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]. Initially 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 © 2006-2025 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:

    https://www.gnu.org/software/libtasn1/manual/