/*

 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#ifndef SHARE_VM_CLASSFILE_SYSTEMDICTIONARY_HPP

#define SHARE_VM_CLASSFILE_SYSTEMDICTIONARY_HPP

#include "classfile/classLoader.hpp"

#include "jvmci/systemDictionary_jvmci.hpp"

#include "oops/objArrayOop.hpp"

#include "oops/symbol.hpp"

#include "runtime/java.hpp"

#include "runtime/reflectionUtils.hpp"

#include "runtime/signature.hpp"

#include "utilities/hashtable.hpp"

// The dictionary in each ClassLoaderData stores all loaded classes, either

// initiatied by its class loader or defined by its class loader:

//

//   class loader -> ClassLoaderData -> [class, protection domain set]

//

// Classes are loaded lazily. The default VM class loader is

// represented as NULL.

// The underlying data structure is an open hash table (Dictionary) per

// ClassLoaderData with a fixed number of buckets. During loading the

// class loader object is locked, (for the VM loader a private lock object is used).

// The global SystemDictionary_lock is held for all additions into the ClassLoaderData

// dictionaries.  TODO: fix lock granularity so that class loading can

// be done concurrently, but only by different loaders.

//

// During loading a placeholder (name, loader) is temporarily placed in

// a side data structure, and is used to detect ClassCircularityErrors

// and to perform verification during GC.  A GC can occur in the midst

// of class loading, as we call out to Java, have to take locks, etc.

//

// When class loading is finished, a new entry is added to the dictionary

// of the class loader and the placeholder is removed. Note that the protection

// domain field of the dictionary entry has not yet been filled in when

// the "real" dictionary entry is created.

//

// Clients of this class who are interested in finding if a class has

// been completely loaded -- not classes in the process of being loaded --

// can read the dictionary unlocked. This is safe because

//    - entries are only deleted at safepoints

//    - readers cannot come to a safepoint while actively examining

//         an entry  (an entry cannot be deleted from under a reader)

//    - entries must be fully formed before they are available to concurrent

//         readers (we must ensure write ordering)

//

// Note that placeholders are deleted at any time, as they are removed

// when a class is completely loaded. Therefore, readers as well as writers

// of placeholders must hold the SystemDictionary_lock.

//

class ClassFileStream;

class Dictionary;

class PlaceholderTable;

class LoaderConstraintTable;

template <MEMFLAGS F> class HashtableBucket;

class ResolutionErrorTable;

class SymbolPropertyTable;

class ProtectionDomainCacheTable;

class ProtectionDomainCacheEntry;

class GCTimer;

class OopStorage;

// Certain classes are preloaded, such as java.lang.Object and java.lang.String.

// They are all "well-known", in the sense that no class loader is allowed

// to provide a different definition.

//

// These klasses must all have names defined in vmSymbols.

#define WK_KLASS_ENUM_NAME(kname)    kname##_knum

// Each well-known class has a short klass name (like object_klass),

// a vmSymbol name (like java_lang_Object), and a flag word

// that makes some minor distinctions, like whether the klass

// is preloaded, optional, release-specific, etc.

// The order of these definitions is significant; it is the order in which

// preloading is actually performed by resolve_preloaded_classes.

#define WK_KLASSES_DO(do_klass)                                                                                          \

  /* well-known classes */                                                                                               \

  do_klass(Object_klass,                                java_lang_Object,                          Pre                 ) \

  do_klass(String_klass,                                java_lang_String,                          Pre                 ) \

  do_klass(Class_klass,                                 java_lang_Class,                           Pre                 ) \

  do_klass(Cloneable_klass,                             java_lang_Cloneable,                       Pre                 ) \

  do_klass(ClassLoader_klass,                           java_lang_ClassLoader,                     Pre                 ) \

  do_klass(Serializable_klass,                          java_io_Serializable,                      Pre                 ) \

  do_klass(System_klass,                                java_lang_System,                          Pre                 ) \

  do_klass(Throwable_klass,                             java_lang_Throwable,                       Pre                 ) \

  do_klass(Error_klass,                                 java_lang_Error,                           Pre                 ) \

  do_klass(ThreadDeath_klass,                           java_lang_ThreadDeath,                     Pre                 ) \

  do_klass(Exception_klass,                             java_lang_Exception,                       Pre                 ) \

