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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
//! Transerialization extends the set of serde-compatible types (for given de/serializers).//! By "hackishly" transmuting references across serde boundaries as u64s.//! Type-safety is enforced using special struct names for each "magic type".//! Memory-safety relies on transerialized values being "pinned" during de/serialization.
pub(crate) const MAGIC_FIELD: &str = "$__v8_magic_field";
pub(crate) trait MagicType {  const NAME: &'static str;  const MAGIC_NAME: &'static str;}
pub(crate) trait ToV8 {  fn to_v8<'a>(    &mut self,    scope: &mut v8::HandleScope<'a>,  ) -> Result<v8::Local<'a, v8::Value>, crate::Error>;}
pub(crate) trait FromV8: Sized {  fn from_v8(    scope: &mut v8::HandleScope,    value: v8::Local<v8::Value>,  ) -> Result<Self, crate::Error>;}
pub(crate) fn magic_serialize<T, S>(  serializer: S,  x: &T,) -> Result<S::Ok, S::Error>where  S: serde::Serializer,  T: MagicType,{  use serde::ser::SerializeStruct;
  let mut s = serializer.serialize_struct(T::MAGIC_NAME, 1)?;  let ptr = opaque_send(x);  s.serialize_field(MAGIC_FIELD, &ptr)?;  s.end()}
pub(crate) fn magic_deserialize<'de, T, D>(  deserializer: D,) -> Result<T, D::Error>where  D: serde::Deserializer<'de>,  T: MagicType,{  struct ValueVisitor<T> {    p1: std::marker::PhantomData<T>,  }
  impl<'de, T: MagicType> serde::de::Visitor<'de> for ValueVisitor<T> {    type Value = T;
    fn expecting(      &self,      formatter: &mut std::fmt::Formatter,    ) -> std::fmt::Result {      formatter.write_str("a ")?;      formatter.write_str(T::NAME)    }
    fn visit_u64<E>(self, ptr: u64) -> Result<Self::Value, E>    where      E: serde::de::Error,    {      // SAFETY: opaque ptr originates from visit_magic, which forgets ownership so we can take it      Ok(unsafe { opaque_take(ptr) })    }  }
  deserializer.deserialize_struct(    T::MAGIC_NAME,    &[MAGIC_FIELD],    ValueVisitor::<T> {      p1: std::marker::PhantomData,    },  )}
pub(crate) fn visit_magic<'de, T, V, E>(visitor: V, x: T) -> Result<V::Value, E>where  V: serde::de::Visitor<'de>,  E: serde::de::Error,{  let y = visitor.visit_u64::<E>(opaque_send(&x));  std::mem::forget(x);  y}
/// Constructs an "opaque" ptr from a reference to transerializepub(crate) fn opaque_send<T: Sized>(x: &T) -> u64 {  (x as *const T) as u64}
/// Copies an "opaque" ptr from a reference to an opaque ptr (transerialized)/// NOTE: ptr-to-ptr, extra indirectionpub(crate) unsafe fn opaque_recv<T: ?Sized>(ptr: &T) -> u64 {  *(ptr as *const T as *const u64)}
/// Transmutes an "opaque" ptr back into a referencepub(crate) unsafe fn opaque_deref_mut<'a, T>(ptr: u64) -> &'a mut T {  std::mem::transmute(ptr as usize)}
/// Transmutes & copies the value from the "opaque" ptr/// NOTE: takes ownership & requires other end to forget its ownershippub(crate) unsafe fn opaque_take<T>(ptr: u64) -> T {  std::mem::transmute_copy::<T, T>(std::mem::transmute(ptr as usize))}
macro_rules! impl_magic {  ($t:ty) => {    impl crate::magic::transl8::MagicType for $t {      const NAME: &'static str = stringify!($t);      const MAGIC_NAME: &'static str = concat!("$__v8_magic_", stringify!($t));    }
    impl serde::Serialize for $t {      fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>      where        S: serde::Serializer,      {        crate::magic::transl8::magic_serialize(serializer, self)      }    }
    impl<'de> serde::Deserialize<'de> for $t {      fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>      where        D: serde::Deserializer<'de>,      {        crate::magic::transl8::magic_deserialize(deserializer)      }    }  };}pub(crate) use impl_magic;
macro_rules! impl_wrapper {  ($i:item) => {    #[derive(      PartialEq,      Eq,      Clone,      Debug,      Default,      derive_more::Deref,      derive_more::DerefMut,      derive_more::AsRef,      derive_more::AsMut,      derive_more::From,    )]    #[as_mut(forward)]    #[as_ref(forward)]    #[from(forward)]    $i  };}pub(crate) use impl_wrapper;