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Commit 5000615e authored by Andrei Homescu's avatar Andrei Homescu
Browse files

binder_rs: Add in-place deserialization methods 

This adds deserialize_from methods to the Deserialize
and DeserializeOption traits in libbinder_rs that perform
in-place deserialization of values on top of existing objects.
The new methods are used for partial deserialization of parcelables
in the AIDL compiler.
Also adds a helper impl_deserialize_for_parcelable! helper macro.

Bug: 186724059
Test: m
Change-Id: I9fcbd4c7fa4ab85d8ab84792c9c5595ee149879f
parent 7e563f09

libs/binder/rust/src/parcel.rs

+7 −0
Original line number Diff line number Diff line
@@ -219,6 +219,13 @@ impl Parcel { 
        D::deserialize(self)

    }



    /// Attempt to read a type that implements [`Deserialize`] from this

    /// `Parcel` onto an existing value. This operation will overwrite the old

    /// value partially or completely, depending on how much data is available.

    pub fn read_onto<D: Deserialize>(&self, x: &mut D) -> Result<()> {

        x.deserialize_from(self)

    }



    /// Read a vector size from the `Parcel` and resize the given output vector

    /// to be correctly sized for that amount of data.

    ///

libs/binder/rust/src/parcel/parcelable.rs

+85 −0
Original line number Diff line number Diff line
@@ -39,6 +39,14 @@ pub trait Serialize { 
pub trait Deserialize: Sized {

    /// Deserialize an instance from the given [`Parcel`].

    fn deserialize(parcel: &Parcel) -> Result<Self>;



    /// Deserialize an instance from the given [`Parcel`] onto the

    /// current object. This operation will overwrite the old value

    /// partially or completely, depending on how much data is available.

    fn deserialize_from(&mut self, parcel: &Parcel) -> Result<()> {

        *self = Self::deserialize(parcel)?;

        Ok(())

    }

}



/// Helper trait for types that can be serialized as arrays.
@@ -184,6 +192,14 @@ pub trait DeserializeOption: Deserialize { 
            parcel.read().map(Some)

        }

    }



    /// Deserialize an Option of this type from the given [`Parcel`] onto the

    /// current object. This operation will overwrite the current value

    /// partially or completely, depending on how much data is available.

    fn deserialize_option_from(this: &mut Option<Self>, parcel: &Parcel) -> Result<()> {

        *this = Self::deserialize_option(parcel)?;

        Ok(())

    }

}



/// Callback to allocate a vector for parcel array read functions.
@@ -677,6 +693,75 @@ impl<T: DeserializeOption> Deserialize for Option<T> { 
    fn deserialize(parcel: &Parcel) -> Result<Self> {

        DeserializeOption::deserialize_option(parcel)

    }



    fn deserialize_from(&mut self, parcel: &Parcel) -> Result<()> {

        DeserializeOption::deserialize_option_from(self, parcel)

    }

}



/// Implement `Deserialize` trait and friends for a parcelable

///

/// This is an internal macro used by the AIDL compiler to implement

/// `Deserialize`, `DeserializeArray` and `DeserializeOption` for

/// structured parcelables. The target type must implement a

/// `deserialize_parcelable` method with the following signature:

/// ```no_run

/// fn deserialize_parcelable(

///     &mut self,

///     parcel: &binder::parcel::Parcelable,

/// ) -> binder::Result<()> {

///     // ...

/// }

/// ```

#[macro_export]

macro_rules! impl_deserialize_for_parcelable {

    ($parcelable:ident) => {

        impl $crate::parcel::Deserialize for $parcelable {

            fn deserialize(

                parcel: &$crate::parcel::Parcel,

            ) -> $crate::Result<Self> {

                $crate::parcel::DeserializeOption::deserialize_option(parcel)

                    .transpose()

                    .unwrap_or(Err($crate::StatusCode::UNEXPECTED_NULL))

            }

            fn deserialize_from(

                &mut self,

                parcel: &$crate::parcel::Parcel,

            ) -> $crate::Result<()> {

                let status: i32 = parcel.read()?;

                if status == 0 {

                    Err($crate::StatusCode::UNEXPECTED_NULL)

                } else {

                    self.deserialize_parcelable(parcel)

                }

            }

        }



        impl $crate::parcel::DeserializeArray for $parcelable {}



        impl $crate::parcel::DeserializeOption for $parcelable {

            fn deserialize_option(

                parcel: &$crate::parcel::Parcel,

            ) -> $crate::Result<Option<Self>> {

                let mut result = None;

                Self::deserialize_option_from(&mut result, parcel)?;

                Ok(result)

            }

            fn deserialize_option_from(

                this: &mut Option<Self>,

                parcel: &$crate::parcel::Parcel,

            ) -> $crate::Result<()> {

                let status: i32 = parcel.read()?;

                if status == 0 {

                    *this = None;

                    Ok(())

                } else {

                    this.get_or_insert_with(Self::default)

                        .deserialize_parcelable(parcel)

                }

            }

        }

    }

}



#[test]