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Implement To/FromWasmAbi for arrays #2649

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Implement To/FromWasmAbi for arrays #2649

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f3f7506
Implement To/FromWasmAbi for arrays
Jules-Bertholet Jul 13, 2021
0d07583
Remmove panic by adding `Default` bound
Jules-Bertholet Aug 9, 2021
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34 changes: 34 additions & 0 deletions src/convert/slices.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,8 @@ cfg_if! {
}

if_std! {
use std::convert::TryFrom;

impl<T> IntoWasmAbi for Vec<T> where Box<[T]>: IntoWasmAbi<Abi = WasmSlice> {
type Abi = <Box<[T]> as IntoWasmAbi>::Abi;

Expand Down Expand Up @@ -174,6 +176,38 @@ if_std! {
fn is_none(abi: &WasmSlice) -> bool { abi.ptr == 0 }
}

impl<T, const N: usize> IntoWasmAbi for [T; N] where Box<[T]>: IntoWasmAbi<Abi = WasmSlice> {
type Abi = <Box<[T]> as IntoWasmAbi>::Abi;

#[inline]
fn into_abi(self) -> Self::Abi {
<Box<[T]>>::from(self).into_abi()
}
}

impl<T, const N: usize> OptionIntoWasmAbi for [T; N] where Box<[T]>: IntoWasmAbi<Abi = WasmSlice> {
#[inline]
fn none() -> WasmSlice { null_slice() }
}

impl<T, const N: usize> FromWasmAbi for [T; N] where Box<[T]>: FromWasmAbi<Abi = WasmSlice> {
type Abi = <Box<[T]> as FromWasmAbi>::Abi;

#[inline]
unsafe fn from_abi(js: Self::Abi) -> Self {
let result = <[T; N]>::try_from(<Vec<T>>::from(<Box<[T]>>::from_abi(js)));
return match result {
Ok(arr) => arr,
Err(_) => panic!("JS array length does not match Rust array")
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This is not ideal. I see a few alternatives here:

  1. Accept the panic
  2. Add a T: Default bound and fill missing values with default()
  3. Add a T: JsCast bound and fill missing values with JsValue::UNDEFINED

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I've gone ahead and implemented alternative 2

}
}
}

impl<T, const N: usize> OptionFromWasmAbi for [T; N] where Box<[T]>: FromWasmAbi<Abi = WasmSlice> {
#[inline]
fn is_none(abi: &WasmSlice) -> bool { abi.ptr == 0 }
}

impl IntoWasmAbi for String {
type Abi = <Vec<u8> as IntoWasmAbi>::Abi;

Expand Down
6 changes: 6 additions & 0 deletions src/describe.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -155,6 +155,12 @@ if_std! {
<Box<[T]>>::describe();
}
}

impl<T, const N: usize> WasmDescribe for [T; N] where Box<[T]>: WasmDescribe {
fn describe() {
<Box<[T]>>::describe();
}
}
}

impl<T: WasmDescribe> WasmDescribe for Option<T> {
Expand Down