libs/hwui/jni/android_graphics_HardwareRendererObserver.cpp

/*
 * Copyright (C) 2019 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 "android_graphics_HardwareRendererObserver.h"

#include "graphics_jni_helpers.h"
#include "nativehelper/jni_macros.h"

#include <array>

namespace android {

struct {
    jmethodID callback;
} gHardwareRendererObserverClassInfo;

static JNIEnv* getenv(JavaVM* vm) {
    JNIEnv* env;
    if (vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK) {
        LOG_ALWAYS_FATAL("Failed to get JNIEnv for JavaVM: %p", vm);
    }
    return env;
}

HardwareRendererObserver::HardwareRendererObserver(JavaVM *vm, jobject observer) : mVm(vm) {
    mObserverWeak = getenv(mVm)->NewWeakGlobalRef(observer);
    LOG_ALWAYS_FATAL_IF(mObserverWeak == nullptr,
            "unable to create frame stats observer reference");
}

HardwareRendererObserver::~HardwareRendererObserver() {
    JNIEnv* env = getenv(mVm);
    env->DeleteWeakGlobalRef(mObserverWeak);
}

bool HardwareRendererObserver::getNextBuffer(JNIEnv* env, jlongArray metrics, int* dropCount) {
    jsize bufferSize = env->GetArrayLength(reinterpret_cast<jarray>(metrics));
    LOG_ALWAYS_FATAL_IF(bufferSize != HardwareRendererObserver::kBufferSize,
                        "Mismatched Java/Native FrameMetrics data format.");

    FrameMetricsNotification& elem = mRingBuffer[mNextInQueue];
    if (elem.hasData.load()) {
        env->SetLongArrayRegion(metrics, 0, kBufferSize, elem.buffer);
        *dropCount = elem.dropCount;
        mNextInQueue = (mNextInQueue + 1) % kRingSize;
        elem.hasData = false;
        return true;
    }

    return false;
}

void HardwareRendererObserver::notify(const int64_t* stats) {
    FrameMetricsNotification& elem = mRingBuffer[mNextFree];

    if (!elem.hasData.load()) {
        memcpy(elem.buffer, stats, kBufferSize * sizeof(stats[0]));

        elem.dropCount = mDroppedReports;
        mDroppedReports = 0;
        mNextFree = (mNextFree + 1) % kRingSize;
        elem.hasData = true;

        JNIEnv* env = getenv(mVm);
        jobject target = env->NewLocalRef(mObserverWeak);
        if (target != nullptr) {
            env->CallVoidMethod(target, gHardwareRendererObserverClassInfo.callback);
            env->DeleteLocalRef(target);
        }
    } else {
        mDroppedReports++;
    }
}

static jlong android_graphics_HardwareRendererObserver_createObserver(JNIEnv* env,
                                                                      jobject observerObj) {
    JavaVM* vm = nullptr;
    if (env->GetJavaVM(&vm) != JNI_OK) {
        LOG_ALWAYS_FATAL("Unable to get Java VM");
        return 0;
    }

    HardwareRendererObserver* observer = new HardwareRendererObserver(vm, observerObj);
    return reinterpret_cast<jlong>(observer);
}

static jint android_graphics_HardwareRendererObserver_getNextBuffer(JNIEnv* env, jobject,
                                                                    jlong observerPtr,
                                                                    jlongArray metrics) {
    HardwareRendererObserver* observer = reinterpret_cast<HardwareRendererObserver*>(observerPtr);
    int dropCount = 0;
    if (observer->getNextBuffer(env, metrics, &dropCount)) {
        return dropCount;
    } else {
        return -1;
    }
}

static const std::array gMethods = {
    MAKE_JNI_NATIVE_METHOD("nCreateObserver", "()J",
                           android_graphics_HardwareRendererObserver_createObserver),
    MAKE_JNI_NATIVE_METHOD("nGetNextBuffer", "(J[J)I",
                           android_graphics_HardwareRendererObserver_getNextBuffer),
};

int register_android_graphics_HardwareRendererObserver(JNIEnv* env) {

    jclass observerClass = FindClassOrDie(env, "android/graphics/HardwareRendererObserver");
    gHardwareRendererObserverClassInfo.callback = GetMethodIDOrDie(env, observerClass,
                                                                   "notifyDataAvailable", "()V");

    return RegisterMethodsOrDie(env, "android/graphics/HardwareRendererObserver",
                                gMethods.data(), gMethods.size());

}

} // namespace android