【WIP】aap-core安卓音频插件框架开源项目底层技术研究

https://github.com/atsushieno/aap-core

关于宿主Host加载app插件

1. 程序入口：libandroidaudioplugin.so
2. 入口函数：GetAndroidAudioPluginFactory

aap::PluginInstance* aap::PluginHost::instantiateLocalPlugin(const PluginInformation *descriptor)
{
    dlerror(); // clean up any previous error state
    auto file = descriptor->getLocalPluginSharedLibrary();
    auto metadataFullPath = descriptor->getMetadataFullPath();
    if (!metadataFullPath.empty()) {
        size_t idx = metadataFullPath.find_last_of('/');
        if (idx > 0) {
            auto soFullPath = metadataFullPath.substr(0, idx + 1) + file;
            struct stat st;
            if (stat(soFullPath.c_str(), &st) == 0)
                file = soFullPath;
        }
    }
    auto entrypoint = descriptor->getLocalPluginLibraryEntryPoint();
    auto dl = dlopen(file.length() > 0 ? file.c_str() : "libandroidaudioplugin.so", RTLD_LAZY);
    if (dl == nullptr) {
        aap::a_log_f(AAP_LOG_LEVEL_ERROR, LOG_TAG, "aap::PluginHost: AAP library %s could not be loaded: %s", file.c_str(), dlerror());
        return nullptr;
    }
    auto factoryGetter = (aap_factory_t) dlsym(dl, entrypoint.length() > 0 ? entrypoint.c_str() : "GetAndroidAudioPluginFactory");
    if (factoryGetter == nullptr) {
        aap::a_log_f(AAP_LOG_LEVEL_ERROR, LOG_TAG, "aap::PluginHost: AAP factory entrypoint function %s was not found in %s.", entrypoint.c_str(), file.c_str());
        return nullptr;
    }
    auto pluginFactory = factoryGetter();
    if (pluginFactory == nullptr) {
        aap::a_log_f(AAP_LOG_LEVEL_ERROR, LOG_TAG, "aap::PluginHost: AAP factory entrypoint function %s could not instantiate a plugin.", entrypoint.c_str());
        return nullptr;
    }
    auto instance = new LocalPluginInstance(this,
                                            aapxs_definition_registry,
                                            localInstanceIdSerial++,
                                            descriptor, pluginFactory, event_midi2_input_buffer_size);
    instances.emplace_back(instance);
    return instance;
}

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