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use core::{
any::type_name,
fmt::{self, Debug},
marker::PhantomData,
};
use crate::{
deserialize::{DeIter, Deserialize, DeserializeError, Deserializer, SizedDeIter},
formula::{unwrap_size, BareFormula, Formula},
};
/// Wrapper for lazy deserialization.
/// `Lazy<F>` may deserialize data from formula `F`.
/// Then any it may produce any type `T` that can be deserialized from formula `F`.
#[derive(Clone)]
pub struct Lazy<'de, F: ?Sized> {
de: Deserializer<'de>,
marker: PhantomData<fn(&F) -> &F>,
}
impl<'de, F> Debug for Lazy<'de, F>
where
F: ?Sized,
{
#[inline(always)]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "Lazy<{:?}>", type_name::<F>())
}
}
impl<'de, F> Lazy<'de, F>
where
F: BareFormula + ?Sized,
{
/// Deserialize the lazy value.
///
/// # Errors
///
/// Returns `DeserializeError` if deserialization fails.
#[inline(always)]
pub fn get<T>(&self) -> Result<T, DeserializeError>
where
T: Deserialize<'de, F>,
{
<T as Deserialize<'de, F>>::deserialize(self.de.clone())
}
/// Deserialize the lazy value in place.
///
/// # Errors
///
/// Returns `DeserializeError` if deserialization fails.
#[inline(always)]
pub fn get_in_place<T>(&self, place: &mut T) -> Result<(), DeserializeError>
where
T: Deserialize<'de, F> + ?Sized,
{
<T as Deserialize<'de, F>>::deserialize_in_place(place, self.de.clone())
}
}
trait LazySizedIter<'de, F: ?Sized> {
const ELEMENT_SIZE: usize;
fn sized_iter_impl<T>(&self) -> SizedDeIter<'de, F, T>
where
F: Formula,
T: Deserialize<'de, F>;
}
impl<'de, F> LazySizedIter<'de, F> for Lazy<'de, [F]>
where
F: Formula,
{
// Fail compilation.
// Use `Lazy::iter` instead of `Lazy::sized_iter` for unsized formulas.
const ELEMENT_SIZE: usize = unwrap_size(F::MAX_STACK_SIZE);
#[inline(always)]
fn sized_iter_impl<T>(&self) -> SizedDeIter<'de, F, T>
where
T: Deserialize<'de, F>,
{
assert_eq!(Some(Self::ELEMENT_SIZE), F::MAX_STACK_SIZE);
self.de.clone().into_sized_iter()
}
}
impl<'de, F> Lazy<'de, [F]>
where
F: Formula,
{
/// Produce iterator over lazy deserialized values.
/// # Example
///
/// ```
/// # use alkahest::*;
/// let mut buffer = [0u8; 1024];
///
/// let (size, root) = serialize::<[u32], _>([1u8, 2, 3], &mut buffer).unwrap();
/// let lazy = deserialize_with_size::<[u32], Lazy<[u32]>>(&buffer[..size], root).unwrap();
/// let mut iter = lazy.sized_iter::<u32>();
/// assert_eq!(iter.next().unwrap().unwrap(), 1);
/// assert_eq!(iter.next().unwrap().unwrap(), 2);
/// assert_eq!(iter.next().unwrap().unwrap(), 3);
/// assert!(iter.next().is_none());
/// ```
///
/// `sized_iter` cannot be used to deserialize slice of unsized formulas.
/// Attempt to use unsized formula will result in compile error.
///
/// ```compile_fail
/// # use alkahest::*;
/// let mut buffer = [0u8; 1024];
///
/// serialize::<[As<str>], _>(["qwe", "rty"], &mut buffer).unwrap();
/// let (lazy, _) = deserialize::<[As<str>], Lazy<[As<str>]>>(&buffer).unwrap();
/// let mut iter = lazy.sized_iter::<&str>();
/// assert_eq!(iter.next().unwrap().unwrap(), "qwe");
/// assert_eq!(iter.next().unwrap().unwrap(), "rty");
/// assert!(iter.next().is_none());
/// ```
#[inline(always)]
pub fn sized_iter<T>(&self) -> SizedDeIter<'de, F, T>
where
T: Deserialize<'de, F>,
{
self.sized_iter_impl()
}
/// Produce iterator over lazy deserialized values.
///
/// # Example
///
/// ```
/// # use alkahest::*;
/// let mut buffer = [0u8; 1024];
///
/// let (size, root) = serialize::<[u32], _>([1u8, 2, 3], &mut buffer).unwrap();
/// let lazy = deserialize_with_size::<[u32], Lazy<[u32]>>(&buffer[..size], root).unwrap();
/// let mut iter = lazy.iter::<u32>();
/// assert_eq!(iter.next().unwrap().unwrap(), 1);
/// assert_eq!(iter.next().unwrap().unwrap(), 2);
/// assert_eq!(iter.next().unwrap().unwrap(), 3);
/// assert!(iter.next().is_none());
/// ```
///
/// `iter` may be used to deserialize slice of unsized formulas.
///
/// ```
/// # use alkahest::*;
/// let mut buffer = [0u8; 1024];
///
/// let (size, root) = serialize::<[As<str>], _>(["qwe", "rty"], &mut buffer).unwrap();
/// let seq = deserialize_with_size::<[As<str>], Lazy<[As<str>]>>(&buffer[..size], root).unwrap();
/// let mut iter = seq.iter::<&str>();
/// assert_eq!(iter.next().unwrap().unwrap(), "qwe");
/// assert_eq!(iter.next().unwrap().unwrap(), "rty");
/// assert!(iter.next().is_none());
/// ```
#[inline(always)]
pub fn iter<T>(&self) -> DeIter<'de, F, T>
where
T: Deserialize<'de, F>,
{
self.de.clone().into_unsized_iter()
}
}
impl<'de, 'fe: 'de, F> Deserialize<'fe, F> for Lazy<'de, F>
where
F: BareFormula + ?Sized,
{
#[inline(always)]
fn deserialize(de: Deserializer<'fe>) -> Result<Self, DeserializeError> {
Ok(Lazy {
de,
marker: PhantomData,
})
}
#[inline(always)]
fn deserialize_in_place(&mut self, de: Deserializer<'fe>) -> Result<(), DeserializeError> {
self.de = de;
Ok(())
}
}