// Copyright (c) 2005, Google Inc.
// All rights reserved.
// 
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// 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.
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// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
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// this software without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// 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: Craig Silverstein
//
// This is just a very thin wrapper over densehashtable.h, just
// like sgi stl's stl_hash_map is a very thin wrapper over
// stl_hashtable.  The major thing we define is operator[], because
// we have a concept of a data_type which stl_hashtable doesn't
// (it only has a key and a value).
//
// NOTE: this is exactly like sparse_hash_map.h, with the word
// "sparse" replaced by "dense", except for the addition of
// set_empty_key().
//
//   YOU MUST CALL SET_EMPTY_KEY() IMMEDIATELY AFTER CONSTRUCTION.
//
// Otherwise your program will die in mysterious ways.
//
// In other respects, we adhere mostly to the STL semantics for
// hash-map.  One important exception is that insert() invalidates
// iterators entirely.  On the plus side, though, erase() doesn't
// invalidate iterators at all, or even change the ordering of elements.
//
// Here are a few "power user" tips:
//
//    1) set_deleted_key():
//         If you want to use erase() you must call set_deleted_key(),
//         in addition to set_empty_key(), after construction.
//         The deleted and empty keys must differ.
//
//    2) resize(0):
//         When an item is deleted, its memory isn't freed right
//         away.  This allows you to iterate over a hashtable,
//         and call erase(), without invalidating the iterator.
//         To force the memory to be freed, call resize(0).
//
// Guide to what kind of hash_map to use:
//   (1) dense_hash_map: fastest, uses the most memory
//   (2) sparse_hash_map: slowest, uses the least memory
//   (3) hash_map (STL): in the middle
// Typically I use sparse_hash_map when I care about space and/or when
// I need to save the hashtable on disk.  I use hash_map otherwise.  I
// don't personally use dense_hash_map ever; the only use of
// dense_hash_map I know of is to work around malloc() bugs in some
// systems (dense_hash_map has a particularly simple allocation scheme).
//
// - dense_hash_map has, typically, a factor of 2 memory overhead (if your
//   data takes up X bytes, the hash_map uses X more bytes in overhead).
// - sparse_hash_map has about 2 bits overhead per entry.
// - sparse_hash_map can be 3-7 times slower than the others for lookup and,
//   especially, inserts.  See time_hash_map.cc for details.
//
// See /usr/(local/)?doc/sparsehash-0.1/dense_hash_map.html
// for information about how to use this class.

#ifndef _DENSE_HASH_MAP_H_
#define _DENSE_HASH_MAP_H_

#include <google/sparsehash/sparseconfig.h>
#include <stdio.h>                   // for FILE * in read()/write()
#include <algorithm>                 // for the default template args
#include <functional>                // for equal_to
#include <memory>                    // for alloc<>
#include <utility>                   // for pair<>
#include HASH_FUN_H                  // defined in config.h
#include <google/sparsehash/densehashtable.h>


_START_GOOGLE_NAMESPACE_

using STL_NAMESPACE::pair;

template <class Key, class T,
          class HashFcn = HASH_NAMESPACE::hash<Key>,
          class EqualKey = STL_NAMESPACE::equal_to<Key>,
          class Alloc = STL_NAMESPACE::allocator<T> >
class dense_hash_map {
 private:
  // Apparently select1st is not stl-standard, so we define our own
  struct SelectKey {
    const Key& operator()(const pair<const Key, T>& p) const {
      return p.first;
    }
  };

  // The actual data
  typedef dense_hashtable<pair<const Key, T>, Key, HashFcn,
                          SelectKey, EqualKey, Alloc> ht;
  ht rep;

 public:
  typedef typename ht::key_type key_type;
  typedef T data_type;
  typedef T mapped_type;
  typedef typename ht::value_type value_type;
  typedef typename ht::hasher hasher;
  typedef typename ht::key_equal key_equal;

  typedef typename ht::size_type size_type;
  typedef typename ht::difference_type difference_type;
  typedef typename ht::pointer pointer;
  typedef typename ht::const_pointer const_pointer;
  typedef typename ht::reference reference;
  typedef typename ht::const_reference const_reference;

  typedef typename ht::iterator iterator;
  typedef typename ht::const_iterator const_iterator;

