vendor/windows/src/core/type.rs

use super::*;

#[doc(hidden)]
pub trait TypeKind {
    type TypeKind;
}

#[doc(hidden)]
pub struct ReferenceType;

#[doc(hidden)]
pub struct ValueType;

#[doc(hidden)]
pub struct CopyType;

#[doc(hidden)]
pub trait Type<T: TypeKind, C = <T as TypeKind>::TypeKind>: TypeKind + Sized {
    type Abi;
    type Default;

    fn abi(&self) -> Self::Abi {
        unsafe { std::mem::transmute_copy(self) }
    }

    /// # Safety
    unsafe fn from_abi(abi: Self::Abi) -> Result<Self>;
    fn from_default(default: &Self::Default) -> Result<Self>;

    // TODO: this only used by ManuallyDrop
    /// # Safety
    unsafe fn from_abi_ref(abi: &Self::Abi) -> Option<&Self>;
}

impl<T> Type<T, ReferenceType> for T
where
    T: TypeKind<TypeKind = ReferenceType> + Clone,
{
    type Abi = *mut std::ffi::c_void;
    type Default = Option<Self>;

    unsafe fn from_abi(abi: Self::Abi) -> Result<Self> {
        if !abi.is_null() {
            Ok(std::mem::transmute_copy(&abi))
        } else {
            Err(Error::OK)
        }
    }

    unsafe fn from_abi_ref(abi: &Self::Abi) -> Option<&Self> {
        if !abi.is_null() {
            Some(std::mem::transmute(abi))
        } else {
            None
        }
    }

    fn from_default(default: &Self::Default) -> Result<Self> {
        default.as_ref().cloned().ok_or(Error::OK)
    }
}

impl<T> Type<T, ValueType> for T
where
    T: TypeKind<TypeKind = ValueType> + Clone,
{
    type Abi = std::mem::MaybeUninit<Self>;
    type Default = Self;

    unsafe fn from_abi(abi: std::mem::MaybeUninit<Self>) -> Result<Self> {
        Ok(abi.assume_init())
    }

    unsafe fn from_abi_ref(abi: &Self::Abi) -> Option<&Self> {
        Some(std::mem::transmute(abi))
    }

    fn from_default(default: &Self::Default) -> Result<Self> {
        Ok(default.clone())
    }
}

impl<T> Type<T, CopyType> for T
where
    T: TypeKind<TypeKind = CopyType> + Clone,
{
    type Abi = Self;
    type Default = Self;

    unsafe fn from_abi(abi: Self) -> Result<Self> {
        Ok(abi)
    }

    unsafe fn from_abi_ref(abi: &Self::Abi) -> Option<&Self> {
        Some(abi)
    }

    fn from_default(default: &Self) -> Result<Self> {
        Ok(default.clone())
    }
}

impl<T: Interface> TypeKind for T {
    type TypeKind = ReferenceType;
}

impl<T> TypeKind for *mut T {
    type TypeKind = CopyType;
}

macro_rules! primitives {
    ($($t:ty),+) => {
        $(
            impl TypeKind for $t {
                type TypeKind = CopyType;
            }
        )*
    };
}

primitives!(bool, i8, u8, i16, u16, i32, u32, i64, u64, f32, f64, usize, isize);

#[doc(hidden)]
pub type AbiType<T> = <T as Type<T>>::Abi;

#[doc(hidden)]
pub unsafe fn from_abi<T: Type<T>>(abi: T::Abi) -> Result<T> {
    T::from_abi(abi)
}

#[doc(hidden)]
pub fn zeroed<T: Type<T>>() -> T::Abi {
    unsafe { std::mem::zeroed() }
}