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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_INL_H_
     18 #define ART_RUNTIME_IMTABLE_INL_H_
     19 
     20 #include "imtable.h"
     21 
     22 #include "art_method-inl.h"
     23 #include "dex/dex_file.h"
     24 #include "dex/utf.h"
     25 
     26 namespace art {
     27 
     28 static constexpr bool kImTableHashUseName = true;
     29 static constexpr bool kImTableHashUseCoefficients = true;
     30 
     31 // Magic configuration that minimizes some common runtime calls.
     32 static constexpr uint32_t kImTableHashCoefficientClass = 427;
     33 static constexpr uint32_t kImTableHashCoefficientName = 16;
     34 static constexpr uint32_t kImTableHashCoefficientSignature = 14;
     35 
     36 inline void ImTable::GetImtHashComponents(ArtMethod* method,
     37                                           uint32_t* class_hash,
     38                                           uint32_t* name_hash,
     39                                           uint32_t* signature_hash) {
     40   if (kImTableHashUseName) {
     41     if (method->IsProxyMethod()) {
     42       *class_hash = 0;
     43       *name_hash = 0;
     44       *signature_hash = 0;
     45       return;
     46     }
     47 
     48     const DexFile* dex_file = method->GetDexFile();
     49     const DexFile::MethodId& method_id = dex_file->GetMethodId(method->GetDexMethodIndex());
     50 
     51     // Class descriptor for the class component.
     52     *class_hash = ComputeModifiedUtf8Hash(dex_file->GetMethodDeclaringClassDescriptor(method_id));
     53 
     54     // Method name for the method component.
     55     *name_hash = ComputeModifiedUtf8Hash(dex_file->GetMethodName(method_id));
     56 
     57     const DexFile::ProtoId& proto_id = dex_file->GetMethodPrototype(method_id);
     58 
     59     // Read the proto for the signature component.
     60     uint32_t tmp = ComputeModifiedUtf8Hash(
     61         dex_file->GetTypeDescriptor(dex_file->GetTypeId(proto_id.return_type_idx_)));
     62 
     63     // Mix in the argument types.
     64     // Note: we could consider just using the shorty. This would be faster, at the price of
     65     //       potential collisions.
     66     const DexFile::TypeList* param_types = dex_file->GetProtoParameters(proto_id);
     67     if (param_types != nullptr) {
     68       for (size_t i = 0; i != param_types->Size(); ++i) {
     69         const DexFile::TypeItem& type = param_types->GetTypeItem(i);
     70         tmp = 31 * tmp + ComputeModifiedUtf8Hash(
     71             dex_file->GetTypeDescriptor(dex_file->GetTypeId(type.type_idx_)));
     72       }
     73     }
     74 
     75     *signature_hash = tmp;
     76     return;
     77   } else {
     78     *class_hash = method->GetDexMethodIndex();
     79     *name_hash = 0;
     80     *signature_hash = 0;
     81     return;
     82   }
     83 }
     84 
     85 inline uint32_t ImTable::GetImtIndex(ArtMethod* method) {
     86   uint32_t class_hash, name_hash, signature_hash;
     87   GetImtHashComponents(method, &class_hash, &name_hash, &signature_hash);
     88 
     89   uint32_t mixed_hash;
     90   if (!kImTableHashUseCoefficients) {
     91     mixed_hash = class_hash + name_hash + signature_hash;
     92   } else {
     93     mixed_hash = kImTableHashCoefficientClass * class_hash +
     94                  kImTableHashCoefficientName * name_hash +
     95                  kImTableHashCoefficientSignature * signature_hash;
     96   }
     97 
     98   return mixed_hash % ImTable::kSize;
     99 }
    100 
    101 }  // namespace art
    102 
    103 #endif  // ART_RUNTIME_IMTABLE_INL_H_
    104 
    105