natclass.cc

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// Interface Dispatch Table" whose size is (number of methods + 1) words.
// The first word is a pointer to the interface (i.e. the java.lang.Class
// instance for that interface).  The remaining words are pointers to the
// actual methods that implement the methods declared in the interface,
// in order of declaration.
//
// Append partial interface dispatch table for "iface" to "itable", at
// position itable_pos.
// Returns the offset at which the next partial ITable should be appended.
jshort
_Jv_AppendPartialITable (jclass klass, jclass iface, void **itable, 
                         jshort pos)
{
  using namespace java::lang::reflect;

  itable[pos++] = (void *) iface;
  _Jv_Method *meth;
  
  for (int j=0; j < iface->method_count; j++)
    {
      meth = NULL;
      for (jclass cl = klass; cl; cl = cl->getSuperclass())
        {
	  meth = _Jv_GetMethodLocal (cl, iface->methods[j].name,
				     iface->methods[j].signature);
		 
	  if (meth)
	    break;
	}

      if (meth && (meth->name->data[0] == '<'))
	{
	  // leave a placeholder in the itable for hidden init methods.
          itable[pos] = NULL;	
	}
      else if (meth)
        {
	  if (Modifier::isStatic(meth->accflags))
	    throw new java::lang::IncompatibleClassChangeError
	      (_Jv_GetMethodString (klass, meth->name));
	  if (Modifier::isAbstract(meth->accflags))
	    throw new java::lang::AbstractMethodError
	      (_Jv_GetMethodString (klass, meth->name));
	  if (! Modifier::isPublic(meth->accflags))
	    throw new java::lang::IllegalAccessError
	      (_Jv_GetMethodString (klass, meth->name));

	  itable[pos] = meth->ncode;
	}
      else
        {
	  // The method doesn't exist in klass. Binary compatibility rules
	  // permit this, so we delay the error until runtime using a pointer
	  // to a method which throws an exception.
	  itable[pos] = (void *) _Jv_ThrowNoSuchMethodError;
	}
      pos++;
    }
    
  return pos;
}

static _Jv_Mutex_t iindex_mutex;
static bool iindex_mutex_initialized = false;

// We need to find the correct offset in the Class Interface Dispatch 
// Table for a given interface. Once we have that, invoking an interface 
// method just requires combining the Method's index in the interface 
// (known at compile time) to get the correct method.  Doing a type test 
// (cast or instanceof) is the same problem: Once we have a possible Partial 
// Interface Dispatch Table, we just compare the first element to see if it 
// matches the desired interface. So how can we find the correct offset?  
// Our solution is to keep a vector of candiate offsets in each interface 
// (idt->iface.ioffsets), and in each class we have an index 
// (idt->cls.iindex) used to select the correct offset from ioffsets.
//
// Calculate and return iindex for a new class. 
// ifaces is a vector of num interfaces that the class implements.
// offsets[j] is the offset in the interface dispatch table for the
// interface corresponding to ifaces[j].
// May extend the interface ioffsets if required.
jshort
_Jv_FindIIndex (jclass *ifaces, jshort *offsets, jshort num)
{
  int i;
  int j;
  
  // Acquire a global lock to prevent itable corruption in case of multiple 
  // classes that implement an intersecting set of interfaces being linked
  // simultaneously. We can assume that the mutex will be initialized
  // single-threaded.
  if (! iindex_mutex_initialized)
    {
      _Jv_MutexInit (&iindex_mutex);
      iindex_mutex_initialized = true;
    }
  
  _Jv_MutexLock (&iindex_mutex);
  
  for (i=1;; i++)  /* each potential position in ioffsets */
    {
      for (j=0;; j++)  /* each iface */
        {
	  if (j >= num)
	    goto found;
	  if (i >= ifaces[j]->idt->iface.ioffsets[0])
	    continue;
	  int ioffset = ifaces[j]->idt->iface.ioffsets[i];
	  /* We can potentially share this position with another class. */
	  if (ioffset >= 0 && ioffset != offsets[j])
	    break; /* Nope. Try next i. */	  
	}
    }
  found:
  for (j = 0; j < num; j++)
    {
      int len = ifaces[j]->idt->iface.ioffsets[0];
      if (i >= len) 
	{
	  /* Resize ioffsets. */
	  int newlen = 2 * len;
	  if (i >= newlen)
	    newlen = i + 3;
	  jshort *old_ioffsets = ifaces[j]->idt->iface.ioffsets;
	  jshort *new_ioffsets = (jshort *) _Jv_Realloc (old_ioffsets, 
	                                  newlen * sizeof(jshort));	  
	  new_ioffsets[0] = newlen;

	  while (len < newlen)
	    new_ioffsets[len++] = -1;
	  
	  ifaces[j]->idt->iface.ioffsets = new_ioffsets;
	}
      ifaces[j]->idt->iface.ioffsets[i] = offsets[j];
    }

