2 .\" Copyright (c) 2000 Poul-Henning Kamp and Dag-Erling Coïdan Smørgrav
3 .\" All rights reserved.
5 .\" Redistribution and use in source and binary forms, with or without
6 .\" modification, are permitted provided that the following conditions
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16 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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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 ,
62 .Nd safe string composition
66 .Ft typedef\ int ( sbuf_drain_func ) ( void\ *arg, const\ char\ *data, int\ len ) ;
105 .Fa "const void *buf"
111 .Fa "const void *buf"
117 .Fa "const char *str"
122 .Fa "const char *str"
127 .Fa "const char *fmt" "..."
132 .Fa "const char *fmt"
143 .Fa "sbuf_drain_func *func"
175 .Fo sbuf_start_section
177 .Fa "ssize_t *old_lenp"
182 .Fa "ssize_t old_len"
188 .Fa "struct sbuf *sb"
191 .Fa "const char *hdr"
204 .Fa "const void *uaddr"
210 .Fa "const void *uaddr"
215 .Fo sbuf_new_for_sysctl
219 .Fa "struct sysctl_req *req"
221 .Fd #endif /* _KERNEL */
225 family of functions allows one to safely allocate, compose and
226 release strings in kernel or user space.
228 Instead of arrays of characters, these functions operate on structures
234 Any errors encountered during the allocation or composition of the
235 string will be latched in the data structure,
236 making a single error test at the end of the composition
237 sufficient to determine success or failure of the entire process.
241 function initializes the
243 pointed to by its first argument.
253 argument is a pointer to a buffer in which to store the actual string;
257 will allocate one using
261 is the initial size of the storage buffer.
264 may be comprised of the following flags:
265 .Bl -tag -width ".Dv SBUF_AUTOEXTEND"
267 The storage buffer is fixed at its initial size.
268 Attempting to extend the sbuf beyond this size results in an overflow condition.
269 .It Dv SBUF_AUTOEXTEND
270 This indicates that the storage buffer may be extended as necessary, so long
271 as resources allow, to hold additional data.
272 .It Dv SBUF_INCLUDENUL
273 This causes the final nulterm byte to be counted in the length of the data.
274 .It Dv SBUF_DRAINTOEOR
275 Treat top-level sections started with
276 .Fn sbuf_start_section
277 as a record boundary marker that will be used during drain operations to avoid
279 If a record grows sufficiently large such that it fills the
281 and therefore cannot be drained without being split, an error of EDEADLK is set.
288 it must point to an array of at least
291 The result of accessing that array directly while it is in use by the
296 function is a shortcut for creating a completely dynamic
298 It is the equivalent of calling
305 .Dv SBUF_AUTOEXTEND .
308 .Fn sbuf_new_for_sysctl
309 function will set up an sbuf with a drain function to use
311 when the internal buffer fills.
312 Note that if the various functions which append to an sbuf are used while
313 a non-sleepable lock is held, the user buffer should be wired using
314 .Fn sysctl_wire_old_buffer .
320 and frees any memory allocated for it.
321 There must be a call to
325 Any attempt to access the sbuf after it has been deleted will fail.
329 function invalidates the contents of the
331 and resets its position to zero.
335 function returns the current user flags.
340 functions set or clear one or more user flags, respectively.
341 The user flags are described under the
351 which is a value between zero and one less than the size of the
353 This effectively truncates the sbuf at the new position.
357 function appends the first
359 bytes from the buffer
368 bytes from the specified userland address into the
373 function replaces the contents of the
377 bytes from the buffer
382 function appends the NUL-terminated string
386 at the current position.
390 function sets a drain function
394 and records a pointer
396 to be passed to the drain on callback.
397 The drain function cannot be changed while
401 The registered drain function
403 will be called with the argument
409 to a byte string that is the contents of the sbuf, and the length
412 If the drain function exists, it will be called when the sbuf internal
413 buffer is full, or on behalf of
415 The drain function may drain some or all of the data, but must drain
417 The return value from the drain function, if positive, indicates how
418 many bytes were drained.
