google/protobuf/repeated_field.h

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Author: kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.
//
// RepeatedField and RepeatedPtrField are used by generated protocol message
// classes to manipulate repeated fields.  These classes are very similar to
// STL's vector, but include a number of optimizations found to be useful
// specifically in the case of Protocol Buffers.  RepeatedPtrField is
// particularly different from STL vector as it manages ownership of the
// pointers that it contains.
//
// Typically, clients should not need to access RepeatedField objects directly,
// but should instead use the accessor functions generated automatically by the
// protocol compiler.

#ifndef GOOGLE_PROTOBUF_REPEATED_FIELD_H__
#define GOOGLE_PROTOBUF_REPEATED_FIELD_H__

#ifdef _MSC_VER
// This is required for min/max on VS2013 only.
#include <algorithm>
#endif

#include <string>
#include <iterator>
#include <google/protobuf/stubs/common.h>
#include <google/protobuf/stubs/type_traits.h>
#include <google/protobuf/generated_message_util.h>
#include <google/protobuf/message_lite.h>

namespace google {

namespace upb {
namespace google_opensource {
class GMR_Handlers;
}  // namespace google_opensource
}  // namespace upb

namespace protobuf {

class Message;

namespace internal {

static const int kMinRepeatedFieldAllocationSize = 4;

// A utility function for logging that doesn't need any template types.
void LogIndexOutOfBounds(int index, int size);

template <typename Iter>
inline int CalculateReserve(Iter begin, Iter end, std::forward_iterator_tag) {
  return std::distance(begin, end);
}

template <typename Iter>
inline int CalculateReserve(Iter /*begin*/, Iter /*end*/,
                            std::input_iterator_tag) {
  return -1;
}

template <typename Iter>
inline int CalculateReserve(Iter begin, Iter end) {
  typedef typename std::iterator_traits<Iter>::iterator_category Category;
  return CalculateReserve(begin, end, Category());
}
}  // namespace internal


// RepeatedField is used to represent repeated fields of a primitive type (in
// other words, everything except strings and nested Messages).  Most users will
// not ever use a RepeatedField directly; they will use the get-by-index,
// set-by-index, and add accessors that are generated for all repeated fields.
template <typename Element>
class RepeatedField {
 public:
  RepeatedField();
  RepeatedField(const RepeatedField& other);
  template <typename Iter>
  RepeatedField(Iter begin, const Iter& end);
  ~RepeatedField();

  RepeatedField& operator=(const RepeatedField& other);

  bool empty() const;
  int size() const;

  const Element& Get(int index) const;
  Element* Mutable(int index);
  void Set(int index, const Element& value);
  void Add(const Element& value);
  Element* Add();
  // Remove the last element in the array.
  void RemoveLast();

  // Extract elements with indices in "[start .. start+num-1]".
  // Copy them into "elements[0 .. num-1]" if "elements" is not NULL.
  // Caution: implementation also moves elements with indices [start+num ..].
  // Calling this routine inside a loop can cause quadratic behavior.
  void ExtractSubrange(int start, int num, Element* elements);

  void Clear();
  void MergeFrom(const RepeatedField& other);
  void CopyFrom(const RepeatedField& other);

  // Reserve space to expand the field to at least the given size.  If the
  // array is grown, it will always be at least doubled in size.
  void Reserve(int new_size);

  // Resize the RepeatedField to a new, smaller size.  This is O(1).
  void Truncate(int new_size);

  void AddAlreadyReserved(const Element& value);
  Element* AddAlreadyReserved();
  int Capacity() const;

  // Like STL resize.  Uses value to fill appended elements.
  // Like Truncate() if new_size <= size(), otherwise this is
  // O(new_size - size()).
  void Resize(int new_size, const Element& value);

  // Gets the underlying array.  This pointer is possibly invalidated by
  // any add or remove operation.
  Element* mutable_data();
  const Element* data() const;

  // Swap entire contents with "other".
  void Swap(RepeatedField* other);

  // Swap two elements.
  void SwapElements(int index1, int index2);

  // STL-like iterator support
  typedef Element* iterator;
  typedef const Element* const_iterator;
  typedef Element value_type;
  typedef value_type& reference;
  typedef const value_type& const_reference;
  typedef value_type* pointer;
  typedef const value_type* const_pointer;
  typedef int size_type;
  typedef ptrdiff_t difference_type;

  iterator begin();
  const_iterator begin() const;
  iterator end();
  const_iterator end() const;

  // Reverse iterator support
  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
  typedef std::reverse_iterator<iterator> reverse_iterator;
  reverse_iterator rbegin() {
    return reverse_iterator(end());
  }
  const_reverse_iterator rbegin() const {
    return const_reverse_iterator(end());
  }
  reverse_iterator rend() {
    return reverse_iterator(begin());
  }
  const_reverse_iterator rend() const {
    return const_reverse_iterator(begin());
  }

  // Returns the number of bytes used by the repeated field, excluding
  // sizeof(*this)
  int SpaceUsedExcludingSelf() const;

 private:
  static const int kInitialSize = 0;

  Element* elements_;
  int      current_size_;
  int      total_size_;

  // Move the contents of |from| into |to|, possibly clobbering |from| in the
  // process.  For primitive types this is just a memcpy(), but it could be
  // specialized for non-primitive types to, say, swap each element instead.
  void MoveArray(Element to[], Element from[], int size);

  // Copy the elements of |from| into |to|.
  void CopyArray(Element to[], const Element from[], int size);
};

namespace internal {
template <typename It> class RepeatedPtrIterator;
template <typename It, typename VoidPtr> class RepeatedPtrOverPtrsIterator;
}  // namespace internal

namespace internal {

// This is a helper template to copy an array of elements effeciently when they
// have a trivial copy constructor, and correctly otherwise. This really
// shouldn't be necessary, but our compiler doesn't optimize std::copy very
// effectively.
template <typename Element,
          bool HasTrivialCopy = has_trivial_copy<Element>::value>
struct ElementCopier {
  void operator()(Element to[], const Element from[], int array_size);
};

