1 files changed, 402 insertions, 0 deletions
diff --git a/vendor/zerovec/src/ule/encode.rs b/vendor/zerovec/src/ule/encode.rs
new file mode 100644
index 000000000..3043bbd0a
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+++ b/vendor/zerovec/src/ule/encode.rs
@@ -0,0 +1,402 @@
+// This file is part of ICU4X. For terms of use, please see the file
+// called LICENSE at the top level of the ICU4X source tree
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+use crate::ule::*;
+use crate::varzerovec::VarZeroVecFormat;
+use crate::{VarZeroSlice, VarZeroVec, ZeroSlice, ZeroVec};
+use alloc::borrow::{Cow, ToOwned};
+use alloc::boxed::Box;
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::mem;
+
+/// Allows types to be encoded as VarULEs. This is highly useful for implementing VarULE on
+/// custom DSTs where the type cannot be obtained as a reference to some other type.
+///
+/// [`Self::encode_var_ule_as_slices()`] should be implemented by providing an encoded slice for each field
+/// of the VarULE type to the callback, in order. For an implementation to be safe, the slices
+/// to the callback must, when concatenated, be a valid instance of the VarULE type.
+///
+/// See the [custom VarULEdocumentation](crate::ule::custom) for examples.
+///
+/// [`Self::encode_var_ule_as_slices()`] is only used to provide default implementations for [`Self::encode_var_ule_write()`]
+/// and [`Self::encode_var_ule_len()`]. If you override the default implementations it is totally valid to
+/// replace [`Self::encode_var_ule_as_slices()`]'s body with `unreachable!()`. This can be done for cases where
+/// it is not possible to implement [`Self::encode_var_ule_as_slices()`] but the other methods still work.
+///
+/// A typical implementation will take each field in the order found in the [`VarULE`] type,
+/// convert it to ULE, call [`ULE::as_byte_slice()`] on them, and pass the slices to `cb` in order.
+/// A trailing [`ZeroVec`](crate::ZeroVec) or [`VarZeroVec`](crate::VarZeroVec) can have their underlying
+/// byte representation passed through.
+///
+/// In case the compiler is not optimizing [`Self::encode_var_ule_len()`], it can be overridden. A typical
+/// implementation will add up the sizes of each field on the [`VarULE`] type and then add in the byte length of the
+/// dynamically-sized part.
+///
+/// # Safety
+///
+/// The safety invariants of [`Self::encode_var_ule_as_slices()`] are:
+/// - It must call `cb` (only once)
+/// - The slices passed to `cb`, if concatenated, should be a valid instance of the `T` [`VarULE`] type
+///   (i.e. if fed to [`VarULE::validate_byte_slice()`] they must produce a successful result)
+/// - It must return the return value of `cb` to the caller
+///
+/// One or more of [`Self::encode_var_ule_len()`] and [`Self::encode_var_ule_write()`] may be provided.
+/// If both are, then `zerovec` code is guaranteed to not call [`Self::encode_var_ule_as_slices()`], and it may be replaced
+/// with `unreachable!()`.
+///
+/// The safety invariants of [`Self::encode_var_ule_len()`] are:
+/// - It must return the length of the corresponding VarULE type
+///
+/// The safety invariants of [`Self::encode_var_ule_write()`] are:
+/// - The slice written to `dst` must be a valid instance of the `T` [`VarULE`] type
+pub unsafe trait EncodeAsVarULE<T: VarULE + ?Sized> {
+    /// Calls `cb` with a piecewise list of byte slices that when concatenated
+    /// produce the memory pattern of the corresponding instance of `T`.
+    ///
+    /// Do not call this function directly; instead use the other two. Some implementors
+    /// may define this function to panic.
