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 ,
55 .Nm sbuf_start_section ,
56 .Nm sbuf_end_section ,
58 .Nd safe string composition
62 .Ft typedef\ int ( sbuf_drain_func ) ( void\ *arg, const\ char\ *data, int\ len ) ;
65 .Fn sbuf_new "struct sbuf *s" "char *buf" "int length" "int flags"
69 .Fn sbuf_clear "struct sbuf *s"
71 .Fn sbuf_setpos "struct sbuf *s" "int pos"
73 .Fn sbuf_bcat "struct sbuf *s" "const void *buf" "size_t len"
75 .Fn sbuf_bcopyin "struct sbuf *s" "const void *uaddr" "size_t len"
77 .Fn sbuf_bcpy "struct sbuf *s" "const void *buf" "size_t len"
79 .Fn sbuf_cat "struct sbuf *s" "const char *str"
81 .Fn sbuf_copyin "struct sbuf *s" "const void *uaddr" "size_t len"
83 .Fn sbuf_cpy "struct sbuf *s" "const char *str"
85 .Fn sbuf_printf "struct sbuf *s" "const char *fmt" "..."
87 .Fn sbuf_vprintf "struct sbuf *s" "const char *fmt" "va_list ap"
89 .Fn sbuf_putc "struct sbuf *s" "int c"
91 .Fn sbuf_set_drain "struct sbuf *s" "sbuf_drain_func *func" "void *arg"
93 .Fn sbuf_trim "struct sbuf *s"
95 .Fn sbuf_error "struct sbuf *s"
97 .Fn sbuf_finish "struct sbuf *s"
99 .Fn sbuf_data "struct sbuf *s"
101 .Fn sbuf_len "struct sbuf *s"
103 .Fn sbuf_done "struct sbuf *s"
105 .Fn sbuf_delete "struct sbuf *s"
107 .Fn sbuf_start_section "struct sbuf *s" "ssize_t *old_lenp"
109 .Fn sbuf_end_section "struct sbuf *s" "ssize_t old_len" "size_t pad" "int c"
112 .Fa "struct sbuf *sb"
115 .Fa "const char *hdr"
120 .Fn sbuf_new_for_sysctl "struct sbuf *s" "char *buf" "int length" "struct sysctl_req *req"
124 family of functions allows one to safely allocate, compose and
125 release strings in kernel or user space.
127 Instead of arrays of characters, these functions operate on structures
133 Any errors encountered during the allocation or composition of the
134 string will be latched in the data structure,
135 making a single error test at the end of the composition
136 sufficient to determine success or failure of the entire process.
140 function initializes the
142 pointed to by its first argument.
152 argument is a pointer to a buffer in which to store the actual string;
156 will allocate one using
160 is the initial size of the storage buffer.
163 may be comprised of the following flags:
164 .Bl -tag -width ".Dv SBUF_AUTOEXTEND"
166 The storage buffer is fixed at its initial size.
167 Attempting to extend the sbuf beyond this size results in an overflow condition.
168 .It Dv SBUF_AUTOEXTEND
169 This indicates that the storage buffer may be extended as necessary, so long
170 as resources allow, to hold additional data.
177 it must point to an array of at least
180 The result of accessing that array directly while it is in use by the
185 function is a shortcut for creating a completely dynamic
187 It is the equivalent of calling
194 .Dv SBUF_AUTOEXTEND .
197 .Fn sbuf_new_for_sysctl
198 function will set up an sbuf with a drain function to use
200 when the internal buffer fills.
201 Note that if the various functions which append to an sbuf are used while
202 a non-sleepable lock is held, the user buffer should be wired using
203 .Fn sysctl_wire_old_buffer .
209 and frees any memory allocated for it.
210 There must be a call to
214 Any attempt to access the sbuf after it has been deleted will fail.
218 function invalidates the contents of the
220 and resets its position to zero.
228 which is a value between zero and one less than the size of the
230 This effectively truncates the sbuf at the new position.
234 function appends the first
236 bytes from the buffer
245 bytes from the specified userland address into the
250 function replaces the contents of the
254 bytes from the buffer
259 function appends the NUL-terminated string
263 at the current position.
267 function sets a drain function
271 and records a pointer
273 to be passed to the drain on callback.
