Use google dense hash table instead of std::map in BindingManager.

Reviewed by Marcelo Lira <marcelo.lira@openbossa.org>

5 files changed, 1937 insertions, 0 deletions

diff --git a/ext/sparsehash/google/dense_hash_map b/ext/sparsehash/google/dense_hash_map
new file mode 100644
index 000000000..09b0c4428
--- /dev/null
+++ b/ext/sparsehash/google/dense_hash_map
@@ -0,0 +1,310 @@
+// Copyright (c) 2005, Google Inc.
+// All rights reserved.
+//
+// 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: 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).
+//         For tr1 compatibility, this can also be called as rehash(0).
+//
+//    3) min_load_factor(0.0)
+//         Setting the minimum load factor to 0.0 guarantees that
+//         the hash table will never shrink.
+//
+// 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_set ever; some people use it for
+// small sets with lots of lookups.
+//
+// - 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-*/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 = SPARSEHASH_HASH<Key>,   // defined in sparseconfig.h
+          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;
+    }
+  };
+  struct SetKey {
+    void operator()(pair<const Key, T>* value, const Key& new_key) const {
+      *const_cast<Key*>(&value->first) = new_key;
+      // It would be nice to clear the rest of value here as well, in
+      // case it's taking up a lot of memory.  We do this by clearing
+      // the value.  This assumes T has a zero-arg constructor!
+      value->second = T();
+    }
+  };
+
+  // The actual data
+  typedef dense_hashtable<pair<const Key, T>, Key, HashFcn,
+                          SelectKey, SetKey, 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 Alloc allocator_type;
+
+  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;
+  typedef typename ht::local_iterator local_iterator;
+  typedef typename ht::const_local_iterator const_local_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(); }
+
+
+  // These come from tr1's unordered_map. For us, a bucket has 0 or 1 elements.
+  local_iterator begin(size_type i)              { return rep.begin(i); }
+  local_iterator end(size_type i)                { return rep.end(i); }
+  const_local_iterator begin(size_type i) const  { return rep.begin(i); }
+  const_local_iterator end(size_type i) const    { return rep.end(i); }
+
+  // Accessor functions
+  // TODO(csilvers): implement Alloc get_allocator() const;
+  hasher hash_funct() const                      { return rep.hash_funct(); }
+  hasher hash_function() const                   { return hash_funct(); }
+  key_equal key_eq() const                       { return rep.key_eq(); }
+
+
+  // Constructors
+  explicit dense_hash_map(size_type expected_max_items_in_table = 0,
+                          const hasher& hf = hasher(),
+                          const key_equal& eql = key_equal())
+    : rep(expected_max_items_in_table, hf, eql) { }
+
+  template <class InputIterator>
+  dense_hash_map(InputIterator f, InputIterator l,
+                 size_type expected_max_items_in_table = 0,
+                 const hasher& hf = hasher(),
+                 const key_equal& eql = key_equal())
+    : rep(expected_max_items_in_table, hf, eql) {
+    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(); }
+
+  // These are tr1 methods.  bucket() is the bucket the key is or would be in.
+  size_type bucket_size(size_type i) const    { return rep.bucket_size(i); }
+  size_type bucket(const key_type& key) const { return rep.bucket(key); }
+  float load_factor() const {
+    return size() * 1.0f / bucket_count();
+  }
+  float max_load_factor() const {
+    float shrink, grow;
+    rep.get_resizing_parameters(&shrink, &grow);
+    return grow;
+  }
+  void max_load_factor(float new_grow) {
+    float shrink, grow;
+    rep.get_resizing_parameters(&shrink, &grow);
+    rep.set_resizing_parameters(shrink, new_grow);
+  }
+  // These aren't tr1 methods but perhaps ought to be.
+  float min_load_factor() const {
+    float shrink, grow;
+    rep.get_resizing_parameters(&shrink, &grow);
+    return shrink;
+  }
+  void min_load_factor(float new_shrink) {
+    float shrink, grow;
+    rep.get_resizing_parameters(&shrink, &grow);
+    rep.set_resizing_parameters(new_shrink, grow);
+  }
+  // Deprecated; use min_load_factor() or max_load_factor() instead.
+  void set_resizing_parameters(float shrink, float grow) {
+    return rep.set_resizing_parameters(shrink, grow);
+  }
+
+  void resize(size_type hint)         { rep.resize(hint); }
+  void rehash(size_type hint)         { resize(hint); }      // the tr1 name
+
+  // 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(key);
+  }
+  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_ */
diff --git a/ext/sparsehash/google/dense_hash_set b/ext/sparsehash/google/dense_hash_set
new file mode 100644
index 000000000..faa21dc59
--- /dev/null
+++ b/ext/sparsehash/google/dense_hash_set
@@ -0,0 +1,287 @@
+// Copyright (c) 2005, Google Inc.
+// All rights reserved.
+//
+// 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: Craig Silverstein
+//
+// This is just a very thin wrapper over densehashtable.h, just
+// like sgi stl's stl_hash_set 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).
+//
+// This is more different from dense_hash_map than you might think,
+// because all iterators for sets are const (you obviously can't
+// change the key, and for sets there is no value).
+//
+// NOTE: this is exactly like sparse_hash_set.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-set.  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).
+//         For tr1 compatibility, this can also be called as rehash(0).
+//
+//    3) min_load_factor(0.0)
+//         Setting the minimum load factor to 0.0 guarantees that
+//         the hash table will never shrink.
+//
+// Guide to what kind of hash_set to use:
+//   (1) dense_hash_set: fastest, uses the most memory
+//   (2) sparse_hash_set: slowest, uses the least memory
+//   (3) hash_set (STL): in the middle
+// Typically I use sparse_hash_set when I care about space and/or when
+// I need to save the hashtable on disk.  I use hash_set otherwise.  I
+// don't personally use dense_hash_set ever; some people use it for
+// small sets with lots of lookups.
+//
+// - dense_hash_set has, typically, a factor of 2 memory overhead (if your
+//   data takes up X bytes, the hash_set uses X more bytes in overhead).
+// - sparse_hash_set 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-*/dense_hash_set.html
+// for information about how to use this class.