}  // namespace internal

namespace internal {

// This is the common base class for RepeatedPtrFields.  It deals only in void*
// pointers.  Users should not use this interface directly.
//
// The methods of this interface correspond to the methods of RepeatedPtrField,
// but may have a template argument called TypeHandler.  Its signature is:
//   class TypeHandler {
//    public:
//     typedef MyType Type;
//     static Type* New();
//     static void Delete(Type*);
//     static void Clear(Type*);
//     static void Merge(const Type& from, Type* to);
//
//     // Only needs to be implemented if SpaceUsedExcludingSelf() is called.
//     static int SpaceUsed(const Type&);
//   };
class LIBPROTOBUF_EXPORT RepeatedPtrFieldBase {
 protected:
  // The reflection implementation needs to call protected methods directly,
  // reinterpreting pointers as being to Message instead of a specific Message
  // subclass.
  friend class GeneratedMessageReflection;

  // ExtensionSet stores repeated message extensions as
  // RepeatedPtrField<MessageLite>, but non-lite ExtensionSets need to
  // implement SpaceUsed(), and thus need to call SpaceUsedExcludingSelf()
  // reinterpreting MessageLite as Message.  ExtensionSet also needs to make
  // use of AddFromCleared(), which is not part of the public interface.
  friend class ExtensionSet;

  // To parse directly into a proto2 generated class, the upb class GMR_Handlers
  // needs to be able to modify a RepeatedPtrFieldBase directly.
  friend class LIBPROTOBUF_EXPORT upb::google_opensource::GMR_Handlers;

  RepeatedPtrFieldBase();

  // Must be called from destructor.
  template <typename TypeHandler>
  void Destroy();

  bool empty() const;
  int size() const;

  template <typename TypeHandler>
  const typename TypeHandler::Type& Get(int index) const;
  template <typename TypeHandler>
  typename TypeHandler::Type* Mutable(int index);
  template <typename TypeHandler>
  typename TypeHandler::Type* Add();
  template <typename TypeHandler>
  void RemoveLast();
  template <typename TypeHandler>
  void Clear();
  template <typename TypeHandler>
  void MergeFrom(const RepeatedPtrFieldBase& other);
  template <typename TypeHandler>
  void CopyFrom(const RepeatedPtrFieldBase& other);

  void CloseGap(int start, int num) {
    // Close up a gap of "num" elements starting at offset "start".
    for (int i = start + num; i < allocated_size_; ++i)
      elements_[i - num] = elements_[i];
    current_size_ -= num;
    allocated_size_ -= num;
  }

  void Reserve(int new_size);

  int Capacity() const;

  // Used for constructing iterators.
  void* const* raw_data() const;
  void** raw_mutable_data() const;

  template <typename TypeHandler>
  typename TypeHandler::Type** mutable_data();
  template <typename TypeHandler>
  const typename TypeHandler::Type* const* data() const;

  void Swap(RepeatedPtrFieldBase* other);

  void SwapElements(int index1, int index2);

  template <typename TypeHandler>
  int SpaceUsedExcludingSelf() const;


  // Advanced memory management --------------------------------------

  // Like Add(), but if there are no cleared objects to use, returns NULL.
  template <typename TypeHandler>
  typename TypeHandler::Type* AddFromCleared();

  template <typename TypeHandler>
  void AddAllocated(typename TypeHandler::Type* value);
  template <typename TypeHandler>
  typename TypeHandler::Type* ReleaseLast();

  int ClearedCount() const;
  template <typename TypeHandler>
  void AddCleared(typename TypeHandler::Type* value);
  template <typename TypeHandler>
  typename TypeHandler::Type* ReleaseCleared();

 private:
  static const int kInitialSize = 0;

  void** elements_;
  int    current_size_;
  int    allocated_size_;
  int    total_size_;

  template <typename TypeHandler>
  static inline typename TypeHandler::Type* cast(void* element) {
    return reinterpret_cast<typename TypeHandler::Type*>(element);
  }
  template <typename TypeHandler>
  static inline const typename TypeHandler::Type* cast(const void* element) {
    return reinterpret_cast<const typename TypeHandler::Type*>(element);
  }

  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RepeatedPtrFieldBase);
};

template <typename GenericType>
class GenericTypeHandler {
 public:
  typedef GenericType Type;
  static GenericType* New() { return new GenericType; }
  static void Delete(GenericType* value) { delete value; }
  static void Clear(GenericType* value) { value->Clear(); }
  static void Merge(const GenericType& from, GenericType* to) {
    to->MergeFrom(from);
  }
  static int SpaceUsed(const GenericType& value) { return value.SpaceUsed(); }
  static const Type& default_instance() { return Type::default_instance(); }
};

template <>
inline void GenericTypeHandler<MessageLite>::Merge(
    const MessageLite& from, MessageLite* to) {
  to->CheckTypeAndMergeFrom(from);
}

template <>
inline const MessageLite& GenericTypeHandler<MessageLite>::default_instance() {
  // Yes, the behavior of the code is undefined, but this function is only
  // called when we're already deep into the world of undefined, because the
  // caller called Get(index) out of bounds.
  MessageLite* null = NULL;
  return *null;
}

template <>
inline const Message& GenericTypeHandler<Message>::default_instance() {
  // Yes, the behavior of the code is undefined, but this function is only
  // called when we're already deep into the world of undefined, because the
  // caller called Get(index) out of bounds.
  Message* null = NULL;
  return *null;
}


// HACK:  If a class is declared as DLL-exported in MSVC, it insists on
//   generating copies of all its methods -- even inline ones -- to include
//   in the DLL.  But SpaceUsed() calls StringSpaceUsedExcludingSelf() which
//   isn't in the lite library, therefore the lite library cannot link if
//   StringTypeHandler is exported.  So, we factor out StringTypeHandlerBase,
//   export that, then make StringTypeHandler be a subclass which is NOT
//   exported.
// TODO(kenton):  There has to be a better way.
class LIBPROTOBUF_EXPORT StringTypeHandlerBase {
 public:
  typedef string Type;
  static string* New();
  static void Delete(string* value);
  static void Clear(string* value) { value->clear(); }
  static void Merge(const string& from, string* to) { *to = from; }
  static const Type& default_instance() {
    return ::google::protobuf::internal::GetEmptyString();
  }
};

class StringTypeHandler : public StringTypeHandlerBase {
 public:
  static int SpaceUsed(const string& value)  {
    return sizeof(value) + StringSpaceUsedExcludingSelf(value);
  }
};


}  // namespace internal

// RepeatedPtrField is like RepeatedField, but used for repeated strings or
// Messages.
template <typename Element>
class RepeatedPtrField : public internal::RepeatedPtrFieldBase {
 public:
  RepeatedPtrField();
  RepeatedPtrField(const RepeatedPtrField& other);
  template <typename Iter>
  RepeatedPtrField(Iter begin, const Iter& end);
  ~RepeatedPtrField();

