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/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_INTERN_TABLE_H_
#define ART_RUNTIME_INTERN_TABLE_H_
#include <unordered_set>
#include "atomic.h"
#include "base/allocator.h"
#include "base/hash_set.h"
#include "base/mutex.h"
#include "gc_root.h"
#include "gc/weak_root_state.h"
#include "object_callbacks.h"
namespace art {
namespace gc {
namespace space {
class ImageSpace;
} // namespace space
} // namespace gc
enum VisitRootFlags : uint8_t;
namespace mirror {
class String;
} // namespace mirror
class Transaction;
/**
* Used to intern strings.
*
* There are actually two tables: one that holds strong references to its strings, and one that
* holds weak references. The former is used for string literals, for which there is an effective
* reference from the constant pool. The latter is used for strings interned at runtime via
* String.intern. Some code (XML parsers being a prime example) relies on being able to intern
* arbitrarily many strings for the duration of a parse without permanently increasing the memory
* footprint.
*/
class InternTable {
public:
InternTable();
// Interns a potentially new string in the 'strong' table. May cause thread suspension.
ObjPtr<mirror::String> InternStrong(int32_t utf16_length, const char* utf8_data)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!Roles::uninterruptible_);
// Only used by image writer. Special version that may not cause thread suspension since the GC
// cannot be running while we are doing image writing. Maybe be called while while holding a
// lock since there will not be thread suspension.
ObjPtr<mirror::String> InternStrongImageString(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_);
// Interns a potentially new string in the 'strong' table. May cause thread suspension.
ObjPtr<mirror::String> InternStrong(const char* utf8_data) REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Roles::uninterruptible_);
// Interns a potentially new string in the 'strong' table. May cause thread suspension.
ObjPtr<mirror::String> InternStrong(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Roles::uninterruptible_);
// Interns a potentially new string in the 'weak' table. May cause thread suspension.
ObjPtr<mirror::String> InternWeak(ObjPtr<mirror::String> s) REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Roles::uninterruptible_);
void SweepInternTableWeaks(IsMarkedVisitor* visitor) REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Locks::intern_table_lock_);
bool ContainsWeak(ObjPtr<mirror::String> s) REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Locks::intern_table_lock_);
// Lookup a strong intern, returns null if not found.
ObjPtr<mirror::String> LookupStrong(Thread* self, ObjPtr<mirror::String> s)
REQUIRES(!Locks::intern_table_lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
ObjPtr<mirror::String> LookupStrong(Thread* self, uint32_t utf16_length, const char* utf8_data)
REQUIRES(!Locks::intern_table_lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Lookup a weak intern, returns null if not found.
ObjPtr<mirror::String> LookupWeak(Thread* self, ObjPtr<mirror::String> s)
REQUIRES(!Locks::intern_table_lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Total number of interned strings.
size_t Size() const REQUIRES(!Locks::intern_table_lock_);
// Total number of weakly live interned strings.
size_t StrongSize() const REQUIRES(!Locks::intern_table_lock_);
// Total number of strongly live interned strings.
size_t WeakSize() const REQUIRES(!Locks::intern_table_lock_);
void VisitRoots(RootVisitor* visitor, VisitRootFlags flags)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_);
void DumpForSigQuit(std::ostream& os) const REQUIRES(!Locks::intern_table_lock_);
void BroadcastForNewInterns();
// Adds all of the resolved image strings from the image spaces into the intern table. The
// advantage of doing this is preventing expensive DexFile::FindStringId calls. Sets
// images_added_to_intern_table_ to true.
void AddImagesStringsToTable(const std::vector<gc::space::ImageSpace*>& image_spaces)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_);
// Add a new intern table for inserting to, previous intern tables are still there but no
// longer inserted into and ideally unmodified. This is done to prevent dirty pages.
void AddNewTable()
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_);
// Read the intern table from memory. The elements aren't copied, the intern hash set data will
// point to somewhere within ptr. Only reads the strong interns.
size_t AddTableFromMemory(const uint8_t* ptr) REQUIRES(!Locks::intern_table_lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Write the post zygote intern table to a pointer. Only writes the strong interns since it is
// expected that there is no weak interns since this is called from the image writer.
size_t WriteToMemory(uint8_t* ptr) REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Locks::intern_table_lock_);
// Change the weak root state. May broadcast to waiters.
void ChangeWeakRootState(gc::WeakRootState new_state)
REQUIRES(!Locks::intern_table_lock_);
private:
// Modified UTF-8-encoded string treated as UTF16.
class Utf8String {
public:
Utf8String(uint32_t utf16_length, const char* utf8_data, int32_t hash)
: hash_(hash), utf16_length_(utf16_length), utf8_data_(utf8_data) { }
int32_t GetHash() const { return hash_; }
uint32_t GetUtf16Length() const { return utf16_length_; }
const char* GetUtf8Data() const { return utf8_data_; }
private:
int32_t hash_;
uint32_t utf16_length_;
const char* utf8_data_;
};
class StringHashEquals {
public:
std::size_t operator()(const GcRoot<mirror::String>& root) const NO_THREAD_SAFETY_ANALYSIS;
bool operator()(const GcRoot<mirror::String>& a, const GcRoot<mirror::String>& b) const
NO_THREAD_SAFETY_ANALYSIS;
// Utf8String can be used for lookup.
