Move ScopedSetInsertion to third_party/base/stl_util.h

third_party/base/stl_util.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_
 #define PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_
 
 #include <algorithm>
+#include <set>
 
 #include "third_party/base/numerics/safe_conversions.h"
 
 namespace pdfium {
 
 // Test to see if a set, map, hash_set or hash_map contains a particular key.
 // Returns true if the key is in the collection.
 template <typename Collection, typename Key>
 bool ContainsKey(const Collection& collection, const Key& key) {
   return collection.find(key) != collection.end();
 }
 
 // Test to see if a collection like a vector contains a particular value.
 // Returns true if the value is in the collection.
 template <typename Collection, typename Value>
 bool ContainsValue(const Collection& collection, const Value& value) {
   return std::find(collection.begin(), collection.end(), value) !=
          collection.end();
 }
 
 // Convenience routine for "int-fected" code, so that the stl collection
 // size_t size() method return values will be checked.
 template <typename ResultType, typename Collection>
 ResultType CollectionSize(const Collection& collection) {
   return pdfium::base::checked_cast<ResultType, size_t>(collection.size());
 }
 
+// Track the addition of an object to a set, removing it automatically when
+// the ScopedSetInsertion goes out of scope.
+template <typename T>
+class ScopedSetInsertion {
+ public:
+  ScopedSetInsertion(std::set<T>* org_set, T elem)
+      : m_Set(org_set), m_Entry(elem) {
+    m_Set->insert(m_Entry);
+  }
+  ~ScopedSetInsertion() { m_Set->erase(m_Entry); }
+
+ private:
+  std::set<T>* const m_Set;
+  const T m_Entry;
+};
+
 }  // namespace pdfium
 
 #endif  // PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_