  RepeatedPtrField& operator=(const RepeatedPtrField& other);

  bool empty() const;
  int size() const;

  const Element& Get(int index) const;
  Element* Mutable(int index);
  Element* Add();

  // Remove the last element in the array.
  // Ownership of the element is retained by the array.
  void RemoveLast();

  // Delete elements with indices in the range [start .. start+num-1].
  // Caution: implementation moves all elements with indices [start+num .. ].
  // Calling this routine inside a loop can cause quadratic behavior.
  void DeleteSubrange(int start, int num);

  void Clear();
  void MergeFrom(const RepeatedPtrField& other);
  void CopyFrom(const RepeatedPtrField& other);

  // Reserve space to expand the field to at least the given size.  This only
  // resizes the pointer array; it doesn't allocate any objects.  If the
  // array is grown, it will always be at least doubled in size.
  void Reserve(int new_size);

  int Capacity() const;

  // Gets the underlying array.  This pointer is possibly invalidated by
  // any add or remove operation.
  Element** mutable_data();
  const Element* const* data() const;

  // Swap entire contents with "other".
  void Swap(RepeatedPtrField* other);

  // Swap two elements.
  void SwapElements(int index1, int index2);

  // STL-like iterator support
  typedef internal::RepeatedPtrIterator<Element> iterator;
  typedef internal::RepeatedPtrIterator<const Element> const_iterator;
  typedef Element value_type;
  typedef value_type& reference;
  typedef const value_type& const_reference;
  typedef value_type* pointer;
  typedef const value_type* const_pointer;
  typedef int size_type;
  typedef ptrdiff_t difference_type;

  iterator begin();
  const_iterator begin() const;
  iterator end();
  const_iterator end() const;

  // Reverse iterator support
  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
  typedef std::reverse_iterator<iterator> reverse_iterator;
  reverse_iterator rbegin() {
    return reverse_iterator(end());
  }
  const_reverse_iterator rbegin() const {
    return const_reverse_iterator(end());
  }
  reverse_iterator rend() {
    return reverse_iterator(begin());
  }
  const_reverse_iterator rend() const {
    return const_reverse_iterator(begin());
  }

  // Custom STL-like iterator that iterates over and returns the underlying
  // pointers to Element rather than Element itself.
  typedef internal::RepeatedPtrOverPtrsIterator<Element, void*>
  pointer_iterator;
  typedef internal::RepeatedPtrOverPtrsIterator<const Element, const void*>
  const_pointer_iterator;
  pointer_iterator pointer_begin();
  const_pointer_iterator pointer_begin() const;
  pointer_iterator pointer_end();
  const_pointer_iterator pointer_end() const;

  // Returns (an estimate of) the number of bytes used by the repeated field,
  // excluding sizeof(*this).
  int SpaceUsedExcludingSelf() const;

  // Advanced memory management --------------------------------------
  // When hardcore memory management becomes necessary -- as it sometimes
  // does here at Google -- the following methods may be useful.

  // Add an already-allocated object, passing ownership to the
  // RepeatedPtrField.
  void AddAllocated(Element* value);
  // Remove the last element and return it, passing ownership to the caller.
  // Requires:  size() > 0
  Element* ReleaseLast();

  // Extract elements with indices in the range "[start .. start+num-1]".
  // The caller assumes ownership of the extracted elements and is responsible
  // for deleting them when they are no longer needed.
  // If "elements" is non-NULL, then pointers to the extracted elements
  // are stored in "elements[0 .. num-1]" for the convenience of the caller.
  // If "elements" is NULL, then the caller must use some other mechanism
  // to perform any further operations (like deletion) on these elements.
  // Caution: implementation also moves elements with indices [start+num ..].
  // Calling this routine inside a loop can cause quadratic behavior.
  void ExtractSubrange(int start, int num, Element** elements);

  // When elements are removed by calls to RemoveLast() or Clear(), they
  // are not actually freed.  Instead, they are cleared and kept so that
  // they can be reused later.  This can save lots of CPU time when
  // repeatedly reusing a protocol message for similar purposes.
  //
  // Hardcore programs may choose to manipulate these cleared objects
  // to better optimize memory management using the following routines.

  // Get the number of cleared objects that are currently being kept
  // around for reuse.
  int ClearedCount() const;
  // Add an element to the pool of cleared objects, passing ownership to
  // the RepeatedPtrField.  The element must be cleared prior to calling
  // this method.
  void AddCleared(Element* value);
  // Remove a single element from the cleared pool and return it, passing
  // ownership to the caller.  The element is guaranteed to be cleared.
  // Requires:  ClearedCount() > 0
  Element* ReleaseCleared();

 protected:
  // Note:  RepeatedPtrField SHOULD NOT be subclassed by users.  We only
  //   subclass it in one place as a hack for compatibility with proto1.  The
  //   subclass needs to know about TypeHandler in order to call protected
  //   methods on RepeatedPtrFieldBase.
  class TypeHandler;

};

// implementation ====================================================

template <typename Element>
inline RepeatedField<Element>::RepeatedField()
  : elements_(NULL),
    current_size_(0),
    total_size_(kInitialSize) {
}

template <typename Element>
inline RepeatedField<Element>::RepeatedField(const RepeatedField& other)
  : elements_(NULL),
    current_size_(0),
    total_size_(kInitialSize) {
  CopyFrom(other);
}

template <typename Element>
template <typename Iter>
inline RepeatedField<Element>::RepeatedField(Iter begin, const Iter& end)
  : elements_(NULL),
    current_size_(0),
    total_size_(kInitialSize) {
  int reserve = internal::CalculateReserve(begin, end);
  if (reserve != -1) {
    Reserve(reserve);
    for (; begin != end; ++begin) {
      AddAlreadyReserved(*begin);
    }
  } else {
    for (; begin != end; ++begin) {
      Add(*begin);
    }
  }
}

template <typename Element>
RepeatedField<Element>::~RepeatedField() {
  delete [] elements_;
}

template <typename Element>
inline RepeatedField<Element>&
RepeatedField<Element>::operator=(const RepeatedField& other) {
  if (this != &other)
    CopyFrom(other);
  return *this;
}

template <typename Element>
inline bool RepeatedField<Element>::empty() const {
  return current_size_ == 0;
}

template <typename Element>
inline int RepeatedField<Element>::size() const {
  return current_size_;
}

template <typename Element>
inline int RepeatedField<Element>::Capacity() const {
  return total_size_;
}

