Add getFdStateDebug to access Looper's callbacks

Added getFdStateDebug to access Looper's internal state.

Flag: EXEMPT testing
Test: TEST=libutils_test; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST --gtest_filter="LooperTest.getFdStateDebug*"
Change-Id: I253ed4a6fa1040053117dcea3be80e55eef9a9b0

libutils/Looper.cpp

@@ -496,6 +496,21 @@ int Looper::addFd(int fd, int ident, int events, const sp<LooperCallback>& callb
     return 1;
 }
 
+bool Looper::getFdStateDebug(int fd, int* ident, int* events, sp<LooperCallback>* cb, void** data) {
+    AutoMutex _l(mLock);
+    if (auto seqNumIt = mSequenceNumberByFd.find(fd); seqNumIt != mSequenceNumberByFd.cend()) {
+        if (auto reqIt = mRequests.find(seqNumIt->second); reqIt != mRequests.cend()) {
+            const Request& request = reqIt->second;
+            if (ident) *ident = request.ident;
+            if (events) *events = request.events;
+            if (cb) *cb = request.callback;
+            if (data) *data = request.data;
+            return true;
+        }
+    }
+    return false;
+}
+
 int Looper::removeFd(int fd) {
     AutoMutex _l(mLock);
     const auto& it = mSequenceNumberByFd.find(fd);

libutils/Looper_test.cpp

@@ -410,6 +410,52 @@ TEST_F(LooperTest, AddFd_WhenNoCallbackAndAllowNonCallbacksIsFalse_ReturnsError)
             << "addFd should return -1 because arguments were invalid";
 }
 
+class LooperCallbackStub final : public LooperCallback {
+  public:
+    LooperCallbackStub(std::function<int()> callback) : mCallback{callback} {}
+
+    int handleEvent(int /*fd*/, int /*events*/, void* /*data*/) override { return mCallback(); }
+
+  private:
+    std::function<int()> mCallback;
+};
+
+TEST_F(LooperTest, getFdStateDebug_WhenFdIsInRequests_ReturnsTrue) {
+    Pipe pipe;
+    const int fd = pipe.receiveFd;
+    constexpr int expectedIdent{Looper::POLL_CALLBACK};
+    sp<LooperCallback> expectedCallback =
+            sp<LooperCallbackStub>::make([]() constexpr -> int { return 0; });
+    void* expectedData = this;
+
+    EXPECT_EQ(1, mLooper->addFd(fd, expectedIdent, Looper::EVENT_INPUT, expectedCallback,
+                                expectedData));
+
+    int ident;
+    int events;
+    sp<LooperCallback> callback;
+    void* data;
+
+    EXPECT_TRUE(mLooper->getFdStateDebug(fd, &ident, &events, &callback, &data));
+
+    EXPECT_EQ(ident, expectedIdent);
+    EXPECT_EQ(events, Looper::EVENT_INPUT);
+    EXPECT_EQ(callback, expectedCallback);
+    EXPECT_EQ(data, expectedData);
+}
+
+TEST_F(LooperTest, getFdStateDebug_WhenFdIsNotInRequests_ReturnsFalse) {
+    Pipe pipe;
+    const int notAddedFd = pipe.receiveFd;
+
+    int ident;
+    int events;
+    sp<LooperCallback> callback;
+    void* data;
+
+    EXPECT_FALSE(mLooper->getFdStateDebug(notAddedFd, &ident, &events, &callback, &data));
+}
+
 TEST_F(LooperTest, RemoveFd_WhenCallbackNotAdded_ReturnsZero) {
     int result = mLooper->removeFd(1);
 

libutils/include/utils/Looper.h

@@ -322,6 +322,12 @@ public:
     int addFd(int fd, int ident, int events, Looper_callbackFunc callback, void* data);
     int addFd(int fd, int ident, int events, const sp<LooperCallback>& callback, void* data);
 
+    /**
+     * May be useful for testing, instead of executing a looper on another thread for code expecting
+     * a looper, you can call callbacks directly.
+     */
+    bool getFdStateDebug(int fd, int* ident, int* events, sp<LooperCallback>* cb, void** data);
+
     /**
      * Removes a previously added file descriptor from the looper.
      *