lang/reflect/natVMProxy.cc

// natVMProxy.cc -- Implementation of VMProxy methods.

/* Copyright (C) 2006, 2007
   Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

// The idea of behind this code is to utilize libffi's ability to
// create closures to provide a fast "cut-through" way to generate
// proxy classes.  Instead of generating bytecode and then
// interpreting that, we copy the method definitions for each of the
// methods we're supposed to be prxying and generate a libffi closure
// for each one.

#include <config.h>
#include <platform.h>
#include <sysdep/descriptor.h>

#include <limits.h>
#include <string.h>
#include <stddef.h>
#include <stdio.h>

#include <gcj/cni.h>
#include <gcj/javaprims.h>
#include <jvm.h>
#include <jni.h>
#include <java-threads.h>
#include <java-interp.h>
#include <ffi.h>
#include <execution.h>
#include <gcj/method.h>

#include <gnu/gcj/runtime/BootClassLoader.h>
#include <java/lang/Class.h>
#include <java/lang/ClassCastException.h>
#include <java/lang/Error.h>
#include <java/lang/IllegalArgumentException.h>
#include <java/lang/Integer.h>
#include <java/lang/StringBuffer.h>
#include <java/lang/UnsupportedOperationException.h>
#include <java/lang/VMClassLoader.h>
#include <java/lang/VMCompiler.h>
#include <java/lang/reflect/InvocationHandler.h>
#include <java/lang/reflect/Method.h>
#include <java/lang/reflect/Proxy$ClassFactory.h>
#include <java/lang/reflect/Proxy$ProxyData.h>
#include <java/lang/reflect/Proxy.h>
#include <java/lang/reflect/UndeclaredThrowableException.h>
#include <java/lang/reflect/VMProxy.h>

#include <java/lang/Byte.h>
#include <java/lang/Short.h>
#include <java/lang/Integer.h>
#include <java/lang/Long.h>
#include <java/lang/Float.h>
#include <java/lang/Double.h>
#include <java/lang/Boolean.h>
#include <java/lang/Character.h>


using namespace java::lang::reflect;
using namespace java::lang;

#ifndef INTERPRETER
jclass
java::lang::reflect::VMProxy::generateProxyClass
  (ClassLoader *, Proxy$ProxyData *)
{
  throw new UnsupportedOperationException (
    JvNewStringLatin1 ("Interpreter not available"));
}
#else
typedef void (*closure_fun) (ffi_cif*, void*, void**, void*);
static void *ncode (int method_index, jclass klass, _Jv_Method *self, closure_fun fun);
static void run_proxy (ffi_cif*, void*, void**, void*);

typedef jobject
#if defined (X86_WIN32) && !defined (__CYGWIN__)
 __attribute__ ((thiscall))
#endif
 invoke_t (jobject, Proxy *, Method *, JArray< jobject > *);

// True if pc points to a proxy frame.

bool
_Jv_is_proxy (void *pc)
{
  return pc == UNWRAP_FUNCTION_DESCRIPTOR ((void*)&run_proxy);
}

// Generate a proxy class by using libffi closures for each entry
// point.

jclass
java::lang::reflect::VMProxy::generateProxyClass
  (ClassLoader *loader, Proxy$ProxyData *d)
{
  // If we're precompiling, generate bytecode and allow VMCompiler to
  // precompile it.
  if (VMCompiler::precompiles ())
    return (new Proxy$ClassFactory(d))->generate(loader);

  jclass klass = new Class ();

  // Synchronize on the class, so that it is not attempted initialized
  // until we're done.
  JvSynchronize sync (klass);

  klass->superclass = &Proxy::class$;
  klass->engine = &_Jv_soleIndirectCompiledEngine;
  klass->size_in_bytes = -1;
  klass->vtable_method_count = -1;

