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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ART_RUNTIME_IMTABLE_H_
     18 #define ART_RUNTIME_IMTABLE_H_
     19 
     20 #ifndef IMT_SIZE
     21 #error IMT_SIZE not defined
     22 #endif
     23 
     24 #include "base/enums.h"
     25 #include "base/macros.h"
     26 #include "base/mutex.h"
     27 
     28 namespace art {
     29 
     30 class ArtMethod;
     31 class DexFile;
     32 
     33 class ImTable {
     34  public:
     35   // Interface method table size. Increasing this value reduces the chance of two interface methods
     36   // colliding in the interface method table but increases the size of classes that implement
     37   // (non-marker) interfaces.
     38   static constexpr size_t kSize = IMT_SIZE;
     39 
     40   uint8_t* AddressOfElement(size_t index, PointerSize pointer_size) {
     41     return reinterpret_cast<uint8_t*>(this) + OffsetOfElement(index, pointer_size);
     42   }
     43 
     44   ArtMethod* Get(size_t index, PointerSize pointer_size) {
     45     DCHECK_LT(index, kSize);
     46     uint8_t* ptr = AddressOfElement(index, pointer_size);
     47     if (pointer_size == PointerSize::k32) {
     48       uint32_t value = *reinterpret_cast<uint32_t*>(ptr);
     49       return reinterpret_cast<ArtMethod*>(value);
     50     } else {
     51       uint64_t value = *reinterpret_cast<uint64_t*>(ptr);
     52       return reinterpret_cast<ArtMethod*>(value);
     53     }
     54   }
     55 
     56   void Set(size_t index, ArtMethod* method, PointerSize pointer_size) {
     57     DCHECK_LT(index, kSize);
     58     uint8_t* ptr = AddressOfElement(index, pointer_size);
     59     if (pointer_size == PointerSize::k32) {
     60       uintptr_t value = reinterpret_cast<uintptr_t>(method);
     61       DCHECK_EQ(static_cast<uint32_t>(value), value);  // Check that we dont lose any non 0 bits.
     62       *reinterpret_cast<uint32_t*>(ptr) = static_cast<uint32_t>(value);
     63     } else {
     64       *reinterpret_cast<uint64_t*>(ptr) = reinterpret_cast<uint64_t>(method);
     65     }
     66   }
     67 
     68   static size_t OffsetOfElement(size_t index, PointerSize pointer_size) {
     69     return index * static_cast<size_t>(pointer_size);
     70   }
     71 
     72   void Populate(ArtMethod** data, PointerSize pointer_size) {
     73     for (size_t i = 0; i < kSize; ++i) {
     74       Set(i, data[i], pointer_size);
     75     }
     76   }
     77 
     78   constexpr static size_t SizeInBytes(PointerSize pointer_size) {
     79     return kSize * static_cast<size_t>(pointer_size);
     80   }
     81 
     82   // Converts a method to the base hash components used in GetImtIndex.
     83   ALWAYS_INLINE static inline void GetImtHashComponents(ArtMethod* method,
     84                                                         uint32_t* class_hash,
     85                                                         uint32_t* name_hash,
     86                                                         uint32_t* signature_hash)
     87       REQUIRES_SHARED(Locks::mutator_lock_);
     88 
     89   // The (complete) hashing scheme to map an ArtMethod to a slot in the Interface Method Table
     90   // (IMT).
     91   ALWAYS_INLINE static inline uint32_t GetImtIndex(ArtMethod* method)
     92       REQUIRES_SHARED(Locks::mutator_lock_);
     93 };
     94 
     95 }  // namespace art
     96 
     97 #endif  // ART_RUNTIME_IMTABLE_H_
     98 
     99