419 If negative, the return value indicates the negative error code which
420 will be returned from this or a later call to
422 The returned drained length cannot be zero.
423 To do unbuffered draining, initialize the sbuf with a two-byte buffer.
424 The drain will be called for every byte added to the sbuf.
431 functions cannot be used on an sbuf with a drain.
435 function copies a NUL-terminated string from the specified userland
440 argument is non-zero, no more than
442 characters (not counting the terminating NUL) are copied; otherwise
443 the entire string, or as much of it as can fit in the
449 function replaces the contents of the
451 with those of the NUL-terminated string
453 This is equivalent to calling
457 or one which position has been reset to zero with
464 function formats its arguments according to the format string pointed
467 and appends the resulting string to the
469 at the current position.
473 function behaves the same as
475 except that the arguments are obtained from the variable-length argument list
480 function appends the character
484 at the current position.
488 function removes trailing whitespace from the
493 function returns any error value that the
495 may have accumulated, either from the drain function, or ENOMEM if the
498 This function is generally not needed and instead the error code from
500 is the preferred way to discover whether an sbuf had an error.
504 function will call the attached drain function if one exists until all
508 If there is no attached drain,
512 In either case it marks the
514 as finished, which means that it may no longer be modified using
523 is used to reset the sbuf.
527 function returns the actual string;
529 only works on a finished
533 function returns the length of the string.
536 with an attached drain,
538 returns the length of the un-drained data.
540 returns non-zero if the
545 .Fn sbuf_start_section
548 functions may be used for automatic section alignment.
553 specify the padding size and a character used for padding.
558 are to save and restore the current section length when nested sections
560 For the top level section
562 and \-1 can be specified for
570 function prints an array of bytes to the supplied sbuf, along with an ASCII
571 representation of the bytes if possible.
574 man page for more details on the interface.
578 function printfs the sbuf to stdout if in userland, and to the console
579 and log if in the kernel.
580 It does not drain the buffer or update any pointers.
582 If an operation caused an
584 to overflow, most subsequent operations on it will fail until the
590 or its position is reset to a value between 0 and one less than the
591 size of its storage buffer using
593 or it is reinitialized to a sufficiently short string using
596 Drains in user-space will not always function as indicated.
597 While the drain function will be called immediately on overflow from
606 currently have no way to determine whether there will be an overflow
607 until after it occurs, and cannot do a partial expansion of the format
609 Thus when using libsbuf the buffer may be extended to allow completion
610 of a single printf call, even though a drain is attached.
616 if it failed to allocate a storage buffer, and a pointer to the new
622 function returns \-1 if
624 was invalid, and zero otherwise.
635 all return \-1 if the buffer overflowed, and zero otherwise.
639 function returns a non-zero value if the buffer has an overflow or
640 drain error, and zero otherwise.
644 function returns \-1 if the buffer overflowed.
649 returns \-1 if copying string from userland failed, and number of bytes
654 function returns the section length or \-1 if the buffer has an error.
658 function (the kernel version) returns ENOMEM if the sbuf overflowed before
660 or returns the error code from the drain if one is attached.
664 function (the userland version)
665 will return zero for success and \-1 and set errno on error.
667 .Bd -literal -compact
668 #include <sys/types.h>
669 #include <sys/sbuf.h>
673 sb = sbuf_new_auto();
674 sbuf_cat(sb, "Customers found:\en");
675 TAILQ_FOREACH(foo, &foolist, list) {
676 sbuf_printf(sb, " %4d %s\en", foo->index, foo->name);
677 sbuf_printf(sb, " Address: %s\en", foo->address);
678 sbuf_printf(sb, " Zip: %s\en", foo->zipcode);
680 if (sbuf_finish(sb) != 0) /* Check for any and all errors */
681 err(1, "Could not generate message");
682 transmit_msg(sbuf_data(sb), sbuf_len(sb));
696 family of functions first appeared in
702 family of functions was designed by
703 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org
705 .An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .
706 Additional improvements were suggested by
707 .An Justin T. Gibbs Aq Mt gibbs@FreeBSD.org .
708 Auto-extend support added by
709 .An Kelly Yancey Aq Mt kbyanc@FreeBSD.org .
710 Drain functionality added by
711 .An Matthew Fleming Aq Mt mdf@FreeBSD.org .
713 This manual page was written by
714 .An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .