audio: Add StreamWorker to aidl/common

This utility class has been copied from HIDL VTS.
It will be used both for the default implementation
and AIDL VTS, and might need modifications.

Bug: 205884982
Test: atest libaudioaidlcommon_test
Change-Id: I43b35b0c23ae45305dca66e15b60820cad19635e

audio/aidl/common/Android.bp

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2022 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 {
+    // See: http://go/android-license-faq
+    // A large-scale-change added 'default_applicable_licenses' to import
+    // all of the 'license_kinds' from "hardware_interfaces_license"
+    // to get the below license kinds:
+    //   SPDX-license-identifier-Apache-2.0
+    default_applicable_licenses: ["hardware_interfaces_license"],
+}
+
+cc_library_headers {
+    name: "libaudioaidlcommon",
+    host_supported: true,
+    vendor_available: true,
+    export_include_dirs: ["include"],
+    header_libs: [
+        "libbase_headers",
+    ],
+    export_header_lib_headers: [
+        "libbase_headers",
+    ],
+}
+
+cc_test {
+    name: "libaudioaidlcommon_test",
+    host_supported: true,
+    vendor_available: true,
+    header_libs: [
+        "libaudioaidlcommon",
+    ],
+    shared_libs: [
+        "liblog",
+    ],
+    cflags: [
+        "-Wall",
+        "-Wextra",
+        "-Werror",
+        "-Wthread-safety",
+    ],
+    srcs: [
+        "tests/streamworker_tests.cpp",
+    ],
+    test_suites: [
+        "general-tests",
+    ],
+}

audio/aidl/common/TEST_MAPPING

@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "libaudioaidlcommon_test"
+    }
+  ]
+}

