JDK14/Java14源码在线阅读
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#ifndef SHARE_OOPS_KLASS_HPP
#define SHARE_OOPS_KLASS_HPP
#include "classfile/classLoaderData.hpp"
#include "memory/iterator.hpp"
#include "memory/memRegion.hpp"
#include "oops/markWord.hpp"
#include "oops/metadata.hpp"
#include "oops/oop.hpp"
#include "oops/oopHandle.hpp"
#include "utilities/accessFlags.hpp"
#include "utilities/macros.hpp"
#if INCLUDE_JFR
#include "jfr/support/jfrTraceIdExtension.hpp"
#endif
// Klass IDs for all subclasses of Klass
enum KlassID {
InstanceKlassID,
InstanceRefKlassID,
InstanceMirrorKlassID,
InstanceClassLoaderKlassID,
TypeArrayKlassID,
ObjArrayKlassID
};
const uint KLASS_ID_COUNT = 6;
//
// A Klass provides:
// 1: language level class object (method dictionary etc.)
// 2: provide vm dispatch behavior for the object
// Both functions are combined into one C++ class.
// One reason for the oop/klass dichotomy in the implementation is
// that we don't want a C++ vtbl pointer in every object. Thus,
// normal oops don't have any virtual functions. Instead, they
// forward all "virtual" functions to their klass, which does have
// a vtbl and does the C++ dispatch depending on the object's
// actual type. (See oop.inline.hpp for some of the forwarding code.)
// ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
// Forward declarations.
template <class T> class Array;
template <class T> class GrowableArray;
class fieldDescriptor;
class KlassSizeStats;
class klassVtable;
class ModuleEntry;
class PackageEntry;
class ParCompactionManager;
class PSPromotionManager;
class vtableEntry;
class Klass : public Metadata {
friend class VMStructs;
friend class JVMCIVMStructs;
protected:
// If you add a new field that points to any metaspace object, you
// must add this field to Klass::metaspace_pointers_do().
// note: put frequently-used fields together at start of klass structure
// for better cache behavior (may not make much of a difference but sure won't hurt)
enum { _primary_super_limit = 8 };
// The "layout helper" is a combined descriptor of object layout.
// For klasses which are neither instance nor array, the value is zero.
//
// For instances, layout helper is a positive number, the instance size.
// This size is already passed through align_object_size and scaled to bytes.
// The low order bit is set if instances of this class cannot be
// allocated using the fastpath.
//
// For arrays, layout helper is a negative number, containing four
// distinct bytes, as follows:
// MSB:[tag, hsz, ebt, log2(esz)]:LSB
// where:
// tag is 0x80 if the elements are oops, 0xC0 if non-oops
// hsz is array header size in bytes (i.e., offset of first element)
// ebt is the BasicType of the elements
// esz is the element size in bytes
// This packed word is arranged so as to be quickly unpacked by the
// various fast paths that use the various subfields.
//
// The esz bits can be used directly by a SLL instruction, without masking.
//
// Note that the array-kind tag looks like 0x00 for instance klasses,
// since their length in bytes is always less than 24Mb.
//
// Final note: This comes first, immediately after C++ vtable,
// because it is frequently queried.
jint _layout_helper;
// Klass identifier used to implement devirtualized oop closure dispatching.
const KlassID _id;
// The fields _super_check_offset, _secondary_super_cache, _secondary_supers
// and _primary_supers all help make fast subtype checks. See big discussion
// in doc/server_compiler/checktype.txt
//
// Where to look to observe a supertype (it is &_secondary_super_cache for
// secondary supers, else is &_primary_supers[depth()].
juint _super_check_offset;
// Class name. Instance classes: java/lang/String, etc. Array classes: [I,
// [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
Symbol* _name;
// Cache of last observed secondary supertype
Klass* _secondary_super_cache;
// Array of all secondary supertypes
Array<Klass*>* _secondary_supers;
// Ordered list of all primary supertypes
Klass* _primary_supers[_primary_super_limit];
// java/lang/Class instance mirroring this class
OopHandle _java_mirror;
// Superclass
Klass* _super;
// First subclass (NULL if none); _subklass->next_sibling() is next one
Klass* volatile _subklass;
// Sibling link (or NULL); links all subklasses of a klass
Klass* volatile _next_sibling;
// All klasses loaded by a class loader are chained through these links
Klass* _next_link;
// The VM's representation of the ClassLoader used to load this class.
// Provide access the corresponding instance java.lang.ClassLoader.
ClassLoaderData* _class_loader_data;
jint _modifier_flags; // Processed access flags, for use by Class.getModifiers.
AccessFlags _access_flags; // Access flags. The class/interface distinction is stored here.
JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
// Biased locking implementation and statistics
// (the 64-bit chunk goes first, to avoid some fragmentation)
jlong _last_biased_lock_bulk_revocation_time;
markWord _prototype_header; // Used when biased locking is both enabled and disabled for this type
jint _biased_lock_revocation_count;
// vtable length
int _vtable_len;
private:
// This is an index into FileMapHeader::_shared_path_table[], to
// associate this class with the JAR file where it's loaded from during
// dump time. If a class is not loaded from the shared archive, this field is
// -1.
jshort _shared_class_path_index;
#if INCLUDE_CDS
// Flags of the current shared class.
u2 _shared_class_flags;
enum {
_has_raw_archived_mirror = 1
};
#endif
// The _archived_mirror is set at CDS dump time pointing to the cached mirror
// in the open archive heap region when archiving java object is supported.
CDS_JAVA_HEAP_ONLY(narrowOop _archived_mirror;)
protected:
// Constructor
Klass(KlassID id);
Klass() : _id(KlassID(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
public:
int id() { return _id; }
enum DefaultsLookupMode { find_defaults, skip_defaults };
enum OverpassLookupMode { find_overpass, skip_overpass };
enum StaticLookupMode { find_static, skip_static };
enum PrivateLookupMode { find_private, skip_private };
bool is_klass() const volatile { return true; }
// super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
// to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
// If this is not what your code expects, you're probably looking for Klass::java_super().
Klass* super() const { return _super; }
void set_super(Klass* k) { _super = k; }
// initializes _super link, _primary_supers & _secondary_supers arrays
void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
// klass-specific helper for initializing _secondary_supers
virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
Array<InstanceKlass*>* transitive_interfaces);
// java_super is the Java-level super type as specified by Class.getSuperClass.
virtual InstanceKlass* java_super() const { return NULL; }
juint super_check_offset() const { return _super_check_offset; }
void set_super_check_offset(juint o) { _super_check_offset = o; }
Klass* secondary_super_cache() const { return _secondary_super_cache; }
void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
Array<Klass*>* secondary_supers() const { return _secondary_supers; }
void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
// Return the element of the _super chain of the given depth.
// If there is no such element, return either NULL or this.
Klass* primary_super_of_depth(juint i) const {
assert(i < primary_super_limit(), "oob");
Klass* super = _primary_supers[i];
assert(super == NULL || super->super_depth() == i, "correct display");
return super;
}
// Can this klass be a primary super? False for interfaces and arrays of
// interfaces. False also for arrays or classes with long super chains.
bool can_be_primary_super() const {
const juint secondary_offset = in_bytes(secondary_super_cache_offset());
return super_check_offset() != secondary_offset;
}
virtual bool can_be_primary_super_slow() const;
// Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
juint super_depth() const {
if (!can_be_primary_super()) {
return primary_super_limit();
} else {
juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
assert(d < primary_super_limit(), "oob");
assert(_primary_supers[d] == this, "proper init");
return d;
}
}
// java mirror
oop java_mirror() const;
oop java_mirror_no_keepalive() const;
void set_java_mirror(Handle m);
oop archived_java_mirror_raw() NOT_CDS_JAVA_HEAP_RETURN_(NULL); // no GC barrier
narrowOop archived_java_mirror_raw_narrow() NOT_CDS_JAVA_HEAP_RETURN_(0); // no GC barrier
void set_archived_java_mirror_raw(oop m) NOT_CDS_JAVA_HEAP_RETURN; // no GC barrier
// Temporary mirror switch used by RedefineClasses
// Both mirrors are on the ClassLoaderData::_handles list already so no
// barriers are needed.
void set_java_mirror_handle(OopHandle mirror) { _java_mirror = mirror; }
OopHandle java_mirror_handle() const {
return _java_mirror;
}
// modifier flags
jint modifier_flags() const { return _modifier_flags; }
void set_modifier_flags(jint flags) { _modifier_flags = flags; }
// size helper
int layout_helper() const { return _layout_helper; }
void set_layout_helper(int lh) { _layout_helper = lh; }
// Note: for instances layout_helper() may include padding.