  _Jv_MutexUnlock (&iindex_mutex);

  return i;
}

// Only used by serialization
java::lang::reflect::Field *
java::lang::Class::getPrivateField (jstring name)
{
  int hash = name->hashCode ();

  java::lang::reflect::Field* rfield;
  for (int i = 0;  i < field_count;  i++)
    {
      _Jv_Field *field = &fields[i];
      if (! _Jv_equal (field->name, name, hash))
	continue;
      rfield = new java::lang::reflect::Field ();
      rfield->offset = (char*) field - (char*) fields;
      rfield->declaringClass = this;
      rfield->name = name;
      return rfield;
    }
  jclass superclass = getSuperclass();
  if (superclass == NULL)
    return NULL;
  rfield = superclass->getPrivateField(name);
  for (int i = 0; i < interface_count && rfield == NULL; ++i)
    rfield = interfaces[i]->getPrivateField (name);
  return rfield;
}

// Only used by serialization
java::lang::reflect::Method *
java::lang::Class::getPrivateMethod (jstring name, JArray<jclass> *param_types)
{
  jstring partial_sig = getSignature (param_types, false);
  jint p_len = partial_sig->length();
  _Jv_Utf8Const *utf_name = _Jv_makeUtf8Const (name);
  for (Class *klass = this; klass; klass = klass->getSuperclass())
    {
      int i = klass->isPrimitive () ? 0 : klass->method_count;
      while (--i >= 0)
	{
	  if (_Jv_equalUtf8Consts (klass->methods[i].name, utf_name)
	      && _Jv_equaln (klass->methods[i].signature, partial_sig, p_len))
	    {
	      // Found it.
	      using namespace java::lang::reflect;

	      Method *rmethod = new Method ();
	      rmethod->offset = ((char *) (&klass->methods[i])
				 - (char *) klass->methods);
	      rmethod->declaringClass = klass;
	      return rmethod;
	    }
	}
    }
  throw new java::lang::NoSuchMethodException;
}

// Private accessor method for Java code to retrieve the protection domain.
java::security::ProtectionDomain *
java::lang::Class::getProtectionDomain0 ()
{
  return protectionDomain;
}

// Functions for indirect dispatch (symbolic virtual method binding) support.

// Resolve entries in the virtual method offset symbol table 
// (klass->otable_syms). The vtable offset (in bytes) for each resolved method 
// is placed at the corresponding position in the virtual method offset table 
// (klass->otable). A single otable and otable_syms pair may be shared by many 
// classes.
void
_Jv_LinkOffsetTable(jclass klass)
{
  //// FIXME: Need to lock the otable ////
  
  if (klass->otable == NULL
      || klass->otable->state != 0)
    return;
  
  klass->otable->state = 1;

  int index = 0;
  _Jv_MethodSymbol sym = klass->otable_syms[0];

  while (sym.name != NULL)
    {
      jclass target_class = _Jv_FindClass (sym.class_name, NULL);
      _Jv_Method *meth = NULL;            
      
      if (target_class != NULL)
	if (target_class->isInterface())
	  {
	    // FIXME: This does not yet fully conform to binary compatibility
	    // rules. It will break if a declaration is moved into a 
	    // superinterface.
	    for (int i=0; i < target_class->method_count; i++)
	      {
		meth = &target_class->methods[i];
		if (_Jv_equalUtf8Consts (sym.name, meth->name)
		    && _Jv_equalUtf8Consts (sym.signature, meth->signature))
		  {
		    klass->otable->offsets[index] = i + 1;
		    break;
		  }
	      }
	  }
	else
	  {
	    // If the target class does not have a vtable_method_count yet, 
	    // then we can't tell the offsets for its methods, so we must lay 
	    // it out now.
	    if (target_class->vtable_method_count == -1)
	      {
		JvSynchronize sync (target_class);
		_Jv_LayoutVTableMethods (target_class);
	      }

            meth = _Jv_LookupDeclaredMethod(target_class, sym.name, 
					    sym.signature);

	    if (meth != NULL)
	      {
		klass->otable->offsets[index] = 
		  _Jv_VTable::idx_to_offset (meth->index);
	      }
	  }

      if (meth == NULL)
	// FIXME: This should be special index for ThrowNoSuchMethod().
	klass->otable->offsets[index] = -1;

      sym = klass->otable_syms[++index];
    }
}

// Returns true if METH should get an entry in a VTable.
static jboolean
isVirtualMethod (_Jv_Method *meth)
{
  using namespace java::lang::reflect;
  return (((meth->accflags & (Modifier::STATIC | Modifier::PRIVATE)) == 0)
          && meth->name->data[0] != '<');
}

