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_LIBDEXFILE_DEX_STRING_REFERENCE_H_
18 #define ART_LIBDEXFILE_DEX_STRING_REFERENCE_H_
19 
20 #include <stdint.h>
21 
22 #include <android-base/logging.h>
23 
24 #include "dex/dex_file-inl.h"
25 #include "dex/dex_file_reference.h"
26 #include "dex/dex_file_types.h"
27 #include "dex/utf-inl.h"
28 
29 namespace art {
30 
31 // A string is located by its DexFile and the string_ids_ table index into that DexFile.
32 class StringReference : public DexFileReference {
33  public:
StringReference(const DexFile * file,dex::StringIndex index)34   StringReference(const DexFile* file, dex::StringIndex index)
35      : DexFileReference(file, index.index_) {}
36 
StringIndex()37   dex::StringIndex StringIndex() const {
38     return dex::StringIndex(index);
39   }
40 
GetStringData()41   const char* GetStringData() const {
42     return dex_file->GetStringData(dex_file->GetStringId(StringIndex()));
43   }
44 };
45 
46 // Compare the actual referenced string values. Used for string reference deduplication.
47 struct StringReferenceValueComparator {
operatorStringReferenceValueComparator48   bool operator()(const StringReference& sr1, const StringReference& sr2) const {
49     // Note that we want to deduplicate identical strings even if they are referenced
50     // by different dex files, so we need some (any) total ordering of strings, rather
51     // than references. However, the references should usually be from the same dex file,
52     // so we choose the dex file string ordering so that we can simply compare indexes
53     // and avoid the costly string comparison in the most common case.
54     if (sr1.dex_file == sr2.dex_file) {
55       // Use the string order enforced by the dex file verifier.
56       DCHECK_EQ(
57           sr1.index < sr2.index,
58           CompareModifiedUtf8ToModifiedUtf8AsUtf16CodePointValues(sr1.GetStringData(),
59                                                                   sr2.GetStringData()) < 0);
60       return sr1.index < sr2.index;
61     } else {
62       // Cannot compare indexes, so do the string comparison.
63       return CompareModifiedUtf8ToModifiedUtf8AsUtf16CodePointValues(sr1.GetStringData(),
64                                                                      sr2.GetStringData()) < 0;
65     }
66   }
67 };
68 
69 }  // namespace art
70 
71 #endif  // ART_LIBDEXFILE_DEX_STRING_REFERENCE_H_
72