NAME¶
asn1_read_value - API function
SYNOPSIS¶
#include <libtasn1.h>
int asn1_read_value(asn1_node root, const char *
name, void * ivalue, int * len);
ARGUMENTS¶
- asn1_node 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.
COPYRIGHT¶
Copyright © 2006-2013 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.
SEE ALSO¶
The full documentation for
libtasn1 is maintained as a Texinfo manual. If
the
info and
libtasn1 programs are properly installed at your
site, the command
- info libtasn1
should give you access to the complete manual. As an alternative you may obtain
the manual from:
- http://www.gnu.org/software/libtasn1/manual/