274 The drain function cannot be changed while
278 The registered drain function
280 will be called with the argument
286 to a byte string that is the contents of the sbuf, and the length
289 If the drain function exists, it will be called when the sbuf internal
290 buffer is full, or on behalf of
292 The drain function may drain some or all of the data, but must drain
294 The return value from the drain function, if positive, indicates how
295 many bytes were drained.
296 If negative, the return value indicates the negative error code which
297 will be returned from this or a later call to
299 The returned drained length cannot be zero.
300 To do unbuffered draining, initialize the sbuf with a two-byte buffer.
301 The drain will be called for every byte added to the sbuf.
308 functions cannot be used on an sbuf with a drain.
312 function copies a NUL-terminated string from the specified userland
317 argument is non-zero, no more than
319 characters (not counting the terminating NUL) are copied; otherwise
320 the entire string, or as much of it as can fit in the
326 function replaces the contents of the
328 with those of the NUL-terminated string
330 This is equivalent to calling
334 or one which position has been reset to zero with
341 function formats its arguments according to the format string pointed
344 and appends the resulting string to the
346 at the current position.
350 function behaves the same as
352 except that the arguments are obtained from the variable-length argument list
357 function appends the character
361 at the current position.
365 function removes trailing whitespace from the
370 function returns any error value that the
372 may have accumulated, either from the drain function, or ENOMEM if the
375 This function is generally not needed and instead the error code from
377 is the preferred way to discover whether an sbuf had an error.
381 function will call the attached drain function if one exists until all
385 If there is no attached drain,
389 In either case it marks the
391 as finished, which means that it may no longer be modified using
400 is used to reset the sbuf.
404 function returns the actual string;
406 only works on a finished
410 function returns the length of the string.
413 with an attached drain,
415 returns the length of the un-drained data.
417 returns non-zero if the
422 .Fn sbuf_start_section
425 functions may be used for automatic section alignment.
430 specify the padding size and a character used for padding.
435 are to save and restore the current section length when nested sections
437 For the top level section
439 and \-1 can be specified for
447 function prints an array of bytes to the supplied sbuf, along with an ASCII
448 representation of the bytes if possible.
451 man page for more details on the interface.
453 If an operation caused an
455 to overflow, most subsequent operations on it will fail until the
461 or its position is reset to a value between 0 and one less than the
462 size of its storage buffer using
464 or it is reinitialized to a sufficiently short string using
467 Drains in user-space will not always function as indicated.
468 While the drain function will be called immediately on overflow from
477 currently have no way to determine whether there will be an overflow
478 until after it occurs, and cannot do a partial expansion of the format
480 Thus when using libsbuf the buffer may be extended to allow completion
481 of a single printf call, even though a drain is attached.
487 if it failed to allocate a storage buffer, and a pointer to the new
493 function returns \-1 if
495 was invalid, and zero otherwise.
505 all return \-1 if the buffer overflowed, and zero otherwise.
509 function returns a non-zero value if the buffer has an overflow or
510 drain error, and zero otherwise.
514 function returns \-1 if the buffer overflowed.
519 returns \-1 if copying string from userland failed, and number of bytes
524 function returns the section length or \-1 if the buffer has an error.
528 function (the kernel version) returns ENOMEM if the sbuf overflowed before
530 or returns the error code from the drain if one is attached.
534 function (the userland version)
535 will return zero for success and \-1 and set errno on error.
537 .Bd -literal -compact
538 #include <sys/sbuf.h>
542 sb = sbuf_new_auto();
543 sbuf_cat(sb, "Customers found:\en");
544 TAILQ_FOREACH(foo, &foolist, list) {
545 sbuf_printf(sb, " %4d %s\en", foo->index, foo->name);
546 sbuf_printf(sb, " Address: %s\en", foo->address);
547 sbuf_printf(sb, " Zip: %s\en", foo->zipcode);
549 if (sbuf_finish(sb) != 0) /* Check for any and all errors */
550 err(1, "Could not generate message");
551 transmit_msg(sbuf_data(sb), sbuf_len(sb));
565 family of functions first appeared in
571 family of functions was designed by
572 .An Poul-Henning Kamp Aq phk@FreeBSD.org
574 .An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
575 Additional improvements were suggested by
576 .An Justin T. Gibbs Aq gibbs@FreeBSD.org .
577 Auto-extend support added by
578 .An Kelly Yancey Aq kbyanc@FreeBSD.org .
579 Drain functionality added by
580 .An Matthew Fleming Aq mdf@FreeBSD.org .
582 This manual page was written by
583 .An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .