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 
AddressOfElement(size_t index,PointerSize pointer_size)40   uint8_t* AddressOfElement(size_t index, PointerSize pointer_size) {
41     return reinterpret_cast<uint8_t*>(this) + OffsetOfElement(index, pointer_size);
42   }
43 
Get(size_t index,PointerSize pointer_size)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 
Set(size_t index,ArtMethod * method,PointerSize pointer_size)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 
OffsetOfElement(size_t index,PointerSize pointer_size)68   static size_t OffsetOfElement(size_t index, PointerSize pointer_size) {
69     return index * static_cast<size_t>(pointer_size);
70   }
71 
Populate(ArtMethod ** data,PointerSize pointer_size)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 
SizeInBytes(PointerSize pointer_size)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