.TH scan_asn1dertag 3
.SH NAME
scan_asn1dertag \- decode an unsigned integer from ASN.1 DER length encoding
.SH SYNTAX
.B #include <libowfat/scan.h>

size_t \fBscan_asn1dertag\fP(const char *\fIsrc\fR,size_t \fIlen\fR,unsigned long long *\fIdest\fR);
.SH DESCRIPTION
scan_asn1dertag decodes an unsigned integer in ASN.1 DER tag encoding
from a memory area holding binary data.  It writes the decode value in
\fIdest\fR and returns the number of bytes it read from \fIsrc\fR.

scan_asn1dertag never reads more than \fIlen\fR bytes from \fIsrc\fR.  If the
sequence is longer than that, or the memory area contains an invalid
sequence, scan_asn1dertag returns 0 and does not touch \fIdest\fR.

The length of the longest ASN.1 DER length sequence is 128 bytes.  In
practice the largest sequence is sizeof(*dest)+1.
.SH "SEE ALSO"
fmt_asn1dertag(3)