+
+#ifndef _DENSE_HASH_SET_H_
+#define _DENSE_HASH_SET_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 Value,
+          class HashFcn = SPARSEHASH_HASH<Value>,  // defined in sparseconfig.h
+          class EqualKey = STL_NAMESPACE::equal_to<Value>,
+          class Alloc = STL_NAMESPACE::allocator<Value> >
+class dense_hash_set {
+ private:
+  // Apparently identity is not stl-standard, so we define our own
+  struct Identity {
+    Value& operator()(Value& v) const { return v; }
+    const Value& operator()(const Value& v) const { return v; }
+  };
+  struct SetKey {
+    void operator()(Value* value, const Value& new_key) const {
+      *value = new_key;
+    }
+  };
+
+  // The actual data
+  typedef dense_hashtable<Value, Value, HashFcn,
+                          Identity, SetKey, EqualKey, Alloc> ht;
+  ht rep;
+
+ public:
+  typedef typename ht::key_type key_type;
+  typedef typename ht::value_type value_type;
+  typedef typename ht::hasher hasher;
+  typedef typename ht::key_equal key_equal;
+  typedef Alloc allocator_type;
+
+  typedef typename ht::size_type size_type;
+  typedef typename ht::difference_type difference_type;
+  typedef typename ht::const_pointer pointer;
+  typedef typename ht::const_pointer const_pointer;
+  typedef typename ht::const_reference reference;
+  typedef typename ht::const_reference const_reference;
+
+  typedef typename ht::const_iterator iterator;
+  typedef typename ht::const_iterator const_iterator;
+  typedef typename ht::const_local_iterator local_iterator;
+  typedef typename ht::const_local_iterator const_local_iterator;
+
+
+  // Iterator functions -- recall all iterators are const
+  iterator begin() const                  { return rep.begin(); }
+  iterator end() const                    { return rep.end(); }
+
+  // These come from tr1's unordered_set. For us, a bucket has 0 or 1 elements.
+  local_iterator begin(size_type i) const { return rep.begin(i); }
+  local_iterator end(size_type i) const   { return rep.end(i); }
+
+
+  // Accessor functions
+  hasher hash_funct() const               { return rep.hash_funct(); }
+  key_equal key_eq() const                { return rep.key_eq(); }
+
+
+  // Constructors
+  explicit dense_hash_set(size_type expected_max_items_in_table = 0,
+                          const hasher& hf = hasher(),
+                          const key_equal& eql = key_equal())
+    : rep(expected_max_items_in_table, hf, eql) { }
+
+  template <class InputIterator>
+  dense_hash_set(InputIterator f, InputIterator l,
+                 size_type expected_max_items_in_table = 0,
+                 const hasher& hf = hasher(),
+                 const key_equal& eql = key_equal())
+      : rep(expected_max_items_in_table, hf, eql) {
+    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 set 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_set& 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(); }
+
+  // These are tr1 methods.  bucket() is the bucket the key is or would be in.
+  size_type bucket_size(size_type i) const    { return rep.bucket_size(i); }
+  size_type bucket(const key_type& key) const { return rep.bucket(key); }
+  float load_factor() const {
+    return size() * 1.0f / bucket_count();
+  }
+  float max_load_factor() const {
+    float shrink, grow;
+    rep.get_resizing_parameters(&shrink, &grow);
+    return grow;
+  }
+  void max_load_factor(float new_grow) {
+    float shrink, grow;
+    rep.get_resizing_parameters(&shrink, &grow);
+    rep.set_resizing_parameters(shrink, new_grow);
+  }
+  // These aren't tr1 methods but perhaps ought to be.
+  float min_load_factor() const {
+    float shrink, grow;
+    rep.get_resizing_parameters(&shrink, &grow);
+    return shrink;
+  }
+  void min_load_factor(float new_shrink) {
+    float shrink, grow;
+    rep.get_resizing_parameters(&shrink, &grow);
+    rep.set_resizing_parameters(new_shrink, grow);
+  }
+  // Deprecated; use min_load_factor() or max_load_factor() instead.
+  void set_resizing_parameters(float shrink, float grow) {
+    return rep.set_resizing_parameters(shrink, grow);
+  }
+
+  void resize(size_type hint)         { rep.resize(hint); }
+  void rehash(size_type hint)         { resize(hint); }     // the tr1 name
+
+  // Lookup routines
+  iterator find(const key_type& key) const           { return rep.find(key); }
+
+  size_type count(const key_type& key) const         { return rep.count(key); }
+
+  pair<iterator, iterator> equal_range(const key_type& key) const {
+    return rep.equal_range(key);
+  }
+
+  // Insertion routines
+  pair<iterator, bool> insert(const value_type& obj) {
+    pair<typename ht::iterator, bool> p = rep.insert(obj);
+    return pair<iterator, bool>(p.first, p.second);   // const to non-const
+  }
+  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)     { rep.set_empty_key(key); }
+  void set_deleted_key(const key_type& key)   { rep.set_deleted_key(key); }
+  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_set& hs) const    { return rep == hs.rep; }
+  bool operator!=(const dense_hash_set& 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); }
+};
+
+template <class Val, class HashFcn, class EqualKey, class Alloc>
+inline void swap(dense_hash_set<Val, HashFcn, EqualKey, Alloc>& hs1,
+                 dense_hash_set<Val, HashFcn, EqualKey, Alloc>& hs2) {
+  hs1.swap(hs2);
+}
+
+_END_GOOGLE_NAMESPACE_
+
+#endif /* _DENSE_HASH_SET_H_ */
diff --git a/ext/sparsehash/google/sparsehash/densehashtable.h b/ext/sparsehash/google/sparsehash/densehashtable.h
new file mode 100644
index 000000000..ad7657682
--- /dev/null
+++ b/ext/sparsehash/google/sparsehash/densehashtable.h
@@ -0,0 +1,1062 @@
+// Copyright (c) 2005, Google Inc.
+// All rights reserved.
+//
+// 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: Craig Silverstein
+//
+// A dense hashtable is a particular implementation of
+// a hashtable: one that is meant to minimize memory allocation.
+// It does this by using an array to store all the data.  We
+// steal a value from the key space to indicate "empty" array
+// elements (ie indices where no item lives) and another to indicate
+// "deleted" elements.
+//
+// (Note it is possible to change the value of the delete key
+// on the fly; you can even remove it, though after that point
+// the hashtable is insert_only until you set it again.  The empty
+// value however can't be changed.)
+//
+// To minimize allocation and pointer overhead, we use internal
+// probing, in which the hashtable is a single table, and collisions
+// are resolved by trying to insert again in another bucket.  The
+// most cache-efficient internal probing schemes are linear probing
+// (which suffers, alas, from clumping) and quadratic probing, which
+// is what we implement by default.
+//
+// Type requirements: value_type is required to be Copy Constructible
+// and Default Constructible. It is not required to be (and commonly
+// isn't) Assignable.
+//
+// You probably shouldn't use this code directly.  Use
+// <google/dense_hash_map> or <google/dense_hash_set> instead.
+
+// You can change the following below:
+// HT_OCCUPANCY_FLT      -- how full before we double size
+// HT_EMPTY_FLT          -- how empty before we halve size
+// HT_MIN_BUCKETS        -- default smallest bucket size
+//
+// You can also change enlarge_resize_percent (which defaults to
+// HT_OCCUPANCY_FLT), and shrink_resize_percent (which defaults to
+// HT_EMPTY_FLT) with set_resizing_parameters().
+//
+// How to decide what values to use?
+// shrink_resize_percent's default of .4 * OCCUPANCY_FLT, is probably good.
+// HT_MIN_BUCKETS is probably unnecessary since you can specify
+// (indirectly) the starting number of buckets at construct-time.
+// For enlarge_resize_percent, you can use this chart to try to trade-off
+// expected lookup time to the space taken up.  By default, this
+// code uses quadratic probing, though you can change it to linear
+// via _JUMP below if you really want to.
+//
+// From http://www.augustana.ca/~mohrj/courses/1999.fall/csc210/lecture_notes/hashing.html
+// NUMBER OF PROBES / LOOKUP       Successful            Unsuccessful
+// Quadratic collision resolution   1 - ln(1-L) - L/2    1/(1-L) - L - ln(1-L)
+// Linear collision resolution     [1+1/(1-L)]/2         [1+1/(1-L)2]/2
+//
+// -- enlarge_resize_percent --         0.10  0.50  0.60  0.75  0.80  0.90  0.99
+// QUADRATIC COLLISION RES.
+//    probes/successful lookup    1.05  1.44  1.62  2.01  2.21  2.85  5.11
+//    probes/unsuccessful lookup  1.11  2.19  2.82  4.64  5.81  11.4  103.6
+// LINEAR COLLISION RES.
+//    probes/successful lookup    1.06  1.5   1.75  2.5   3.0   5.5   50.5
+//    probes/unsuccessful lookup  1.12  2.5   3.6   8.5   13.0  50.0  5000.0
+
+#ifndef _DENSEHASHTABLE_H_
+#define _DENSEHASHTABLE_H_
+
+// The probing method
+// Linear probing
+// #define JUMP_(key, num_probes)    ( 1 )
+// Quadratic-ish probing
+#define JUMP_(key, num_probes)    ( num_probes )
+
+
+#include "google/sparsehash/sparseconfig.h"
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>             // for abort()
+#include <algorithm>            // For swap(), eg
+#include <iostream>             // For cerr
+#include <memory>               // For uninitialized_fill, uninitialized_copy
+#include <utility>              // for pair<>
+#include <iterator>             // for facts about iterator tags
+#include "google/type_traits.h" // for true_type, integral_constant, etc.
+
+_START_GOOGLE_NAMESPACE_
+
+using STL_NAMESPACE::pair;
+
+// Hashtable class, used to implement the hashed associative containers
+// hash_set and hash_map.
+
+// Value: what is stored in the table (each bucket is a Value).
+// Key: something in a 1-to-1 correspondence to a Value, that can be used
+//      to search for a Value in the table (find() takes a Key).
+// HashFcn: Takes a Key and returns an integer, the more unique the better.
+// ExtractKey: given a Value, returns the unique Key associated with it.
+// SetKey: given a Value* and a Key, modifies the value such that
+//         ExtractKey(value) == key.  We guarantee this is only called
+//         with key == deleted_key or key == empty_key.
+// EqualKey: Given two Keys, says whether they are the same (that is,
+//           if they are both associated with the same Value).
+// Alloc: STL allocator to use to allocate memory.  Currently ignored.
+
+template <class Value, class Key, class HashFcn,
+          class ExtractKey, class SetKey, class EqualKey, class Alloc>
+class dense_hashtable;
+
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+struct dense_hashtable_iterator;
+
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+struct dense_hashtable_const_iterator;
+
+// We're just an array, but we need to skip over empty and deleted elements
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+struct dense_hashtable_iterator {
+ public:
+  typedef dense_hashtable_iterator<V,K,HF,ExK,SetK,EqK,A>       iterator;
+  typedef dense_hashtable_const_iterator<V,K,HF,ExK,SetK,EqK,A> const_iterator;
+
+  typedef STL_NAMESPACE::forward_iterator_tag iterator_category;
+  typedef V value_type;
+  typedef ptrdiff_t difference_type;
+  typedef size_t size_type;
+  typedef V& reference;                // Value
+  typedef V* pointer;
+
+  // "Real" constructor and default constructor
+  dense_hashtable_iterator(const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *h,
+                           pointer it, pointer it_end, bool advance)
+    : ht(h), pos(it), end(it_end)   {
+    if (advance)  advance_past_empty_and_deleted();
+  }
+  dense_hashtable_iterator() { }
+  // The default destructor is fine; we don't define one
+  // The default operator= is fine; we don't define one
+
+  // Happy dereferencer
+  reference operator*() const { return *pos; }
+  pointer operator->() const { return &(operator*()); }
+
+  // Arithmetic.  The only hard part is making sure that
+  // we're not on an empty or marked-deleted array element
+  void advance_past_empty_and_deleted() {
+    while ( pos != end && (ht->test_empty(*this) || ht->test_deleted(*this)) )
+      ++pos;
+  }
+  iterator& operator++()   {
+    assert(pos != end); ++pos; advance_past_empty_and_deleted(); return *this;
+  }
+  iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; }
+
+  // Comparison.
+  bool operator==(const iterator& it) const { return pos == it.pos; }
+  bool operator!=(const iterator& it) const { return pos != it.pos; }
+
+
+  // The actual data
+  const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht;
+  pointer pos, end;
+};
+
+
+// Now do it all again, but with const-ness!
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+struct dense_hashtable_const_iterator {
+ public:
+  typedef dense_hashtable_iterator<V,K,HF,ExK,SetK,EqK,A>       iterator;
+  typedef dense_hashtable_const_iterator<V,K,HF,ExK,SetK,EqK,A> const_iterator;
+
+  typedef STL_NAMESPACE::forward_iterator_tag iterator_category;
+  typedef V value_type;
+  typedef ptrdiff_t difference_type;
+  typedef size_t size_type;
+  typedef const V& reference;                // Value
+  typedef const V* pointer;
+
+  // "Real" constructor and default constructor
+  dense_hashtable_const_iterator(
+      const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *h,
+      pointer it, pointer it_end, bool advance)
+    : ht(h), pos(it), end(it_end)   {
+    if (advance)  advance_past_empty_and_deleted();
+  }
+  dense_hashtable_const_iterator() { }
+  // This lets us convert regular iterators to const iterators
+  dense_hashtable_const_iterator(const iterator &it)
+    : ht(it.ht), pos(it.pos), end(it.end) { }
+  // The default destructor is fine; we don't define one
+  // The default operator= is fine; we don't define one
+
+  // Happy dereferencer
+  reference operator*() const { return *pos; }
+  pointer operator->() const { return &(operator*()); }
+
+  // Arithmetic.  The only hard part is making sure that
+  // we're not on an empty or marked-deleted array element
+  void advance_past_empty_and_deleted() {
+    while ( pos != end && (ht->test_empty(*this) || ht->test_deleted(*this)) )
+      ++pos;
+  }
+  const_iterator& operator++()   {
+    assert(pos != end); ++pos; advance_past_empty_and_deleted(); return *this;
+  }
+  const_iterator operator++(int) { const_iterator tmp(*this); ++*this; return tmp; }
+
+  // Comparison.
