.\" $OpenBSD: ober_get_string.3,v 1.5 2021/03/03 20:15:54 martijn Exp $
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.\" Copyright (c) 2007, 2012 Reyk Floeter <reyk@openbsd.org>
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.Dd $Mdocdate: March 3 2021 $
.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.
If the storage location is
.Dv NULL
then only a type check is performed.
Additionally,
.Fn ober_get_nstring
and
.Fn ober_get_bitstring
save the number of bytes contained in the string into
.Pf * Fa size .
If
.Fa buf
is
.Dv NULL
and size is not
.Dv NULL ,
size is set.
.Fa size
must not be
.Dv NULL
to return a valid
.Fa buf .
.Pp
.Fn ober_scanf_elements
retrieves the values from zero or more elements starting at
.Fa root .
For each character 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 character.
The following characters are valid:
.Bl -column "( or {" "ober_get_enumerated()" "1: struct ber_element **" -offset indent
.It Sy character Ta Sy function Ta Sy arguments
.It $ Ta see below              Ta 0
.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.
A
.Sq $
mandates the end of a sequence or set.
.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 .