Introduce pdfium::FakeUniquePtr for keys to sets of unique ptrs.

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();
 }
 
+// Means of generating a key for searching STL collections of std::unique_ptr
+// that avoids the side effect of deleting the pointer.
+template <class T>
+class FakeUniquePtr : public std::unique_ptr<T> {
+ public:
+  using std::unique_ptr<T>::unique_ptr;
+  ~FakeUniquePtr() { std::unique_ptr<T>::release(); }
+};
+
 // 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_