Android Binder详解(中英文对照)

I will use call IAudioFlinger::setMode API as a sample scenario to show how the Android IPC

system works. AudioFlinger is a service in the media_server program

Service Manager Run

service_manager provide service manager service to other process. It must be started before any

other service gets running.

int main(int argc, char **argv)

{

svcmgr_handle = svcmgr;

}

other process.

bwr.read_consumed = 0;

res = binder_parse(bs, 0, readbuf, bwr.read_consumed, func);

break;

LOGE("binder_loop: io error %d %s\n", res, strerror(errno));

break;

BINDER_SERVICE_MANAGER is the registered handle for service_manager. The other process

ProcessState::self()->getContextObject(NULL));

return gDefaultServiceManager;

gDefaultServiceManager is defined in libutil, so any program or library which included libutil will

have this symbol, it’s unique in one process. The first time gDefaultServiceManager is NULL, so

it will first get a ProcessState instance through ProcessState::self(). One process has only one

ProcessState instance. ProcessState will open “/dev/binder” driver for IPCThreadState use.

{

}

reserved for service manager, which will be explained later.)

sp<IBinder> result;

IBinder* b = e->binder;

if (b == NULL || !e->refs->attemptIncWeak(this)) {

e->binder = b;

if (b) e->refs = b->getWeakRefs();

result = b;

// This little bit of nastyness is to allow us to add a primary

proxy class for remote binder object.

, mObitsSent(0)

{

}

mOut.writeInt32(BC_INCREFS);

Now getContextObject returns a BpBinder instance, it will be interface_cast to IServiceManager.

interface_cast is defined in IInterface.h. It will be extended as:

Now let’s take a look at definition of IServiceManager.

{

public:

DECLARE_META_INTERFACE(ServiceManager);

* if it doesn't yet exist.

virtual Vector<String16> listServices() = 0;

ADD_SERVICE_TRANSACTION,

The code will be extended like this.

return IServiceManager::descriptor;

}

{

sp<IServiceManager> intr;

if (obj != NULL) {

intr = static_cast<IServiceManager*>(