  // Declare  private static transient java.lang.reflect.Method[] $Proxy0.m
  klass->field_count = klass->static_field_count = 1;
  klass->fields = (_Jv_Field*)_Jv_AllocRawObj (sizeof (_Jv_Field));
  klass->fields[0].name = _Jv_makeUtf8Const ("m");
  klass->fields[0].type = d->methods->getClass();
  klass->fields[0].flags = (Modifier::PRIVATE | Modifier::STATIC
			    | Modifier::TRANSIENT);

  // Record the defining loader.  For the bootstrap class loader,
  // we record NULL.
  if (loader != VMClassLoader::bootLoader)
    klass->loader = loader;

  {
    StringBuffer *sb = new StringBuffer();
    sb->append(JvNewStringLatin1 ("$Proxy"));
    sb->append(Integer::toString (d->id));
    klass->name = _Jv_makeUtf8Const (sb->toString());
  }

  // Allocate space for the interfaces.
  klass->interface_count = d->interfaces->length;
  klass->interfaces = (jclass*) _Jv_AllocRawObj (klass->interface_count
						 *sizeof (jclass));
  for (int i = 0; i < klass->interface_count; i++)
    klass->interfaces[i] = elements(d->interfaces)[i];

  size_t count = d->methods->length;

  {
    size_t total_count = count + Proxy::class$.method_count + 1;
    if (total_count >= 65536)
      throw new IllegalArgumentException ();
    // Allocate space for the methods.  This is a worst case
    // estimate.
    klass->methods
      = (_Jv_Method *) _Jv_AllocRawObj (sizeof (_Jv_Method)
					* total_count);
  }

  jshort &method_count = klass->method_count;

  // Copy all reachable methods from Proxy.
  for (int i = 0; i < Proxy::class$.method_count; i++)
    {
      if (_Jv_CheckAccess (klass, &Proxy::class$,
			   Proxy::class$.methods[i].accflags))
	{
	  klass->methods[method_count] = Proxy::class$.methods[i];
	  method_count++;
	}
    }

  _Jv_Method *init_method
    = (_Jv_Linker::search_method_in_class
       (klass, klass,
	_Jv_makeUtf8Const ("<init>"),
	_Jv_makeUtf8Const ("(Ljava.lang.reflect.InvocationHandler;)V"),
	false));
  init_method->accflags |= Modifier::PUBLIC;

  // Create the methods for all of the interfaces.
  for (size_t i = 0; i < count; i++)
    {
      _Jv_Method &method = klass->methods[method_count++];
      const _Jv_Method &imethod
	= *_Jv_FromReflectedMethod (elements(d->methods)[i]);
      // We use a shallow copy of IMETHOD rather than a deep copy;
      // this means that the pointer fields of METHOD point into the
      // interface.  As long as this subclass of Proxy is reachable,
      // the interfaces of which it is a proxy will also be reachable,
      // so this is safe.
      method = imethod;
      method.ncode = ncode (i, klass, &method, run_proxy);
      method.accflags &= ~Modifier::ABSTRACT;
    }

  _Jv_Linker::layout_vtable_methods (klass);
  _Jv_RegisterInitiatingLoader (klass, klass->loader);

  // Set $Proxy0.m to point to the methods arrray
  java::lang::reflect::Field *f
    = klass->getDeclaredField (JvNewStringLatin1 ("m"));
  f->flag = true;
  f->set(NULL, d->methods);

  return klass;
}


// Box things with primitive types.
static inline jobject
box (void *thing, jclass klass, FFI_TYPE type)
{
  jobject o;

  switch (type)
    {
    case FFI_TYPE_VOID:
      return NULL;

    case FFI_TYPE_POINTER:
      o = *(jobject*)thing;
      return o;

