Integrate ART with NativeBridge interfaces

Native-bridge will provide the following interfaces to ART:

struct NativeBridgeCallbacks {
  bool  (*initialize   )(NativeBridgeArtCallbacks* vm_itf);
  void* (*loadLibrary  )(const char* libpath, int flag);
  void* (*getTrampoline)(void* handle, const char* name, const char* shorty,
                         uint32_t len);
  bool  (*isSupported  )(const char* libpath);

Native-bridge will expose a symbol NativeBridgeItf with the
type of NativeBridgeCallbacks to ART.

And ART will provide the interfaces below to native-bridge:

struct NativeBridgeArtCallbacks {
  int   (*logger               )(int prio, const char* tag, const char* fmt, ...);
  const char* (*getMethodShorty)(JNIEnv* env, jmethodID mid);
  int   (*getNativeMethodCount )(JNIEnv* env, jclass clazz);
  int   (*getNativeMethods     )(JNIEnv* env, jclass clazz, JNINativeMethod* methods,
                                 uint32_t method_count);

Based on the interfaces, if an ART call to dlopen fails to open a native library,
it queries the native bridge by using NativeBridgeCallbacks::isSupported(). If the
native library is supported by native-bridge, ART can load the native library
using NativeBridgeCallbacks::loadLibrary() and get a trampoline for a specific
native method using NativeBridgeCallbacks::getTrampoline(). ART can then call
the native method using the normal signature and the address of the trampoline.

On the other side, in the case of a native method calling JNI native function
CallXXXXMethodY(), native-bridge calls back to Art for the shorty of the method
using NativeBridgeArtCallbacks::getMethodShorty() so that it can prepare based
on host calling convention.

In case of JNI function RegisterNatives()/UnregisterNatives(), native bridge can
call back to NativeBridgeArtCallbacks::getNativeMethodCount() and NativeBridgeArtCallbacks
::getNativeMethods() to get all native methods of specified class so that all
corresponding trampolines can be prepared/destroyed.

Class NativeBridge is created to encapsulate the function pointers of
NativeBridgeCallbacks and provides better abstraction to ART.

Note: functionality is turned off in at the moment.

Change-Id: I652755044957a7960254648652b538cce70dd011
4 files changed