  // Iterator functions
  iterator begin()                    { return rep.begin(); }
  iterator end()                      { return rep.end(); }
  const_iterator begin() const        { return rep.begin(); }
  const_iterator end() const          { return rep.end(); }


  // Accessor functions
  hasher hash_funct() const { return rep.hash_funct(); }
  key_equal key_eq() const  { return rep.key_eq(); }


  // Constructors
  explicit dense_hash_map(size_type n = 0,
                          const hasher& hf = hasher(),
                          const key_equal& eql = key_equal())
    : rep(n, hf, eql) { }

  template <class InputIterator>
  dense_hash_map(InputIterator f, InputIterator l,
                 size_type n = 0,
                 const hasher& hf = hasher(),
                 const key_equal& eql = key_equal()) {
    rep.insert(f, l);
  }
  // We use the default copy constructor
  // We use the default operator=()
  // We use the default destructor

  void clear()                        { rep.clear(); }
  // This clears the hash map without resizing it down to the minimum
  // bucket count, but rather keeps the number of buckets constant
  void clear_no_resize()              { rep.clear_no_resize(); }
  void swap(dense_hash_map& hs)       { rep.swap(hs.rep); }


  // Functions concerning size
  size_type size() const              { return rep.size(); }
  size_type max_size() const          { return rep.max_size(); }
  bool empty() const                  { return rep.empty(); }
  size_type bucket_count() const      { return rep.bucket_count(); }
  size_type max_bucket_count() const  { return rep.max_bucket_count(); }

  void resize(size_type hint)         { rep.resize(hint); }


  // Lookup routines
  iterator find(const key_type& key)                 { return rep.find(key); }
  const_iterator find(const key_type& key) const     { return rep.find(key); }

  data_type& operator[](const key_type& key) {       // This is our value-add!
    iterator it = find(key);
    if (it != end()) {
      return it->second;
    } else {
      return insert(value_type(key, data_type())).first->second;
    }
  }

  size_type count(const key_type& key) const         { return rep.count(key); }

  pair<iterator, iterator> equal_range(const key_type& key) {
    return rep.equal_range(key);
  }
  pair<const_iterator, const_iterator> equal_range(const key_type& key) const {
    return rep.equal_range(key);
  }

  // Insertion routines
  pair<iterator, bool> insert(const value_type& obj) { return rep.insert(obj); }
  template <class InputIterator>
  void insert(InputIterator f, InputIterator l)      { rep.insert(f, l); }
  void insert(const_iterator f, const_iterator l)    { rep.insert(f, l); }
  // required for std::insert_iterator; the passed-in iterator is ignored
  iterator insert(iterator, const value_type& obj)   { return insert(obj).first; }


  // Deletion and empty routines
  // THESE ARE NON-STANDARD!  I make you specify an "impossible" key
  // value to identify deleted and empty buckets.  You can change the
  // deleted key as time goes on, or get rid of it entirely to be insert-only.
  void set_empty_key(const key_type& key)   {           // YOU MUST CALL THIS!
    rep.set_empty_key(value_type(key, data_type()));    // rep wants a value
  }
  void set_deleted_key(const key_type& key)   {
    rep.set_deleted_key(value_type(key, data_type()));  // rep wants a value
  }
  void clear_deleted_key()                    { rep.clear_deleted_key(); }

  // These are standard
  size_type erase(const key_type& key)               { return rep.erase(key); }
  void erase(iterator it)                            { rep.erase(it); }
  void erase(iterator f, iterator l)                 { rep.erase(f, l); }


  // Comparison
  bool operator==(const dense_hash_map& hs) const    { return rep == hs.rep; }
  bool operator!=(const dense_hash_map& hs) const    { return rep != hs.rep; }


  // I/O -- this is an add-on for writing metainformation to disk
  bool write_metadata(FILE *fp)       { return rep.write_metadata(fp); }
  bool read_metadata(FILE *fp)        { return rep.read_metadata(fp); }
  bool write_nopointer_data(FILE *fp) { return rep.write_nopointer_data(fp); }
  bool read_nopointer_data(FILE *fp)  { return rep.read_nopointer_data(fp); }
};

// We need a global swap as well
template <class Key, class T, class HashFcn, class EqualKey, class Alloc>
inline void swap(dense_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm1,
                 dense_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm2) {
  hm1.swap(hm2);
}

_END_GOOGLE_NAMESPACE_

#endif /* _DENSE_HASH_MAP_H_ */