  do_klass(RuntimeException_klass,                      java_lang_RuntimeException,                Pre                 ) \

  do_klass(SecurityManager_klass,                       java_lang_SecurityManager,                 Pre                 ) \

  do_klass(ProtectionDomain_klass,                      java_security_ProtectionDomain,            Pre                 ) \

  do_klass(AccessControlContext_klass,                  java_security_AccessControlContext,        Pre                 ) \

  do_klass(SecureClassLoader_klass,                     java_security_SecureClassLoader,           Pre                 ) \

  do_klass(ClassNotFoundException_klass,                java_lang_ClassNotFoundException,          Pre                 ) \

  do_klass(NoClassDefFoundError_klass,                  java_lang_NoClassDefFoundError,            Pre                 ) \

  do_klass(LinkageError_klass,                          java_lang_LinkageError,                    Pre                 ) \

  do_klass(ClassCastException_klass,                    java_lang_ClassCastException,              Pre                 ) \

  do_klass(ArrayStoreException_klass,                   java_lang_ArrayStoreException,             Pre                 ) \

  do_klass(VirtualMachineError_klass,                   java_lang_VirtualMachineError,             Pre                 ) \

  do_klass(OutOfMemoryError_klass,                      java_lang_OutOfMemoryError,                Pre                 ) \

  do_klass(StackOverflowError_klass,                    java_lang_StackOverflowError,              Pre                 ) \

  do_klass(IllegalMonitorStateException_klass,          java_lang_IllegalMonitorStateException,    Pre                 ) \

  do_klass(Reference_klass,                             java_lang_ref_Reference,                   Pre                 ) \

                                                                                                                         \

  /* Preload ref klasses and set reference types */                                                                      \

  do_klass(SoftReference_klass,                         java_lang_ref_SoftReference,               Pre                 ) \

  do_klass(WeakReference_klass,                         java_lang_ref_WeakReference,               Pre                 ) \

  do_klass(FinalReference_klass,                        java_lang_ref_FinalReference,              Pre                 ) \

  do_klass(PhantomReference_klass,                      java_lang_ref_PhantomReference,            Pre                 ) \

  do_klass(Finalizer_klass,                             java_lang_ref_Finalizer,                   Pre                 ) \

                                                                                                                         \

  do_klass(Thread_klass,                                java_lang_Thread,                          Pre                 ) \

  do_klass(ThreadGroup_klass,                           java_lang_ThreadGroup,                     Pre                 ) \

  do_klass(Properties_klass,                            java_util_Properties,                      Pre                 ) \

  do_klass(Module_klass,                                java_lang_Module,                          Pre                 ) \

  do_klass(reflect_AccessibleObject_klass,              java_lang_reflect_AccessibleObject,        Pre                 ) \

  do_klass(reflect_Field_klass,                         java_lang_reflect_Field,                   Pre                 ) \

  do_klass(reflect_Parameter_klass,                     java_lang_reflect_Parameter,               Opt                 ) \

  do_klass(reflect_Method_klass,                        java_lang_reflect_Method,                  Pre                 ) \

  do_klass(reflect_Constructor_klass,                   java_lang_reflect_Constructor,             Pre                 ) \

                                                                                                                         \

  /* NOTE: needed too early in bootstrapping process to have checks based on JDK version */                              \

  /* It's okay if this turns out to be NULL in non-1.4 JDKs. */                                                          \

  do_klass(reflect_MagicAccessorImpl_klass,             reflect_MagicAccessorImpl,                 Opt                 ) \

  do_klass(reflect_MethodAccessorImpl_klass,            reflect_MethodAccessorImpl,                Pre                 ) \

  do_klass(reflect_ConstructorAccessorImpl_klass,       reflect_ConstructorAccessorImpl,           Pre                 ) \

  do_klass(reflect_DelegatingClassLoader_klass,         reflect_DelegatingClassLoader,             Opt                 ) \

  do_klass(reflect_ConstantPool_klass,                  reflect_ConstantPool,                      Opt                 ) \

  do_klass(reflect_UnsafeStaticFieldAccessorImpl_klass, reflect_UnsafeStaticFieldAccessorImpl,     Opt                 ) \

  do_klass(reflect_CallerSensitive_klass,               reflect_CallerSensitive,                   Opt                 ) \

