (c) 2000 Poul-Henning Kamp and Dag-Erling Coïdan Smørgrav
3 .\" All rights reserved.
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35 .Nm sbuf_new_for_sysctl ,
39 .Nm sbuf_clear_flags ,
58 .Nm sbuf_start_section ,
59 .Nm sbuf_end_section ,
61 .Nd safe string composition
65 .Ft typedef\ int ( sbuf_drain_func ) ( void\ *arg, const\ char\ *data, int\ len ) ;
68 .Fn sbuf_new "struct sbuf *s" "char *buf" "int length" "int flags"
72 .Fn sbuf_clear "struct sbuf *s"
74 .Fn sbuf_get_flags "struct sbuf *s"
76 .Fn sbuf_set_flags "struct sbuf *s" "int flags"
78 .Fn sbuf_clear_flags "struct sbuf *s" "int flags"
80 .Fn sbuf_setpos "struct sbuf *s" "int pos"
82 .Fn sbuf_bcat "struct sbuf *s" "const void *buf" "size_t len"
84 .Fn sbuf_bcopyin "struct sbuf *s" "const void *uaddr" "size_t len"
86 .Fn sbuf_bcpy "struct sbuf *s" "const void *buf" "size_t len"
88 .Fn sbuf_cat "struct sbuf *s" "const char *str"
90 .Fn sbuf_copyin "struct sbuf *s" "const void *uaddr" "size_t len"
92 .Fn sbuf_cpy "struct sbuf *s" "const char *str"
94 .Fn sbuf_printf "struct sbuf *s" "const char *fmt" "..."
96 .Fn sbuf_vprintf "struct sbuf *s" "const char *fmt" "va_list ap"
98 .Fn sbuf_putc "struct sbuf *s" "int c"
100 .Fn sbuf_set_drain "struct sbuf *s" "sbuf_drain_func *func" "void *arg"
102 .Fn sbuf_trim "struct sbuf *s"
104 .Fn sbuf_error "struct sbuf *s"
106 .Fn sbuf_finish "struct sbuf *s"
108 .Fn sbuf_data "struct sbuf *s"
110 .Fn sbuf_len "struct sbuf *s"
112 .Fn sbuf_done "struct sbuf *s"
114 .Fn sbuf_delete "struct sbuf *s"
116 .Fn sbuf_start_section "struct sbuf *s" "ssize_t *old_lenp"
118 .Fn sbuf_end_section "struct sbuf *s" "ssize_t old_len" "size_t pad" "int c"
121 .Fa "struct sbuf *sb"
124 .Fa "const char *hdr"
129 .Fn sbuf_new_for_sysctl "struct sbuf *s" "char *buf" "int length" "struct sysctl_req *req"
133 family of functions allows one to safely allocate, compose and
134 release strings in kernel or user space.
136 Instead of arrays of characters, these functions operate on structures
142 Any errors encountered during the allocation or composition of the
143 string will be latched in the data structure,
144 making a single error test at the end of the composition
145 sufficient to determine success or failure of the entire process.
149 function initializes the
151 pointed to by its first argument.
161 argument is a pointer to a buffer in which to store the actual string;
165 will allocate one using
169 is the initial size of the storage buffer.
172 may be comprised of the following flags:
173 .Bl -tag -width ".Dv SBUF_AUTOEXTEND"
175 The storage buffer is fixed at its initial size.
176 Attempting to extend the sbuf beyond this size results in an overflow condition.
177 .It Dv SBUF_AUTOEXTEND
178 This indicates that the storage buffer may be extended as necessary, so long
179 as resources allow, to hold additional data.
180 .It Dv SBUF_INCLUDENUL
181 This causes the final nulterm byte to be counted in the length of the data.
188 it must point to an array of at least
191 The result of accessing that array directly while it is in use by the
196 function is a shortcut for creating a completely dynamic
198 It is the equivalent of calling
205 .Dv SBUF_AUTOEXTEND .
208 .Fn sbuf_new_for_sysctl
209 function will set up an sbuf with a drain function to use
211 when the internal buffer fills.
212 Note that if the various functions which append to an sbuf are used while
213 a non-sleepable lock is held, the user buffer should be wired using
214 .Fn sysctl_wire_old_buffer .
220 and frees any memory allocated for it.
221 There must be a call to
225 Any attempt to access the sbuf after it has been deleted will fail.
229 function invalidates the contents of the
231 and resets its position to zero.
235 function returns the current user flags.
240 functions set or clear one or more user flags, respectively.
241 The user flags are described under the
251 which is a value between zero and one less than the size of the
253 This effectively truncates the sbuf at the new position.
257 function appends the first
259 bytes from the buffer
268 bytes from the specified userland address into the
273 function replaces the contents of the
277 bytes from the buffer
282 function appends the NUL-terminated string
286 at the current position.