audio/aidl/common/include/StreamWorker.h

@@ -0,0 +1,156 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+#pragma once
+
+#include <sched.h>
+
+#include <condition_variable>
+#include <mutex>
+#include <thread>
+
+#include <android-base/thread_annotations.h>
+
+template <typename Impl>
+class StreamWorker {
+    enum class WorkerState { STOPPED, RUNNING, PAUSE_REQUESTED, PAUSED, RESUME_REQUESTED, ERROR };
+
+  public:
+    StreamWorker() = default;
+    ~StreamWorker() { stop(); }
+    bool start() {
+        mWorker = std::thread(&StreamWorker::workerThread, this);
+        std::unique_lock<std::mutex> lock(mWorkerLock);
+        android::base::ScopedLockAssertion lock_assertion(mWorkerLock);
+        mWorkerCv.wait(lock, [&]() {
+            android::base::ScopedLockAssertion lock_assertion(mWorkerLock);
+            return mWorkerState != WorkerState::STOPPED;
+        });
+        return mWorkerState == WorkerState::RUNNING;
+    }
+    void pause() { switchWorkerStateSync(WorkerState::RUNNING, WorkerState::PAUSE_REQUESTED); }
+    void resume() { switchWorkerStateSync(WorkerState::PAUSED, WorkerState::RESUME_REQUESTED); }
+    bool hasError() {
+        std::lock_guard<std::mutex> lock(mWorkerLock);
+        return mWorkerState == WorkerState::ERROR;
+    }
+    void stop() {
+        {
+            std::lock_guard<std::mutex> lock(mWorkerLock);
+            if (mWorkerState == WorkerState::STOPPED) return;
+            mWorkerState = WorkerState::STOPPED;
+        }
+        if (mWorker.joinable()) {
+            mWorker.join();
+        }
+    }
+    bool waitForAtLeastOneCycle() {
+        WorkerState newState;
+        switchWorkerStateSync(WorkerState::RUNNING, WorkerState::PAUSE_REQUESTED, &newState);
+        if (newState != WorkerState::PAUSED) return false;
+        switchWorkerStateSync(newState, WorkerState::RESUME_REQUESTED, &newState);
+        return newState == WorkerState::RUNNING;
+    }
+
+    // Methods that need to be provided by subclasses:
+    //
+    // Called once at the beginning of the thread loop. Must return
+    // 'true' to enter the thread loop, otherwise the thread loop
+    // exits and the worker switches into the 'error' state.
+    // bool workerInit();
+    //
+    // Called for each thread loop unless the thread is in 'paused' state.
+    // Must return 'true' to continue running, otherwise the thread loop
+    // exits and the worker switches into the 'error' state.
+    // bool workerCycle();
+
+  private:
+    void switchWorkerStateSync(WorkerState oldState, WorkerState newState,
+                               WorkerState* finalState = nullptr) {
+        std::unique_lock<std::mutex> lock(mWorkerLock);
+        android::base::ScopedLockAssertion lock_assertion(mWorkerLock);
+        if (mWorkerState != oldState) {
+            if (finalState) *finalState = mWorkerState;
+            return;
+        }
+        mWorkerState = newState;
+        mWorkerCv.wait(lock, [&]() {
+            android::base::ScopedLockAssertion lock_assertion(mWorkerLock);
+            return mWorkerState != newState;
+        });
+        if (finalState) *finalState = mWorkerState;
+    }
+    void workerThread() {
+        bool success = static_cast<Impl*>(this)->workerInit();
+        {
+            std::lock_guard<std::mutex> lock(mWorkerLock);
+            mWorkerState = success ? WorkerState::RUNNING : WorkerState::ERROR;
+        }
+        mWorkerCv.notify_one();
+        if (!success) return;
+
+        for (WorkerState state = WorkerState::RUNNING; state != WorkerState::STOPPED;) {
+            bool needToNotify = false;
+            if (state != WorkerState::PAUSED ? static_cast<Impl*>(this)->workerCycle()
+                                             : (sched_yield(), true)) {
+                //
+                // Pause and resume are synchronous. One worker cycle must complete
+                // before the worker indicates a state change. This is how 'mWorkerState' and
+                // 'state' interact:
+                //
+                // mWorkerState == RUNNING
+                // client sets mWorkerState := PAUSE_REQUESTED
+                // last workerCycle gets executed, state := mWorkerState := PAUSED by us
+                //   (or the workers enters the 'error' state if workerCycle fails)
+                // client gets notified about state change in any case
+                // thread is doing a busy wait while 'state == PAUSED'
+                // client sets mWorkerState := RESUME_REQUESTED
+                // state := mWorkerState (RESUME_REQUESTED)
+                // mWorkerState := RUNNING, but we don't notify the client yet
+                // first workerCycle gets executed, the code below triggers a client notification
+                //   (or if workerCycle fails, worker enters 'error' state and also notifies)
+                // state := mWorkerState (RUNNING)
+                if (state == WorkerState::RESUME_REQUESTED) {
+                    needToNotify = true;
+                }
+                std::lock_guard<std::mutex> lock(mWorkerLock);
+                state = mWorkerState;
+                if (mWorkerState == WorkerState::PAUSE_REQUESTED) {
+                    state = mWorkerState = WorkerState::PAUSED;
+                    needToNotify = true;
+                } else if (mWorkerState == WorkerState::RESUME_REQUESTED) {
+                    mWorkerState = WorkerState::RUNNING;
+                }
+            } else {
+                std::lock_guard<std::mutex> lock(mWorkerLock);
+                if (state == WorkerState::RESUME_REQUESTED ||
+                    mWorkerState == WorkerState::PAUSE_REQUESTED) {
+                    needToNotify = true;
+                }
+                mWorkerState = WorkerState::ERROR;
+                state = WorkerState::STOPPED;
+            }
+            if (needToNotify) {
+                mWorkerCv.notify_one();
+            }
+        }
+    }
+
+    std::thread mWorker;
+    std::mutex mWorkerLock;
+    std::condition_variable mWorkerCv;
+    WorkerState mWorkerState GUARDED_BY(mWorkerLock) = WorkerState::STOPPED;
+};