+    fn encode_var_ule_as_slices<R>(&self, cb: impl FnOnce(&[&[u8]]) -> R) -> R;
+
+    /// Return the length, in bytes, of the corresponding [`VarULE`] type
+    fn encode_var_ule_len(&self) -> usize {
+        self.encode_var_ule_as_slices(|slices| slices.iter().map(|s| s.len()).sum())
+    }
+
+    /// Write the corresponding [`VarULE`] type to the `dst` buffer. `dst` should
+    /// be the size of [`Self::encode_var_ule_len()`]
+    fn encode_var_ule_write(&self, mut dst: &mut [u8]) {
+        debug_assert_eq!(self.encode_var_ule_len(), dst.len());
+        self.encode_var_ule_as_slices(move |slices| {
+            #[allow(clippy::indexing_slicing)] // by debug_assert
+            for slice in slices {
+                dst[..slice.len()].copy_from_slice(slice);
+                dst = &mut dst[slice.len()..];
+            }
+        });
+    }
+}
+
+/// Given an [`EncodeAsVarULE`] type `S`, encode it into a `Box<T>`
+///
+/// This is primarily useful for generating `Deserialize` impls for VarULE types
+pub fn encode_varule_to_box<S: EncodeAsVarULE<T>, T: VarULE + ?Sized>(x: &S) -> Box<T> {
+    let mut vec: Vec<u8> = Vec::new();
+    // zero-fill the vector to avoid uninitialized data UB
+    vec.resize(x.encode_var_ule_len(), 0);
+    x.encode_var_ule_write(&mut vec);
+    let boxed = vec.into_boxed_slice();
+    unsafe {
+        // Safety: `ptr` is a box, and `T` is a VarULE which guarantees it has the same memory layout as `[u8]`
+        // and can be recouped via from_byte_slice_unchecked()
+        let ptr: *mut T = T::from_byte_slice_unchecked(&boxed) as *const T as *mut T;
+        mem::forget(boxed);
+
+        // Safety: we can construct an owned version since we have mem::forgotten the older owner
+        Box::from_raw(ptr)
+    }
+}
+
+unsafe impl<T: VarULE + ?Sized> EncodeAsVarULE<T> for T {
+    fn encode_var_ule_as_slices<R>(&self, cb: impl FnOnce(&[&[u8]]) -> R) -> R {
+        cb(&[T::as_byte_slice(self)])
+    }
+}
+
+unsafe impl<T: VarULE + ?Sized> EncodeAsVarULE<T> for &'_ T {
+    fn encode_var_ule_as_slices<R>(&self, cb: impl FnOnce(&[&[u8]]) -> R) -> R {
+        cb(&[T::as_byte_slice(self)])
+    }
+}
+
+unsafe impl<T: VarULE + ?Sized> EncodeAsVarULE<T> for Cow<'_, T>
+where
+    T: ToOwned,
+{
+    fn encode_var_ule_as_slices<R>(&self, cb: impl FnOnce(&[&[u8]]) -> R) -> R {
+        cb(&[T::as_byte_slice(self.as_ref())])
+    }
+}
+
+unsafe impl<T: VarULE + ?Sized> EncodeAsVarULE<T> for Box<T> {
+    fn encode_var_ule_as_slices<R>(&self, cb: impl FnOnce(&[&[u8]]) -> R) -> R {
+        cb(&[T::as_byte_slice(&*self)])
+    }
+}
+
+unsafe impl EncodeAsVarULE<str> for String {
+    fn encode_var_ule_as_slices<R>(&self, cb: impl FnOnce(&[&[u8]]) -> R) -> R {
+        cb(&[self.as_bytes()])
+    }
+}
+
+// Note: This impl could technically use `T: AsULE`, but we want users to prefer `ZeroSlice<T>`
+// for cases where T is not a ULE. Therefore, we can use the more efficient `memcpy` impl here.
+unsafe impl<T> EncodeAsVarULE<[T]> for Vec<T>
+where
+    T: ULE,
+{
+    fn encode_var_ule_as_slices<R>(&self, cb: impl FnOnce(&[&[u8]]) -> R) -> R {
+        cb(&[<[T] as VarULE>::as_byte_slice(&*self)])
+    }
+}
+
+unsafe impl<T> EncodeAsVarULE<ZeroSlice<T>> for &'_ [T]
+where
+    T: AsULE + 'static,
+{
+    fn encode_var_ule_as_slices<R>(&self, _: impl FnOnce(&[&[u8]]) -> R) -> R {
+        // unnecessary if the other two are implemented
+        unreachable!()
+    }
+
+    #[inline]
+    fn encode_var_ule_len(&self) -> usize {
+        self.len() * core::mem::size_of::<T::ULE>()
+    }
+
+    fn encode_var_ule_write(&self, dst: &mut [u8]) {
+        #[allow(non_snake_case)]
+        let S = core::mem::size_of::<T::ULE>();
+        debug_assert_eq!(self.len() * S, dst.len());
+        for (item, ref mut chunk) in self.iter().zip(dst.chunks_mut(S)) {
+            let ule = item.to_unaligned();
+            chunk.copy_from_slice(ULE::as_byte_slice(core::slice::from_ref(&ule)));
+        }
+    }
+}
+
+unsafe impl<T> EncodeAsVarULE<ZeroSlice<T>> for Vec<T>
+where
+    T: AsULE + 'static,
+{
+    fn encode_var_ule_as_slices<R>(&self, _: impl FnOnce(&[&[u8]]) -> R) -> R {
+        // unnecessary if the other two are implemented
+        unreachable!()
+    }
+
+    #[inline]
+    fn encode_var_ule_len(&self) -> usize {
+        self.as_slice().encode_var_ule_len()
+    }
+
+    #[inline]
+    fn encode_var_ule_write(&self, dst: &mut [u8]) {
+        self.as_slice().encode_var_ule_write(dst)
+    }
+}
+
+unsafe impl<T> EncodeAsVarULE<ZeroSlice<T>> for ZeroVec<'_, T>
+where
+    T: AsULE + 'static,
+{
+    fn encode_var_ule_as_slices<R>(&self, _: impl FnOnce(&[&[u8]]) -> R) -> R {
+        // unnecessary if the other two are implemented
+        unreachable!()
+    }
+
+    #[inline]
+    fn encode_var_ule_len(&self) -> usize {
+        self.as_bytes().len()
+    }
+
+    fn encode_var_ule_write(&self, dst: &mut [u8]) {
+        debug_assert_eq!(self.as_bytes().len(), dst.len());
+        dst.copy_from_slice(self.as_bytes());
+    }
+}
+
+unsafe impl<T, E, F> EncodeAsVarULE<VarZeroSlice<T, F>> for &'_ [E]
+where
+    T: VarULE + ?Sized,
+    E: EncodeAsVarULE<T>,
+    F: VarZeroVecFormat,
+{
+    fn encode_var_ule_as_slices<R>(&self, _: impl FnOnce(&[&[u8]]) -> R) -> R {
+        // unnecessary if the other two are implemented
+        unimplemented!()
+    }
+
+    #[allow(clippy::unwrap_used)] // TODO(#1410): Rethink length errors in VZV.
+    fn encode_var_ule_len(&self) -> usize {
+        crate::varzerovec::components::compute_serializable_len::<T, E, F>(self).unwrap() as usize
+    }
+
+    fn encode_var_ule_write(&self, dst: &mut [u8]) {
+        crate::varzerovec::components::write_serializable_bytes::<T, E, F>(self, dst)
+    }
+}
+
+unsafe impl<T, E, F> EncodeAsVarULE<VarZeroSlice<T, F>> for Vec<E>
+where
+    T: VarULE + ?Sized,
+    E: EncodeAsVarULE<T>,
+    F: VarZeroVecFormat,
+{
+    fn encode_var_ule_as_slices<R>(&self, _: impl FnOnce(&[&[u8]]) -> R) -> R {
+        // unnecessary if the other two are implemented
+        unreachable!()
+    }
+
+    #[inline]
+    fn encode_var_ule_len(&self) -> usize {
+        <_ as EncodeAsVarULE<VarZeroSlice<T, F>>>::encode_var_ule_len(&self.as_slice())
+    }
+
+    #[inline]
+    fn encode_var_ule_write(&self, dst: &mut [u8]) {
+        <_ as EncodeAsVarULE<VarZeroSlice<T, F>>>::encode_var_ule_write(&self.as_slice(), dst)
+    }
+}
+
+unsafe impl<T, F> EncodeAsVarULE<VarZeroSlice<T, F>> for VarZeroVec<'_, T, F>
+where
+    T: VarULE + ?Sized,
+    F: VarZeroVecFormat,
+{
+    fn encode_var_ule_as_slices<R>(&self, _: impl FnOnce(&[&[u8]]) -> R) -> R {
+        // unnecessary if the other two are implemented
+        unreachable!()
+    }
+
+    #[inline]
+    fn encode_var_ule_len(&self) -> usize {
+        self.as_bytes().len()
+    }
+
+    #[inline]
+    fn encode_var_ule_write(&self, dst: &mut [u8]) {
+        debug_assert_eq!(self.as_bytes().len(), dst.len());
+        dst.copy_from_slice(self.as_bytes());
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const STRING_ARRAY: [&str; 2] = ["hello", "world"];
+
+    const STRING_SLICE: &[&str] = &STRING_ARRAY;
+
+    const U8_ARRAY: [u8; 8] = [0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07];
+
+    const U8_2D_ARRAY: [&[u8]; 2] = [&U8_ARRAY, &U8_ARRAY];
+
+    const U8_2D_SLICE: &[&[u8]] = &[&U8_ARRAY, &U8_ARRAY];
+
+    const U8_3D_ARRAY: [&[&[u8]]; 2] = [U8_2D_SLICE, U8_2D_SLICE];
+
+    const U8_3D_SLICE: &[&[&[u8]]] = &[U8_2D_SLICE, U8_2D_SLICE];
+
+    const U32_ARRAY: [u32; 4] = [0x00010203, 0x04050607, 0x08090A0B, 0x0C0D0E0F];
+
+    const U32_2D_ARRAY: [&[u32]; 2] = [&U32_ARRAY, &U32_ARRAY];
+
+    const U32_2D_SLICE: &[&[u32]] = &[&U32_ARRAY, &U32_ARRAY];
+
+    const U32_3D_ARRAY: [&[&[u32]]; 2] = [U32_2D_SLICE, U32_2D_SLICE];
+
+    const U32_3D_SLICE: &[&[&[u32]]] = &[U32_2D_SLICE, U32_2D_SLICE];
+
+    #[test]
+    fn test_vzv_from() {
+        type VZV<'a, T> = VarZeroVec<'a, T>;
+        type ZS<T> = ZeroSlice<T>;
+        type VZS<T> = VarZeroSlice<T>;
+
+        let u8_zerovec: ZeroVec<u8> = ZeroVec::from_slice_or_alloc(&U8_ARRAY);
+        let u8_2d_zerovec: [ZeroVec<u8>; 2] = [u8_zerovec.clone(), u8_zerovec.clone()];
+        let u8_2d_vec: Vec<Vec<u8>> = vec![U8_ARRAY.into(), U8_ARRAY.into()];
+        let u8_3d_vec: Vec<Vec<Vec<u8>>> = vec![u8_2d_vec.clone(), u8_2d_vec.clone()];
+
+        let u32_zerovec: ZeroVec<u32> = ZeroVec::from_slice_or_alloc(&U32_ARRAY);
+        let u32_2d_zerovec: [ZeroVec<u32>; 2] = [u32_zerovec.clone(), u32_zerovec.clone()];
+        let u32_2d_vec: Vec<Vec<u32>> = vec![U32_ARRAY.into(), U32_ARRAY.into()];
+        let u32_3d_vec: Vec<Vec<Vec<u32>>> = vec![u32_2d_vec.clone(), u32_2d_vec.clone()];
+
+        let a: VZV<str> = VarZeroVec::from(&STRING_ARRAY);
+        let b: VZV<str> = VarZeroVec::from(STRING_SLICE);
+        let c: VZV<str> = VarZeroVec::from(&Vec::from(STRING_SLICE));
+        assert_eq!(a, STRING_SLICE);
+        assert_eq!(a, b);
+        assert_eq!(a, c);
+
+        let a: VZV<[u8]> = VarZeroVec::from(&U8_2D_ARRAY);
+        let b: VZV<[u8]> = VarZeroVec::from(U8_2D_SLICE);
+        let c: VZV<[u8]> = VarZeroVec::from(&u8_2d_vec);
+        assert_eq!(a, U8_2D_SLICE);
+        assert_eq!(a, b);
+        assert_eq!(a, c);
+        let u8_3d_vzv_brackets = &[a.clone(), a.clone()];
+
+        let a: VZV<ZS<u8>> = VarZeroVec::from(&U8_2D_ARRAY);
+        let b: VZV<ZS<u8>> = VarZeroVec::from(U8_2D_SLICE);
+        let c: VZV<ZS<u8>> = VarZeroVec::from(&u8_2d_vec);
+        let d: VZV<ZS<u8>> = VarZeroVec::from(&u8_2d_zerovec);
+        assert_eq!(a, U8_2D_SLICE);
+        assert_eq!(a, b);
+        assert_eq!(a, c);
+        assert_eq!(a, d);
+        let u8_3d_vzv_zeroslice = &[a.clone(), a.clone()];
+
+        let a: VZV<VZS<[u8]>> = VarZeroVec::from(&U8_3D_ARRAY);
+        let b: VZV<VZS<[u8]>> = VarZeroVec::from(U8_3D_SLICE);
+        let c: VZV<VZS<[u8]>> = VarZeroVec::from(&u8_3d_vec);
+        let d: VZV<VZS<[u8]>> = VarZeroVec::from(u8_3d_vzv_brackets);
+        assert_eq!(
+            a.iter()
+                .map(|x| x.iter().map(|y| y.to_vec()).collect::<Vec<Vec<u8>>>())
+                .collect::<Vec<Vec<Vec<u8>>>>(),
+            u8_3d_vec
+        );
+        assert_eq!(a, b);
+        assert_eq!(a, c);
+        assert_eq!(a, d);
+
+        let a: VZV<VZS<ZS<u8>>> = VarZeroVec::from(&U8_3D_ARRAY);
+        let b: VZV<VZS<ZS<u8>>> = VarZeroVec::from(U8_3D_SLICE);
+        let c: VZV<VZS<ZS<u8>>> = VarZeroVec::from(&u8_3d_vec);
+        let d: VZV<VZS<ZS<u8>>> = VarZeroVec::from(u8_3d_vzv_zeroslice);
+        assert_eq!(
+            a.iter()
+                .map(|x| x
+                    .iter()
+                    .map(|y| y.iter().collect::<Vec<u8>>())
+                    .collect::<Vec<Vec<u8>>>())
+                .collect::<Vec<Vec<Vec<u8>>>>(),
+            u8_3d_vec
+        );
+        assert_eq!(a, b);
+        assert_eq!(a, c);
+        assert_eq!(a, d);
+
+        let a: VZV<ZS<u32>> = VarZeroVec::from(&U32_2D_ARRAY);
+        let b: VZV<ZS<u32>> = VarZeroVec::from(U32_2D_SLICE);
+        let c: VZV<ZS<u32>> = VarZeroVec::from(&u32_2d_vec);
+        let d: VZV<ZS<u32>> = VarZeroVec::from(&u32_2d_zerovec);
+        assert_eq!(a, u32_2d_zerovec);
+        assert_eq!(a, b);
+        assert_eq!(a, c);
+        assert_eq!(a, d);
+        let u32_3d_vzv = &[a.clone(), a.clone()];
+
+        let a: VZV<VZS<ZS<u32>>> = VarZeroVec::from(&U32_3D_ARRAY);
+        let b: VZV<VZS<ZS<u32>>> = VarZeroVec::from(U32_3D_SLICE);
+        let c: VZV<VZS<ZS<u32>>> = VarZeroVec::from(&u32_3d_vec);
+        let d: VZV<VZS<ZS<u32>>> = VarZeroVec::from(u32_3d_vzv);
+        assert_eq!(
+            a.iter()
+                .map(|x| x
+                    .iter()
+                    .map(|y| y.iter().collect::<Vec<u32>>())
+                    .collect::<Vec<Vec<u32>>>())
+                .collect::<Vec<Vec<Vec<u32>>>>(),
+            u32_3d_vec
+        );
+        assert_eq!(a, b);
+        assert_eq!(a, c);
+        assert_eq!(a, d);
+    }
+}