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
8 .\" 1. Redistributions of source code must retain the above copyright
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14 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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16 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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19 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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35 .Nm sbuf_new_for_sysctl ,
39 .Nm sbuf_clear_flags ,
47 .Nm sbuf_nl_terminate ,
59 .Nm sbuf_start_section ,
60 .Nm sbuf_end_section ,
62 .Nm sbuf_printf_drain ,
64 .Nd safe string composition
71 .Fa "const char *data"
112 .Fa "const void *buf"
118 .Fa "const void *buf"
124 .Fa "const char *str"
129 .Fa "const char *str"
132 .Fn sbuf_nl_terminate "struct sbuf *"
136 .Fa "const char *fmt" "..."
141 .Fa "const char *fmt"
152 .Fa "sbuf_drain_func *func"
184 .Fo sbuf_start_section
186 .Fa "ssize_t *old_lenp"
191 .Fa "ssize_t old_len"
197 .Fa "struct sbuf *sb"
200 .Fa "const char *hdr"
204 .Fo sbuf_printf_drain
206 .Fa "const char *data"
219 .Fa "const void *uaddr"
225 .Fa "const void *uaddr"
230 .Fo sbuf_new_for_sysctl
234 .Fa "struct sysctl_req *req"
236 .Fd #endif /* _KERNEL */
240 family of functions allows one to safely allocate, compose and
241 release strings in kernel or user space.
243 Instead of arrays of characters, these functions operate on structures
249 Any errors encountered during the allocation or composition of the
250 string will be latched in the data structure,
251 making a single error test at the end of the composition
252 sufficient to determine success or failure of the entire process.
256 function initializes the
258 pointed to by its first argument.
268 argument is a pointer to a buffer in which to store the actual string;
272 will allocate one using
276 is the initial size of the storage buffer.
279 may be comprised of the following flags:
280 .Bl -tag -width ".Dv SBUF_AUTOEXTEND"
282 The storage buffer is fixed at its initial size.
283 Attempting to extend the sbuf beyond this size results in an overflow condition.
284 .It Dv SBUF_AUTOEXTEND
285 This indicates that the storage buffer may be extended as necessary, so long
286 as resources allow, to hold additional data.
287 .It Dv SBUF_INCLUDENUL
288 This causes the final nulterm byte to be counted in the length of the data.
289 .It Dv SBUF_DRAINTOEOR
290 Treat top-level sections started with
291 .Fn sbuf_start_section
292 as a record boundary marker that will be used during drain operations to avoid
294 If a record grows sufficiently large such that it fills the
296 and therefore cannot be drained without being split, an error of
300 Indicates that attempts to extend the storage buffer should fail in low memory
310 it must point to an array of at least
313 The result of accessing that array directly while it is in use by the
318 function is a shortcut for creating a completely dynamic
320 It is the equivalent of calling
327 .Dv SBUF_AUTOEXTEND .
330 .Fn sbuf_new_for_sysctl
331 function will set up an sbuf with a drain function to use
333 when the internal buffer fills.
334 Note that if the various functions which append to an sbuf are used while
335 a non-sleepable lock is held, the user buffer should be wired using
336 .Fn sysctl_wire_old_buffer .
342 and frees any memory allocated for it.
343 There must be a call to
347 Any attempt to access the sbuf after it has been deleted will fail.
351 function invalidates the contents of the
353 and resets its position to zero.
357 function returns the current user flags.
362 functions set or clear one or more user flags, respectively.
363 The user flags are described under the
373 which is a value between zero and one less than the size of the
375 This effectively truncates the sbuf at the new position.
379 function appends the first
381 bytes from the buffer
390 bytes from the specified userland address into the
395 function replaces the contents of the
399 bytes from the buffer
404 function appends the NUL-terminated string
408 at the current position.
412 function sets a drain function
416 and records a pointer
418 to be passed to the drain on callback.
419 The drain function cannot be changed while
423 The registered drain function
425 will be called with the argument
431 to a byte string that is the contents of the sbuf, and the length
434 If the drain function exists, it will be called when the sbuf internal
435 buffer is full, or on behalf of
437 The drain function may drain some or all of the data, but must drain
439 The return value from the drain function, if positive, indicates how
440 many bytes were drained.
441 If negative, the return value indicates the negative error code which
442 will be returned from this or a later call to
444 If the returned drained length is 0, an error of
447 To do unbuffered draining, initialize the sbuf with a two-byte buffer.
448 The drain will be called for every byte added to the sbuf.
459 functions cannot be used on an sbuf with a drain.
