Tribblix: manual page: asn1_read

asn1_read_value(3) libtasn1 asn1_read_value(3)

NAME

asn1_read_value - API function

SYNOPSIS

#include <libtasn1.h>

int asn1_read_value(asn1_node_const root, const char * name, void *
ivalue, int * len);

ARGUMENTS

asn1_node_const root
pointer to a structure.

const char * name
the name of the element inside a structure that you want
to read.

void * ivalue
vector that will contain the element's content, must be a
pointer to memory cells already allocated (may be NULL).

int * len number of bytes of *value: value[0]..value[len-1].
Initialy holds the sizeof value.

DESCRIPTION

Returns the value of one element inside a structure. If an element
is OPTIONAL and this returns ASN1_ELEMENT_NOT_FOUND, it means that
this element wasn't present in the der encoding that created the
structure. The first element of a SEQUENCE_OF or SET_OF is named
"?1". The second one "?2" and so on. If the root provided is a node
to specific sequence element, then the keyword "?CURRENT" is also
acceptable and indicates the current sequence element of this node.

Note that there can be valid values with length zero. In these case
this function will succeed and len will be zero.

INTEGER

VALUE will contain a two's complement form integer.

integer=-1 -> value[0]=0xFF , len=1. integer=1 -> value[0]=0x01 ,
len=1.

ENUMERATED

As INTEGER (but only with not negative numbers).

BOOLEAN

VALUE will be the null terminated string "TRUE" or "FALSE" and LEN=5
or LEN=6.

OBJECT IDENTIFIER: VALUE will be a null terminated string with each
number separated by a dot (i.e. "1.2.3.543.1").

LEN = strlen(VALUE)+1

UTCTIME

VALUE will be a null terminated string in one of these formats:
"YYMMDDhhmmss+hh'mm'" or "YYMMDDhhmmss-hh'mm'". LEN=strlen(VALUE)+1.

GENERALIZEDTIME

VALUE will be a null terminated string in the same format used to set
the value.

OCTET STRING: VALUE will contain the octet string and LEN will be the
number of octets.

GENERALSTRING

VALUE will contain the generalstring and LEN will be the number of
octets.

BIT STRING: VALUE will contain the bit string organized by bytes and
LEN will be the number of bits.

CHOICE

If NAME indicates a choice type, VALUE will specify the alternative
selected.

ANY

If NAME indicates an any type, VALUE will indicate the DER encoding
of the structure actually used.

RETURNS

ASN1_SUCCESS if value is returned, ASN1_ELEMENT_NOT_FOUND if name is
not a valid element, ASN1_VALUE_NOT_FOUND if there isn't any value
for the element selected, and ASN1_MEM_ERROR if The value vector
isn't big enough to store the result, and in this case len will
contain the number of bytes needed. On the occasion that the stored
data are of zero-length this function may return ASN1_SUCCESS even if
the provided len is zero.

COPYRIGHT

Copyright (C) 2006-2022 Free Software Foundation, Inc..
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.