1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 // Derived from google3/util/gtl/stl_util.h
7 #ifndef BASE_STL_UTIL_H_
8 #define BASE_STL_UTIL_H_
13 // Clears internal memory of an STL object.
14 // STL clear()/reserve(0) does not always free internal memory allocated
15 // This function uses swap/destructor to ensure the internal memory is freed.
17 void STLClearObject(T
* obj
) {
20 // Sometimes "T tmp" allocates objects with memory (arena implementation?).
21 // Hence using additional reserve(0) even if it doesn't always work.
25 // For a range within a container of pointers, calls delete (non-array version)
27 // NOTE: for these three functions, we could just implement a DeleteObject
28 // functor and then call for_each() on the range and functor, but this
29 // requires us to pull in all of algorithm.h, which seems expensive.
30 // For hash_[multi]set, it is important that this deletes behind the iterator
31 // because the hash_set may call the hash function on the iterator when it is
32 // advanced, which could result in the hash function trying to deference a
34 template <class ForwardIterator
>
35 void STLDeleteContainerPointers(ForwardIterator begin
, ForwardIterator end
) {
36 while (begin
!= end
) {
37 ForwardIterator temp
= begin
;
43 // For a range within a container of pairs, calls delete (non-array version) on
44 // BOTH items in the pairs.
45 // NOTE: Like STLDeleteContainerPointers, it is important that this deletes
46 // behind the iterator because if both the key and value are deleted, the
47 // container may call the hash function on the iterator when it is advanced,
48 // which could result in the hash function trying to dereference a stale
50 template <class ForwardIterator
>
51 void STLDeleteContainerPairPointers(ForwardIterator begin
,
52 ForwardIterator end
) {
53 while (begin
!= end
) {
54 ForwardIterator temp
= begin
;
61 // For a range within a container of pairs, calls delete (non-array version) on
62 // the FIRST item in the pairs.
63 // NOTE: Like STLDeleteContainerPointers, deleting behind the iterator.
64 template <class ForwardIterator
>
65 void STLDeleteContainerPairFirstPointers(ForwardIterator begin
,
66 ForwardIterator end
) {
67 while (begin
!= end
) {
68 ForwardIterator temp
= begin
;
74 // For a range within a container of pairs, calls delete.
75 // NOTE: Like STLDeleteContainerPointers, deleting behind the iterator.
76 // Deleting the value does not always invalidate the iterator, but it may
77 // do so if the key is a pointer into the value object.
78 template <class ForwardIterator
>
79 void STLDeleteContainerPairSecondPointers(ForwardIterator begin
,
80 ForwardIterator end
) {
81 while (begin
!= end
) {
82 ForwardIterator temp
= begin
;
88 // To treat a possibly-empty vector as an array, use these functions.
89 // If you know the array will never be empty, you can use &*v.begin()
90 // directly, but that is undefined behaviour if |v| is empty.
92 inline T
* vector_as_array(std::vector
<T
>* v
) {
93 return v
->empty() ? NULL
: &*v
->begin();
97 inline const T
* vector_as_array(const std::vector
<T
>* v
) {
98 return v
->empty() ? NULL
: &*v
->begin();
101 // Return a mutable char* pointing to a string's internal buffer,
102 // which may not be null-terminated. Writing through this pointer will
103 // modify the string.
105 // string_as_array(&str)[i] is valid for 0 <= i < str.size() until the
106 // next call to a string method that invalidates iterators.
108 // As of 2006-04, there is no standard-blessed way of getting a
109 // mutable reference to a string's internal buffer. However, issue 530
110 // (http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-active.html#530)
111 // proposes this as the method. According to Matt Austern, this should
112 // already work on all current implementations.
113 inline char* string_as_array(std::string
* str
) {
114 // DO NOT USE const_cast<char*>(str->data())
115 return str
->empty() ? NULL
: &*str
->begin();
118 // The following functions are useful for cleaning up STL containers whose
119 // elements point to allocated memory.
121 // STLDeleteElements() deletes all the elements in an STL container and clears
122 // the container. This function is suitable for use with a vector, set,
123 // hash_set, or any other STL container which defines sensible begin(), end(),
124 // and clear() methods.
126 // If container is NULL, this function is a no-op.
128 // As an alternative to calling STLDeleteElements() directly, consider
129 // STLElementDeleter (defined below), which ensures that your container's
130 // elements are deleted when the STLElementDeleter goes out of scope.
132 void STLDeleteElements(T
* container
) {
135 STLDeleteContainerPointers(container
->begin(), container
->end());
139 // Given an STL container consisting of (key, value) pairs, STLDeleteValues
140 // deletes all the "value" components and clears the container. Does nothing
141 // in the case it's given a NULL pointer.
143 void STLDeleteValues(T
* container
) {
146 for (typename
T::iterator
i(container
->begin()); i
!= container
->end(); ++i
)
152 // The following classes provide a convenient way to delete all elements or
153 // values from STL containers when they goes out of scope. This greatly
154 // simplifies code that creates temporary objects and has multiple return
155 // statements. Example:
157 // vector<MyProto *> tmp_proto;
158 // STLElementDeleter<vector<MyProto *> > d(&tmp_proto);
159 // if (...) return false;
163 // Given a pointer to an STL container this class will delete all the element
164 // pointers when it goes out of scope.
166 class STLElementDeleter
{
168 STLElementDeleter
<T
>(T
* container
) : container_(container
) {}
169 ~STLElementDeleter
<T
>() { STLDeleteElements(container_
); }
175 // Given a pointer to an STL container this class will delete all the value
176 // pointers when it goes out of scope.
178 class STLValueDeleter
{
180 STLValueDeleter
<T
>(T
* container
) : container_(container
) {}
181 ~STLValueDeleter
<T
>() { STLDeleteValues(container_
); }
187 // Test to see if a set, map, hash_set or hash_map contains a particular key.
188 // Returns true if the key is in the collection.
189 template <typename Collection
, typename Key
>
190 bool ContainsKey(const Collection
& collection
, const Key
& key
) {
191 return collection
.find(key
) != collection
.end();
194 #endif // BASE_STL_UTIL_H_