/*
* 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 "base/allocator.h"
#include "base/hash_set.h"
#include "base/mutex.h"
#include "gc_root.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. (See above.)
mirror::String* InternStrong(int32_t utf16_length, const char* utf8_data)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Interns a potentially new string in the 'strong' table. (See above.)
mirror::String* InternStrong(const char* utf8_data)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Interns a potentially new string in the 'strong' table. (See above.)
mirror::String* InternStrong(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Interns a potentially new string in the 'weak' table. (See above.)
mirror::String* InternWeak(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
void SweepInternTableWeaks(IsMarkedCallback* callback, void* arg)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
bool ContainsWeak(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Total number of interned strings.
size_t Size() const LOCKS_EXCLUDED(Locks::intern_table_lock_);
// Total number of weakly live interned strings.
size_t StrongSize() const LOCKS_EXCLUDED(Locks::intern_table_lock_);
// Total number of strongly live interned strings.
size_t WeakSize() const LOCKS_EXCLUDED(Locks::intern_table_lock_);
void VisitRoots(RootVisitor* visitor, VisitRootFlags flags)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
void DumpForSigQuit(std::ostream& os) const;
void DisallowNewInterns() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
void AllowNewInterns() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
void EnsureNewInternsDisallowed() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Adds all of the resolved image strings from the image space into the intern table. The
// advantage of doing this is preventing expensive DexFile::FindStringId calls.
void AddImageStringsToTable(gc::space::ImageSpace* image_space)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) LOCKS_EXCLUDED(Locks::intern_table_lock_);
// Copy the post zygote tables to pre zygote to save memory by preventing dirty pages.
void SwapPostZygoteWithPreZygote()
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) LOCKS_EXCLUDED(Locks::intern_table_lock_);
// Add an intern table which was serialized to the image.
void AddImageInternTable(gc::space::ImageSpace* image_space)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) LOCKS_EXCLUDED(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 ReadFromMemory(const uint8_t* ptr) LOCKS_EXCLUDED(Locks::intern_table_lock_)
SHARED_LOCKS_REQUIRED(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) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
LOCKS_EXCLUDED(Locks::intern_table_lock_);
private:
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;
};
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:
mirror::String* Find(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void Insert(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void Remove(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void VisitRoots(RootVisitor* visitor)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void SweepWeaks(IsMarkedCallback* callback, void* arg)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void SwapPostZygoteWithPreZygote() EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
size_t Size() const EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
// Read pre zygote table is called from ReadFromMemory which happens during runtime creation
// when we load the image intern table. Returns how many bytes were read.
size_t ReadIntoPreZygoteTable(const uint8_t* ptr)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// The image writer calls WritePostZygoteTable through WriteToMemory, it writes the interns in
// the post zygote table. Returns how many bytes were written.
size_t WriteFromPostZygoteTable(uint8_t* ptr)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
private:
typedef HashSet<GcRoot<mirror::String>, GcRootEmptyFn, StringHashEquals, StringHashEquals,
TrackingAllocator<GcRoot<mirror::String>, kAllocatorTagInternTable>> UnorderedSet;
void SweepWeaks(UnorderedSet* set, IsMarkedCallback* callback, void* arg)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
// We call SwapPostZygoteWithPreZygote when we create the zygote to reduce private dirty pages
// caused by modifying the zygote intern table hash table. The pre zygote table are the
// interned strings which were interned before we created the zygote space. Post zygote is self
// explanatory.
UnorderedSet pre_zygote_table_;
UnorderedSet post_zygote_table_;
};
// Insert if non null, otherwise return null.
mirror::String* Insert(mirror::String* s, bool is_strong)
LOCKS_EXCLUDED(Locks::intern_table_lock_)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
mirror::String* LookupStrong(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
mirror::String* LookupWeak(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
mirror::String* InsertStrong(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
mirror::String* InsertWeak(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void RemoveStrong(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void RemoveWeak(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
// Transaction rollback access.
mirror::String* LookupStringFromImage(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
mirror::String* InsertStrongFromTransaction(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
mirror::String* InsertWeakFromTransaction(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void RemoveStrongFromTransaction(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
void RemoveWeakFromTransaction(mirror::String* s)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_);
friend class Transaction;
size_t ReadFromMemoryLocked(const uint8_t* ptr)
EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
bool image_added_to_intern_table_ GUARDED_BY(Locks::intern_table_lock_);
bool log_new_roots_ GUARDED_BY(Locks::intern_table_lock_);
bool allow_new_interns_ GUARDED_BY(Locks::intern_table_lock_);
ConditionVariable new_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_);
};
} // namespace art
#endif // ART_RUNTIME_INTERN_TABLE_H_