290 function sets a drain function
294 and records a pointer
296 to be passed to the drain on callback.
297 The drain function cannot be changed while
301 The registered drain function
303 will be called with the argument
309 to a byte string that is the contents of the sbuf, and the length
312 If the drain function exists, it will be called when the sbuf internal
313 buffer is full, or on behalf of
315 The drain function may drain some or all of the data, but must drain
317 The return value from the drain function, if positive, indicates how
318 many bytes were drained.
319 If negative, the return value indicates the negative error code which
320 will be returned from this or a later call to
322 The returned drained length cannot be zero.
323 To do unbuffered draining, initialize the sbuf with a two-byte buffer.
324 The drain will be called for every byte added to the sbuf.
331 functions cannot be used on an sbuf with a drain.
335 function copies a NUL-terminated string from the specified userland
340 argument is non-zero, no more than
342 characters (not counting the terminating NUL) are copied; otherwise
343 the entire string, or as much of it as can fit in the
349 function replaces the contents of the
351 with those of the NUL-terminated string
353 This is equivalent to calling
357 or one which position has been reset to zero with
364 function formats its arguments according to the format string pointed
367 and appends the resulting string to the
369 at the current position.
373 function behaves the same as
375 except that the arguments are obtained from the variable-length argument list
380 function appends the character
384 at the current position.
388 function removes trailing whitespace from the
393 function returns any error value that the
395 may have accumulated, either from the drain function, or ENOMEM if the
398 This function is generally not needed and instead the error code from
400 is the preferred way to discover whether an sbuf had an error.
404 function will call the attached drain function if one exists until all
408 If there is no attached drain,
412 In either case it marks the
414 as finished, which means that it may no longer be modified using
423 is used to reset the sbuf.
427 function returns the actual string;
429 only works on a finished
433 function returns the length of the string.
436 with an attached drain,
438 returns the length of the un-drained data.
440 returns non-zero if the
445 .Fn sbuf_start_section
448 functions may be used for automatic section alignment.
453 specify the padding size and a character used for padding.
458 are to save and restore the current section length when nested sections
460 For the top level section
462 and \-1 can be specified for
470 function prints an array of bytes to the supplied sbuf, along with an ASCII
471 representation of the bytes if possible.
474 man page for more details on the interface.
476 If an operation caused an
478 to overflow, most subsequent operations on it will fail until the
484 or its position is reset to a value between 0 and one less than the
485 size of its storage buffer using
487 or it is reinitialized to a sufficiently short string using
490 Drains in user-space will not always function as indicated.
491 While the drain function will be called immediately on overflow from
500 currently have no way to determine whether there will be an overflow
501 until after it occurs, and cannot do a partial expansion of the format
503 Thus when using libsbuf the buffer may be extended to allow completion
504 of a single printf call, even though a drain is attached.
510 if it failed to allocate a storage buffer, and a pointer to the new
516 function returns \-1 if
518 was invalid, and zero otherwise.
528 all return \-1 if the buffer overflowed, and zero otherwise.
532 function returns a non-zero value if the buffer has an overflow or
533 drain error, and zero otherwise.
537 function returns \-1 if the buffer overflowed.
542 returns \-1 if copying string from userland failed, and number of bytes
547 function returns the section length or \-1 if the buffer has an error.
551 function (the kernel version) returns ENOMEM if the sbuf overflowed before
553 or returns the error code from the drain if one is attached.
557 function (the userland version)
558 will return zero for success and \-1 and set errno on error.
560 .Bd -literal -compact
561 #include <sys/sbuf.h>
565 sb = sbuf_new_auto();
566 sbuf_cat(sb, "Customers found:\en");
567 TAILQ_FOREACH(foo, &foolist, list) {
568 sbuf_printf(sb, " %4d %s\en", foo->index, foo->name);
569 sbuf_printf(sb, " Address: %s\en", foo->address);
570 sbuf_printf(sb, " Zip: %s\en", foo->zipcode);
572 if (sbuf_finish(sb) != 0) /* Check for any and all errors */
573 err(1, "Could not generate message");
574 transmit_msg(sbuf_data(sb), sbuf_len(sb));
588 family of functions first appeared in
594 family of functions was designed by
595 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org
597 .An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .
598 Additional improvements were suggested by
599 .An Justin T. Gibbs Aq Mt gibbs@FreeBSD.org .
600 Auto-extend support added by
601 .An Kelly Yancey Aq Mt kbyanc@FreeBSD.org .
602 Drain functionality added by
603 .An Matthew Fleming Aq Mt mdf@FreeBSD.org .
605 This manual page was written by
606 .An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .