man fmt_asn1dertag (3): encode unsigned integer like ASN.1 DER tag

SYNTAX

#include <fmt.h>

size_t fmt_asn1dertag(char *dest,unsigned long long source);

fmt_asn1dertag encodes an unsigned integer using the ASN.1 DER for encoding tag. This takes one byte for every 7 bits in the number.

If dest equals FMT_LEN (i.e. is NULL), fmt_asn1dertag returns the number of bytes it would have written.

For convenience, fmt.h defines the integer FMT_ASN1TAG to be big enough to contain every possible fmt_asn1dertag output.