diff --git a/libs/binder/rust/Android.bp b/libs/binder/rust/Android.bp
index 16811ee..0234820 100644
--- a/libs/binder/rust/Android.bp
+++ b/libs/binder/rust/Android.bp
@@ -3,12 +3,24 @@
     crate_name: "binder",
     srcs: ["src/lib.rs"],
     shared_libs: [
-        "libbinder_ndk",
         "libutils",
     ],
     rustlibs: [
         "liblibc",
-        "libbinder_ndk_bindgen",
+        "libbinder_ndk_sys",
+    ],
+    host_supported: true,
+}
+
+rust_library {
+    name: "libbinder_ndk_sys",
+    crate_name: "binder_ndk_sys",
+    srcs: [
+        "sys/lib.rs",
+        ":libbinder_ndk_bindgen",
+    ],
+    shared_libs: [
+        "libbinder_ndk",
     ],
     host_supported: true,
 }
@@ -16,8 +28,8 @@
 rust_bindgen {
     name: "libbinder_ndk_bindgen",
     crate_name: "binder_ndk_bindgen",
-    wrapper_src: "BinderBindings.h",
-    source_stem: "ndk_bindings",
+    wrapper_src: "sys/BinderBindings.h",
+    source_stem: "bindings",
     cflags: [
         "-x c++",
     ],
@@ -69,6 +81,6 @@
     ],
     rustlibs: [
         "liblibc",
-        "libbinder_ndk_bindgen",
+        "libbinder_ndk_sys",
     ],
 }
diff --git a/libs/binder/rust/src/error.rs b/libs/binder/rust/src/error.rs
index 289b157..4492cf7 100644
--- a/libs/binder/rust/src/error.rs
+++ b/libs/binder/rust/src/error.rs
@@ -43,14 +43,6 @@
     }
 }
 
-// impl Display for StatusCode {
-//     fn fmt(&self, f: &mut Formatter) -> FmtResult {
-//         write!(f, "StatusCode::{:?}", self)
-//     }
-// }
-
-// impl error::Error for StatusCode {}
-
 fn parse_status_code(code: i32) -> StatusCode {
     match code {
         e if e == StatusCode::OK as i32 => StatusCode::OK,
diff --git a/libs/binder/rust/src/lib.rs b/libs/binder/rust/src/lib.rs
index 4b9cccf..8ee6a62 100644
--- a/libs/binder/rust/src/lib.rs
+++ b/libs/binder/rust/src/lib.rs
@@ -102,7 +102,7 @@
 mod native;
 mod state;
 
-use binder_ndk_bindgen as sys;
+use binder_ndk_sys as sys;
 
 pub mod parcel;
 
diff --git a/libs/binder/rust/src/parcel.rs b/libs/binder/rust/src/parcel.rs
index 43850fe..a248f5c 100644
--- a/libs/binder/rust/src/parcel.rs
+++ b/libs/binder/rust/src/parcel.rs
@@ -21,6 +21,7 @@
 use crate::proxy::SpIBinder;
 use crate::sys;
 
+use std::cell::RefCell;
 use std::convert::TryInto;
 use std::mem::ManuallyDrop;
 use std::ptr;
@@ -117,6 +118,55 @@
         }
     }
 
+    /// Perform a series of writes to the `Parcel`, prepended with the length
+    /// (in bytes) of the written data.
+    ///
+    /// The length `0i32` will be written to the parcel first, followed by the
+    /// writes performed by the callback. The initial length will then be
+    /// updated to the length of all data written by the callback, plus the
+    /// size of the length elemement itself (4 bytes).
+    ///
+    /// # Examples
+    ///
+    /// After the following call:
+    ///
+    /// ```
+    /// # use binder::{Binder, Interface, Parcel};
+    /// # let mut parcel = Parcel::Owned(std::ptr::null_mut());
+    /// parcel.sized_write(|subparcel| {
+    ///     subparcel.write(&1u32)?;
+    ///     subparcel.write(&2u32)?;
+    ///     subparcel.write(&3u32)
+    /// });
+    /// ```
+    ///
+    /// `parcel` will contain the following:
+    ///
+    /// ```ignore
+    /// [16i32, 1u32, 2u32, 3u32]
+    /// ```
+    pub fn sized_write<F>(&mut self, f: F) -> Result<()>
+    where for<'a>
+        F: Fn(&'a WritableSubParcel<'a>) -> Result<()>
+    {
+        let start = self.get_data_position();
+        self.write(&0i32)?;
+        {
+            let subparcel = WritableSubParcel(RefCell::new(self));
+            f(&subparcel)?;
+        }
+        let end = self.get_data_position();
+        unsafe {
+            self.set_data_position(start)?;
+        }
+        assert!(end >= start);
+        self.write(&(end - start))?;
+        unsafe {
+            self.set_data_position(end)?;
+        }
+        Ok(())
+    }
+
     /// Returns the current position in the parcel data.
     pub fn get_data_position(&self) -> i32 {
         unsafe {
@@ -143,6 +193,16 @@
     }
 }
 
