1## Upgrading from 3.x to 4.0
2
3### Ber Object and Header
4
5The `class`, `structured` and `tag` fields were duplicated in `BerObject` and the header.
6Now, a header is always created and embedded in the BER object, with the following changes:
7
8- To access these fields, use the header: `obj.tag` becomes `obj.header.tag`, etc.
9- `BerObject::to_header()` is now deprecated
10- The `len` field is now public. However, in some cases it can be 0 (when creating an object, 0 means that serialization will calculate the length)
11- As a consequence, `PartialEq` on BER objects and headers compare `len` only if set in both objects
12
13### BER String types verification
14
15Some BER String types (`IA5String`, `NumericString`, `PrintableString` and `UTF8String`) are now
16verified, and will now only parse if the characters are valid.
17
18Their types have change from slice to `str` in the `BerObjectContent` enum.
19
20### BerClass
21
22The `class` field of `BerObject` struct now uses the newtype `BerClass`. Use the provided constants
23(for ex `BerClass:Universal`). To access the value, just use `class.0`.
24
25### Maximum depth
26
27The `depth` argument of functions (for ex. `ber_read_element_content_as`) has changed, and is now the maximum possible depth while parsing.
28Change it (usually from `0`) to a possible limit, for ex `der_parser::ber::MAX_RECURSION`.
29
30### Oid
31
32This is probably the most impacting change.
33
34OID objects have been refactored, and are now zero-copy. This has several consequences:
35
36- `Oid` struct now has a lifetime, which must be propagated to objects using them
37  - This makes having globally static structs difficult. Obtaining a `'static` object is possible
38    using the `oid` macro. For ex:
39
40```rust
41const SOME_STATIC_OID: Oid<'static> = oid!(1.2.456);
42```
43
44- Due to limitations of procedural macros  ([rust
45  issue](https://github.com/rust-lang/rust/issues/54727)) and constants used in patterns ([rust issue](https://github.com/rust-lang/rust/issues/31434)), the `oid` macro can not directly be used in patterns, also not through constants.
46You can do this, though:
47
48```rust
49# use der_parser::{oid, oid::Oid};
50# let some_oid: Oid<'static> = oid!(1.2.456);
51const SOME_OID: Oid<'static> = oid!(1.2.456);
52if some_oid == SOME_OID || some_oid == oid!(1.2.456) {
53    println!("match");
54}
55
56// Alternatively, compare the DER encoded form directly:
57const SOME_OID_RAW: &[u8] = &oid!(raw 1.2.456);
58match some_oid.bytes() {
59    SOME_OID_RAW => println!("match"),
60    _ => panic!("no match"),
61}
62```
63*Attention*, be aware that the latter version might not handle the case of a relative oid correctly. An
64extra check might be necessary.
65
66- To build an `Oid`, the `from`, `new` or `new_relative` methods can be used.
67- The `from` method now returns a `Result` (failure can happen if the first components are too
68  large, for ex)
69- An `oid` macro has also been added in the `der-oid-macro` crate to easily build an `Oid` (see
70  above).
71