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_STRING_REFERENCE_H_ 18 #define ART_RUNTIME_STRING_REFERENCE_H_ 19 20 #include <stdint.h> 21 22 #include "base/logging.h" 23 #include "dex_file-inl.h" 24 #include "dex_file_types.h" 25 #include "utf-inl.h" 26 27 namespace art { 28 29 // A string is located by its DexFile and the string_ids_ table index into that DexFile. 30 struct StringReference { StringReferenceStringReference31 StringReference(const DexFile* file, dex::StringIndex index) 32 : dex_file(file), string_index(index) { } 33 GetStringDataStringReference34 const char* GetStringData() const { 35 return dex_file->GetStringData(dex_file->GetStringId(string_index)); 36 } 37 38 const DexFile* dex_file; 39 dex::StringIndex string_index; 40 }; 41 42 // Compare only the reference and not the string contents. 43 struct StringReferenceComparator { operatorStringReferenceComparator44 bool operator()(const StringReference& a, const StringReference& b) const { 45 if (a.dex_file != b.dex_file) { 46 return a.dex_file < b.dex_file; 47 } 48 return a.string_index < b.string_index; 49 } 50 }; 51 52 // Compare the actual referenced string values. Used for string reference deduplication. 53 struct StringReferenceValueComparator { operatorStringReferenceValueComparator54 bool operator()(StringReference sr1, StringReference sr2) const { 55 // Note that we want to deduplicate identical strings even if they are referenced 56 // by different dex files, so we need some (any) total ordering of strings, rather 57 // than references. However, the references should usually be from the same dex file, 58 // so we choose the dex file string ordering so that we can simply compare indexes 59 // and avoid the costly string comparison in the most common case. 60 if (sr1.dex_file == sr2.dex_file) { 61 // Use the string order enforced by the dex file verifier. 62 DCHECK_EQ( 63 sr1.string_index < sr2.string_index, 64 CompareModifiedUtf8ToModifiedUtf8AsUtf16CodePointValues(sr1.GetStringData(), 65 sr2.GetStringData()) < 0); 66 return sr1.string_index < sr2.string_index; 67 } else { 68 // Cannot compare indexes, so do the string comparison. 69 return CompareModifiedUtf8ToModifiedUtf8AsUtf16CodePointValues(sr1.GetStringData(), 70 sr2.GetStringData()) < 0; 71 } 72 } 73 }; 74 75 } // namespace art 76 77 #endif // ART_RUNTIME_STRING_REFERENCE_H_ 78