xref: /freebsd/share/man/man9/sbuf.9 (revision 863edaec4d32fbcaf33215112d81ab15f4f30ec7)

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.Dd December 10, 2000
.Dt sbuf 9
.Os FreeBSD
.Sh NAME
.Nm sbuf_new ,
.Nm sbuf_setpos ,
.Nm sbuf_cat ,
.Nm sbuf_cpy ,
.Nm sbuf_printf ,
.Nm sbuf_putc ,
.Nm sbuf_finish ,
.Nm sbuf_data ,
.Nm sbuf_len ,
.Nm sbuf_delete
.Nd safe string formatting
.Sh SYNOPSIS
.Fd #include <sys/sbuf.h>
.Ft int
.Fn sbuf_new "struct sbuf *s" "char *buf" "size_t length" "int flags"
.Ft int
.Fn sbuf_setpos "struct sbuf *s" "size_t pos"
.Ft int
.Fn sbuf_cat "struct sbuf *s" "char *str"
.Ft int
.Fn sbuf_cpy "struct sbuf *s" "char *str"
.Ft int
.Fn sbuf_printf "struct sbuf *s" "char *fmt" "..."
.Ft int
.Fn sbuf_putc "struct sbuf *s" "int c"
.Ft int
.Fn sbuf_finish "struct sbuf *s"
.Ft char *
.Fn sbuf_data "struct sbuf *s"
.Ft size_t
.Fn sbuf_len "struct sbuf *s"
.Ft void
.Fn sbuf_delete "struct sbuf *s"
.Sh DESCRIPTION
The
.Nm sbuf
family of functions allow 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
.Fa sbufs ,
defined in
.Aq Pa sys/sbuf.h .
.Pp
The
.Fn sbuf_new
function initializes the
.Fa sbuf
pointed to by its first argument.
The
.Fa buf
argument is a pointer to a buffer in which to store the actual string;
if it is
.Dv NULL ,
.Fn sbuf_new
will allocate one using
.Xr malloc 9 .
The
.Fa length
is the intended size of the storage buffer.
The fourth argument,
.Fa flags ,
is currently unused and should always be set to zero.
.Pp
Note that if
.Fa buf
is not
.Dv NULL ,
it must point to an array of at least
.Fa length
characters.
.Pp
The
.Fn sbuf_setpos
function sets the
.Fa sbuf Ns 's
current position to
.Fa pos ,
which is a value between zero and one less than the size of the
storage buffer.
.Pp
The
.Fn sbuf_cat
function appends the string
.Fa str
to the
.Fa sbuf
at the current position.
.Pp
The
.Fn sbuf_cpy
function replaces the contents of the
.Fa sbuf
with those of the string
.Fa str .
This is equivalent to calling
.Fn sbuf_cat
with a fresh
.Fa sbuf
or one which position has been reset to zero with
.Fn sbuf_setpos .
.Pp
The
.Fn sbuf_printf
function formats its arguments according to the format string pointed
to by
.Fa fmt
and appends the resulting string to the
.Fa sbuf
at the current position.
.Pp
The
.Fn sbuf_putc
function appends the character
.Fa c
to the
.Fa sbuf
at the current position.
.Pp
The
.Fn sbuf_finish
function null-terminates the
.Fa sbuf
and marks it as finished, which means that it may no longer be
modified using
.Fn sbuf_setpos ,
.Fn sbuf_cat ,
.Fn sbuf_cpu ,
.Fn sbuf_printf
or
.Fn sbuf_putc .
.Pp
The
.Fn sbuf_data
and
.Fn sbuf_len
functions return the actual string and its length, respectively, and
only work on a finished and non-overflowed
.Fa sbuf .
.Pp
Finally, the
.Fn sbuf_delete
function clears the
.Fa sbuf
and frees its storage buffer if it was allocated by
.Fn sbuf_new .
.Sh NOTES
If an operation caused an
.Fa sbuf
to overflow, most subsequent operations (including
.Fn sbuf_finish )
on it will fail until the
.Fa sbuf Ns 's
position is reset to a value between 0 and one less than the size of
its storage buffer using
.Fn sbuf_setpos ,
or it is reinitialized to a sufficiently short string using
.Fn sbuf_cpy .
.Sh RETURN VALUES
.Fn sbuf_new
returns \-1 if it failed to allocate a storage buffer, and zero
otherwise.
.Pp
.Fn sbuf_setpos
returns \-1 if
.Fa pos
was invalid, and zero otherwise.
.Pp
.Fn sbuf_cat ,
.Fn sbuf_cpy ,
.Fn sbuf_printf ,
.Fn sbuf_putc ,
and
.Fn sbuf_finish
all return \-1 if the buffer overflowed, and zero otherwise.
.Pp
.Fn sbuf_data
and
.Fn sbuf_len
return
.Dv NULL
and 0, respectively, if the buffer overflowed.
.Sh SEE ALSO
.Xr printf 3 ,
.Xr strcat 3 ,
.Xr strcpy 3
.Sh HISTORY
The
.Nm sbuf
family of functions first appeared in
.Fx 4.3 .
.Sh AUTHORS
.An -nosplit
The
.Nm sbuf
family of functions was designed by
.An Poul-Henning Kamp Aq phk@FreeBSD.org
and implemented by
.An Dag-Erling Co\(:idan Sm\(/orgrav Aq des@FreeBSD.org .
.Pp
This manual page was written by
.An Dag-Erling Co\(:idan Sm\(/orgrav .