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SBUF(9)		       FreeBSD Kernel Developer's Manual	       SBUF(9)

     sbuf, sbuf_new, sbuf_new_auto, sbuf_clear,	sbuf_setpos, sbuf_bcat,
     sbuf_bcopyin, sbuf_bcpy, sbuf_cat,	sbuf_copyin, sbuf_cpy, sbuf_printf,
     sbuf_vprintf, sbuf_putc, sbuf_trim, sbuf_overflowed, sbuf_finish,
     sbuf_data,	sbuf_len, sbuf_done, sbuf_delete -- safe string	formatting

     #include <sys/types.h>
     #include <sys/sbuf.h>

     struct sbuf *
     sbuf_new(struct sbuf *s, char *buf, int length, int flags);

     struct sbuf *

     sbuf_clear(struct sbuf *s);

     sbuf_setpos(struct	sbuf *s, int pos);

     sbuf_bcat(struct sbuf *s, const void *buf,	size_t len);

     sbuf_bcopyin(struct sbuf *s, const	void *uaddr, size_t len);

     sbuf_bcpy(struct sbuf *s, const void *buf,	size_t len);

     sbuf_cat(struct sbuf *s, const char *str);

     sbuf_copyin(struct	sbuf *s, const void *uaddr, size_t len);

     sbuf_cpy(struct sbuf *s, const char *str);

     sbuf_printf(struct	sbuf *s, const char *fmt, ...);

     sbuf_vprintf(struct sbuf *s, const	char *fmt, va_list ap);

     sbuf_putc(struct sbuf *s, int c);

     sbuf_trim(struct sbuf *s);

     sbuf_overflowed(struct sbuf *s);

     sbuf_finish(struct	sbuf *s);

     char *
     sbuf_data(struct sbuf *s);

     sbuf_len(struct sbuf *s);

     sbuf_done(struct sbuf *s);

     sbuf_delete(struct	sbuf *s);

     The sbuf family of	functions allows one to	safely allocate, construct and
     release bounded null-terminated strings in	kernel space.  Instead of
     arrays of characters, these functions operate on structures called	sbufs,
     defined in	<sys/sbuf.h>.

     The sbuf_new() function initializes the sbuf pointed to by	its first
     argument.	If that	pointer	is NULL, sbuf_new() allocates a	struct sbuf
     using malloc(9).  The buf argument	is a pointer to	a buffer in which to
     store the actual string; if it is NULL, sbuf_new()	will allocate one
     using malloc(9).  The length is the initial size of the storage buffer.
     The fourth	argument, flags, may be	comprised of the following flags:

     SBUF_FIXEDLEN    The storage buffer is fixed at its initial size.
		      Attempting to extend the sbuf beyond this	size results
		      in an overflow condition.

     SBUF_AUTOEXTEND  This indicates that the storage buffer may be extended
		      as necessary, so long as resources allow,	to hold	addi-
		      tional data.

     Note that if buf is not NULL, it must point to an array of	at least
     length characters.	 The result of accessing that array directly while it
     is	in use by the sbuf is undefined.

     The sbuf_new_auto() function is a shortcut	for creating a completely
     dynamic sbuf.  It is the equivalent of calling sbuf_new() with values

     The sbuf_delete() function	clears the sbuf	and frees any memory allocated
     for it.  There must be a call to sbuf_delete() for	every call to
     sbuf_new().  Any attempt to access	the sbuf after it has been deleted
     will fail.

     The sbuf_clear() function invalidates the contents	of the sbuf and	resets
     its position to zero.

     The sbuf_setpos() function	sets the sbuf's	end position to	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.

     The sbuf_bcat() function appends the first	len bytes from the buffer buf
     to	the sbuf.

     The sbuf_bcopyin()	function copies	len bytes from the specified userland
     address into the sbuf.

     The sbuf_bcpy() function replaces the contents of the sbuf	with the first
     len bytes from the	buffer buf.

     The sbuf_cat() function appends the NUL-terminated	string str to the sbuf
     at	the current position.

     The sbuf_copyin() function	copies a NUL-terminated	string from the	speci-
     fied userland address into	the sbuf.  If the len argument is non-zero, no
     more than len characters (not counting the	terminating NUL) are copied;
     otherwise the entire string, or as	much of	it as can fit in the sbuf, is

     The sbuf_cpy() function replaces the contents of the sbuf with those of
     the NUL-terminated	string str.  This is equivalent	to calling sbuf_cat()
     with a fresh sbuf or one which position has been reset to zero with
     sbuf_clear() or sbuf_setpos().

     The sbuf_printf() function	formats	its arguments according	to the format
     string pointed to by fmt and appends the resulting	string to the sbuf at
     the current position.

     The sbuf_vprintf()	function behaves the same as sbuf_printf() except that
     the arguments are obtained	from the variable-length argument list ap.

     The sbuf_putc() function appends the character c to the sbuf at the cur-
     rent position.

     The sbuf_trim() function removes trailing whitespace from the sbuf.

     The sbuf_overflowed() function returns a non-zero value if	the sbuf over-

     The sbuf_finish() function	null-terminates	the sbuf and marks it as fin-
     ished, which means	that it	may no longer be modified using	sbuf_setpos(),
     sbuf_cat(), sbuf_cpy(), sbuf_printf() or sbuf_putc().

     The sbuf_data() and sbuf_len() functions return the actual	string and its
     length, respectively; sbuf_data() only works on a finished	sbuf.
     sbuf_done() returns non-zero if the sbuf is finished.

     If	an operation caused an sbuf to overflow, most subsequent operations on
     it	will fail until	the sbuf is finished using sbuf_finish() or reset
     using sbuf_clear(), or its	position is reset to a value between 0 and one
     less than the size	of its storage buffer using sbuf_setpos(), or it is
     reinitialized to a	sufficiently short string using	sbuf_cpy().

     The sbuf_new() function returns NULL if it	failed to allocate a storage
     buffer, and a pointer to the new sbuf otherwise.

     The sbuf_setpos() function	returns	-1 if pos was invalid, and zero	other-

     The sbuf_cat(), sbuf_cpy(), sbuf_printf(),	sbuf_putc(), and sbuf_trim()
     functions all return -1 if	the buffer overflowed, and zero	otherwise.

     The sbuf_overflowed() function returns a non-zero value if	the buffer
     overflowed, and zero otherwise.

     The sbuf_data() and sbuf_len() functions return NULL and -1, respec-
     tively, if	the buffer overflowed.

     The sbuf_copyin() function	returns	-1 if copying string from userland
     failed, and number	of bytes copied	otherwise.

     printf(3),	strcat(3), strcpy(3), copyin(9), copyinstr(9), printf(9)

     The sbuf family of	functions first	appeared in FreeBSD 4.4.

     The sbuf family of	functions was designed by Poul-Henning Kamp
     <> and implemented by Dag-Erling Smorgrav
     <>.	 Additional improvements were suggested	by Justin T.
     Gibbs <>.	 Auto-extend support added by Kelly Yancey

     This manual page was written by Dag-Erling	Smorgrav <>.

FreeBSD	11.1			 May 17, 2009			  FreeBSD 11.1


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