    default:
      ;
    }

  if (klass == JvPrimClass (byte))
    o = new Byte (*(jbyte*)thing);
  else if (klass == JvPrimClass (short))
    o = new Short (*(jshort*)thing);
  else if (klass == JvPrimClass (int))
    o = new Integer (*(jint*)thing);
  else if (klass == JvPrimClass (long))
    o = new Long (*(jlong*)thing);
  else if (klass == JvPrimClass (float))
    o = new Float (*(jfloat*)thing);
  else if (klass == JvPrimClass (double))
    o = new Double (*(jdouble*)thing);
  else if (klass == JvPrimClass (boolean))
    o = new Boolean (*(jboolean*)thing);
  else if (klass == JvPrimClass (char))
    o = new Character (*(jchar*)thing);
  else
    JvFail ("Bad ffi type in proxy");

  return o;
}


// Unbox things with primitive types.
static inline void
unbox (jobject o, jclass klass, void *rvalue, FFI_TYPE type)
{
  switch (type)
    {
    case FFI_TYPE_VOID:
      return;

    case FFI_TYPE_POINTER:
      _Jv_CheckCast (klass, o);
      *(jobject*)rvalue = o;
      return;

    default:
      ;
    }

  // If the value returned ... is null and the interface method's
  // return type is primitive, then a NullPointerException will be
  // thrown ...
  if (klass == JvPrimClass (byte))
    {
      _Jv_CheckCast (&Byte::class$, o);
      *(jbyte*)rvalue = ((Byte*)o)->byteValue();
    }
  else if (klass == JvPrimClass (short))
    {
      _Jv_CheckCast (&Short::class$, o);
      *(jshort*)rvalue = ((Short*)o)->shortValue();
    }
  else if (klass == JvPrimClass (int))
    {
      _Jv_CheckCast (&Integer::class$, o);
      *(jint*)rvalue = ((Integer*)o)->intValue();
    }
  else if (klass == JvPrimClass (long))
    {
      _Jv_CheckCast (&Long::class$, o);
      *(jlong*)rvalue = ((Long*)o)->longValue();
    }
  else if (klass == JvPrimClass (float))
    {
      _Jv_CheckCast (&Float::class$, o);
      *(jfloat*)rvalue = ((Float*)o)->floatValue();
    }
  else if (klass == JvPrimClass (double))
    {
      _Jv_CheckCast (&Double::class$, o);
      *(jdouble*)rvalue = ((Double*)o)->doubleValue();
    }
  else if (klass == JvPrimClass (boolean))
    {
      _Jv_CheckCast (&Boolean::class$, o);
      *(jboolean*)rvalue = ((Boolean*)o)->booleanValue();
    }
  else if (klass == JvPrimClass (char))
    {
      _Jv_CheckCast (&Character::class$, o);
      *(jchar*)rvalue = ((Character*)o)->charValue();
    }
  else
    JvFail ("Bad ffi type in proxy");
}

// _Jv_getFieldInternal is declared as a friend of reflect.Field in
// libjava/headers.txt.  This gives us a way to call the private
// method Field.get (Class caller, Object obj).
extern inline jobject
_Jv_getFieldInternal (java::lang::reflect::Field *f, jclass c, jobject o)
{
  return f->get(c, o);
}

// run_proxy is the entry point for all proxy methods.  It boxes up
// all the arguments and then invokes the invocation handler's invoke()
// method.  Exceptions are caught and propagated.

typedef struct {
  ffi_closure  closure;
  _Jv_ClosureList list;
  ffi_cif   cif;
  _Jv_Method *self;
  int method_index;
  ffi_type *arg_types[0];
} ncode_closure;

static void
run_proxy (ffi_cif *cif,
	   void *rvalue,
	   void **args,
	   void*user_data)
{
  using namespace java::lang::reflect;

  Proxy *proxy = *(Proxy**)args[0];
  ncode_closure *self = (ncode_closure *) user_data;

  jclass proxyClass = proxy->getClass();

