Symmetric keyguard-bound superencryption
Bug: 163866361
Test: keystore2_test
Test: atest android.keystore.cts.CipherTest#testEmptyPlaintextEncryptsAndDecryptsWhenUnlockedRequired
Change-Id: I8b6136dce9ae93ffbeea04f41eaf468f82c67a91
diff --git a/keystore2/src/try_insert.rs b/keystore2/src/try_insert.rs
new file mode 100644
index 0000000..6dd3962
--- /dev/null
+++ b/keystore2/src/try_insert.rs
@@ -0,0 +1,100 @@
+// Copyright 2021, 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.
+
+//! The TryInsert trait adds to Option<T> the method
+//! get_or_try_to_insert_with, which is analogous to
+//! get_or_insert_with, but allows the called function to fail and propagates the failure.
+
+/// The TryInsert trait adds to Option<T> the method
+/// get_or_try_to_insert_with, which is analogous to
+/// get_or_insert_with, but allows the called function to fail and propagates the failure.
+pub trait TryInsert {
+ /// Type of the Ok branch of the Result
+ type Item;
+ /// Inserts a value computed from `f` into the option if it is [`None`],
+ /// then returns a mutable reference to the contained value. If `f`
+ /// returns Err, the Option is unchanged.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let mut x = None;
+ /// assert_eq!(x.get_or_try_to_insert_with(Err("oops".to_string())), Err("oops".to_string()))
+ /// {
+ /// let y: &mut u32 = x.get_or_try_to_insert_with(|| Ok(5))?;
+ /// assert_eq!(y, &5);
+ ///
+ /// *y = 7;
+ /// }
+ ///
+ /// assert_eq!(x, Some(7));
+ /// ```
+ fn get_or_try_to_insert_with<E, F: FnOnce() -> Result<Self::Item, E>>(
+ &mut self,
+ f: F,
+ ) -> Result<&mut Self::Item, E>;
+}
+
+impl<T> TryInsert for Option<T> {
+ type Item = T;
+ fn get_or_try_to_insert_with<E, F: FnOnce() -> Result<Self::Item, E>>(
+ &mut self,
+ f: F,
+ ) -> Result<&mut Self::Item, E> {
+ if self.is_none() {
+ *self = Some(f()?);
+ }
+
+ match self {
+ Some(v) => Ok(v),
+ // SAFETY: a `None` variant for `self` would have been replaced by a `Some`
+ // variant in the code above.
+ None => unsafe { std::hint::unreachable_unchecked() },
+ }
+ }
+}
+
+#[cfg(test)]
+mod test {
+ use super::*;
+
+ fn fails() -> Result<i32, String> {
+ Err("fail".to_string())
+ }
+
+ fn succeeds() -> Result<i32, String> {
+ Ok(99)
+ }
+
+ #[test]
+ fn test() {
+ let mut x = None;
+ assert_eq!(x.get_or_try_to_insert_with(fails), Err("fail".to_string()));
+ assert_eq!(x, None);
+ assert_eq!(*x.get_or_try_to_insert_with(succeeds).unwrap(), 99);
+ assert_eq!(x, Some(99));
+ x = Some(42);
+ assert_eq!(*x.get_or_try_to_insert_with(fails).unwrap(), 42);
+ assert_eq!(x, Some(42));
+ assert_eq!(*x.get_or_try_to_insert_with(succeeds).unwrap(), 42);
+ assert_eq!(x, Some(42));
+ *x.get_or_try_to_insert_with(fails).unwrap() = 2;
+ assert_eq!(x, Some(2));
+ *x.get_or_try_to_insert_with(succeeds).unwrap() = 3;
+ assert_eq!(x, Some(3));
+ x = None;
+ *x.get_or_try_to_insert_with(succeeds).unwrap() = 5;
+ assert_eq!(x, Some(5));
+ }
+}