template<typename Element>
inline void RepeatedField<Element>::AddAlreadyReserved(const Element& value) {
  GOOGLE_DCHECK_LT(size(), Capacity());
  elements_[current_size_++] = value;
}

template<typename Element>
inline Element* RepeatedField<Element>::AddAlreadyReserved() {
  GOOGLE_DCHECK_LT(size(), Capacity());
  return &elements_[current_size_++];
}

template<typename Element>
inline void RepeatedField<Element>::Resize(int new_size, const Element& value) {
  GOOGLE_DCHECK_GE(new_size, 0);
  if (new_size > size()) {
    Reserve(new_size);
    std::fill(&elements_[current_size_], &elements_[new_size], value);
  }
  current_size_ = new_size;
}

template <typename Element>
inline const Element& RepeatedField<Element>::Get(int index) const {
  GOOGLE_DCHECK_GE(index, 0);
  GOOGLE_DCHECK_LT(index, size());
  return elements_[index];
}

template <typename Element>
inline Element* RepeatedField<Element>::Mutable(int index) {
  GOOGLE_DCHECK_GE(index, 0);
  GOOGLE_DCHECK_LT(index, size());
  return elements_ + index;
}

template <typename Element>
inline void RepeatedField<Element>::Set(int index, const Element& value) {
  GOOGLE_DCHECK_GE(index, 0);
  GOOGLE_DCHECK_LT(index, size());
  elements_[index] = value;
}

template <typename Element>
inline void RepeatedField<Element>::Add(const Element& value) {
  if (current_size_ == total_size_) Reserve(total_size_ + 1);
  elements_[current_size_++] = value;
}

template <typename Element>
inline Element* RepeatedField<Element>::Add() {
  if (current_size_ == total_size_) Reserve(total_size_ + 1);
  return &elements_[current_size_++];
}

template <typename Element>
inline void RepeatedField<Element>::RemoveLast() {
  GOOGLE_DCHECK_GT(current_size_, 0);
  --current_size_;
}

template <typename Element>
void RepeatedField<Element>::ExtractSubrange(
    int start, int num, Element* elements) {
  GOOGLE_DCHECK_GE(start, 0);
  GOOGLE_DCHECK_GE(num, 0);
  GOOGLE_DCHECK_LE(start + num, this->size());

  // Save the values of the removed elements if requested.
  if (elements != NULL) {
    for (int i = 0; i < num; ++i)
      elements[i] = this->Get(i + start);
  }

  // Slide remaining elements down to fill the gap.
  if (num > 0) {
    for (int i = start + num; i < this->size(); ++i)
      this->Set(i - num, this->Get(i));
    this->Truncate(this->size() - num);
  }
}

template <typename Element>
inline void RepeatedField<Element>::Clear() {
  current_size_ = 0;
}

template <typename Element>
inline void RepeatedField<Element>::MergeFrom(const RepeatedField& other) {
  GOOGLE_CHECK_NE(&other, this);
  if (other.current_size_ != 0) {
    Reserve(current_size_ + other.current_size_);
    CopyArray(elements_ + current_size_, other.elements_, other.current_size_);
    current_size_ += other.current_size_;
  }
}

template <typename Element>
inline void RepeatedField<Element>::CopyFrom(const RepeatedField& other) {
  if (&other == this) return;
  Clear();
  MergeFrom(other);
}

template <typename Element>
inline Element* RepeatedField<Element>::mutable_data() {
  return elements_;
}

template <typename Element>
inline const Element* RepeatedField<Element>::data() const {
  return elements_;
}


template <typename Element>
void RepeatedField<Element>::Swap(RepeatedField* other) {
  if (this == other) return;
  Element* swap_elements     = elements_;
  int      swap_current_size = current_size_;
  int      swap_total_size   = total_size_;

  elements_     = other->elements_;
  current_size_ = other->current_size_;
  total_size_   = other->total_size_;

  other->elements_     = swap_elements;
  other->current_size_ = swap_current_size;
  other->total_size_   = swap_total_size;
}

template <typename Element>
void RepeatedField<Element>::SwapElements(int index1, int index2) {
  using std::swap;  // enable ADL with fallback
  swap(elements_[index1], elements_[index2]);
}

template <typename Element>
inline typename RepeatedField<Element>::iterator
RepeatedField<Element>::begin() {
  return elements_;
}
template <typename Element>
inline typename RepeatedField<Element>::const_iterator
RepeatedField<Element>::begin() const {
  return elements_;
}
template <typename Element>
inline typename RepeatedField<Element>::iterator
RepeatedField<Element>::end() {
  return elements_ + current_size_;
}
template <typename Element>
inline typename RepeatedField<Element>::const_iterator
RepeatedField<Element>::end() const {
  return elements_ + current_size_;
}

template <typename Element>
inline int RepeatedField<Element>::SpaceUsedExcludingSelf() const {
  return (elements_ != NULL) ? total_size_ * sizeof(elements_[0]) : 0;
}

// Avoid inlining of Reserve(): new, copy, and delete[] lead to a significant
// amount of code bloat.
template <typename Element>
void RepeatedField<Element>::Reserve(int new_size) {
  if (total_size_ >= new_size) return;

  Element* old_elements = elements_;
  total_size_ = max(google::protobuf::internal::kMinRepeatedFieldAllocationSize,
                    max(total_size_ * 2, new_size));
  elements_ = new Element[total_size_];
  if (old_elements != NULL) {
    MoveArray(elements_, old_elements, current_size_);
    delete [] old_elements;
  }
}

template <typename Element>
inline void RepeatedField<Element>::Truncate(int new_size) {
  GOOGLE_DCHECK_LE(new_size, current_size_);
  current_size_ = new_size;
}

template <typename Element>
inline void RepeatedField<Element>::MoveArray(
    Element to[], Element from[], int array_size) {
  CopyArray(to, from, array_size);
}

template <typename Element>
inline void RepeatedField<Element>::CopyArray(
    Element to[], const Element from[], int array_size) {
  internal::ElementCopier<Element>()(to, from, array_size);
}

namespace internal {

template <typename Element, bool HasTrivialCopy>
void ElementCopier<Element, HasTrivialCopy>::operator()(
    Element to[], const Element from[], int array_size) {
  std::copy(from, from + array_size, to);
}

template <typename Element>
struct ElementCopier<Element, true> {
  void operator()(Element to[], const Element from[], int array_size) {
    memcpy(to, from, array_size * sizeof(Element));
  }
};