  // FRAME_DESC registers this particular invocation as the top-most
  // interpreter frame.  This lets the stack tracing code (for
  // Throwable) print information about the Proxy being run rather
  // than about Proxy.class itself.  FRAME_DESC has a destructor so it
  // cleans up automatically when this proxy invocation returns.
  Thread *thread = Thread::currentThread();
  _Jv_InterpFrame frame_desc (self->self, thread, proxyClass,
			      NULL, frame_proxy);

  // The method to invoke is saved in $Proxy0.m[method_index].
  // FIXME: We could somewhat improve efficiency by storing a pointer
  // to the method (rather than its index) in ncode_closure.  This
  // would avoid the lookup, but it probably wouldn't make a huge
  // difference.  We'd still have to save the method array because
  // ncode structs are not scanned by the gc.
  Field *f = proxyClass->getDeclaredField (JvNewStringLatin1 ("m"));
  JArray<Method*> *methods
    = (JArray<Method*>*)_Jv_getFieldInternal (f, proxyClass, NULL);
  Method *meth = elements(methods)[self->method_index];

  JArray<jclass> *parameter_types = meth->internalGetParameterTypes ();
  JArray<jclass> *exception_types = meth->internalGetExceptionTypes ();

  InvocationHandler *handler = proxy->h;
  JArray<jobject> *argsArray = NULL;
  jobject *jargs = NULL;
  if (parameter_types->length)
    {
      void *poo
	= _Jv_NewObjectArray (parameter_types->length, &Object::class$, NULL);
      argsArray = (JArray<jobject> *) poo;
      jargs = elements(argsArray);
    }

  // FIXME: It must be possible to use fast interface dispatch here,
  // but I've not quite figured out how to do it.
  invoke_t *invoke
    = (invoke_t *)(_Jv_LookupInterfaceMethod
		   (handler->getClass (),
		    _Jv_makeUtf8Const ("invoke"),
		    (_Jv_makeUtf8Const
		     ("(Ljava.lang.Object;Ljava.lang.reflect.Method;[Ljava.lang.Object;)"
		      "Ljava.lang.Object;"))));

  // Copy and box all the args.
  int index = 1;
  for (int i = 0; i < parameter_types->length; i++, index++)
    jargs[i] = box (args[index], elements(parameter_types)[i],
		    cif->arg_types[index]->type);

  jobject ret;
  try
    {
      ret = invoke (handler, proxy, meth, argsArray);
    }
  catch (Throwable *t)
    {
      if (_Jv_IsInstanceOf (t, &RuntimeException::class$)
	  || _Jv_IsInstanceOf (t, &Error::class$))
	throw t;

      Class **throwables = elements (exception_types);
      for (int i = 0; i < exception_types->length; i++)
	if (_Jv_IsInstanceOf (t, throwables[i]))
	  throw t;

      throw new UndeclaredThrowableException (t);
    }

  unbox (ret, meth->return_type, rvalue, cif->rtype->type);
}


// Given a method and a closure function, create libffi CIF and return
// the address of its closure.

static void *
ncode (int method_index, jclass klass, _Jv_Method *self, closure_fun fun)
{
  using namespace java::lang::reflect;

  jboolean staticp = (self->accflags & Modifier::STATIC) != 0;
  int arg_count = _Jv_count_arguments (self->signature, staticp);

  void *code;
  ncode_closure *closure =
    (ncode_closure*)ffi_closure_alloc (sizeof (ncode_closure)
				       + arg_count * sizeof (ffi_type*),
				       &code);
  closure->method_index = method_index;
  closure->list.registerClosure (klass, closure);

  _Jv_init_cif (self->signature,
		arg_count,
		staticp,
		&closure->cif,
		&closure->arg_types[0],
		NULL);
  closure->self = self;

  JvAssert ((self->accflags & Modifier::NATIVE) == 0);

  ffi_prep_closure_loc (&closure->closure,
			&closure->cif,
			fun,
			code,
			code);

  self->ncode = code;
  return self->ncode;
}

#endif // INTERPRETER