                                                                                                                         \

  /* support for dynamic typing; it's OK if these are NULL in earlier JDKs */                                            \

  do_klass(DirectMethodHandle_klass,                    java_lang_invoke_DirectMethodHandle,       Opt                 ) \

  do_klass(MethodHandle_klass,                          java_lang_invoke_MethodHandle,             Pre                 ) \

  do_klass(VarHandle_klass,                             java_lang_invoke_VarHandle,                Pre                 ) \

  do_klass(MemberName_klass,                            java_lang_invoke_MemberName,               Pre                 ) \

  do_klass(ResolvedMethodName_klass,                    java_lang_invoke_ResolvedMethodName,       Pre                 ) \

  do_klass(MethodHandleNatives_klass,                   java_lang_invoke_MethodHandleNatives,      Pre                 ) \

  do_klass(LambdaForm_klass,                            java_lang_invoke_LambdaForm,               Opt                 ) \

  do_klass(MethodType_klass,                            java_lang_invoke_MethodType,               Pre                 ) \

  do_klass(BootstrapMethodError_klass,                  java_lang_BootstrapMethodError,            Pre                 ) \

  do_klass(CallSite_klass,                              java_lang_invoke_CallSite,                 Pre                 ) \

  do_klass(Context_klass,                               java_lang_invoke_MethodHandleNatives_CallSiteContext, Pre      ) \

  do_klass(ConstantCallSite_klass,                      java_lang_invoke_ConstantCallSite,         Pre                 ) \

  do_klass(MutableCallSite_klass,                       java_lang_invoke_MutableCallSite,          Pre                 ) \

  do_klass(VolatileCallSite_klass,                      java_lang_invoke_VolatileCallSite,         Pre                 ) \

  /* Note: MethodHandle must be first, and VolatileCallSite last in group */                                             \

                                                                                                                         \

  do_klass(AssertionStatusDirectives_klass,             java_lang_AssertionStatusDirectives,       Pre                 ) \

  do_klass(StringBuffer_klass,                          java_lang_StringBuffer,                    Pre                 ) \

  do_klass(StringBuilder_klass,                         java_lang_StringBuilder,                   Pre                 ) \

  do_klass(internal_Unsafe_klass,                       jdk_internal_misc_Unsafe,                  Pre                 ) \

  do_klass(module_Modules_klass,                        jdk_internal_module_Modules,               Pre                 ) \

                                                                                                                         \

  /* support for CDS */                                                                                                  \

  do_klass(ByteArrayInputStream_klass,                  java_io_ByteArrayInputStream,              Pre                 ) \

  do_klass(URL_klass,                                   java_net_URL,                              Pre                 ) \

  do_klass(Jar_Manifest_klass,                          java_util_jar_Manifest,                    Pre                 ) \

  do_klass(jdk_internal_loader_ClassLoaders_klass,      jdk_internal_loader_ClassLoaders,          Pre                 ) \

  do_klass(jdk_internal_loader_ClassLoaders_AppClassLoader_klass,      jdk_internal_loader_ClassLoaders_AppClassLoader,       Pre ) \

  do_klass(jdk_internal_loader_ClassLoaders_PlatformClassLoader_klass, jdk_internal_loader_ClassLoaders_PlatformClassLoader,  Pre ) \

  do_klass(CodeSource_klass,                            java_security_CodeSource,                  Pre                 ) \

  do_klass(Configuration_klass,                         java_lang_module_Configuration,            Pre                 ) \

  do_klass(ImmutableCollections_ListN_klass,            java_util_ImmutableCollections_ListN,      Pre                 ) \

  do_klass(ImmutableCollections_MapN_klass,             java_util_ImmutableCollections_MapN,       Pre                 ) \

  do_klass(ImmutableCollections_SetN_klass,             java_util_ImmutableCollections_SetN,       Pre                 ) \

  do_klass(ArchivedModuleGraph_klass,                   jdk_internal_module_ArchivedModuleGraph,   Pre                 ) \

                                                                                                                         \

  do_klass(StackTraceElement_klass,                     java_lang_StackTraceElement,               Opt                 ) \

                                                                                                                         \

  /* It's okay if this turns out to be NULL in non-1.4 JDKs. */                                                          \

  do_klass(nio_Buffer_klass,                            java_nio_Buffer,                           Opt                 ) \

