IServiceManager.h
namespace android {
// ----------------------------------------------------------------------
class IServiceManager : public IInterface
{
public:
DECLARE_META_INTERFACE(ServiceManager)
/**
* Retrieve an existing service, blocking for a few seconds
* if it doesn't yet exist.
*/
virtual sp<IBinder> getService( const String16& name) const = 0;
/**
* Retrieve an existing service, non-blocking.
*/
virtual sp<IBinder> checkService( const String16& name) const = 0;
/**
* Register a service.
*/
virtual status_t addService( const String16& name,
const sp<IBinder>& service,
bool allowIsolated = false) = 0;
/**
* Return list of all existing services.
*/
virtual Vector<String16> listServices() = 0;
// ServiceManager Proxy 提供的接口
enum {
GET_SERVICE_TRANSACTION = IBinder::FIRST_CALL_TRANSACTION,
CHECK_SERVICE_TRANSACTION,
ADD_SERVICE_TRANSACTION,
LIST_SERVICES_TRANSACTION,
};
};
sp<IServiceManager> defaultServiceManager();
template<typename INTERFACE>
status_t getService(const String16& name, sp<INTERFACE>* outService)
{
const sp<IServiceManager> sm = defaultServiceManager();
if (sm != NULL) {
*outService = interface_cast<INTERFACE>(sm->getService(name));
if ((*outService) != NULL) return NO_ERROR;
}
return NAME_NOT_FOUND;
}
}; // namespace android
IServiceManager.cpp
namespace android {
sp<IServiceManager> defaultServiceManager()
{
if (gDefaultServiceManager != NULL) return gDefaultServiceManager;
{
AutoMutex _l(gDefaultServiceManagerLock);
while (gDefaultServiceManager == NULL) {
gDefaultServiceManager = interface_cast<IServiceManager>(
ProcessState::self()->getContextObject(NULL));
if (gDefaultServiceManager == NULL)
sleep(1);
}
}
return gDefaultServiceManager;
}
/*
* 1. ProcessState::self()->getContextObject(NULL): 返回的是一个 BpBinder. ServiceManager 的 desc 默认为0.
* 2. interface_cast 就是将 BpBinder 封装为 IServiceManager,这样可以直接调用 IServiceManager 的接口.
*/
/*
* 这里,有一个设计思想.
* 1. defaultServiceManager 首先实例化 BpBinder.
* 2. interface_cast 就是 实例化 BpXXX,并将 BpBinder 交给其管理.
*
* Proxy 端的用户无法直接看到 BpBinder , BpBinder 由 BpXXX 持有.用户本身不关心 BpBinder 的能力,只关心 IXXX 定义的 接口.
* 所以这里很好的进行了封装.
*/
/***************************************************************************************************************/
template<typename INTERFACE>
inline sp<INTERFACE> interface_cast(const sp<IBinder>& obj) // 调用了 IServiceManager::asInterface
{
return INTERFACE::asInterface(obj);
}
#define IMPLEMENT_META_INTERFACE(INTERFACE, NAME) \
const ::android::String16 I##INTERFACE::descriptor(NAME); \
const ::android::String16& \
I##INTERFACE::getInterfaceDescriptor() const { \
return I##INTERFACE::descriptor; \
} \
::android::sp<I##INTERFACE> I##INTERFACE::asInterface( \
const ::android::sp<::android::IBinder>& obj) \
{ \
::android::sp<I##INTERFACE> intr; \
if (obj != NULL) { \
intr = static_cast<I##INTERFACE*>( \
obj->queryLocalInterface( \
I##INTERFACE::descriptor).get()); \
if (intr == NULL) { \
intr = new Bp##INTERFACE(obj); \
} \
} \
return intr; \
} \
I##INTERFACE::I##INTERFACE() { } \
I##INTERFACE::~I##INTERFACE() { } \
// 展开: IMPLEMENT_META_INTERFACE(ServiceManager, "android.os.IServiceManager");
const ::android::String16 IServiceManager::descriptor("android.os.IServiceManager");
const ::android::String16&
IServiceManager::getInterfaceDescriptor() const {
return IServiceManager::descriptor;
}
::android::sp<IServiceManager> IServiceManager::asInterface(
const ::android::sp<::android::IBinder>& obj) // obj 就是 BpBinder
{
::android::sp<IServiceManager> intr;
if (obj != NULL) {
intr = static_cast<IServiceManager*>(
obj->queryLocalInterface( // BpBinder 的 queryLocalInterface 返回 NULL
IServiceManager::descriptor).get());
if (intr == NULL) { // 此时,创建 BpServiceManager.
intr = new BpServiceManager(obj);
}
}
return intr;
}
IServiceManager::IServiceManager() { }
IServiceManager::~IServiceManager() { }
/***************************************************************************************************************/
// ----------------------------------------------------------------------
class BpServiceManager : public BpInterface<IServiceManager>
{
public:
explicit BpServiceManager(const sp<IBinder>& impl)
: BpInterface<IServiceManager>(impl)
{
}
virtual sp<IBinder> getService(const String16& name) const
{
unsigned n;
for (n = 0; n < 5; n++){
if (n > 0) {
if (!strcmp(ProcessState::self()->getDriverName().c_str(), "/dev/vndbinder")) {
ALOGI("Waiting for vendor service %s...", String8(name).string());
CallStack stack(LOG_TAG);
} else {
ALOGI("Waiting for service %s...", String8(name).string());
}
sleep(1);
}
sp<IBinder> svc = checkService(name);
if (svc != NULL) return svc;
}
return NULL;
}
virtual sp<IBinder> checkService( const String16& name) const
{
Parcel data, reply;
data.writeInterfaceToken(IServiceManager::getInterfaceDescriptor());
data.writeString16(name);
remote()->transact(CHECK_SERVICE_TRANSACTION, data, &reply);
return reply.readStrongBinder();
}
virtual status_t addService(const String16& name, const sp<IBinder>& service,
bool allowIsolated)
{
Parcel data, reply;
data.writeInterfaceToken(IServiceManager::getInterfaceDescriptor());
data.writeString16(name);
data.writeStrongBinder(service);
data.writeInt32(allowIsolated ? 1 : 0);
status_t err = remote()->transact(ADD_SERVICE_TRANSACTION, data, &reply);
return err == NO_ERROR ? reply.readExceptionCode() : err;
}
virtual Vector<String16> listServices()
{
Vector<String16> res;
int n = 0;
for (;;) {
Parcel data, reply;
data.writeInterfaceToken(IServiceManager::getInterfaceDescriptor());
data.writeInt32(n++);
status_t err = remote()->transact(LIST_SERVICES_TRANSACTION, data, &reply);
if (err != NO_ERROR)
break;
res.add(reply.readString16());
}
return res;
}
};
IMPLEMENT_META_INTERFACE(ServiceManager, "android.os.IServiceManager");
}; // namespace android