audio/aidl/common/tests/streamworker_tests.cpp

@@ -0,0 +1,210 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+#include <sched.h>
+#include <unistd.h>
+#include <atomic>
+
+#include <StreamWorker.h>
+
+#include <gtest/gtest.h>
+#define LOG_TAG "StreamWorker_Test"
+#include <log/log.h>
+
+struct TestStream {
+    std::atomic<bool> error = false;
+};
+
+class TestWorker : public StreamWorker<TestWorker> {
+  public:
+    // Use nullptr to test error reporting from the worker thread.
+    explicit TestWorker(TestStream* stream) : mStream(stream) {}
+
+    size_t getWorkerCycles() const { return mWorkerCycles; }
+    bool hasWorkerCycleCalled() const { return mWorkerCycles != 0; }
+    bool hasNoWorkerCycleCalled(useconds_t usec) {
+        const size_t cyclesBefore = mWorkerCycles;
+        usleep(usec);
+        return mWorkerCycles == cyclesBefore;
+    }
+
+    bool workerInit() { return mStream; }
+    bool workerCycle() {
+        do {
+            mWorkerCycles++;
+        } while (mWorkerCycles == 0);
+        return !mStream->error;
+    }
+
+  private:
+    TestStream* const mStream;
+    std::atomic<size_t> mWorkerCycles = 0;
+};
+
+// The parameter specifies whether an extra call to 'stop' is made at the end.
+class StreamWorkerInvalidTest : public testing::TestWithParam<bool> {
+  public:
+    StreamWorkerInvalidTest() : StreamWorkerInvalidTest(nullptr) {}
+    void TearDown() override {
+        if (GetParam()) {
+            worker.stop();
+        }
+    }
+
+  protected:
+    StreamWorkerInvalidTest(TestStream* stream) : testing::TestWithParam<bool>(), worker(stream) {}
+    TestWorker worker;
+};
+
+TEST_P(StreamWorkerInvalidTest, Uninitialized) {
+    EXPECT_FALSE(worker.hasWorkerCycleCalled());
+    EXPECT_FALSE(worker.hasError());
+}
+
+TEST_P(StreamWorkerInvalidTest, UninitializedPauseIgnored) {
+    EXPECT_FALSE(worker.hasError());
+    worker.pause();
+    EXPECT_FALSE(worker.hasError());
+}
+
+TEST_P(StreamWorkerInvalidTest, UninitializedResumeIgnored) {
+    EXPECT_FALSE(worker.hasError());
+    worker.resume();
+    EXPECT_FALSE(worker.hasError());
+}
+
+TEST_P(StreamWorkerInvalidTest, Start) {
+    EXPECT_FALSE(worker.start());
+    EXPECT_FALSE(worker.hasWorkerCycleCalled());
+    EXPECT_TRUE(worker.hasError());
+}
+
+TEST_P(StreamWorkerInvalidTest, PauseIgnored) {
+    EXPECT_FALSE(worker.start());
+    EXPECT_TRUE(worker.hasError());
+    worker.pause();
+    EXPECT_TRUE(worker.hasError());
+}
+
+TEST_P(StreamWorkerInvalidTest, ResumeIgnored) {
+    EXPECT_FALSE(worker.start());
+    EXPECT_TRUE(worker.hasError());
+    worker.resume();
+    EXPECT_TRUE(worker.hasError());
+}
+
+INSTANTIATE_TEST_SUITE_P(StreamWorkerInvalid, StreamWorkerInvalidTest, testing::Bool());
+
+class StreamWorkerTest : public StreamWorkerInvalidTest {
+  public:
+    StreamWorkerTest() : StreamWorkerInvalidTest(&stream) {}
+
+  protected:
+    TestStream stream;
+};
+
+static constexpr unsigned kWorkerIdleCheckTime = 50 * 1000;