                                                                                                                         \

  /* Stack Walking */                                                                                                    \

  do_klass(StackWalker_klass,                           java_lang_StackWalker,                     Opt                 ) \

  do_klass(AbstractStackWalker_klass,                   java_lang_StackStreamFactory_AbstractStackWalker, Opt          ) \

  do_klass(StackFrameInfo_klass,                        java_lang_StackFrameInfo,                  Opt                 ) \

  do_klass(LiveStackFrameInfo_klass,                    java_lang_LiveStackFrameInfo,              Opt                 ) \

                                                                                                                         \

  /* support for stack dump lock analysis */                                                                             \

  do_klass(java_util_concurrent_locks_AbstractOwnableSynchronizer_klass, java_util_concurrent_locks_AbstractOwnableSynchronizer, Pre ) \

                                                                                                                         \

  /* Preload boxing klasses */                                                                                           \

  do_klass(Boolean_klass,                               java_lang_Boolean,                         Pre                 ) \

  do_klass(Character_klass,                             java_lang_Character,                       Pre                 ) \

  do_klass(Float_klass,                                 java_lang_Float,                           Pre                 ) \

  do_klass(Double_klass,                                java_lang_Double,                          Pre                 ) \

  do_klass(Byte_klass,                                  java_lang_Byte,                            Pre                 ) \

  do_klass(Short_klass,                                 java_lang_Short,                           Pre                 ) \

  do_klass(Integer_klass,                               java_lang_Integer,                         Pre                 ) \

  do_klass(Long_klass,                                  java_lang_Long,                            Pre                 ) \

                                                                                                                         \

  /* JVMCI classes. These are loaded on-demand. */                                                                       \

  JVMCI_WK_KLASSES_DO(do_klass)                                                                                          \

                                                                                                                         \

  /*end*/

class SystemDictionary : AllStatic {

  friend class VMStructs;

  friend class SystemDictionaryHandles;

 public:

  enum WKID {

    NO_WKID = 0,

    #define WK_KLASS_ENUM(name, symbol, ignore_o) WK_KLASS_ENUM_NAME(name), WK_KLASS_ENUM_NAME(symbol) = WK_KLASS_ENUM_NAME(name),

    WK_KLASSES_DO(WK_KLASS_ENUM)

    #undef WK_KLASS_ENUM

    WKID_LIMIT,

#if INCLUDE_JVMCI

    FIRST_JVMCI_WKID = WK_KLASS_ENUM_NAME(JVMCI_klass),

    LAST_JVMCI_WKID  = WK_KLASS_ENUM_NAME(Value_klass),

#endif

    FIRST_WKID = NO_WKID + 1

  };

  enum InitOption {

    Pre,                        // preloaded; error if not present

    // Order is significant.  Options before this point require resolve_or_fail.

    // Options after this point will use resolve_or_null instead.

    Opt,                        // preload tried; NULL if not present

#if INCLUDE_JVMCI

    Jvmci,                      // preload tried; error if not present if JVMCI enabled

#endif

    OPTION_LIMIT,

    CEIL_LG_OPTION_LIMIT = 2    // OPTION_LIMIT <= (1<<CEIL_LG_OPTION_LIMIT)

  };

  // Returns a class with a given class name and class loader.  Loads the

  // class if needed. If not found a NoClassDefFoundError or a

  // ClassNotFoundException is thrown, depending on the value on the

  // throw_error flag.  For most uses the throw_error argument should be set

  // to true.

  static Klass* resolve_or_fail(Symbol* class_name, Handle class_loader, Handle protection_domain, bool throw_error, TRAPS);

  // Convenient call for null loader and protection domain.

  static Klass* resolve_or_fail(Symbol* class_name, bool throw_error, TRAPS);

protected:

  // handle error translation for resolve_or_null results

  static Klass* handle_resolution_exception(Symbol* class_name, bool throw_error, Klass* klass, TRAPS);

public:

  // Returns a class with a given class name and class loader.

  // Loads the class if needed. If not found NULL is returned.

  static Klass* resolve_or_null(Symbol* class_name, Handle class_loader, Handle protection_domain, TRAPS);

  // Version with null loader and protection domain

  static Klass* resolve_or_null(Symbol* class_name, TRAPS);

  // Resolve a superclass or superinterface. Called from ClassFileParser,

  // parse_interfaces, resolve_instance_class_or_null, load_shared_class

  // "child_name" is the class whose super class or interface is being resolved.

  static InstanceKlass* resolve_super_or_fail(Symbol* child_name,

                                              Symbol* class_name,

                                              Handle class_loader,

                                              Handle protection_domain,

                                              bool is_superclass,

                                              TRAPS);

  // Parse new stream. This won't update the dictionary or

  // class hierarchy, simply parse the stream. Used by JVMTI RedefineClasses.

