oc2_hlapi/
response.rs

1use crate::call::ApiCall;
2use crate::error::{Error, Result};
3use crate::types::{DeviceDescriptor, MethodDescriptor};
4use serde::de::{self, DeserializeOwned};
5use serde::Deserialize;
6use std::mem::MaybeUninit;
7use std::result::Result as StdResult;
8
9#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Deserialize)]
10#[serde(rename_all = "lowercase", tag = "type", content = "data")]
11pub enum Response<T: ApiCall> {
12    #[serde(alias = "list", alias = "methods", rename = "result")]
13    Response(T::Response),
14    Error(String),
15}
16
17#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Default, Deserialize)]
18pub struct List(pub Vec<DeviceDescriptor>);
19
20#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Default, Deserialize)]
21pub struct Methods(pub Vec<MethodDescriptor>);
22
23#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Default)]
24pub struct Return<R>(pub R);
25
26impl<'de, R: DeserializeOwned + 'static> Deserialize<'de> for Return<R> {
27    fn deserialize<D>(deserializer: D) -> StdResult<Self, D::Error>
28    where
29        D: serde::Deserializer<'de>,
30    {
31        // Generates a zero-sized type 'from thin air'.
32        // When invoking a method in the HLAPI that doesn't have a return value, one might expect
33        // the response to look like `{"type": "result", "data": null}`, but in reality, it looks
34        // like `{"type": "result"}`, and is missing the data field. With a derived Deserialize,
35        // serde_json would complain about a missing `data` field, when it is actually supposed to
36        // be missing. This only happens in the case of the void return type, which is represented
37        // by zero-sized types (usually `()`) in Rust.
38        fn zst<T>() -> T {
39            assert!(std::mem::size_of::<T>() == 0, "`T` must be a ZST");
40
41            // SAFETY: The check above ensures that T is a zero-sized type, and thus can be constructed by
42            // reading a well-aligned pointer, even if that pointer doesn't point to anything valid.
43            #[allow(clippy::uninit_assumed_init)]
44            unsafe {
45                MaybeUninit::uninit().assume_init()
46            }
47        }
48
49        let opt: Option<R> = Deserialize::deserialize(deserializer)?;
50
51        match opt {
52            Some(r) => Ok(Return(r)),
53            None if std::mem::size_of::<R>() == 0 => Ok(Return(zst())),
54            // We actually do expect the `data` field if the return type is not actually zero-sized.
55            // If there's no `data` field when it was expected, that means something went wrong, and
56            // not just that the call didn't return anything.
57            None => Err(de::Error::missing_field("data")),
58        }
59    }
60}
61
62impl<T: ApiCall> From<Response<T>> for Result<T::Response> {
63    fn from(value: Response<T>) -> Self {
64        match value {
65            Response::Response(t) => Ok(t),
66            // This branch should never get executed unless T is serialized to "null" in JSON. This
67            // is the case with Option<T> and (), for example.
68            Response::Error(e) => Err(Error::from(e)),
69        }
70    }
71}
oc2_hlapi/response.rs

oc2_hlapi/
response.rs
