ClassLoaderClassesIterator.cpp

/*******************************************************************************
 * Copyright IBM Corp. and others 1991
 *
 * This program and the accompanying materials are made available under
 * the terms of the Eclipse Public License 2.0 which accompanies this
 * distribution and is available at https://www.eclipse.org/legal/epl-2.0/
 * or the Apache License, Version 2.0 which accompanies this distribution and
 * is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * This Source Code may also be made available under the following
 * Secondary Licenses when the conditions for such availability set
 * forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
 * General Public License, version 2 with the GNU Classpath
 * Exception [1] and GNU General Public License, version 2 with the
 * OpenJDK Assembly Exception [2].
 *
 * [1] https://www.gnu.org/software/classpath/license.html
 * [2] https://openjdk.org/legal/assembly-exception.html
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0 OR GPL-2.0-only WITH OpenJDK-assembly-exception-1.0
 *******************************************************************************/

/**
 * @file
 * @ingroup GC_Structs
 */

#include "ClassLoaderClassesIterator.hpp"

#include "GCExtensionsBase.hpp"

GC_ClassLoaderClassesIterator::GC_ClassLoaderClassesIterator(MM_GCExtensionsBase *extensions, J9ClassLoader *classLoader) :
	_javaVM((J9JavaVM* )extensions->getOmrVM()->_language_vm)
	,_classLoader(classLoader)
	,_vmSegmentIterator(classLoader, MEMORY_TYPE_RAM_CLASS)
	,_vmClassSlotIterator((J9JavaVM* )extensions->getOmrVM()->_language_vm)
	,_mode(TABLE_CLASSES)
	,_iterateArrayClazz(NULL)
	,_arrayState(STATE_VALUETYPEARRAY)
{

	if ((classLoader->flags & J9CLASSLOADER_ANON_CLASS_LOADER) != 0) {
		_mode = ANONYMOUS_CLASSES;
	}
	_nextClass = firstClass();
	_startingClass = _nextClass;
}

J9Class *
GC_ClassLoaderClassesIterator::nextSystemClass() 
{
	return _vmClassSlotIterator.nextSlot();
}

J9Class *
GC_ClassLoaderClassesIterator::firstClass()
{
	J9Class * result;
	if (ANONYMOUS_CLASSES == _mode) {
		result = nextAnonymousClass();
	} else {
		result = _javaVM->internalVMFunctions->hashClassTableStartDo(_classLoader, &_walkState, 0);
		if ( (NULL == result) && switchToSystemMode() ) {
			result = nextSystemClass();
		}
	}
	return result;
}

J9Class *
GC_ClassLoaderClassesIterator::nextAnonymousClass()
{
	J9Class * result = NULL;
	J9MemorySegment *segment;
	if (NULL != (segment = _vmSegmentIterator.nextSegment())) {
		GC_ClassHeapIterator classHeapIterator(_javaVM, segment);
		result = classHeapIterator.nextClass();
	}
	return result;
}


J9Class *
GC_ClassLoaderClassesIterator::nextTableClass()
{
	J9Class * result = _javaVM->internalVMFunctions->hashClassTableNextDo(&_walkState);
	if ( (NULL == result) && switchToSystemMode() ) {
		result = nextSystemClass();
	}
	return result;
}


bool 
GC_ClassLoaderClassesIterator::switchToSystemMode()
{
	bool isSystemClassLoader = (_classLoader == _javaVM->systemClassLoader);
	if (isSystemClassLoader) {
		_mode = SYSTEM_CLASSES;
	}
	return isSystemClassLoader;
}

J9Class *
GC_ClassLoaderClassesIterator::nextArrayClass()
{
	while (_arrayState != STATE_DONE) {
		switch (_arrayState) {
		case STATE_VALUETYPEARRAY:
			{
			/* Setup null-restricted array list walk if it is not empty, switch to array list check otherwise */
#if defined(J9VM_OPT_VALHALLA_FLATTENABLE_VALUE_TYPES)
				J9Class *nullRestrictedArray = J9CLASS_GET_NULLRESTRICTED_ARRAY(_startingClass);
				if (NULL != nullRestrictedArray) {
					_iterateArrayClazz = nullRestrictedArray;
					_arrayState = STATE_VALUETYPEARRAYLIST;
				} else
#endif /* defined(J9VM_OPT_VALHALLA_FLATTENABLE_VALUE_TYPES) */
				{
					_arrayState = STATE_ARRAY;
				}
			}
			break;
		case STATE_VALUETYPEARRAYLIST:
			/* Continue to walk null-restricted array list until empty, switch to array list check if end of the list reached */
			if (NULL != _iterateArrayClazz) {
				_iterateArrayClazz = _iterateArrayClazz->arrayClass;
			} else {
				_arrayState = STATE_ARRAY;
			}
			break;
		case STATE_ARRAY:
			/* Setup array list walk if it is not empty, switch to "done" otherwise */
			if (NULL != _startingClass->arrayClass) {
				_iterateArrayClazz = _startingClass->arrayClass;
				_arrayState = STATE_ARRAYLIST;
			} else {
				_arrayState = STATE_DONE;
			}
			break;
		case STATE_ARRAYLIST:
			/* Continue to walk array list until empty, switch to "done" if end of the list reached */
			if (NULL != _iterateArrayClazz) {
				_iterateArrayClazz = _iterateArrayClazz->arrayClass;
			} else {
				_arrayState = STATE_DONE;
			}
			break;
		case STATE_DONE:
		default:
			break;
		}

		if ((NULL != _iterateArrayClazz) && (_iterateArrayClazz->classLoader == _classLoader)) {
			break;
		}

		/* Cancel list iteration if it is switched to super classloader. */
		_iterateArrayClazz = NULL;
	}
	return _iterateArrayClazz;
}

J9Class *
GC_ClassLoaderClassesIterator::nextClass()
{
	J9Class * result = _nextClass;
	
	if (NULL != result) {
		if (ANONYMOUS_CLASSES == _mode) {
			_nextClass = nextAnonymousClass();
		} else {
			/*
			 * Classloader hash table doesn't include array classes.
			 * However array classes can be reached by scanning lists of
			 * array classes and null-restricted array classes.
			 * Heads of such lists are stored in the mixed object j9class structure.
			 * nextArrayClass() call walks such lists returning array classes one by one.
			 * Returned NULL means lists are empty or walk reaches the end.
			 */
			J9Class *array = nextArrayClass();
			if (NULL != array) {
				/* this class is defined in the loader, so follow its array classes (regular and null-restricted) */
				_nextClass = array;
			} else if (TABLE_CLASSES == _mode) {
				_nextClass = nextTableClass();
				/* Setup array lists walk if any */
				initArrayClassWalk();
			} else {
				_nextClass = nextSystemClass();
				/* Setup array lists walk if any */
				initArrayClassWalk();
			}
		}
	}
	
	return result;
}