Enum Types

Enumerations can be written as sum types with only constants:

enum day {Mon, Tue, Wed, Thur, Fri, Sat, Sun};

type%c day =
| Mon
| Tue
| Wed
| Thur
| Fri
| Sat
| Sun

In the above case an ordinary OCaml sum type named day will be created as well as a value day of type day Ctypes.typ.

In some cases, further annotations are required due to the different syntax rules of OCaml and C:

typedef enum {working = 1, failed = 0} State;

type%c state =
| Working [@cname "working"]
| Failed [@cname "failed"]
[@@cname "State"] [@@typedef]

If your function returns something else, e.g. 3 instead of working or failed, an exception would be thrown. You can suppress this behaviour by providing a custom “unexpected” function of type int64 -> your_type:

type%c state =
| Working
| Failed
[@@unexpected fun x -> Printf.printf "oops, %Ld returned\n%!" x; Failed]

Bit Masks

[@@as_bitmask] can be added to the type definition for functions that expect a bitwise-inclusive OR of enumeration constants (similar to open):

enum foo {
    F1 = (1u << 0),
    F2 = (1u << 1),
    F3 = (1u << 2)
};

type%c foo =
 | F1
 | F2
 | F3 [@@as_bitmask] 
 [@@ unexpected_bits fun (matched:foo list) (remainig_bits:int64) -> ... ]

In this case foo will be of type foo list Ctypes.typ. [@@with_bitmask] would create two values: foo of type foo Ctypes.typ and foo_bitmask of type foo Ctypes.typ.