101 lines
2.9 KiB
Java
101 lines
2.9 KiB
Java
|
/*
|
||
|
|
* 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.
|
||
|
|
*/
|
||
|
|
|
||
|
|
package android.media.permission;
|
||
|
|
|
||
|
|
import android.annotation.NonNull;
|
||
|
|
import android.annotation.Nullable;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* An RAII-style object, used to establish a scope in which a single identity is part of the
|
||
|
|
* context. This is used in order to avoid having to explicitly pass identity information through
|
||
|
|
* deep call-stacks.
|
||
|
|
* <p>
|
||
|
|
* Intended usage:
|
||
|
|
* <pre>
|
||
|
|
* void caller() {
|
||
|
|
* Identity originator = ...;
|
||
|
|
* try (SafeCloseable ignored = IdentityContext.create(originator)) {
|
||
|
|
* // Within this scope the context is established.
|
||
|
|
* callee();
|
||
|
|
* }
|
||
|
|
* // Outside the scope the context is restored to its prior state.
|
||
|
|
*
|
||
|
|
* void callee() {
|
||
|
|
* // Here we can access the identity without having to explicitly take it as an argument.
|
||
|
|
* // This is true even if this were a deeply nested call.
|
||
|
|
* Identity originator = IdentityContext.getNonNull();
|
||
|
|
* ...
|
||
|
|
* }
|
||
|
|
* </pre>
|
||
|
|
*
|
||
|
|
* @hide
|
||
|
|
*/
|
||
|
|
public class IdentityContext implements SafeCloseable {
|
||
|
|
private static ThreadLocal<Identity> sThreadLocalIdentity = new ThreadLocal<>();
|
||
|
|
private @Nullable Identity mPrior = get();
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Create a scoped identity context.
|
||
|
|
*
|
||
|
|
* @param identity The identity to establish with the scope.
|
||
|
|
* @return A {@link SafeCloseable}, to be used in a try-with-resources block to establish a
|
||
|
|
* scope.
|
||
|
|
*/
|
||
|
|
public static @NonNull
|
||
|
|
SafeCloseable create(@Nullable Identity identity) {
|
||
|
|
return new IdentityContext(identity);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Get the current identity context.
|
||
|
|
*
|
||
|
|
* @return The identity, or null if it has not been established.
|
||
|
|
*/
|
||
|
|
public static @Nullable
|
||
|
|
Identity get() {
|
||
|
|
return sThreadLocalIdentity.get();
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Get the current identity context. Throws a {@link NullPointerException} if it has not been
|
||
|
|
* established.
|
||
|
|
*
|
||
|
|
* @return The identity.
|
||
|
|
*/
|
||
|
|
public static @NonNull
|
||
|
|
Identity getNonNull() {
|
||
|
|
Identity result = get();
|
||
|
|
if (result == null) {
|
||
|
|
throw new NullPointerException("Identity context is not set");
|
||
|
|
}
|
||
|
|
return result;
|
||
|
|
}
|
||
|
|
|
||
|
|
private IdentityContext(@Nullable Identity identity) {
|
||
|
|
set(identity);
|
||
|
|
}
|
||
|
|
|
||
|
|
@Override
|
||
|
|
public void close() {
|
||
|
|
set(mPrior);
|
||
|
|
}
|
||
|
|
|
||
|
|
private static void set(@Nullable Identity identity) {
|
||
|
|
sThreadLocalIdentity.set(identity);
|
||
|
|
}
|
||
|
|
}
|