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1 /*
2  * Copyright (C) 2011 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_BASE_STL_UTIL_H_
18 #define ART_RUNTIME_BASE_STL_UTIL_H_
19 
20 #include <algorithm>
21 #include <set>
22 #include <sstream>
23 
24 #include "base/logging.h"
25 
26 namespace art {
27 
28 // STLDeleteContainerPointers()
29 //  For a range within a container of pointers, calls delete
30 //  (non-array version) on these pointers.
31 // NOTE: for these three functions, we could just implement a DeleteObject
32 // functor and then call for_each() on the range and functor, but this
33 // requires us to pull in all of algorithm.h, which seems expensive.
34 // For hash_[multi]set, it is important that this deletes behind the iterator
35 // because the hash_set may call the hash function on the iterator when it is
36 // advanced, which could result in the hash function trying to deference a
37 // stale pointer.
38 template <class ForwardIterator>
STLDeleteContainerPointers(ForwardIterator begin,ForwardIterator end)39 void STLDeleteContainerPointers(ForwardIterator begin,
40                                 ForwardIterator end) {
41   while (begin != end) {
42     ForwardIterator temp = begin;
43     ++begin;
44     delete *temp;
45   }
46 }
47 
48 // STLDeleteElements() deletes all the elements in an STL container and clears
49 // the container.  This function is suitable for use with a vector, set,
50 // hash_set, or any other STL container which defines sensible begin(), end(),
51 // and clear() methods.
52 //
53 // If container is null, this function is a no-op.
54 //
55 // As an alternative to calling STLDeleteElements() directly, consider
56 // using a container of std::unique_ptr, which ensures that your container's
57 // elements are deleted when the container goes out of scope.
58 template <class T>
STLDeleteElements(T * container)59 void STLDeleteElements(T *container) {
60   if (container != nullptr) {
61     STLDeleteContainerPointers(container->begin(), container->end());
62     container->clear();
63   }
64 }
65 
66 // Given an STL container consisting of (key, value) pairs, STLDeleteValues
67 // deletes all the "value" components and clears the container.  Does nothing
68 // in the case it's given a null pointer.
69 template <class T>
STLDeleteValues(T * v)70 void STLDeleteValues(T *v) {
71   if (v != nullptr) {
72     for (typename T::iterator i = v->begin(); i != v->end(); ++i) {
73       delete i->second;
74     }
75     v->clear();
76   }
77 }
78 
79 // Deleter using free() for use with std::unique_ptr<>. See also UniqueCPtr<> below.
80 struct FreeDelete {
81   // NOTE: Deleting a const object is valid but free() takes a non-const pointer.
operatorFreeDelete82   void operator()(const void* ptr) const {
83     free(const_cast<void*>(ptr));
84   }
85 };
86 
87 // Alias for std::unique_ptr<> that uses the C function free() to delete objects.
88 template <typename T>
89 using UniqueCPtr = std::unique_ptr<T, FreeDelete>;
90 
91 // Find index of the first element with the specified value known to be in the container.
92 template <typename Container, typename T>
IndexOfElement(const Container & container,const T & value)93 size_t IndexOfElement(const Container& container, const T& value) {
94   auto it = std::find(container.begin(), container.end(), value);
95   DCHECK(it != container.end());  // Must exist.
96   return std::distance(container.begin(), it);
97 }
98 
99 // Remove the first element with the specified value known to be in the container.
100 template <typename Container, typename T>
RemoveElement(Container & container,const T & value)101 void RemoveElement(Container& container, const T& value) {
102   auto it = std::find(container.begin(), container.end(), value);
103   DCHECK(it != container.end());  // Must exist.
104   container.erase(it);
105 }
106 
107 // Replace the first element with the specified old_value known to be in the container.
108 template <typename Container, typename T>
ReplaceElement(Container & container,const T & old_value,const T & new_value)109 void ReplaceElement(Container& container, const T& old_value, const T& new_value) {
110   auto it = std::find(container.begin(), container.end(), old_value);
111   DCHECK(it != container.end());  // Must exist.
112   *it = new_value;
113 }
114 
115 // Search for an element with the specified value and return true if it was found, false otherwise.
116 template <typename Container, typename T>
117 bool ContainsElement(const Container& container, const T& value, size_t start_pos = 0u) {
118   DCHECK_LE(start_pos, container.size());
119   auto start = container.begin();
120   std::advance(start, start_pos);
121   auto it = std::find(start, container.end(), value);
122   return it != container.end();
123 }
124 
125 // 32-bit FNV-1a hash function suitable for std::unordered_map.
126 // It can be used with any container which works with range-based for loop.
127 // See http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
128 template <typename Vector>
129 struct FNVHash {
operatorFNVHash130   size_t operator()(const Vector& vector) const {
131     uint32_t hash = 2166136261u;
132     for (const auto& value : vector) {
133       hash = (hash ^ value) * 16777619u;
134     }
135     return hash;
136   }
137 };
138 
139 // Merge `other` entries into `to_update`.
140 template <typename T>
MergeSets(std::set<T> & to_update,const std::set<T> & other)141 static inline void MergeSets(std::set<T>& to_update, const std::set<T>& other) {
142   to_update.insert(other.begin(), other.end());
143 }
144 
145 // Returns a copy of the passed vector that doesn't memory-own its entries.
146 template <typename T>
MakeNonOwningPointerVector(const std::vector<std::unique_ptr<T>> & src)147 static inline std::vector<T*> MakeNonOwningPointerVector(const std::vector<std::unique_ptr<T>>& src) {
148   std::vector<T*> result;
149   result.reserve(src.size());
150   for (const std::unique_ptr<T>& t : src) {
151     result.push_back(t.get());
152   }
153   return result;
154 }
155 
156 }  // namespace art
157 
158 #endif  // ART_RUNTIME_BASE_STL_UTIL_H_
159