ASN1_STRING_FLAG_BITS_LEFT
pubkey_str.flags = ASN1_STRING_FLAG_BITS_LEFT;
a->flags &= ~(ASN1_STRING_FLAG_BITS_LEFT | 0x07); /* clear, set on write */
if (a->flags & ASN1_STRING_FLAG_BITS_LEFT) {
str->flags |= ASN1_STRING_FLAG_BITS_LEFT | (num & 0x07);
seed.flags = ASN1_STRING_FLAG_BITS_LEFT;