+
+TEST_P(StreamWorkerTest, Uninitialized) {
+    EXPECT_FALSE(worker.hasWorkerCycleCalled());
+    EXPECT_FALSE(worker.hasError());
+}
+
+TEST_P(StreamWorkerTest, Start) {
+    ASSERT_TRUE(worker.start());
+    worker.waitForAtLeastOneCycle();
+    EXPECT_FALSE(worker.hasError());
+}
+
+TEST_P(StreamWorkerTest, WorkerError) {
+    ASSERT_TRUE(worker.start());
+    stream.error = true;
+    worker.waitForAtLeastOneCycle();
+    EXPECT_TRUE(worker.hasError());
+    EXPECT_TRUE(worker.hasNoWorkerCycleCalled(kWorkerIdleCheckTime));
+}
+
+TEST_P(StreamWorkerTest, PauseResume) {
+    ASSERT_TRUE(worker.start());
+    worker.waitForAtLeastOneCycle();
+    EXPECT_FALSE(worker.hasError());
+    worker.pause();
+    EXPECT_TRUE(worker.hasNoWorkerCycleCalled(kWorkerIdleCheckTime));
+    EXPECT_FALSE(worker.hasError());
+    const size_t workerCyclesBefore = worker.getWorkerCycles();
+    worker.resume();
+    // 'resume' is synchronous and returns after the worker has looped at least once.
+    EXPECT_GT(worker.getWorkerCycles(), workerCyclesBefore);
+    EXPECT_FALSE(worker.hasError());
+}
+
+TEST_P(StreamWorkerTest, StopPaused) {
+    ASSERT_TRUE(worker.start());
+    worker.waitForAtLeastOneCycle();
+    EXPECT_FALSE(worker.hasError());
+    worker.pause();
+    worker.stop();
+    EXPECT_FALSE(worker.hasError());
+}
+
+TEST_P(StreamWorkerTest, PauseAfterErrorIgnored) {
+    ASSERT_TRUE(worker.start());
+    stream.error = true;
+    worker.waitForAtLeastOneCycle();
+    EXPECT_TRUE(worker.hasError());
+    worker.pause();
+    EXPECT_TRUE(worker.hasNoWorkerCycleCalled(kWorkerIdleCheckTime));
+    EXPECT_TRUE(worker.hasError());
+}
+
+TEST_P(StreamWorkerTest, ResumeAfterErrorIgnored) {
+    ASSERT_TRUE(worker.start());
+    stream.error = true;
+    worker.waitForAtLeastOneCycle();
+    EXPECT_TRUE(worker.hasError());
+    worker.resume();
+    EXPECT_TRUE(worker.hasNoWorkerCycleCalled(kWorkerIdleCheckTime));
+    EXPECT_TRUE(worker.hasError());
+}
+
+TEST_P(StreamWorkerTest, WorkerErrorOnResume) {
+    ASSERT_TRUE(worker.start());
+    worker.waitForAtLeastOneCycle();
+    EXPECT_FALSE(worker.hasError());
+    worker.pause();
+    EXPECT_FALSE(worker.hasError());
+    stream.error = true;
+    EXPECT_FALSE(worker.hasError());
+    worker.resume();
+    worker.waitForAtLeastOneCycle();
+    EXPECT_TRUE(worker.hasError());
+    EXPECT_TRUE(worker.hasNoWorkerCycleCalled(kWorkerIdleCheckTime));
+}
+
+TEST_P(StreamWorkerTest, WaitForAtLeastOneCycle) {
+    ASSERT_TRUE(worker.start());
+    const size_t workerCyclesBefore = worker.getWorkerCycles();
+    EXPECT_TRUE(worker.waitForAtLeastOneCycle());
+    EXPECT_GT(worker.getWorkerCycles(), workerCyclesBefore);
+}
+
+TEST_P(StreamWorkerTest, WaitForAtLeastOneCycleError) {
+    ASSERT_TRUE(worker.start());
+    stream.error = true;
+    EXPECT_FALSE(worker.waitForAtLeastOneCycle());
+}
+
+INSTANTIATE_TEST_SUITE_P(StreamWorker, StreamWorkerTest, testing::Bool());