+  bool operator==(const const_iterator& it) const { return pos == it.pos; }
+  bool operator!=(const const_iterator& it) const { return pos != it.pos; }
+
+
+  // The actual data
+  const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht;
+  pointer pos, end;
+};
+
+template <class Value, class Key, class HashFcn,
+          class ExtractKey, class SetKey, class EqualKey, class Alloc>
+class dense_hashtable {
+ public:
+  typedef Key key_type;
+  typedef Value value_type;
+  typedef HashFcn hasher;
+  typedef EqualKey key_equal;
+
+  typedef size_t            size_type;
+  typedef ptrdiff_t         difference_type;
+  typedef value_type*       pointer;
+  typedef const value_type* const_pointer;
+  typedef value_type&       reference;
+  typedef const value_type& const_reference;
+  typedef dense_hashtable_iterator<Value, Key, HashFcn,
+                                   ExtractKey, SetKey, EqualKey, Alloc>
+  iterator;
+
+  typedef dense_hashtable_const_iterator<Value, Key, HashFcn,
+                                         ExtractKey, SetKey, EqualKey, Alloc>
+  const_iterator;
+
+  // These come from tr1.  For us they're the same as regular iterators.
+  typedef iterator local_iterator;
+  typedef const_iterator const_local_iterator;
+
+  // How full we let the table get before we resize, by default.
+  // Knuth says .8 is good -- higher causes us to probe too much,
+  // though it saves memory.
+  static const float HT_OCCUPANCY_FLT; // = 0.5;
+
+  // How empty we let the table get before we resize lower, by default.
+  // (0.0 means never resize lower.)
+  // It should be less than OCCUPANCY_FLT / 2 or we thrash resizing
+  static const float HT_EMPTY_FLT; // = 0.4 * HT_OCCUPANCY_FLT
+
+  // Minimum size we're willing to let hashtables be.
+  // Must be a power of two, and at least 4.
+  // Note, however, that for a given hashtable, the initial size is a
+  // function of the first constructor arg, and may be >HT_MIN_BUCKETS.
+  static const size_t HT_MIN_BUCKETS = 4;
+
+  // By default, if you don't specify a hashtable size at
+  // construction-time, we use this size.  Must be a power of two, and
+  // at least HT_MIN_BUCKETS.
+  static const size_t HT_DEFAULT_STARTING_BUCKETS = 32;
+
+
+  // ITERATOR FUNCTIONS
+  iterator begin()             { return iterator(this, table,
+                                                 table + num_buckets, true); }
+  iterator end()               { return iterator(this, table + num_buckets,
+                                                 table + num_buckets, true); }
+  const_iterator begin() const { return const_iterator(this, table,
+                                                       table+num_buckets,true);}
+  const_iterator end() const   { return const_iterator(this, table + num_buckets,
+                                                       table+num_buckets,true);}
+
+  // These come from tr1 unordered_map.  They iterate over 'bucket' n.
+  // For sparsehashtable, we could consider each 'group' to be a bucket,
+  // I guess, but I don't really see the point.  We'll just consider
+  // bucket n to be the n-th element of the sparsetable, if it's occupied,
+  // or some empty element, otherwise.
+  local_iterator begin(size_type i) {
+    return local_iterator(this, table + i, table + i+1, false);
+  }
+  local_iterator end(size_type i) {
+    local_iterator it = begin(i);
+    if (!test_empty(i) && !test_deleted(i))
+      ++it;
+    return it;
+  }
+  const_local_iterator begin(size_type i) const {
+    return const_local_iterator(this, table + i, table + i+1, false);
+  }
+  const_local_iterator end(size_type i) const {
+    const_local_iterator it = begin(i);
+    if (!test_empty(i) && !test_deleted(i))
+      ++it;
+    return it;
+  }
+
+  // ACCESSOR FUNCTIONS for the things we templatize on, basically
+  hasher hash_funct() const { return hash; }
+  key_equal key_eq() const  { return equals; }
+
+ private:
+  // Annoyingly, we can't copy values around, because they might have
+  // const components (they're probably pair<const X, Y>).  We use
+  // explicit destructor invocation and placement new to get around
+  // this.  Arg.
+  void set_value(value_type* dst, const value_type& src) {
+    dst->~value_type();
+    new(dst) value_type(src);
+  }
+
+  void destroy_buckets(size_type first, size_type last) {
+    for ( ; first != last; ++first)
+      table[first].~value_type();
+  }
+
+  // DELETE HELPER FUNCTIONS
+  // This lets the user describe a key that will indicate deleted
+  // table entries.  This key should be an "impossible" entry --
+  // if you try to insert it for real, you won't be able to retrieve it!
+  // (NB: while you pass in an entire value, only the key part is looked
+  // at.  This is just because I don't know how to assign just a key.)
+ private:
+  void squash_deleted() {           // gets rid of any deleted entries we have
+    if ( num_deleted ) {            // get rid of deleted before writing
+      dense_hashtable tmp(*this);   // copying will get rid of deleted
+      swap(tmp);                    // now we are tmp
+    }
+    assert(num_deleted == 0);
+  }
+
+ public:
+  void set_deleted_key(const key_type &key) {
+    // the empty indicator (if specified) and the deleted indicator
+    // must be different
+    assert(!use_empty || !equals(key, get_key(emptyval)));
+    // It's only safe to change what "deleted" means if we purge deleted guys
+    squash_deleted();
+    use_deleted = true;
+    delkey = key;
+  }
+  void clear_deleted_key() {
+    squash_deleted();
+    use_deleted = false;
+  }
+
+  // These are public so the iterators can use them
+  // True if the item at position bucknum is "deleted" marker
+  bool test_deleted(size_type bucknum) const {
+    // The num_deleted test is crucial for read(): after read(), the ht values
+    // are garbage, and we don't want to think some of them are deleted.
+    return (use_deleted && num_deleted > 0 &&
+            equals(delkey, get_key(table[bucknum])));
+  }
+  bool test_deleted(const iterator &it) const {
+    return (use_deleted && num_deleted > 0 &&
+            equals(delkey, get_key(*it)));
+  }
+  bool test_deleted(const const_iterator &it) const {
+    return (use_deleted && num_deleted > 0 &&
+            equals(delkey, get_key(*it)));
+  }
+  // Set it so test_deleted is true.  true if object didn't used to be deleted
+  // See below (at erase()) to explain why we allow const_iterators
+  bool set_deleted(const_iterator &it) {
+    assert(use_deleted);             // bad if set_deleted_key() wasn't called
+    bool retval = !test_deleted(it);
+    // &* converts from iterator to value-type
+    set_key(const_cast<value_type*>(&(*it)), delkey);
+    return retval;
+  }
+  // Set it so test_deleted is false.  true if object used to be deleted
+  bool clear_deleted(const_iterator &it) {
+    assert(use_deleted);             // bad if set_deleted_key() wasn't called
+    // happens automatically when we assign something else in its place
+    return test_deleted(it);
+  }
+
+  // EMPTY HELPER FUNCTIONS
+  // This lets the user describe a key that will indicate empty (unused)
+  // table entries.  This key should be an "impossible" entry --
+  // if you try to insert it for real, you won't be able to retrieve it!
