plucky (3) scan_asn1derlengthvalue.3.gz

NAME

       scan_asn1derlengthvalue - decode an unsigned integer from ASN.1 DER length encoding

SYNTAX

       #include <libowfat/scan.h>

       size_t scan_asn1derlengthvalue(const char *src,size_t len,unsigned long long *dest);

DESCRIPTION

       scan_asn1derlengthvalue  decodes  an  unsigned  integer  in  ASN.1 DER length encoding from a memory area
       holding binary data.  It writes the decode value in dest and returns the number of  bytes  it  read  from
       src.

       scan_asn1derlength never reads more than len bytes from src.  If the sequence is longer than that, or the
       memory area contains an invalid sequence, scan_asn1derlength returns 0 and does not touch dest.

       The length of the longest spec-compliant ASN.1 DER length is 128  bytes,  but  this  implementation  will
       return an error if the value does not fit into the target integer type.  In practice the largest sequence
       is sizeof(*dest)+1.

       This implementation will reject values that are not encoded in the minimum amount of bytes.

       If you need to decode the length value so you can parse actual ASN.1 tag/length/value structures,  please
       consider using scan_asn1derlength instead, as it will do additional checking for you.

SEE ALSO

       fmt_asn1derlength(3), scan_asn1derlengthvalue(3)

                                                                                           scan_asn1derlength(3)