  // Also used by Unsafe_DefineAnonymousClass

  static InstanceKlass* parse_stream(Symbol* class_name,

                                     Handle class_loader,

                                     Handle protection_domain,

                                     ClassFileStream* st,

                                     TRAPS) {

    return parse_stream(class_name,

                        class_loader,

                        protection_domain,

                        st,

                        NULL, // host klass

                        NULL, // cp_patches

                        THREAD);

  }

  static InstanceKlass* parse_stream(Symbol* class_name,

                                     Handle class_loader,

                                     Handle protection_domain,

                                     ClassFileStream* st,

                                     const InstanceKlass* host_klass,

                                     GrowableArray<Handle>* cp_patches,

                                     TRAPS);

  // Resolve from stream (called by jni_DefineClass and JVM_DefineClass)

  static InstanceKlass* resolve_from_stream(Symbol* class_name,

                                            Handle class_loader,

                                            Handle protection_domain,

                                            ClassFileStream* st,

                                            TRAPS);

  // Lookup an already loaded class. If not found NULL is returned.

  static Klass* find(Symbol* class_name, Handle class_loader, Handle protection_domain, TRAPS);

  // Lookup an already loaded instance or array class.

  // Do not make any queries to class loaders; consult only the cache.

  // If not found NULL is returned.

  static Klass* find_instance_or_array_klass(Symbol* class_name,

                                               Handle class_loader,

                                               Handle protection_domain,

                                               TRAPS);

  // Lookup an instance or array class that has already been loaded

  // either into the given class loader, or else into another class

  // loader that is constrained (via loader constraints) to produce

  // a consistent class.  Do not take protection domains into account.

  // Do not make any queries to class loaders; consult only the cache.

  // Return NULL if the class is not found.

  //

  // This function is a strict superset of find_instance_or_array_klass.

  // This function (the unchecked version) makes a conservative prediction

  // of the result of the checked version, assuming successful lookup.

  // If both functions return non-null, they must return the same value.

  // Also, the unchecked version may sometimes be non-null where the

  // checked version is null.  This can occur in several ways:

  //   1. No query has yet been made to the class loader.

  //   2. The class loader was queried, but chose not to delegate.

  //   3. ClassLoader.checkPackageAccess rejected a proposed protection domain.

  //   4. Loading was attempted, but there was a linkage error of some sort.

  // In all of these cases, the loader constraints on this type are

  // satisfied, and it is safe for classes in the given class loader

  // to manipulate strongly-typed values of the found class, subject

  // to local linkage and access checks.

  static Klass* find_constrained_instance_or_array_klass(Symbol* class_name,

                                                           Handle class_loader,

                                                           TRAPS);

  static void classes_do(MetaspaceClosure* it);

  // Iterate over all methods in all klasses

  static void methods_do(void f(Method*));

  // Garbage collection support

  // Unload (that is, break root links to) all unmarked classes and

  // loaders.  Returns "true" iff something was unloaded.

  static bool do_unloading(GCTimer* gc_timer,

                           bool do_cleaning = true);

  // Used by DumpSharedSpaces only to remove classes that failed verification

  static void remove_classes_in_error_state();

  static int calculate_systemdictionary_size(int loadedclasses);

  // Applies "f->do_oop" to all root oops in the system dictionary.

  static void oops_do(OopClosure* f);

  // System loader lock

  static oop system_loader_lock()           { return _system_loader_lock_obj; }

public:

  // Sharing support.

  static void reorder_dictionary_for_sharing() NOT_CDS_RETURN;

  static void combine_shared_dictionaries();

  static size_t count_bytes_for_buckets();

  static size_t count_bytes_for_table();

  static void copy_buckets(char* top, char* end);

  static void copy_table(char* top, char* end);

  static void set_shared_dictionary(HashtableBucket<mtClass>* t, int length,

                                    int number_of_entries);