}  // namespace internal


// -------------------------------------------------------------------

namespace internal {

inline RepeatedPtrFieldBase::RepeatedPtrFieldBase()
  : elements_(NULL),
    current_size_(0),
    allocated_size_(0),
    total_size_(kInitialSize) {
}

template <typename TypeHandler>
void RepeatedPtrFieldBase::Destroy() {
  for (int i = 0; i < allocated_size_; i++) {
    TypeHandler::Delete(cast<TypeHandler>(elements_[i]));
  }
  delete [] elements_;
}

inline bool RepeatedPtrFieldBase::empty() const {
  return current_size_ == 0;
}

inline int RepeatedPtrFieldBase::size() const {
  return current_size_;
}

template <typename TypeHandler>
inline const typename TypeHandler::Type&
RepeatedPtrFieldBase::Get(int index) const {
  GOOGLE_DCHECK_GE(index, 0);
  GOOGLE_DCHECK_LT(index, size());
  return *cast<TypeHandler>(elements_[index]);
}


template <typename TypeHandler>
inline typename TypeHandler::Type*
RepeatedPtrFieldBase::Mutable(int index) {
  GOOGLE_DCHECK_GE(index, 0);
  GOOGLE_DCHECK_LT(index, size());
  return cast<TypeHandler>(elements_[index]);
}

template <typename TypeHandler>
inline typename TypeHandler::Type* RepeatedPtrFieldBase::Add() {
  if (current_size_ < allocated_size_) {
    return cast<TypeHandler>(elements_[current_size_++]);
  }
  if (allocated_size_ == total_size_) Reserve(total_size_ + 1);
  typename TypeHandler::Type* result = TypeHandler::New();
  ++allocated_size_;
  elements_[current_size_++] = result;
  return result;
}

template <typename TypeHandler>
inline void RepeatedPtrFieldBase::RemoveLast() {
  GOOGLE_DCHECK_GT(current_size_, 0);
  TypeHandler::Clear(cast<TypeHandler>(elements_[--current_size_]));
}

template <typename TypeHandler>
void RepeatedPtrFieldBase::Clear() {
  for (int i = 0; i < current_size_; i++) {
    TypeHandler::Clear(cast<TypeHandler>(elements_[i]));
  }
  current_size_ = 0;
}

template <typename TypeHandler>
inline void RepeatedPtrFieldBase::MergeFrom(const RepeatedPtrFieldBase& other) {
  GOOGLE_CHECK_NE(&other, this);
  Reserve(current_size_ + other.current_size_);
  for (int i = 0; i < other.current_size_; i++) {
    TypeHandler::Merge(other.template Get<TypeHandler>(i), Add<TypeHandler>());
  }
}

template <typename TypeHandler>
inline void RepeatedPtrFieldBase::CopyFrom(const RepeatedPtrFieldBase& other) {
  if (&other == this) return;
  RepeatedPtrFieldBase::Clear<TypeHandler>();
  RepeatedPtrFieldBase::MergeFrom<TypeHandler>(other);
}

inline int RepeatedPtrFieldBase::Capacity() const {
  return total_size_;
}

inline void* const* RepeatedPtrFieldBase::raw_data() const {
  return elements_;
}

inline void** RepeatedPtrFieldBase::raw_mutable_data() const {
  return elements_;
}

template <typename TypeHandler>
inline typename TypeHandler::Type** RepeatedPtrFieldBase::mutable_data() {
  // TODO(kenton):  Breaks C++ aliasing rules.  We should probably remove this
  //   method entirely.
  return reinterpret_cast<typename TypeHandler::Type**>(elements_);
}

template <typename TypeHandler>
inline const typename TypeHandler::Type* const*
RepeatedPtrFieldBase::data() const {
  // TODO(kenton):  Breaks C++ aliasing rules.  We should probably remove this
  //   method entirely.
  return reinterpret_cast<const typename TypeHandler::Type* const*>(elements_);
}

inline void RepeatedPtrFieldBase::SwapElements(int index1, int index2) {
  using std::swap;  // enable ADL with fallback
  swap(elements_[index1], elements_[index2]);
}

template <typename TypeHandler>
inline int RepeatedPtrFieldBase::SpaceUsedExcludingSelf() const {
  int allocated_bytes =
      (elements_ != NULL) ? total_size_ * sizeof(elements_[0]) : 0;
  for (int i = 0; i < allocated_size_; ++i) {
    allocated_bytes += TypeHandler::SpaceUsed(*cast<TypeHandler>(elements_[i]));
  }
  return allocated_bytes;
}

template <typename TypeHandler>
inline typename TypeHandler::Type* RepeatedPtrFieldBase::AddFromCleared() {
  if (current_size_ < allocated_size_) {
    return cast<TypeHandler>(elements_[current_size_++]);
  } else {
    return NULL;
  }
}

template <typename TypeHandler>
void RepeatedPtrFieldBase::AddAllocated(
    typename TypeHandler::Type* value) {
  // Make room for the new pointer.
  if (current_size_ == total_size_) {
    // The array is completely full with no cleared objects, so grow it.
    Reserve(total_size_ + 1);
    ++allocated_size_;
  } else if (allocated_size_ == total_size_) {
    // There is no more space in the pointer array because it contains some
    // cleared objects awaiting reuse.  We don't want to grow the array in this
    // case because otherwise a loop calling AddAllocated() followed by Clear()
    // would leak memory.
    TypeHandler::Delete(cast<TypeHandler>(elements_[current_size_]));
  } else if (current_size_ < allocated_size_) {
    // We have some cleared objects.  We don't care about their order, so we
    // can just move the first one to the end to make space.
    elements_[allocated_size_] = elements_[current_size_];
    ++allocated_size_;
  } else {
    // There are no cleared objects.
    ++allocated_size_;
  }

  elements_[current_size_++] = value;
}

template <typename TypeHandler>
inline typename TypeHandler::Type* RepeatedPtrFieldBase::ReleaseLast() {
  GOOGLE_DCHECK_GT(current_size_, 0);
  typename TypeHandler::Type* result =
      cast<TypeHandler>(elements_[--current_size_]);
  --allocated_size_;
  if (current_size_ < allocated_size_) {
    // There are cleared elements on the end; replace the removed element
    // with the last allocated element.
    elements_[current_size_] = elements_[allocated_size_];
  }
  return result;
}

inline int RepeatedPtrFieldBase::ClearedCount() const {
  return allocated_size_ - current_size_;
}

template <typename TypeHandler>
inline void RepeatedPtrFieldBase::AddCleared(
    typename TypeHandler::Type* value) {
  if (allocated_size_ == total_size_) Reserve(total_size_ + 1);
  elements_[allocated_size_++] = value;
}

template <typename TypeHandler>
inline typename TypeHandler::Type* RepeatedPtrFieldBase::ReleaseCleared() {
  GOOGLE_DCHECK_GT(allocated_size_, current_size_);
  return cast<TypeHandler>(elements_[--allocated_size_]);
}

