wasmi 2.0.0-beta.4

WebAssembly interpreter
Documentation 
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use crate::{
    Error,
    ExternRef,
    ValType,
    core::{RawVal, Typed, TypedRawVal},
    engine::TranslationError,
};
use core::convert::identity;

/// Returns the number of Wasmi engine cell slots required to represent a [`ValType`] `ty`.
#[inline]
pub fn required_cells_for_ty(ty: ValType) -> u16 {
    match ty {
        #[cfg(feature = "simd")]
        ValType::V128 => 2,
        _ => 1,
    }
}

/// Returns the number of Wasmi engine cell slots required to represent a slice of [`ValType`] `tys`.
#[inline]
pub fn required_cells_for_tys(tys: &[ValType]) -> Result<u16, Error> {
    let len_cells: usize = tys
        .iter()
        .copied()
        .map(required_cells_for_ty)
        .map(usize::from)
        .sum();
    len_cells
        .try_into()
        .map_err(|_| Error::from(TranslationError::SlotAccessOutOfBounds))
}

impl Typed for ExternRef {
    const TY: ValType = ValType::ExternRef;
}

/// A WebAssembly integer. Either `i32` or `i64`.
///
/// # Note
///
/// This trait provides some utility methods useful for translation.
pub trait WasmInteger:
    Copy + Eq + Typed + From<TypedRawVal> + Into<TypedRawVal> + From<RawVal> + Into<RawVal>
{
    /// Returns `true` if `self` is equal to zero (0).
    fn is_zero(self) -> bool;
}

macro_rules! impl_wasm_integer {
    ($($ty:ty),*) => {
        $(
            impl WasmInteger for $ty {
                fn is_zero(self) -> bool {
                    self == 0
                }
            }
        )*
    };
}
impl_wasm_integer!(i32, u32, i64, u64);

/// Implemented by integer types to wrap them to another (smaller) integer type.
pub trait Wrap<T> {
    /// Wraps `self` into a value of type `T`.
    fn wrap(self) -> T;
}

impl<T> Wrap<T> for T {
    #[inline]
    fn wrap(self) -> T {
        self
    }
}

macro_rules! impl_wrap_for {
    ( $($from_ty:ty => $to_ty:ty),* $(,)? ) => {
        $(
            impl Wrap<$to_ty> for $from_ty {
                #[inline]
                fn wrap(self) -> $to_ty { self as _ }
            }
        )*
    };
}
impl_wrap_for! {
    // signed
    i16 => i8,
    i32 => i8,
    i32 => i16,
    i64 => i8,
    i64 => i16,
    i64 => i32,
    // unsigned
    u16 => u8,
    u32 => u8,
    u32 => u16,
    u64 => u8,
    u64 => u16,
    u64 => u32,
}

/// Types that can be converted into bits.
pub trait ToBits {
    /// The output bits type of [`ToBits`].
    type Out: Copy;

    /// Converts `self` into a 32-bit `u32` value.
    fn to_bits(self) -> Self::Out;
}

macro_rules! impl_to_bits {
    ( $($ty:ty as $bits_ty:ty = $expr:expr),* $(,)? ) => {
        $(
            impl ToBits for $ty {
                type Out = $bits_ty;
                fn to_bits(self) -> Self::Out {
                    $expr(self)
                }
            }
        )*
    };
}
impl_to_bits! {
    u8 as u8 = identity,
    u16 as u16 = identity,
    u32 as u32 = identity,
    u64 as u64 = identity,

    f32 as u32 = f32::to_bits,
    f64 as u64 = f64::to_bits,

    i8 as u8 = |v: i8| u8::from_ne_bytes(v.to_ne_bytes()),
    i16 as u16 = |v: i16| u16::from_ne_bytes(v.to_ne_bytes()),
    i32 as u32 = |v: i32| u32::from_ne_bytes(v.to_ne_bytes()),
    i64 as u64 = |v: i64| u64::from_ne_bytes(v.to_ne_bytes()),
}