// This is put in empty vtable slots.
static void
_Jv_abstractMethodError (void)
{
  throw new java::lang::AbstractMethodError();
}

// Prepare virtual method declarations in KLASS, and any superclasses as 
// required, by determining their vtable index, setting method->index, and
// finally setting the class's vtable_method_count. Must be called with the
// lock for KLASS held.
void
_Jv_LayoutVTableMethods (jclass klass)
{
  if (klass->vtable != NULL || klass->isInterface() 
      || klass->vtable_method_count != -1)
    return;

  jclass superclass = klass->superclass;

  if (superclass != NULL && superclass->vtable_method_count == -1)
    {
      JvSynchronize sync (superclass);
      _Jv_LayoutVTableMethods (superclass);
    }

  int index = (superclass == NULL ? 0 : superclass->vtable_method_count);

  for (int i = 0; i < klass->method_count; ++i)
    {
      _Jv_Method *meth = &klass->methods[i];
      _Jv_Method *super_meth = NULL;

      if (! isVirtualMethod (meth))
	continue;

      if (superclass != NULL)
	{
	  super_meth = _Jv_LookupDeclaredMethod (superclass, meth->name, 
						 meth->signature);
	}

      if (super_meth)
        meth->index = super_meth->index;
      else if (! (meth->accflags & java::lang::reflect::Modifier::FINAL)
	       && ! (klass->accflags & java::lang::reflect::Modifier::FINAL))
	meth->index = index++;
    }

  klass->vtable_method_count = index;
}

// Set entries in VTABLE for virtual methods declared in KLASS. If
// KLASS has an immediate abstract parent, recursively do its methods
// first.  FLAGS is used to determine which slots we've actually set.
void
_Jv_SetVTableEntries (jclass klass, _Jv_VTable *vtable, jboolean *flags)
{
  using namespace java::lang::reflect;

  jclass superclass = klass->getSuperclass();

  if (superclass != NULL && (superclass->getModifiers() & Modifier::ABSTRACT))
    _Jv_SetVTableEntries (superclass, vtable, flags);

  for (int i = klass->method_count - 1; i >= 0; i--)
    {
      _Jv_Method *meth = &klass->methods[i];
      if (meth->index == (_Jv_ushort) -1)
	continue;
      if ((meth->accflags & Modifier::ABSTRACT))
	{
	  vtable->set_method(meth->index, (void *) &_Jv_abstractMethodError);
	  flags[meth->index] = false;
	}
      else
	{
	  vtable->set_method(meth->index, meth->ncode);
	  flags[meth->index] = true;
	}
    }
}

// Allocate and lay out the virtual method table for KLASS. This will also
// cause vtables to be generated for any non-abstract superclasses, and
// virtual method layout to occur for any abstract superclasses. Must be
// called with monitor lock for KLASS held.
void
_Jv_MakeVTable (jclass klass)
{
  using namespace java::lang::reflect;  

  if (klass->vtable != NULL || klass->isInterface() 
      || (klass->accflags & Modifier::ABSTRACT))
    return;

  //  out before we can create a vtable. 
  if (klass->vtable_method_count == -1)
    _Jv_LayoutVTableMethods (klass);

  // Allocate the new vtable.
  _Jv_VTable *vtable = _Jv_VTable::new_vtable (klass->vtable_method_count);
  klass->vtable = vtable;

  jboolean flags[klass->vtable_method_count];
  for (int i = 0; i < klass->vtable_method_count; ++i)
    flags[i] = false;

  // Copy the vtable of the closest non-abstract superclass.
  jclass superclass = klass->superclass;
  if (superclass != NULL)
    {
      while ((superclass->accflags & Modifier::ABSTRACT) != 0)
	superclass = superclass->superclass;

      if (superclass->vtable == NULL)
	{
	  JvSynchronize sync (superclass);
	  _Jv_MakeVTable (superclass);
	}

      for (int i = 0; i < superclass->vtable_method_count; ++i)
	{
	  vtable->set_method (i, superclass->vtable->get_method (i));
	  flags[i] = true;
	}
    }

  // Set the class pointer and GC descriptor.
  vtable->clas = klass;
  vtable->gc_descr = _Jv_BuildGCDescr (klass);

  // For each virtual declared in klass and any immediate abstract 
  // superclasses, set new vtable entry or override an old one.
  _Jv_SetVTableEntries (klass, vtable, flags);

  // It is an error to have an abstract method in a concrete class.
  if (! (klass->accflags & Modifier::ABSTRACT))
    {
      for (int i = 0; i < klass->vtable_method_count; ++i)
	if (! flags[i])
	  // FIXME: messsage.
	  throw new java::lang::AbstractMethodError ();
    }
}