463 function copies a NUL-terminated string from the specified userland
468 argument is non-zero, no more than
470 characters (not counting the terminating NUL) are copied; otherwise
471 the entire string, or as much of it as can fit in the
477 function replaces the contents of the
479 with those of the NUL-terminated string
481 This is equivalent to calling
485 or one which position has been reset to zero with
491 .Fn sbuf_nl_terminate
492 function appends a trailing newline character, if the current line is non-empty
493 and not already terminated by a newline character.
497 function formats its arguments according to the format string pointed
500 and appends the resulting string to the
502 at the current position.
506 function behaves the same as
508 except that the arguments are obtained from the variable-length argument list
513 function appends the character
517 at the current position.
521 function removes trailing whitespace from the
526 function returns any error value that the
528 may have accumulated, either from the drain function, or
533 This function is generally not needed and instead the error code from
535 is the preferred way to discover whether an sbuf had an error.
539 function will call the attached drain function if one exists until all
543 If there is no attached drain,
547 In either case it marks the
549 as finished, which means that it may no longer be modified using
558 is used to reset the sbuf.
562 function returns the actual string;
564 only works on a finished
568 function returns the length of the string.
571 with an attached drain,
573 returns the length of the un-drained data.
575 returns non-zero if the
580 .Fn sbuf_start_section
583 functions may be used for automatic section alignment.
588 specify the padding size and a character used for padding.
593 are to save and restore the current section length when nested sections
595 For the top level section
597 and \-1 can be specified for
605 function prints an array of bytes to the supplied sbuf, along with an ASCII
606 representation of the bytes if possible.
609 man page for more details on the interface.
612 .Fn sbuf_printf_drain
613 function is a drain function that will call printf, or log to the console.
618 or a valid pointer to a
624 the total bytes drained will be added to the value pointed to by
629 function printfs the sbuf to stdout if in userland, and to the console
630 and log if in the kernel.
633 must be finished before calling
635 It does not drain the buffer or update any pointers.
637 If an operation caused an
639 to overflow, most subsequent operations on it will fail until the
645 or its position is reset to a value between 0 and one less than the
646 size of its storage buffer using
648 or it is reinitialized to a sufficiently short string using
651 Drains in user-space will not always function as indicated.
652 While the drain function will be called immediately on overflow from
661 currently have no way to determine whether there will be an overflow
662 until after it occurs, and cannot do a partial expansion of the format
664 Thus when using libsbuf the buffer may be extended to allow completion
665 of a single printf call, even though a drain is attached.
671 if it failed to allocate a storage buffer, and a pointer to the new
677 function returns \-1 if
679 was invalid, and zero otherwise.
690 all return \-1 if the buffer overflowed, and zero otherwise.
694 function returns a non-zero value if the buffer has an overflow or
695 drain error, and zero otherwise.
699 function returns \-1 if the buffer overflowed.
704 returns \-1 if copying string from userland failed, and number of bytes
709 function returns the section length or \-1 if the buffer has an error.
713 function (the kernel version) returns
715 if the sbuf overflowed before being finished,
716 or returns the error code from the drain if one is attached.
720 function (the userland version)
721 will return zero for success and \-1 and set errno on error.
723 .Bd -literal -compact
724 #include <sys/types.h>
725 #include <sys/sbuf.h>
729 sb = sbuf_new_auto();
730 sbuf_cat(sb, "Customers found:\en");
731 TAILQ_FOREACH(foo, &foolist, list) {
732 sbuf_printf(sb, " %4d %s\en", foo->index, foo->name);
733 sbuf_printf(sb, " Address: %s\en", foo->address);
734 sbuf_printf(sb, " Zip: %s\en", foo->zipcode);
736 if (sbuf_finish(sb) != 0) /* Check for any and all errors */
737 err(1, "Could not generate message");
738 transmit_msg(sbuf_data(sb), sbuf_len(sb));
752 family of functions first appeared in
758 family of functions was designed by
759 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org
761 .An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .
762 Additional improvements were suggested by
763 .An Justin T. Gibbs Aq Mt gibbs@FreeBSD.org .
764 Auto-extend support added by
765 .An Kelly Yancey Aq Mt kbyanc@FreeBSD.org .
766 Drain functionality added by
767 .An Matthew Fleming Aq Mt mdf@FreeBSD.org .
769 This manual page was written by
770 .An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .