rkyv 0.8.16

Zero-copy deserialization framework for Rust
Documentation 
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use core::cmp::Ordering;

use rancor::{Fallible, ResultExt, Source};

use crate::{
    alloc::{
        alloc::{alloc, handle_alloc_error},
        boxed::Box,
        collections::VecDeque,
        vec::Vec,
    },
    ser::{Allocator, Writer},
    traits::LayoutRaw,
    vec::{ArchivedVec, VecResolver},
    Archive, Deserialize, DeserializeUnsized, Place, Serialize,
};

impl<T: Archive> Archive for VecDeque<T> {
    type Archived = ArchivedVec<T::Archived>;
    type Resolver = VecResolver;

    fn resolve(&self, resolver: Self::Resolver, out: Place<Self::Archived>) {
        ArchivedVec::resolve_from_len(self.len(), resolver, out);
    }
}

impl<T, S> Serialize<S> for VecDeque<T>
where
    T: Serialize<S>,
    S: Fallible + Allocator + Writer + ?Sized,
{
    fn serialize(
        &self,
        serializer: &mut S,
    ) -> Result<Self::Resolver, S::Error> {
        let (a, b) = self.as_slices();
        if b.is_empty() {
            ArchivedVec::<T::Archived>::serialize_from_slice(a, serializer)
        } else if a.is_empty() {
            ArchivedVec::<T::Archived>::serialize_from_slice(b, serializer)
        } else {
            ArchivedVec::<T::Archived>::serialize_from_iter::<T, _, _>(
                self.iter(),
                serializer,
            )
        }
    }
}

impl<T, D> Deserialize<VecDeque<T>, D> for ArchivedVec<T::Archived>
where
    T: Archive,
    [T::Archived]: DeserializeUnsized<[T], D>,
    D: Fallible + ?Sized,
    D::Error: Source,
{
    fn deserialize(
        &self,
        deserializer: &mut D,
    ) -> Result<VecDeque<T>, D::Error> {
        let metadata = self.as_slice().deserialize_metadata();
        let layout = <[T] as LayoutRaw>::layout_raw(metadata).into_error()?;
        let data_address = if layout.size() > 0 {
            let ptr = unsafe { alloc(layout) };
            if ptr.is_null() {
                handle_alloc_error(layout);
            }
            ptr
        } else {
            crate::polyfill::dangling(&layout).as_ptr()
        };
        let out = ptr_meta::from_raw_parts_mut(data_address.cast(), metadata);
        unsafe {
            self.as_slice().deserialize_unsized(deserializer, out)?;
        }
        let boxed = unsafe { Box::<[T]>::from_raw(out) };
        Ok(VecDeque::from(Vec::from(boxed)))
    }
}

impl<T: PartialEq<U>, U> PartialEq<VecDeque<U>> for ArchivedVec<T> {
    fn eq(&self, other: &VecDeque<U>) -> bool {
        self.len() == other.len() && self.iter().eq(other.iter())
    }
}

impl<T: PartialOrd> PartialOrd<VecDeque<T>> for ArchivedVec<T> {
    fn partial_cmp(&self, other: &VecDeque<T>) -> Option<Ordering> {
        self.iter().partial_cmp(other.iter())
    }
}

#[cfg(test)]
mod tests {
    use crate::{
        access_unchecked, alloc::collections::VecDeque, api::test::deserialize,
        rancor::Error, to_bytes, vec::ArchivedVec, Archived,
    };

    #[test]
    fn vecdeque() {
        for n in 2..10 {
            for k in 1..n {
                let mut deque = VecDeque::with_capacity(n as usize + 1);
                for x in k..n {
                    deque.push_back(x);
                }
                for x in (0..k).rev() {
                    deque.push_front(x);
                }
                assert!(deque.iter().copied().eq(0..n));

                // Now serialize and deserialize and verify that the
                // deserialized version contains `0..n`.
                let bytes = to_bytes::<Error>(&deque).unwrap();
                let archived = unsafe {
                    access_unchecked::<ArchivedVec<Archived<i32>>>(&bytes)
                };
                assert!(archived.iter().copied().eq(0..n));

                let deserialized = deserialize::<VecDeque<i32>>(archived);
                assert_eq!(deque, deserialized);
            }
        }
    }
}