+  // (NB: while you pass in an entire value, only the key part is looked
+  // at.  This is just because I don't know how to assign just a key.)
+ public:
+  // These are public so the iterators can use them
+  // True if the item at position bucknum is "empty" marker
+  bool test_empty(size_type bucknum) const {
+    assert(use_empty);              // we always need to know what's empty!
+    return equals(get_key(emptyval), get_key(table[bucknum]));
+  }
+  bool test_empty(const iterator &it) const {
+    assert(use_empty);              // we always need to know what's empty!
+    return equals(get_key(emptyval), get_key(*it));
+  }
+  bool test_empty(const const_iterator &it) const {
+    assert(use_empty);              // we always need to know what's empty!
+    return equals(get_key(emptyval), get_key(*it));
+  }
+
+ private:
+  // You can either set a range empty or an individual element
+  void set_empty(size_type bucknum) {
+    assert(use_empty);
+    set_value(&table[bucknum], emptyval);
+  }
+  void fill_range_with_empty(value_type* table_start, value_type* table_end) {
+    // Like set_empty(range), but doesn't destroy previous contents
+    STL_NAMESPACE::uninitialized_fill(table_start, table_end, emptyval);
+  }
+  void set_empty(size_type buckstart, size_type buckend) {
+    assert(use_empty);
+    destroy_buckets(buckstart, buckend);
+    fill_range_with_empty(table + buckstart, table + buckend);
+  }
+
+ public:
+  // TODO(csilvers): change all callers of this to pass in a key instead,
+  //                 and take a const key_type instead of const value_type.
+  void set_empty_key(const value_type &val) {
+    // Once you set the empty key, you can't change it
+    assert(!use_empty);
+    // The deleted indicator (if specified) and the empty indicator
+    // must be different.
+    assert(!use_deleted || !equals(get_key(val), delkey));
+    use_empty = true;
+    set_value(&emptyval, val);
+
+    assert(!table);                  // must set before first use
+    // num_buckets was set in constructor even though table was NULL
+    table = (value_type *) malloc(num_buckets * sizeof(*table));
+    assert(table);
+    fill_range_with_empty(table, table + num_buckets);
+  }
+
+  // FUNCTIONS CONCERNING SIZE
+ public:
+  size_type size() const      { return num_elements - num_deleted; }
+  // Buckets are always a power of 2
+  size_type max_size() const  { return (size_type(-1) >> 1U) + 1; }
+  bool empty() const          { return size() == 0; }
+  size_type bucket_count() const      { return num_buckets; }
+  size_type max_bucket_count() const  { return max_size(); }
+  size_type nonempty_bucket_count() const { return num_elements; }
+  // These are tr1 methods.  Their idea of 'bucket' doesn't map well to
+  // what we do.  We just say every bucket has 0 or 1 items in it.
+  size_type bucket_size(size_type i) const {
+    return begin(i) == end(i) ? 0 : 1;
+  }
+
+
+
+ private:
+  // Because of the above, size_type(-1) is never legal; use it for errors
+  static const size_type ILLEGAL_BUCKET = size_type(-1);
+
+ private:
+  // This is the smallest size a hashtable can be without being too crowded
+  // If you like, you can give a min #buckets as well as a min #elts
+  size_type min_size(size_type num_elts, size_type min_buckets_wanted) {
+    size_type sz = HT_MIN_BUCKETS;             // min buckets allowed
+    while ( sz < min_buckets_wanted || num_elts >= sz * enlarge_resize_percent )
+      sz *= 2;
+    return sz;
+  }
+
+  // Used after a string of deletes
+  void maybe_shrink() {
+    assert(num_elements >= num_deleted);
+    assert((bucket_count() & (bucket_count()-1)) == 0); // is a power of two
+    assert(bucket_count() >= HT_MIN_BUCKETS);
+
+    // If you construct a hashtable with < HT_DEFAULT_STARTING_BUCKETS,
+    // we'll never shrink until you get relatively big, and we'll never
+    // shrink below HT_DEFAULT_STARTING_BUCKETS.  Otherwise, something
+    // like "dense_hash_set<int> x; x.insert(4); x.erase(4);" will
+    // shrink us down to HT_MIN_BUCKETS buckets, which is too small.
+    if (shrink_threshold > 0 &&
+        (num_elements-num_deleted) < shrink_threshold &&
+        bucket_count() > HT_DEFAULT_STARTING_BUCKETS ) {
+      size_type sz = bucket_count() / 2;    // find how much we should shrink
+      while ( sz > HT_DEFAULT_STARTING_BUCKETS &&
+              (num_elements - num_deleted) < sz * shrink_resize_percent )
+        sz /= 2;                            // stay a power of 2
+      dense_hashtable tmp(*this, sz);       // Do the actual resizing
+      swap(tmp);                            // now we are tmp
+    }
+    consider_shrink = false;                // because we just considered it
+  }
+
+  // We'll let you resize a hashtable -- though this makes us copy all!
+  // When you resize, you say, "make it big enough for this many more elements"
+  void resize_delta(size_type delta) {
+    if ( consider_shrink )                   // see if lots of deletes happened
+      maybe_shrink();
+    if ( bucket_count() > HT_MIN_BUCKETS &&
+         (num_elements + delta) <= enlarge_threshold )
+      return;                                // we're ok as we are
+
+    // Sometimes, we need to resize just to get rid of all the
+    // "deleted" buckets that are clogging up the hashtable.  So when
+    // deciding whether to resize, count the deleted buckets (which
+    // are currently taking up room).  But later, when we decide what
+    // size to resize to, *don't* count deleted buckets, since they
+    // get discarded during the resize.
+    const size_type needed_size = min_size(num_elements + delta, 0);
+    if ( needed_size > bucket_count() ) {      // we don't have enough buckets
+      const size_type resize_to = min_size(num_elements - num_deleted + delta,
+                                           0);
+      dense_hashtable tmp(*this, resize_to);
+      swap(tmp);                             // now we are tmp
+    }
+  }
+
+  // Increase number of buckets, assuming value_type has trivial copy
+  // constructor and destructor.  (Really, we want it to have "trivial
+  // move", because that's what realloc does.  But there's no way to
+  // capture that using type_traits, so we pretend that move(x, y) is
+  // equivalent to "x.~T(); new(x) T(y);" which is pretty much
+  // correct, if a bit conservative.)