}  // namespace internal

// -------------------------------------------------------------------

template <typename Element>
class RepeatedPtrField<Element>::TypeHandler
    : public internal::GenericTypeHandler<Element> {
};

template <>
class RepeatedPtrField<string>::TypeHandler
    : public internal::StringTypeHandler {
};


template <typename Element>
inline RepeatedPtrField<Element>::RepeatedPtrField() {}

template <typename Element>
inline RepeatedPtrField<Element>::RepeatedPtrField(
    const RepeatedPtrField& other)
    : RepeatedPtrFieldBase() {
  CopyFrom(other);
}

template <typename Element>
template <typename Iter>
inline RepeatedPtrField<Element>::RepeatedPtrField(
    Iter begin, const Iter& end) {
  int reserve = internal::CalculateReserve(begin, end);
  if (reserve != -1) {
    Reserve(reserve);
  }
  for (; begin != end; ++begin) {
    *Add() = *begin;
  }
}

template <typename Element>
RepeatedPtrField<Element>::~RepeatedPtrField() {
  Destroy<TypeHandler>();
}

template <typename Element>
inline RepeatedPtrField<Element>& RepeatedPtrField<Element>::operator=(
    const RepeatedPtrField& other) {
  if (this != &other)
    CopyFrom(other);
  return *this;
}

template <typename Element>
inline bool RepeatedPtrField<Element>::empty() const {
  return RepeatedPtrFieldBase::empty();
}

template <typename Element>
inline int RepeatedPtrField<Element>::size() const {
  return RepeatedPtrFieldBase::size();
}

template <typename Element>
inline const Element& RepeatedPtrField<Element>::Get(int index) const {
  return RepeatedPtrFieldBase::Get<TypeHandler>(index);
}


template <typename Element>
inline Element* RepeatedPtrField<Element>::Mutable(int index) {
  return RepeatedPtrFieldBase::Mutable<TypeHandler>(index);
}

template <typename Element>
inline Element* RepeatedPtrField<Element>::Add() {
  return RepeatedPtrFieldBase::Add<TypeHandler>();
}

template <typename Element>
inline void RepeatedPtrField<Element>::RemoveLast() {
  RepeatedPtrFieldBase::RemoveLast<TypeHandler>();
}

template <typename Element>
inline void RepeatedPtrField<Element>::DeleteSubrange(int start, int num) {
  GOOGLE_DCHECK_GE(start, 0);
  GOOGLE_DCHECK_GE(num, 0);
  GOOGLE_DCHECK_LE(start + num, size());
  for (int i = 0; i < num; ++i)
    delete RepeatedPtrFieldBase::Mutable<TypeHandler>(start + i);
  ExtractSubrange(start, num, NULL);
}

template <typename Element>
inline void RepeatedPtrField<Element>::ExtractSubrange(
    int start, int num, Element** elements) {
  GOOGLE_DCHECK_GE(start, 0);
  GOOGLE_DCHECK_GE(num, 0);
  GOOGLE_DCHECK_LE(start + num, size());

  if (num > 0) {
    // Save the values of the removed elements if requested.
    if (elements != NULL) {
      for (int i = 0; i < num; ++i)
        elements[i] = RepeatedPtrFieldBase::Mutable<TypeHandler>(i + start);
    }
    CloseGap(start, num);
  }
}

template <typename Element>
inline void RepeatedPtrField<Element>::Clear() {
  RepeatedPtrFieldBase::Clear<TypeHandler>();
}

template <typename Element>
inline void RepeatedPtrField<Element>::MergeFrom(
    const RepeatedPtrField& other) {
  RepeatedPtrFieldBase::MergeFrom<TypeHandler>(other);
}

template <typename Element>
inline void RepeatedPtrField<Element>::CopyFrom(
    const RepeatedPtrField& other) {
  RepeatedPtrFieldBase::CopyFrom<TypeHandler>(other);
}

template <typename Element>
inline Element** RepeatedPtrField<Element>::mutable_data() {
  return RepeatedPtrFieldBase::mutable_data<TypeHandler>();
}

template <typename Element>
inline const Element* const* RepeatedPtrField<Element>::data() const {
  return RepeatedPtrFieldBase::data<TypeHandler>();
}

template <typename Element>
void RepeatedPtrField<Element>::Swap(RepeatedPtrField* other) {
  RepeatedPtrFieldBase::Swap(other);
}

template <typename Element>
void RepeatedPtrField<Element>::SwapElements(int index1, int index2) {
  RepeatedPtrFieldBase::SwapElements(index1, index2);
}

template <typename Element>
inline int RepeatedPtrField<Element>::SpaceUsedExcludingSelf() const {
  return RepeatedPtrFieldBase::SpaceUsedExcludingSelf<TypeHandler>();
}

template <typename Element>
inline void RepeatedPtrField<Element>::AddAllocated(Element* value) {
  RepeatedPtrFieldBase::AddAllocated<TypeHandler>(value);
}

template <typename Element>
inline Element* RepeatedPtrField<Element>::ReleaseLast() {
  return RepeatedPtrFieldBase::ReleaseLast<TypeHandler>();
}


template <typename Element>
inline int RepeatedPtrField<Element>::ClearedCount() const {
  return RepeatedPtrFieldBase::ClearedCount();
}

template <typename Element>
inline void RepeatedPtrField<Element>::AddCleared(Element* value) {
  return RepeatedPtrFieldBase::AddCleared<TypeHandler>(value);
}

template <typename Element>
inline Element* RepeatedPtrField<Element>::ReleaseCleared() {
  return RepeatedPtrFieldBase::ReleaseCleared<TypeHandler>();
}

template <typename Element>
inline void RepeatedPtrField<Element>::Reserve(int new_size) {
  return RepeatedPtrFieldBase::Reserve(new_size);
}

template <typename Element>
inline int RepeatedPtrField<Element>::Capacity() const {
  return RepeatedPtrFieldBase::Capacity();
}