+/// A segment of a writable parcel, used for [`Parcel::sized_write`].
+pub struct WritableSubParcel<'a>(RefCell<&'a mut Parcel>);
+
+impl<'a> WritableSubParcel<'a> {
+    /// Write a type that implements [`Serialize`] to the sub-parcel.
+    pub fn write<S: Serialize + ?Sized>(&self, parcelable: &S) -> Result<()> {
+        parcelable.serialize(&mut *self.0.borrow_mut())
+    }
+}
+
 // Data deserialization methods
 impl Parcel {
     /// Attempt to read a type that implements [`Deserialize`] from this
@@ -445,3 +505,38 @@
     );
     assert_eq!(parcel.read::<Vec<String>>().unwrap(), [s1, s2, s3]);
 }
+
+#[test]
+fn test_sized_write() {
+    use crate::binder::Interface;
+    use crate::native::Binder;
+
+    let mut service = Binder::new(()).as_binder();
+    let mut parcel = Parcel::new_for_test(&mut service).unwrap();
+    let start = parcel.get_data_position();
+
+    let arr = [1i32, 2i32, 3i32];
+
+    parcel.sized_write(|subparcel| {
+        subparcel.write(&arr[..])
+    }).expect("Could not perform sized write");
+
+    // i32 sub-parcel length + i32 array length + 3 i32 elements
+    let expected_len = 20i32;
+
+    assert_eq!(parcel.get_data_position(), start + expected_len);
+
+    unsafe {
+        parcel.set_data_position(start).unwrap();
+    }
+
+    assert_eq!(
+        expected_len,
+        parcel.read().unwrap(),
+    );
+
+    assert_eq!(
+        parcel.read::<Vec<i32>>().unwrap(),
+        &arr,
+    );
+}
diff --git a/libs/binder/rust/src/proxy.rs b/libs/binder/rust/src/proxy.rs
index f9519b4..13e5619 100644
--- a/libs/binder/rust/src/proxy.rs
+++ b/libs/binder/rust/src/proxy.rs
@@ -122,6 +122,14 @@
     }
 }
 
+impl PartialEq for SpIBinder {
+    fn eq(&self, other: &Self) -> bool {
+        ptr::eq(self.0, other.0)
+    }
+}
+
+impl Eq for SpIBinder {}
+
 impl Clone for SpIBinder {
     fn clone(&self) -> Self {
         unsafe {
@@ -363,6 +371,18 @@
         assert!(!ptr.is_null());
         Self(ptr)
     }
+
+    /// Promote this weak reference to a strong reference to the binder object.
+    pub fn promote(&self) -> Option<SpIBinder> {
+        unsafe {
+            // Safety: `WpIBinder` always contains a valid weak reference, so we
+            // can pass this pointer to `AIBinder_Weak_promote`. Returns either
+            // null or an AIBinder owned by the caller, both of which are valid
+            // to pass to `SpIBinder::from_raw`.
+            let ptr = sys::AIBinder_Weak_promote(self.0);
+            SpIBinder::from_raw(ptr)
+        }
+    }
 }
 
 /// Rust wrapper around DeathRecipient objects.
diff --git a/libs/binder/rust/BinderBindings.h b/libs/binder/rust/sys/BinderBindings.h
similarity index 100%
rename from libs/binder/rust/BinderBindings.h
rename to libs/binder/rust/sys/BinderBindings.h
diff --git a/libs/binder/rust/sys/lib.rs b/libs/binder/rust/sys/lib.rs
new file mode 100644
index 0000000..9095af2
--- /dev/null
+++ b/libs/binder/rust/sys/lib.rs
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! Generated Rust bindings to libbinder_ndk
+
+#![allow(
+    non_camel_case_types,
+    non_snake_case,
+    non_upper_case_globals,
+    unused,
+    improper_ctypes,
+    missing_docs
+)]
+use std::error::Error;
+use std::fmt;
+
+include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
+
+impl Error for android_c_interface_StatusCode {}
+
+impl fmt::Display for android_c_interface_StatusCode {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "StatusCode::{:?}", self)
+    }
+}