std/asn1

DER, the ASN.1 encoding of keys and certificates, read and written, for std/publickey and for reading what X.509 holds.

import "std/asn1"

Asn1 value = der_read(data)?
if value.is(ASN1_SEQUENCE) then
    print(value.children[0].oid())    // 1.2.840.10045.2.1
end
bytes der = der_write(der_sequence([der_integer(1), der_octet_string(key)]))

Function or method	Result
`der_read(data)`	the value DER `data` encodes, which must be all of it; an `ERROR` of kind `"invalid_der"` for lengths that are not DER's, data cut short, or values nested more than 64 deep
`der_write(value)`	its DER
`der_sequence(children)`, `der_set(children)`, `der_context(n, children)`	constructed values, holding `children` in the order given (DER sorts a SET's: give them sorted)
`der_integer(n)`, `der_unsigned(bytes)`, `der_octet_string(bytes)`, `der_bit_string(bytes)`, `der_null()`, `der_utf8(text)`, `der_oid(dotted)`	the universal values
`v.is(tag)`, `v.is_context(n)`	whether it is the universal value of `tag` (`ASN1_INTEGER`, `ASN1_SEQUENCE`, and the other constants), or context-specific `[n]`
`v.integer()`, `v.unsigned_bytes()`, `v.oid()`, `v.bits()`, `v.text()`	what an INTEGER, OBJECT IDENTIFIER, BIT STRING, or string holds

An Asn1 has its class (0 universal, 1 application, 2 context-specific, 3 private), tag, whether it is constructed, its content, and the children of a constructed value.