// Use InstanceKlass::contains_field_offset to classify field offsets.
// sub/superklass links
Klass* subklass(bool log = false) const;
Klass* next_sibling(bool log = false) const;
InstanceKlass* superklass() const;
void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
void set_next_link(Klass* k) { _next_link = k; }
Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
// class loader data
ClassLoaderData* class_loader_data() const { return _class_loader_data; }
void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
int shared_classpath_index() const {
return _shared_class_path_index;
};
void set_shared_classpath_index(int index) {
_shared_class_path_index = index;
};
void set_has_raw_archived_mirror() {
CDS_ONLY(_shared_class_flags |= _has_raw_archived_mirror;)
}
void clear_has_raw_archived_mirror() {
CDS_ONLY(_shared_class_flags &= ~_has_raw_archived_mirror;)
}
bool has_raw_archived_mirror() const {
CDS_ONLY(return (_shared_class_flags & _has_raw_archived_mirror) != 0;)
NOT_CDS(return false;)
}
// Obtain the module or package for this class
virtual ModuleEntry* module() const = 0;
virtual PackageEntry* package() const = 0;
protected: // internal accessors
void set_subklass(Klass* s);
void set_next_sibling(Klass* s);
public:
// Compiler support
static ByteSize super_offset() { return in_ByteSize(offset_of(Klass, _super)); }
static ByteSize super_check_offset_offset() { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
static ByteSize primary_supers_offset() { return in_ByteSize(offset_of(Klass, _primary_supers)); }
static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
static ByteSize secondary_supers_offset() { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
static ByteSize java_mirror_offset() { return in_ByteSize(offset_of(Klass, _java_mirror)); }
static ByteSize class_loader_data_offset() { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
static ByteSize modifier_flags_offset() { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
static ByteSize layout_helper_offset() { return in_ByteSize(offset_of(Klass, _layout_helper)); }
static ByteSize access_flags_offset() { return in_ByteSize(offset_of(Klass, _access_flags)); }
// Unpacking layout_helper:
static const int _lh_neutral_value = 0; // neutral non-array non-instance value
static const int _lh_instance_slow_path_bit = 0x01;
static const int _lh_log2_element_size_shift = BitsPerByte*0;
static const int _lh_log2_element_size_mask = BitsPerLong-1;
static const int _lh_element_type_shift = BitsPerByte*1;
static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
static const int _lh_header_size_shift = BitsPerByte*2;
static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
static const int _lh_array_tag_bits = 2;
static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
static const int _lh_array_tag_obj_value = ~0x01; // 0x80000000 >> 30
static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00, // 0xC0000000 >> 30
static int layout_helper_size_in_bytes(jint lh) {
assert(lh > (jint)_lh_neutral_value, "must be instance");
return (int) lh & ~_lh_instance_slow_path_bit;
}
static bool layout_helper_needs_slow_path(jint lh) {
assert(lh > (jint)_lh_neutral_value, "must be instance");
return (lh & _lh_instance_slow_path_bit) != 0;
}
static bool layout_helper_is_instance(jint lh) {
return (jint)lh > (jint)_lh_neutral_value;
}
static bool layout_helper_is_array(jint lh) {
return (jint)lh < (jint)_lh_neutral_value;
}
static bool layout_helper_is_typeArray(jint lh) {
// _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
}
static bool layout_helper_is_objArray(jint lh) {
// _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
}
static int layout_helper_header_size(jint lh) {
assert(lh < (jint)_lh_neutral_value, "must be array");
int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
return hsize;
}
static BasicType layout_helper_element_type(jint lh) {
assert(lh < (jint)_lh_neutral_value, "must be array");
int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
return (BasicType) btvalue;
}
// Want a pattern to quickly diff against layout header in register
// find something less clever!