  // Printing

  static void print() { return print_on(tty); }

  static void print_on(outputStream* st);

  static void print_shared(outputStream* st);

  static void dump(outputStream* st, bool verbose);

  // Monotonically increasing counter which grows as classes are

  // loaded or modifications such as hot-swapping or setting/removing

  // of breakpoints are performed

  static inline int number_of_modifications()     { assert_locked_or_safepoint(Compile_lock); return _number_of_modifications; }

  // Needed by evolution and breakpoint code

  static inline void notice_modification()        { assert_locked_or_safepoint(Compile_lock); ++_number_of_modifications;      }

  // Verification

  static void verify();

  // Initialization

  static void initialize(TRAPS);

  // Checked fast access to commonly used classes - mostly preloaded

  static InstanceKlass* check_klass(InstanceKlass* k) {

    assert(k != NULL, "klass not loaded");

    return k;

  }

  static InstanceKlass* check_klass_Pre(InstanceKlass* k) { return check_klass(k); }

  static InstanceKlass* check_klass_Opt(InstanceKlass* k) { return k; }

  JVMCI_ONLY(static InstanceKlass* check_klass_Jvmci(InstanceKlass* k) { return k; })

  static bool resolve_wk_klass(WKID id, int init_opt, TRAPS);

  static void resolve_wk_klasses_until(WKID limit_id, WKID &start_id, TRAPS);

  static void resolve_wk_klasses_through(WKID end_id, WKID &start_id, TRAPS) {

    int limit = (int)end_id + 1;

    resolve_wk_klasses_until((WKID) limit, start_id, THREAD);

  }

public:

  #define WK_KLASS_DECLARE(name, symbol, option) \

    static InstanceKlass* name() { return check_klass_##option(_well_known_klasses[WK_KLASS_ENUM_NAME(name)]); } \

    static InstanceKlass** name##_addr() {                                                                       \

      return &SystemDictionary::_well_known_klasses[SystemDictionary::WK_KLASS_ENUM_NAME(name)];           \

    }

  WK_KLASSES_DO(WK_KLASS_DECLARE);

  #undef WK_KLASS_DECLARE

  static InstanceKlass* well_known_klass(WKID id) {

    assert(id >= (int)FIRST_WKID && id < (int)WKID_LIMIT, "oob");

    return _well_known_klasses[id];

  }

  static InstanceKlass** well_known_klass_addr(WKID id) {

    assert(id >= (int)FIRST_WKID && id < (int)WKID_LIMIT, "oob");

    return &_well_known_klasses[id];

  }

  static void well_known_klasses_do(MetaspaceClosure* it);

  // Local definition for direct access to the private array:

  #define WK_KLASS(name) _well_known_klasses[SystemDictionary::WK_KLASS_ENUM_NAME(name)]

  static InstanceKlass* box_klass(BasicType t) {

    assert((uint)t < T_VOID+1, "range check");

    return check_klass(_box_klasses[t]);

  }

  static BasicType box_klass_type(Klass* k);  // inverse of box_klass

protected:

  // Returns the class loader data to be used when looking up/updating the

  // system dictionary.

  static ClassLoaderData *class_loader_data(Handle class_loader) {

    return ClassLoaderData::class_loader_data(class_loader());

  }

public:

  // Tells whether ClassLoader.checkPackageAccess is present

  static bool has_checkPackageAccess()      { return _has_checkPackageAccess; }

  static bool Parameter_klass_loaded()      { return WK_KLASS(reflect_Parameter_klass) != NULL; }

  static bool Class_klass_loaded()          { return WK_KLASS(Class_klass) != NULL; }

  static bool Cloneable_klass_loaded()      { return WK_KLASS(Cloneable_klass) != NULL; }

  static bool Object_klass_loaded()         { return WK_KLASS(Object_klass) != NULL; }

  static bool ClassLoader_klass_loaded()    { return WK_KLASS(ClassLoader_klass) != NULL; }

  // Returns java system loader

  static oop java_system_loader();

  // Returns java platform loader

  static oop java_platform_loader();

  // Compute the java system and platform loaders

  static void compute_java_loaders(TRAPS);

  // Register a new class loader

  static ClassLoaderData* register_loader(Handle class_loader);

protected:

  // Mirrors for primitive classes (created eagerly)

  static oop check_mirror(oop m) {

    assert(m != NULL, "mirror not initialized");

    return m;