std::size_t operator()(const Utf8String& key) const { return key.GetHash(); }
bool operator()(const GcRoot<mirror::String>& a, const Utf8String& b) const
NO_THREAD_SAFETY_ANALYSIS;
};
class GcRootEmptyFn {
public:
void MakeEmpty(GcRoot<mirror::String>& item) const {
item = GcRoot<mirror::String>();
}
bool IsEmpty(const GcRoot<mirror::String>& item) const {
return item.IsNull();
}
};
// Table which holds pre zygote and post zygote interned strings. There is one instance for
// weak interns and strong interns.
class Table {
public:
Table();
ObjPtr<mirror::String> Find(ObjPtr<mirror::String> s) REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(Locks::intern_table_lock_);
ObjPtr<mirror::String> Find(const Utf8String& string) REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(Locks::intern_table_lock_);
void Insert(ObjPtr<mirror::String> s) REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(Locks::intern_table_lock_);
void Remove(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
void VisitRoots(RootVisitor* visitor)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
void SweepWeaks(IsMarkedVisitor* visitor)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
// Add a new intern table that will only be inserted into from now on.
void AddNewTable() REQUIRES(Locks::intern_table_lock_);
size_t Size() const REQUIRES(Locks::intern_table_lock_);
// Read and add an intern table from ptr.
// Tables read are inserted at the front of the table array. Only checks for conflicts in
// debug builds. Returns how many bytes were read.
size_t AddTableFromMemory(const uint8_t* ptr)
REQUIRES(Locks::intern_table_lock_) REQUIRES_SHARED(Locks::mutator_lock_);
// Write the intern tables to ptr, if there are multiple tables they are combined into a single
// one. Returns how many bytes were written.
size_t WriteToMemory(uint8_t* ptr)
REQUIRES(Locks::intern_table_lock_) REQUIRES_SHARED(Locks::mutator_lock_);
private:
typedef HashSet<GcRoot<mirror::String>, GcRootEmptyFn, StringHashEquals, StringHashEquals,
TrackingAllocator<GcRoot<mirror::String>, kAllocatorTagInternTable>> UnorderedSet;
void SweepWeaks(UnorderedSet* set, IsMarkedVisitor* visitor)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
// We call AddNewTable when we create the zygote to reduce private dirty pages caused by
// modifying the zygote intern table. The back of table is modified when strings are interned.
std::vector<UnorderedSet> tables_;
};
// Insert if non null, otherwise return null. Must be called holding the mutator lock.
// If holding_locks is true, then we may also hold other locks. If holding_locks is true, then we
// require GC is not running since it is not safe to wait while holding locks.
ObjPtr<mirror::String> Insert(ObjPtr<mirror::String> s, bool is_strong, bool holding_locks)
REQUIRES(!Locks::intern_table_lock_) REQUIRES_SHARED(Locks::mutator_lock_);
ObjPtr<mirror::String> LookupStrongLocked(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
ObjPtr<mirror::String> LookupWeakLocked(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
ObjPtr<mirror::String> InsertStrong(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
ObjPtr<mirror::String> InsertWeak(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
void RemoveStrong(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
void RemoveWeak(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
// Transaction rollback access.
ObjPtr<mirror::String> InsertStrongFromTransaction(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
ObjPtr<mirror::String> InsertWeakFromTransaction(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
void RemoveStrongFromTransaction(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
void RemoveWeakFromTransaction(ObjPtr<mirror::String> s)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_);
size_t AddTableFromMemoryLocked(const uint8_t* ptr)
REQUIRES(Locks::intern_table_lock_) REQUIRES_SHARED(Locks::mutator_lock_);
// Change the weak root state. May broadcast to waiters.
void ChangeWeakRootStateLocked(gc::WeakRootState new_state)
REQUIRES(Locks::intern_table_lock_);
// Wait until we can read weak roots.
void WaitUntilAccessible(Thread* self)
REQUIRES(Locks::intern_table_lock_) REQUIRES_SHARED(Locks::mutator_lock_);
bool log_new_roots_ GUARDED_BY(Locks::intern_table_lock_);
ConditionVariable weak_intern_condition_ GUARDED_BY(Locks::intern_table_lock_);
// Since this contains (strong) roots, they need a read barrier to
// enable concurrent intern table (strong) root scan. Do not
// directly access the strings in it. Use functions that contain
// read barriers.
Table strong_interns_ GUARDED_BY(Locks::intern_table_lock_);
std::vector<GcRoot<mirror::String>> new_strong_intern_roots_
GUARDED_BY(Locks::intern_table_lock_);
// Since this contains (weak) roots, they need a read barrier. Do
// not directly access the strings in it. Use functions that contain
// read barriers.
Table weak_interns_ GUARDED_BY(Locks::intern_table_lock_);
// Weak root state, used for concurrent system weak processing and more.
gc::WeakRootState weak_root_state_ GUARDED_BY(Locks::intern_table_lock_);
friend class Transaction;
DISALLOW_COPY_AND_ASSIGN(InternTable);
};
} // namespace art
#endif // ART_RUNTIME_INTERN_TABLE_H_