+  void expand_array(size_t resize_to, true_type) {
+    table = (value_type *) realloc(table, resize_to * sizeof(value_type));
+    assert(table);
+    fill_range_with_empty(table + num_buckets, table + resize_to);
+  }
+
+  // Increase number of buckets, without special assumptions about value_type.
+  // TODO(austern): make this exception safe. Handle exceptions from
+  // value_type's copy constructor.
+  void expand_array(size_t resize_to, false_type) {
+    value_type* new_table =
+      (value_type *) malloc(resize_to * sizeof(value_type));
+    assert(new_table);
+    STL_NAMESPACE::uninitialized_copy(table, table + num_buckets, new_table);
+    fill_range_with_empty(new_table + num_buckets, new_table + resize_to);
+    destroy_buckets(0, num_buckets);
+    free(table);
+    table = new_table;
+  }
+
+  // Used to actually do the rehashing when we grow/shrink a hashtable
+  void copy_from(const dense_hashtable &ht, size_type min_buckets_wanted) {
+    clear();            // clear table, set num_deleted to 0
+
+    // If we need to change the size of our table, do it now
+    const size_type resize_to = min_size(ht.size(), min_buckets_wanted);
+    if ( resize_to > bucket_count() ) { // we don't have enough buckets
+      typedef integral_constant<bool,
+          (has_trivial_copy<value_type>::value &&
+           has_trivial_destructor<value_type>::value)>
+          realloc_ok; // we pretend mv(x,y) == "x.~T(); new(x) T(y)"
+      expand_array(resize_to, realloc_ok());
+      num_buckets = resize_to;
+      reset_thresholds();
+    }
+
+    // We use a normal iterator to get non-deleted bcks from ht
+    // We could use insert() here, but since we know there are
+    // no duplicates and no deleted items, we can be more efficient
+    assert((bucket_count() & (bucket_count()-1)) == 0);      // a power of two
+    for ( const_iterator it = ht.begin(); it != ht.end(); ++it ) {
+      size_type num_probes = 0;              // how many times we've probed
+      size_type bucknum;
+      const size_type bucket_count_minus_one = bucket_count() - 1;
+      for (bucknum = hash(get_key(*it)) & bucket_count_minus_one;
+           !test_empty(bucknum);                               // not empty
+           bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one) {
+        ++num_probes;
+        assert(num_probes < bucket_count()); // or else the hashtable is full
+      }
+      set_value(&table[bucknum], *it);       // copies the value to here
+      num_elements++;
+    }
+  }
+
+  // Required by the spec for hashed associative container
+ public:
+  // Though the docs say this should be num_buckets, I think it's much
+  // more useful as req_elements.  As a special feature, calling with
+  // req_elements==0 will cause us to shrink if we can, saving space.
+  void resize(size_type req_elements) {       // resize to this or larger
+    if ( consider_shrink || req_elements == 0 )
+      maybe_shrink();
+    if ( req_elements > num_elements )
+      return resize_delta(req_elements - num_elements);
+  }
+
+  // Get and change the value of shrink_resize_percent and
+  // enlarge_resize_percent.  The description at the beginning of this
+  // file explains how to choose the values.  Setting the shrink
+  // parameter to 0.0 ensures that the table never shrinks.
+  void get_resizing_parameters(float* shrink, float* grow) const {
+    *shrink = shrink_resize_percent;
+    *grow = enlarge_resize_percent;
+  }
+  void set_resizing_parameters(float shrink, float grow) {
+    assert(shrink >= 0.0);
+    assert(grow <= 1.0);
+    if (shrink > grow/2.0f)
+      shrink = grow / 2.0f;     // otherwise we thrash hashtable size
+    shrink_resize_percent = shrink;
+    enlarge_resize_percent = grow;
+    reset_thresholds();
+  }
+
+  // CONSTRUCTORS -- as required by the specs, we take a size,
+  // but also let you specify a hashfunction, key comparator,
+  // and key extractor.  We also define a copy constructor and =.
+  // DESTRUCTOR -- needs to free the table
+  explicit dense_hashtable(size_type expected_max_items_in_table = 0,
+                           const HashFcn& hf = HashFcn(),
+                           const EqualKey& eql = EqualKey(),
+                           const ExtractKey& ext = ExtractKey(),
+                           const SetKey& set = SetKey())
+    : hash(hf), equals(eql), get_key(ext), set_key(set), num_deleted(0),
+      use_deleted(false), use_empty(false),
+      delkey(), emptyval(), enlarge_resize_percent(HT_OCCUPANCY_FLT),
+      shrink_resize_percent(HT_EMPTY_FLT), table(NULL),
+      num_buckets(expected_max_items_in_table == 0
+                  ? HT_DEFAULT_STARTING_BUCKETS
+                  : min_size(expected_max_items_in_table, 0)),
+      num_elements(0) {
+    // table is NULL until emptyval is set.  However, we set num_buckets
+    // here so we know how much space to allocate once emptyval is set
+    reset_thresholds();
+  }
+
+  // As a convenience for resize(), we allow an optional second argument
+  // which lets you make this new hashtable a different size than ht
+  dense_hashtable(const dense_hashtable& ht,
+                  size_type min_buckets_wanted = HT_DEFAULT_STARTING_BUCKETS)
+    : hash(ht.hash), equals(ht.equals),
+      get_key(ht.get_key), set_key(ht.set_key), num_deleted(0),
+      use_deleted(ht.use_deleted), use_empty(ht.use_empty),
+      delkey(ht.delkey), emptyval(ht.emptyval),
+      enlarge_resize_percent(ht.enlarge_resize_percent),
+      shrink_resize_percent(ht.shrink_resize_percent), table(NULL),
+      num_buckets(0), num_elements(0) {
+    reset_thresholds();
+    copy_from(ht, min_buckets_wanted);   // copy_from() ignores deleted entries
+  }
+
+  dense_hashtable& operator= (const dense_hashtable& ht) {
+    if (&ht == this)  return *this;        // don't copy onto ourselves
+    clear();
+    hash = ht.hash;
+    equals = ht.equals;
+    get_key = ht.get_key;
+    set_key = ht.set_key;
+    use_deleted = ht.use_deleted;
+    use_empty = ht.use_empty;
+    delkey = ht.delkey;
+    set_value(&emptyval, ht.emptyval);
+    enlarge_resize_percent = ht.enlarge_resize_percent;
+    shrink_resize_percent = ht.shrink_resize_percent;
+    copy_from(ht, HT_MIN_BUCKETS);         // sets num_deleted to 0 too
+    return *this;
+  }
+
+  ~dense_hashtable() {
+    if (table) {
+      destroy_buckets(0, num_buckets);
+      free(table);
+    }
+  }
+
+  // Many STL algorithms use swap instead of copy constructors
+  void swap(dense_hashtable& ht) {
+    STL_NAMESPACE::swap(hash, ht.hash);
+    STL_NAMESPACE::swap(equals, ht.equals);
+    STL_NAMESPACE::swap(get_key, ht.get_key);
+    STL_NAMESPACE::swap(set_key, ht.set_key);
+    STL_NAMESPACE::swap(num_deleted, ht.num_deleted);
+    STL_NAMESPACE::swap(use_deleted, ht.use_deleted);
+    STL_NAMESPACE::swap(use_empty, ht.use_empty);
+    STL_NAMESPACE::swap(enlarge_resize_percent, ht.enlarge_resize_percent);
+    STL_NAMESPACE::swap(shrink_resize_percent, ht.shrink_resize_percent);
+    STL_NAMESPACE::swap(delkey, ht.delkey);
+    { value_type tmp;     // for annoying reasons, swap() doesn't work
+      set_value(&tmp, emptyval);
+      set_value(&emptyval, ht.emptyval);
+      set_value(&ht.emptyval, tmp);
+    }
+    STL_NAMESPACE::swap(table, ht.table);
+    STL_NAMESPACE::swap(num_buckets, ht.num_buckets);
+    STL_NAMESPACE::swap(num_elements, ht.num_elements);
+    reset_thresholds();
+    ht.reset_thresholds();
+  }
+
+  // It's always nice to be able to clear a table without deallocating it
+  void clear() {
+    if (table)
+      destroy_buckets(0, num_buckets);
+    num_buckets = min_size(0,0);          // our new size
+    reset_thresholds();
+    table = (value_type *) realloc(table, num_buckets * sizeof(*table));
+    assert(table);
+    fill_range_with_empty(table, table + num_buckets);
+    num_elements = 0;
+    num_deleted = 0;
+  }
+
+  // Clear the table without resizing it.