static int layout_helper_boolean_diffbit() {
jint zlh = array_layout_helper(T_BOOLEAN);
jint blh = array_layout_helper(T_BYTE);
assert(zlh != blh, "array layout helpers must differ");
int diffbit = 1;
while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
diffbit <<= 1;
assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
}
return diffbit;
}
static int layout_helper_log2_element_size(jint lh) {
assert(lh < (jint)_lh_neutral_value, "must be array");
int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
assert(l2esz <= LogBytesPerLong,
"sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
return l2esz;
}
static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
return (tag << _lh_array_tag_shift)
| (hsize << _lh_header_size_shift)
| ((int)etype << _lh_element_type_shift)
| (log2_esize << _lh_log2_element_size_shift);
}
static jint instance_layout_helper(jint size, bool slow_path_flag) {
return (size << LogBytesPerWord)
| (slow_path_flag ? _lh_instance_slow_path_bit : 0);
}
static int layout_helper_to_size_helper(jint lh) {
assert(lh > (jint)_lh_neutral_value, "must be instance");
// Note that the following expression discards _lh_instance_slow_path_bit.
return lh >> LogBytesPerWord;
}
// Out-of-line version computes everything based on the etype:
static jint array_layout_helper(BasicType etype);
// What is the maximum number of primary superclasses any klass can have?
static juint primary_super_limit() { return _primary_super_limit; }
// vtables
klassVtable vtable() const;
int vtable_length() const { return _vtable_len; }
// subclass check
bool is_subclass_of(const Klass* k) const;
// subtype check: true if is_subclass_of, or if k is interface and receiver implements it
bool is_subtype_of(Klass* k) const {
juint off = k->super_check_offset();
Klass* sup = *(Klass**)( (address)this + off );
const juint secondary_offset = in_bytes(secondary_super_cache_offset());
if (sup == k) {
return true;
} else if (off != secondary_offset) {
return false;
} else {
return search_secondary_supers(k);
}
}
bool search_secondary_supers(Klass* k) const;
// Find LCA in class hierarchy
Klass *LCA( Klass *k );
// Check whether reflection/jni/jvm code is allowed to instantiate this class;
// if not, throw either an Error or an Exception.
virtual void check_valid_for_instantiation(bool throwError, TRAPS);
// array copying
virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
// tells if the class should be initialized
virtual bool should_be_initialized() const { return false; }
// initializes the klass
virtual void initialize(TRAPS);
virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
OverpassLookupMode overpass_mode,
PrivateLookupMode = find_private) const;
public:
Method* lookup_method(const Symbol* name, const Symbol* signature) const {
return uncached_lookup_method(name, signature, find_overpass);
}
// array class with specific rank
Klass* array_klass(int rank, TRAPS) { return array_klass_impl(false, rank, THREAD); }
// array class with this klass as element type
Klass* array_klass(TRAPS) { return array_klass_impl(false, THREAD); }
// These will return NULL instead of allocating on the heap:
// NB: these can block for a mutex, like other functions with TRAPS arg.
Klass* array_klass_or_null(int rank);
Klass* array_klass_or_null();
virtual oop protection_domain() const = 0;
oop class_loader() const;
// This loads the klass's holder as a phantom. This is useful when a weak Klass
// pointer has been "peeked" and then must be kept alive before it may
// be used safely. All uses of klass_holder need to apply the appropriate barriers,
// except during GC.
oop klass_holder() const { return class_loader_data()->holder_phantom(); }
protected:
virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);
virtual Klass* array_klass_impl(bool or_null, TRAPS);
// Error handling when length > max_length or length < 0
static void check_array_allocation_length(int length, int max_length, TRAPS);
void set_vtable_length(int len) { _vtable_len= len; }
vtableEntry* start_of_vtable() const;
public:
Method* method_at_vtable(int index);
static ByteSize vtable_start_offset();
static ByteSize vtable_length_offset() {
return byte_offset_of(Klass, _vtable_len);
}
// CDS support - remove and restore oops from metadata. Oops are not shared.
virtual void remove_unshareable_info();
virtual void remove_java_mirror();
virtual void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
bool is_unshareable_info_restored() const {
assert(is_shared(), "use this for shared classes only");
if (has_raw_archived_mirror()) {
// _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
return false;
} else if (_java_mirror.ptr_raw() == NULL) {
return false;
} else {
return true;
}
}
public:
// ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
// These functions describe behavior for the oop not the KLASS.