// -------------------------------------------------------------------

namespace internal {

// STL-like iterator implementation for RepeatedPtrField.  You should not
// refer to this class directly; use RepeatedPtrField<T>::iterator instead.
//
// The iterator for RepeatedPtrField<T>, RepeatedPtrIterator<T>, is
// very similar to iterator_ptr<T**> in util/gtl/iterator_adaptors.h,
// but adds random-access operators and is modified to wrap a void** base
// iterator (since RepeatedPtrField stores its array as a void* array and
// casting void** to T** would violate C++ aliasing rules).
//
// This code based on net/proto/proto-array-internal.h by Jeffrey Yasskin
// (jyasskin@google.com).
template<typename Element>
class RepeatedPtrIterator
    : public std::iterator<
          std::random_access_iterator_tag, Element> {
 public:
  typedef RepeatedPtrIterator<Element> iterator;
  typedef std::iterator<
          std::random_access_iterator_tag, Element> superclass;

  // Shadow the value_type in std::iterator<> because const_iterator::value_type
  // needs to be T, not const T.
  typedef typename remove_const<Element>::type value_type;

  // Let the compiler know that these are type names, so we don't have to
  // write "typename" in front of them everywhere.
  typedef typename superclass::reference reference;
  typedef typename superclass::pointer pointer;
  typedef typename superclass::difference_type difference_type;

  RepeatedPtrIterator() : it_(NULL) {}
  explicit RepeatedPtrIterator(void* const* it) : it_(it) {}

  // Allow "upcasting" from RepeatedPtrIterator<T**> to
  // RepeatedPtrIterator<const T*const*>.
  template<typename OtherElement>
  RepeatedPtrIterator(const RepeatedPtrIterator<OtherElement>& other)
      : it_(other.it_) {
    // Force a compiler error if the other type is not convertible to ours.
    if (false) {
      implicit_cast<Element*, OtherElement*>(0);
    }
  }

  // dereferenceable
  reference operator*() const { return *reinterpret_cast<Element*>(*it_); }
  pointer   operator->() const { return &(operator*()); }

  // {inc,dec}rementable
  iterator& operator++() { ++it_; return *this; }
  iterator  operator++(int) { return iterator(it_++); }
  iterator& operator--() { --it_; return *this; }
  iterator  operator--(int) { return iterator(it_--); }

  // equality_comparable
  bool operator==(const iterator& x) const { return it_ == x.it_; }
  bool operator!=(const iterator& x) const { return it_ != x.it_; }

  // less_than_comparable
  bool operator<(const iterator& x) const { return it_ < x.it_; }
  bool operator<=(const iterator& x) const { return it_ <= x.it_; }
  bool operator>(const iterator& x) const { return it_ > x.it_; }
  bool operator>=(const iterator& x) const { return it_ >= x.it_; }

  // addable, subtractable
  iterator& operator+=(difference_type d) {
    it_ += d;
    return *this;
  }
  friend iterator operator+(iterator it, difference_type d) {
    it += d;
    return it;
  }
  friend iterator operator+(difference_type d, iterator it) {
    it += d;
    return it;
  }
  iterator& operator-=(difference_type d) {
    it_ -= d;
    return *this;
  }
  friend iterator operator-(iterator it, difference_type d) {
    it -= d;
    return it;
  }

  // indexable
  reference operator[](difference_type d) const { return *(*this + d); }

  // random access iterator
  difference_type operator-(const iterator& x) const { return it_ - x.it_; }

 private:
  template<typename OtherElement>
  friend class RepeatedPtrIterator;

  // The internal iterator.
  void* const* it_;
};

// Provide an iterator that operates on pointers to the underlying objects
// rather than the objects themselves as RepeatedPtrIterator does.
// Consider using this when working with stl algorithms that change
// the array.
// The VoidPtr template parameter holds the type-agnostic pointer value
// referenced by the iterator.  It should either be "void *" for a mutable
// iterator, or "const void *" for a constant iterator.
template<typename Element, typename VoidPtr>
class RepeatedPtrOverPtrsIterator
    : public std::iterator<std::random_access_iterator_tag, Element*> {
 public:
  typedef RepeatedPtrOverPtrsIterator<Element, VoidPtr> iterator;
  typedef std::iterator<
          std::random_access_iterator_tag, Element*> superclass;

  // Shadow the value_type in std::iterator<> because const_iterator::value_type
  // needs to be T, not const T.
  typedef typename remove_const<Element*>::type value_type;

  // Let the compiler know that these are type names, so we don't have to
  // write "typename" in front of them everywhere.
  typedef typename superclass::reference reference;
  typedef typename superclass::pointer pointer;
  typedef typename superclass::difference_type difference_type;

  RepeatedPtrOverPtrsIterator() : it_(NULL) {}
  explicit RepeatedPtrOverPtrsIterator(VoidPtr* it) : it_(it) {}

  // dereferenceable
  reference operator*() const { return *reinterpret_cast<Element**>(it_); }
  pointer   operator->() const { return &(operator*()); }

  // {inc,dec}rementable
  iterator& operator++() { ++it_; return *this; }
  iterator  operator++(int) { return iterator(it_++); }
  iterator& operator--() { --it_; return *this; }
  iterator  operator--(int) { return iterator(it_--); }

  // equality_comparable
  bool operator==(const iterator& x) const { return it_ == x.it_; }
  bool operator!=(const iterator& x) const { return it_ != x.it_; }

  // less_than_comparable
  bool operator<(const iterator& x) const { return it_ < x.it_; }
  bool operator<=(const iterator& x) const { return it_ <= x.it_; }
  bool operator>(const iterator& x) const { return it_ > x.it_; }
  bool operator>=(const iterator& x) const { return it_ >= x.it_; }

  // addable, subtractable
  iterator& operator+=(difference_type d) {
    it_ += d;
    return *this;
  }
  friend iterator operator+(iterator it, difference_type d) {
    it += d;
    return it;
  }
  friend iterator operator+(difference_type d, iterator it) {
    it += d;
    return it;
  }
  iterator& operator-=(difference_type d) {
    it_ -= d;
    return *this;
  }
  friend iterator operator-(iterator it, difference_type d) {
    it -= d;
    return it;
  }

  // indexable
  reference operator[](difference_type d) const { return *(*this + d); }

  // random access iterator
  difference_type operator-(const iterator& x) const { return it_ - x.it_; }

 private:
  template<typename OtherElement>
  friend class RepeatedPtrIterator;

  // The internal iterator.
  VoidPtr* it_;
};