+  // Mimicks the stl_hashtable's behaviour when clear()-ing in that it
+  // does not modify the bucket count
+  void clear_no_resize() {
+    if (table) {
+      set_empty(0, num_buckets);
+    }
+    // don't consider to shrink before another erase()
+    reset_thresholds();
+    num_elements = 0;
+    num_deleted = 0;
+  }
+
+  // LOOKUP ROUTINES
+ private:
+  // Returns a pair of positions: 1st where the object is, 2nd where
+  // it would go if you wanted to insert it.  1st is ILLEGAL_BUCKET
+  // if object is not found; 2nd is ILLEGAL_BUCKET if it is.
+  // Note: because of deletions where-to-insert is not trivial: it's the
+  // first deleted bucket we see, as long as we don't find the key later
+  pair<size_type, size_type> find_position(const key_type &key) const {
+    size_type num_probes = 0;              // how many times we've probed
+    const size_type bucket_count_minus_one = bucket_count() - 1;
+    size_type bucknum = hash(key) & bucket_count_minus_one;
+    size_type insert_pos = ILLEGAL_BUCKET; // where we would insert
+    while ( 1 ) {                          // probe until something happens
+      if ( test_empty(bucknum) ) {         // bucket is empty
+        if ( insert_pos == ILLEGAL_BUCKET )   // found no prior place to insert
+          return pair<size_type,size_type>(ILLEGAL_BUCKET, bucknum);
+        else
+          return pair<size_type,size_type>(ILLEGAL_BUCKET, insert_pos);
+
+      } else if ( test_deleted(bucknum) ) {// keep searching, but mark to insert
+        if ( insert_pos == ILLEGAL_BUCKET )
+          insert_pos = bucknum;
+
+      } else if ( equals(key, get_key(table[bucknum])) ) {
+        return pair<size_type,size_type>(bucknum, ILLEGAL_BUCKET);
+      }
+      ++num_probes;                        // we're doing another probe
+      bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one;
+      assert(num_probes < bucket_count()); // don't probe too many times!
+    }
+  }
+
+ public:
+  iterator find(const key_type& key) {
+    if ( size() == 0 ) return end();
+    pair<size_type, size_type> pos = find_position(key);
+    if ( pos.first == ILLEGAL_BUCKET )     // alas, not there
+      return end();
+    else
+      return iterator(this, table + pos.first, table + num_buckets, false);
+  }
+
+  const_iterator find(const key_type& key) const {
+    if ( size() == 0 ) return end();
+    pair<size_type, size_type> pos = find_position(key);
+    if ( pos.first == ILLEGAL_BUCKET )     // alas, not there
+      return end();
+    else
+      return const_iterator(this, table + pos.first, table+num_buckets, false);
+  }
+
+  // This is a tr1 method: the bucket a given key is in, or what bucket
+  // it would be put in, if it were to be inserted.  Shrug.
+  size_type bucket(const key_type& key) const {
+    pair<size_type, size_type> pos = find_position(key);
+    return pos.first == ILLEGAL_BUCKET ? pos.second : pos.first;
+  }
+
+  // Counts how many elements have key key.  For maps, it's either 0 or 1.
+  size_type count(const key_type &key) const {
+    pair<size_type, size_type> pos = find_position(key);
+    return pos.first == ILLEGAL_BUCKET ? 0 : 1;
+  }
+
+  // Likewise, equal_range doesn't really make sense for us.  Oh well.
+  pair<iterator,iterator> equal_range(const key_type& key) {
+    iterator pos = find(key);      // either an iterator or end
+    if (pos == end()) {
+      return pair<iterator,iterator>(pos, pos);
+    } else {
+      const iterator startpos = pos++;
+      return pair<iterator,iterator>(startpos, pos);
+    }
+  }
+  pair<const_iterator,const_iterator> equal_range(const key_type& key) const {
+    const_iterator pos = find(key);      // either an iterator or end
+    if (pos == end()) {
+      return pair<const_iterator,const_iterator>(pos, pos);
+    } else {
+      const const_iterator startpos = pos++;
+      return pair<const_iterator,const_iterator>(startpos, pos);
+    }
+  }
+
+
+  // INSERTION ROUTINES
+ private:
+  // If you know *this is big enough to hold obj, use this routine
+  pair<iterator, bool> insert_noresize(const value_type& obj) {
+    // First, double-check we're not inserting delkey or emptyval
+    assert(!use_empty || !equals(get_key(obj), get_key(emptyval)));
+    assert(!use_deleted || !equals(get_key(obj), delkey));
+    const pair<size_type,size_type> pos = find_position(get_key(obj));
+    if ( pos.first != ILLEGAL_BUCKET) {      // object was already there
+      return pair<iterator,bool>(iterator(this, table + pos.first,
+                                          table + num_buckets, false),
+                                 false);          // false: we didn't insert
+    } else {                                 // pos.second says where to put it
+      if ( test_deleted(pos.second) ) {      // just replace if it's been del.