// actual oop size of obj in memory
virtual int oop_size(oop obj) const = 0;
// Size of klass in word size.
virtual int size() const = 0;
#if INCLUDE_SERVICES
virtual void collect_statistics(KlassSizeStats *sz) const;
#endif
// Returns the Java name for a class (Resource allocated)
// For arrays, this returns the name of the element with a leading '['.
// For classes, this returns the name with the package separators
// turned into '.'s.
const char* external_name() const;
// Returns the name for a class (Resource allocated) as the class
// would appear in a signature.
// For arrays, this returns the name of the element with a leading '['.
// For classes, this returns the name with a leading 'L' and a trailing ';'
// and the package separators as '/'.
virtual const char* signature_name() const;
const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
// Returns "interface", "abstract class" or "class".
const char* external_kind() const;
// type testing operations
#ifdef ASSERT
protected:
virtual bool is_instance_klass_slow() const { return false; }
virtual bool is_array_klass_slow() const { return false; }
virtual bool is_objArray_klass_slow() const { return false; }
virtual bool is_typeArray_klass_slow() const { return false; }
#endif // ASSERT
public:
// Fast non-virtual versions
#ifndef ASSERT
#define assert_same_query(xval, xcheck) xval
#else
private:
static bool assert_same_query(bool xval, bool xslow) {
assert(xval == xslow, "slow and fast queries agree");
return xval;
}
public:
#endif
inline bool is_instance_klass() const { return assert_same_query(
layout_helper_is_instance(layout_helper()),
is_instance_klass_slow()); }
inline bool is_array_klass() const { return assert_same_query(
layout_helper_is_array(layout_helper()),
is_array_klass_slow()); }
inline bool is_objArray_klass() const { return assert_same_query(
layout_helper_is_objArray(layout_helper()),
is_objArray_klass_slow()); }
inline bool is_typeArray_klass() const { return assert_same_query(
layout_helper_is_typeArray(layout_helper()),
is_typeArray_klass_slow()); }
#undef assert_same_query
// Access flags
AccessFlags access_flags() const { return _access_flags; }
void set_access_flags(AccessFlags flags) { _access_flags = flags; }
bool is_public() const { return _access_flags.is_public(); }
bool is_final() const { return _access_flags.is_final(); }
bool is_interface() const { return _access_flags.is_interface(); }
bool is_abstract() const { return _access_flags.is_abstract(); }
bool is_super() const { return _access_flags.is_super(); }
bool is_synthetic() const { return _access_flags.is_synthetic(); }
void set_is_synthetic() { _access_flags.set_is_synthetic(); }
bool has_finalizer() const { return _access_flags.has_finalizer(); }
bool has_final_method() const { return _access_flags.has_final_method(); }
void set_has_finalizer() { _access_flags.set_has_finalizer(); }
void set_has_final_method() { _access_flags.set_has_final_method(); }
bool has_vanilla_constructor() const { return _access_flags.has_vanilla_constructor(); }
void set_has_vanilla_constructor() { _access_flags.set_has_vanilla_constructor(); }
bool has_miranda_methods () const { return access_flags().has_miranda_methods(); }
void set_has_miranda_methods() { _access_flags.set_has_miranda_methods(); }
bool is_shared() const { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
void set_is_shared() { _access_flags.set_is_shared_class(); }
bool is_cloneable() const;
void set_is_cloneable();
// Biased locking support
// Note: the prototype header is always set up to be at least the
// prototype markWord. If biased locking is enabled it may further be
// biasable and have an epoch.
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