Class FlatMap

tensorflow/core/lib/gtl/flatmap.h:39–388

template <typename Key, typename Val, class Hash = hash<Key>,
          class Eq = std::equal_to<Key>>
class FlatMap {
 private:
  // Forward declare some internal types needed in public section.
  struct Bucket;

  // We cannot use std::pair<> since internal representation stores
  // keys and values in separate arrays, so we make a custom struct
  // that holds references to the internal key, value elements.
  //
  // We define the struct as private ValueType, and typedef it as public
  // value_type, to work around a gcc bug when compiling the iterators.
  struct ValueType {
    typedef Key first_type;
    typedef Val second_type;

    const Key& first;
    Val& second;
    ValueType(const Key& k, Val& v) : first(k), second(v) {}
  };

 public:
  typedef Key key_type;
  typedef Val mapped_type;
  typedef Hash hasher;
  typedef Eq key_equal;
  typedef size_t size_type;
  typedef ptrdiff_t difference_type;
  typedef ValueType value_type;
  typedef value_type* pointer;
  typedef const value_type* const_pointer;
  typedef value_type& reference;
  typedef const value_type& const_reference;

  FlatMap() : FlatMap(1) {}

  explicit FlatMap(size_t N, const Hash& hf = Hash(), const Eq& eq = Eq())
      : rep_(N, hf, eq) {}

  FlatMap(const FlatMap& src) : rep_(src.rep_) {}

  // Move constructor leaves src in a valid but unspecified state (same as
  // std::unordered_map).
  FlatMap(FlatMap&& src) : rep_(std::move(src.rep_)) {}

  template <typename InputIter>
  FlatMap(InputIter first, InputIter last, size_t N = 1,
          const Hash& hf = Hash(), const Eq& eq = Eq())
      : FlatMap(N, hf, eq) {
    insert(first, last);
  }

  FlatMap(std::initializer_list<std::pair<const Key, Val>> init, size_t N = 1,
          const Hash& hf = Hash(), const Eq& eq = Eq())
      : FlatMap(init.begin(), init.end(), N, hf, eq) {}

  FlatMap& operator=(const FlatMap& src) {
    rep_.CopyFrom(src.rep_);
    return *this;