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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_COMPILER_UTILS_STRING_REFERENCE_H_
     18 #define ART_COMPILER_UTILS_STRING_REFERENCE_H_
     19 
     20 #include <stdint.h>
     21 
     22 #include "base/logging.h"
     23 #include "utf-inl.h"
     24 
     25 namespace art {
     26 
     27 class DexFile;
     28 
     29 // A string is uniquely located by its DexFile and the string_ids_ table index into that DexFile.
     30 struct StringReference {
     31   StringReference(const DexFile* file, uint32_t index) : dex_file(file), string_index(index) { }
     32 
     33   const DexFile* dex_file;
     34   uint32_t string_index;
     35 };
     36 
     37 // Compare the actual referenced string values. Used for string reference deduplication.
     38 struct StringReferenceValueComparator {
     39   bool operator()(StringReference sr1, StringReference sr2) const {
     40     // Note that we want to deduplicate identical strings even if they are referenced
     41     // by different dex files, so we need some (any) total ordering of strings, rather
     42     // than references. However, the references should usually be from the same dex file,
     43     // so we choose the dex file string ordering so that we can simply compare indexes
     44     // and avoid the costly string comparison in the most common case.
     45     if (sr1.dex_file == sr2.dex_file) {
     46       // Use the string order enforced by the dex file verifier.
     47       DCHECK_EQ(
     48           sr1.string_index < sr2.string_index,
     49           CompareModifiedUtf8ToModifiedUtf8AsUtf16CodePointValues(
     50               sr1.dex_file->GetStringData(sr1.dex_file->GetStringId(sr1.string_index)),
     51               sr1.dex_file->GetStringData(sr2.dex_file->GetStringId(sr2.string_index))) < 0);
     52       return sr1.string_index < sr2.string_index;
     53     } else {
     54       // Cannot compare indexes, so do the string comparison.
     55       return CompareModifiedUtf8ToModifiedUtf8AsUtf16CodePointValues(
     56           sr1.dex_file->GetStringData(sr1.dex_file->GetStringId(sr1.string_index)),
     57           sr1.dex_file->GetStringData(sr2.dex_file->GetStringId(sr2.string_index))) < 0;
     58     }
     59   }
     60 };
     61 
     62 }  // namespace art
     63 
     64 #endif  // ART_COMPILER_UTILS_STRING_REFERENCE_H_
     65