}  // namespace internal

template <typename Element>
inline typename RepeatedPtrField<Element>::iterator
RepeatedPtrField<Element>::begin() {
  return iterator(raw_data());
}
template <typename Element>
inline typename RepeatedPtrField<Element>::const_iterator
RepeatedPtrField<Element>::begin() const {
  return iterator(raw_data());
}
template <typename Element>
inline typename RepeatedPtrField<Element>::iterator
RepeatedPtrField<Element>::end() {
  return iterator(raw_data() + size());
}
template <typename Element>
inline typename RepeatedPtrField<Element>::const_iterator
RepeatedPtrField<Element>::end() const {
  return iterator(raw_data() + size());
}

template <typename Element>
inline typename RepeatedPtrField<Element>::pointer_iterator
RepeatedPtrField<Element>::pointer_begin() {
  return pointer_iterator(raw_mutable_data());
}
template <typename Element>
inline typename RepeatedPtrField<Element>::const_pointer_iterator
RepeatedPtrField<Element>::pointer_begin() const {
  return const_pointer_iterator(const_cast<const void**>(raw_mutable_data()));
}
template <typename Element>
inline typename RepeatedPtrField<Element>::pointer_iterator
RepeatedPtrField<Element>::pointer_end() {
  return pointer_iterator(raw_mutable_data() + size());
}
template <typename Element>
inline typename RepeatedPtrField<Element>::const_pointer_iterator
RepeatedPtrField<Element>::pointer_end() const {
  return const_pointer_iterator(
      const_cast<const void**>(raw_mutable_data() + size()));
}


// Iterators and helper functions that follow the spirit of the STL
// std::back_insert_iterator and std::back_inserter but are tailor-made
// for RepeatedField and RepatedPtrField. Typical usage would be:
//
//   std::copy(some_sequence.begin(), some_sequence.end(),
//             google::protobuf::RepeatedFieldBackInserter(proto.mutable_sequence()));
//
// Ported by johannes from util/gtl/proto-array-iterators.h

namespace internal {
// A back inserter for RepeatedField objects.
template<typename T> class RepeatedFieldBackInsertIterator
    : public std::iterator<std::output_iterator_tag, T> {
 public:
  explicit RepeatedFieldBackInsertIterator(
      RepeatedField<T>* const mutable_field)
      : field_(mutable_field) {
  }
  RepeatedFieldBackInsertIterator<T>& operator=(const T& value) {
    field_->Add(value);
    return *this;
  }
  RepeatedFieldBackInsertIterator<T>& operator*() {
    return *this;
  }
  RepeatedFieldBackInsertIterator<T>& operator++() {
    return *this;
  }
  RepeatedFieldBackInsertIterator<T>& operator++(int /* unused */) {
    return *this;
  }

 private:
  RepeatedField<T>* field_;
};

// A back inserter for RepeatedPtrField objects.
template<typename T> class RepeatedPtrFieldBackInsertIterator
    : public std::iterator<std::output_iterator_tag, T> {
 public:
  RepeatedPtrFieldBackInsertIterator(
      RepeatedPtrField<T>* const mutable_field)
      : field_(mutable_field) {
  }
  RepeatedPtrFieldBackInsertIterator<T>& operator=(const T& value) {
    *field_->Add() = value;
    return *this;
  }
  RepeatedPtrFieldBackInsertIterator<T>& operator=(
      const T* const ptr_to_value) {
    *field_->Add() = *ptr_to_value;
    return *this;
  }
  RepeatedPtrFieldBackInsertIterator<T>& operator*() {
    return *this;
  }
  RepeatedPtrFieldBackInsertIterator<T>& operator++() {
    return *this;
  }
  RepeatedPtrFieldBackInsertIterator<T>& operator++(int /* unused */) {
    return *this;
  }

 private:
  RepeatedPtrField<T>* field_;
};

// A back inserter for RepeatedPtrFields that inserts by transfering ownership
// of a pointer.
template<typename T> class AllocatedRepeatedPtrFieldBackInsertIterator
    : public std::iterator<std::output_iterator_tag, T> {
 public:
  explicit AllocatedRepeatedPtrFieldBackInsertIterator(
      RepeatedPtrField<T>* const mutable_field)
      : field_(mutable_field) {
  }
  AllocatedRepeatedPtrFieldBackInsertIterator<T>& operator=(
      T* const ptr_to_value) {
    field_->AddAllocated(ptr_to_value);
    return *this;
  }
  AllocatedRepeatedPtrFieldBackInsertIterator<T>& operator*() {
    return *this;
  }
  AllocatedRepeatedPtrFieldBackInsertIterator<T>& operator++() {
    return *this;
  }
  AllocatedRepeatedPtrFieldBackInsertIterator<T>& operator++(
      int /* unused */) {
    return *this;
  }

 private:
  RepeatedPtrField<T>* field_;
};
}  // namespace internal

// Provides a back insert iterator for RepeatedField instances,
// similar to std::back_inserter().
template<typename T> internal::RepeatedFieldBackInsertIterator<T>
RepeatedFieldBackInserter(RepeatedField<T>* const mutable_field) {
  return internal::RepeatedFieldBackInsertIterator<T>(mutable_field);
}

// Provides a back insert iterator for RepeatedPtrField instances,
// similar to std::back_inserter().
template<typename T> internal::RepeatedPtrFieldBackInsertIterator<T>
RepeatedPtrFieldBackInserter(RepeatedPtrField<T>* const mutable_field) {
  return internal::RepeatedPtrFieldBackInsertIterator<T>(mutable_field);
}

// Special back insert iterator for RepeatedPtrField instances, just in
// case someone wants to write generic template code that can access both
// RepeatedFields and RepeatedPtrFields using a common name.
template<typename T> internal::RepeatedPtrFieldBackInsertIterator<T>
RepeatedFieldBackInserter(RepeatedPtrField<T>* const mutable_field) {
  return internal::RepeatedPtrFieldBackInsertIterator<T>(mutable_field);
}

// Provides a back insert iterator for RepeatedPtrField instances
// similar to std::back_inserter() which transfers the ownership while
// copying elements.
template<typename T> internal::AllocatedRepeatedPtrFieldBackInsertIterator<T>
AllocatedRepeatedPtrFieldBackInserter(
    RepeatedPtrField<T>* const mutable_field) {
  return internal::AllocatedRepeatedPtrFieldBackInsertIterator<T>(
      mutable_field);
}

}  // namespace protobuf

}  // namespace google
#endif  // GOOGLE_PROTOBUF_REPEATED_FIELD_H__