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.\" $OpenBSD: ober_get_string.3,v 1.2 2019/10/25 04:00:10 tb Exp $
.\"
.\" Copyright (c) 2007, 2012 Reyk Floeter <reyk@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: October 25 2019 $
.Dt OBER_GET_STRING 3
.Os
.Sh NAME
.Nm ober_get_null ,
.Nm ober_get_eoc ,
.Nm ober_get_integer ,
.Nm ober_get_enumerated ,
.Nm ober_get_boolean ,
.Nm ober_get_string ,
.Nm ober_get_nstring ,
.Nm ober_get_ostring ,
.Nm ober_get_bitstring ,
.Nm ober_get_oid ,
.Nm ober_getpos ,
.Nm ober_scanf_elements
.Nd access properties of ASN.1 objects decoded from BER
.Sh SYNOPSIS
.In sys/types.h
.In ber.h
.Ft "int"
.Fn "ober_get_null" "struct ber_element *root"
.Ft "int"
.Fn "ober_get_eoc" "struct ber_element *root"
.Ft "int"
.Fn "ober_get_integer" "struct ber_element *root" "long long *val"
.Ft "int"
.Fn "ober_get_enumerated" "struct ber_element *root" "long long *val"
.Ft "int"
.Fn "ober_get_boolean" "struct ber_element *root" "int *bool"
.Ft "int"
.Fn "ober_get_string" "struct ber_element *root" "char **charbuf"
.Ft "int"
.Fn "ober_get_nstring" "struct ber_element *root" "void **buf" "size_t *size"
.Ft "int"
.Fn "ober_get_ostring" "struct ber_element *root" "struct ber_octetstring *ostring"
.Ft "int"
.Fn "ober_get_bitstring" "struct ber_element *root" "void **buf" "size_t *size"
.Ft "int"
.Fn "ober_get_oid" "struct ber_element *root" "struct ber_oid *oid"
.Ft off_t
.Fn "ober_getpos" "struct ber_element *elm"
.Ft "int"
.Fn "ober_scanf_elements" "struct ber_element *root" "char *format" "..."
.Sh DESCRIPTION
Functions which take two arguments save the value contained in the
.Fa root
element into the storage location pointed to by the second argument.
Additionally,
.Fn ober_get_nstring
and
.Fn ober_get_bitstring
save the number of bytes contained in the string into
.Pf * Fa size .
.Pp
.Fn ober_scanf_elements
retrieves the values from zero or more elements starting at
.Fa root .
For each byte in
.Fa fmt ,
arguments of the types given in the following table are consumed
and passed to the function listed, processing one
.Vt ber_element
per byte.
The following bytes are valid:
.Bl -column -offset indent bytes ober_get_enumerated() "1: struct ber_element **"
.It Sy byte Ta Sy function Ta Sy arguments
.It B Ta Fn ober_get_bitstring Ta 2: Vt void ** , size_t *
.It b Ta Fn ober_get_boolean Ta 1: Vt int *
.It d Ta Fn ober_get_integer Ta 1: Vt int *
.It E Ta Fn ober_get_enumerated Ta 1: Vt long long *
.It e Ta see below Ta 1: Vt struct ber_element **
.It i Ta Fn ober_get_integer Ta 1: Vt long long *
.It o Ta Fn ober_get_oid Ta 1: Vt struct ber_oid *
.It p Ta Fn ober_getpos Ta 1: Vt off_t *
.It S Ta see below Ta 0
.It s Ta Fn ober_get_string Ta 1: Vt char **
.It t Ta see below Ta 2: Vt int * , unsigned int *
.It x Ta Fn ober_get_nstring Ta 2: Vt void **, size_t *
.It \&( or { Ta see below Ta 0
.It \&) or } Ta see below Ta 0
.It \&. Ta Fn ober_get_eoc Ta 0
.It 0 Ta Fn ober_get_null Ta 0
.El
.Pp
For
.Sq e ,
.Sq p ,
.Sq S ,
and
.Sq t ,
the type of the element is not checked.
For
.Sq p
and
.Sq t ,
the pointer is not incremented to the next element.
For
.Sq e ,
a pointer to the element is stored in the corresponding pointer variable.
For
.Sq S ,
the element is skipped without extracting any information from it.
For
.Sq t ,
the class and type of the element are stored in the two corresponding
variables, but if the element contains a value, that value is ignored.
.Pp
For an opening parenthesis or brace, it is checked that the element
is a sequence or a set, and parsing continues with its children.
For a closing parenthesis or brace, parsing of the current sequence
or set is ended and parsing continues with the element following
the sequence or set.
.Sh RETURN VALUES
.Fn ober_getpos
returns the value of
.Vt be_offs .
.Pp
.Fn ober_scanf_elements
returns 0 for success or \-1 when encountering elements that do not
agree with the expectations of
.Fa fmt
or when
.Fa fmt
is syntactically invalid.
Even when
.Fn ober_scanf_elements
fails, some of the arguments may already have been filled in.
.Pp
The other functions return 0 if
.Va root
is of the requested type or \-1 otherwise.
.Sh SEE ALSO
.Xr ober_add_string 3 ,
.Xr ober_oid_cmp 3 ,
.Xr ober_read_elements 3 ,
.Xr ober_set_header 3
.Sh STANDARDS
ITU-T Recommendation X.690, also known as ISO/IEC 8825-1:
Information technology - ASN.1 encoding rules.
.Sh HISTORY
These functions first appeared as internal functions in
.Xr snmpd 8
in
.Ox 4.2
and were moved to libutil in
.Ox 6.6 .
.Sh AUTHORS
.An -nosplit
The BER library was written by
.An Claudio Jeker Aq Mt claudio@openbsd.org ,
.An Marc Balmer Aq Mt marc@openbsd.org
and
.An Reyk Floeter Aq Mt reyk@openbsd.org .
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