+        const_iterator delpos(this, table + pos.second,              // shrug:
+                              table + num_buckets, false);// shouldn't need const
+        clear_deleted(delpos);
+        assert( num_deleted > 0);
+        --num_deleted;                       // used to be, now it isn't
+      } else {
+        ++num_elements;                      // replacing an empty bucket
+      }
+      set_value(&table[pos.second], obj);
+      return pair<iterator,bool>(iterator(this, table + pos.second,
+                                          table + num_buckets, false),
+                                 true);           // true: we did insert
+    }
+  }
+
+ public:
+  // This is the normal insert routine, used by the outside world
+  pair<iterator, bool> insert(const value_type& obj) {
+    resize_delta(1);                      // adding an object, grow if need be
+    return insert_noresize(obj);
+  }
+
+  // When inserting a lot at a time, we specialize on the type of iterator
+  template <class InputIterator>
+  void insert(InputIterator f, InputIterator l) {
+    // specializes on iterator type
+    insert(f, l, typename STL_NAMESPACE::iterator_traits<InputIterator>::iterator_category());
+  }
+
+  // Iterator supports operator-, resize before inserting
+  template <class ForwardIterator>
+  void insert(ForwardIterator f, ForwardIterator l,
+              STL_NAMESPACE::forward_iterator_tag) {
+    size_type n = STL_NAMESPACE::distance(f, l);   // TODO(csilvers): standard?
+    resize_delta(n);
+    for ( ; n > 0; --n, ++f)
+      insert_noresize(*f);
+  }
+
+  // Arbitrary iterator, can't tell how much to resize
+  template <class InputIterator>
+  void insert(InputIterator f, InputIterator l,
+              STL_NAMESPACE::input_iterator_tag) {
+    for ( ; f != l; ++f)
+      insert(*f);
+  }
+
+
+  // DELETION ROUTINES
+  size_type erase(const key_type& key) {
+    // First, double-check we're not trying to erase delkey or emptyval
+    assert(!use_empty || !equals(key, get_key(emptyval)));
+    assert(!use_deleted || !equals(key, delkey));
+    const_iterator pos = find(key);   // shrug: shouldn't need to be const
+    if ( pos != end() ) {
+      assert(!test_deleted(pos));  // or find() shouldn't have returned it
+      set_deleted(pos);
+      ++num_deleted;
+      consider_shrink = true;      // will think about shrink after next insert
+      return 1;                    // because we deleted one thing
+    } else {
+      return 0;                    // because we deleted nothing
+    }
+  }
+
+  // This is really evil: really it should be iterator, not const_iterator.
+  // But...the only reason keys are const is to allow lookup.
+  // Since that's a moot issue for deleted keys, we allow const_iterators
+  void erase(const_iterator pos) {
+    if ( pos == end() ) return;    // sanity check
+    if ( set_deleted(pos) ) {      // true if object has been newly deleted
+      ++num_deleted;
+      consider_shrink = true;      // will think about shrink after next insert
+    }
+  }
+
+  void erase(const_iterator f, const_iterator l) {
+    for ( ; f != l; ++f) {
+      if ( set_deleted(f)  )       // should always be true
+        ++num_deleted;
+    }
+    consider_shrink = true;        // will think about shrink after next insert
+  }
+
+
+  // COMPARISON
+  bool operator==(const dense_hashtable& ht) const {
+    if (size() != ht.size()) {
+      return false;
+    } else if (this == &ht) {
+      return true;
+    } else {
+      // Iterate through the elements in "this" and see if the
+      // corresponding element is in ht
+      for ( const_iterator it = begin(); it != end(); ++it ) {
+        const_iterator it2 = ht.find(get_key(*it));
+        if ((it2 == ht.end()) || (*it != *it2)) {
+          return false;
+        }
+      }
+      return true;
+    }
+  }
+  bool operator!=(const dense_hashtable& ht) const {
+    return !(*this == ht);
+  }
+
+
+  // I/O
+  // We support reading and writing hashtables to disk.  Alas, since
+  // I don't know how to write a hasher or key_equal, you have to make
+  // sure everything but the table is the same.  We compact before writing
+  //
+  // NOTE: These functions are currently TODO.  They've not been implemented.
+  bool write_metadata(FILE *fp) {
+    squash_deleted();           // so we don't have to worry about delkey
+    return false;               // TODO
+  }
+
+  bool read_metadata(FILE *fp) {
+    num_deleted = 0;            // since we got rid before writing
+    assert(use_empty);          // have to set this before calling us
+    if (table)  free(table);    // we'll make our own
+    // TODO: read magic number
+    // TODO: read num_buckets
+    reset_thresholds();
+    table = (value_type *) malloc(num_buckets * sizeof(*table));
+    assert(table);
+    fill_range_with_empty(table, table + num_buckets);
+    // TODO: read num_elements
+    for ( size_type i = 0; i < num_elements; ++i ) {
+      // TODO: read bucket_num
+      // TODO: set with non-empty, non-deleted value
+    }
+    return false;               // TODO
+  }
+
+  // If your keys and values are simple enough, we can write them to
+  // disk for you.  "simple enough" means value_type is a POD type
+  // that contains no pointers.  However, we don't try to normalize
+  // endianness
+  bool write_nopointer_data(FILE *fp) const {
+    for ( const_iterator it = begin(); it != end(); ++it ) {
+      // TODO: skip empty/deleted values
+      if ( !fwrite(&*it, sizeof(*it), 1, fp) )  return false;
+    }
+    return false;
+  }
+
+  // When reading, we have to override the potential const-ness of *it
+  bool read_nopointer_data(FILE *fp) {
+    for ( iterator it = begin(); it != end(); ++it ) {
+      // TODO: skip empty/deleted values
+      if ( !fread(reinterpret_cast<void*>(&(*it)), sizeof(*it), 1, fp) )
+        return false;
+    }
+    return false;
+  }
+
+ private:
+  // The actual data
+  hasher hash;                      // required by hashed_associative_container
+  key_equal equals;
+  ExtractKey get_key;
+  SetKey set_key;
+  size_type num_deleted;        // how many occupied buckets are marked deleted
+  bool use_deleted;                          // false until delkey has been set
+  bool use_empty;                          // you must do this before you start
+  // TODO(csilvers): make a pointer, and get rid of use_deleted (benchmark!)
+  key_type delkey;                           // which key marks deleted entries
+  value_type emptyval;                        // which key marks unused entries
+  float enlarge_resize_percent;                       // how full before resize
+  float shrink_resize_percent;                       // how empty before resize
+  size_type shrink_threshold;            // num_buckets * shrink_resize_percent
+  size_type enlarge_threshold;          // num_buckets * enlarge_resize_percent
+  value_type *table;
+  size_type num_buckets;
+  size_type num_elements;
+  bool consider_shrink;   // true if we should try to shrink before next insert
+
+  void reset_thresholds() {
+    enlarge_threshold = static_cast<size_type>(num_buckets
+                                               * enlarge_resize_percent);
+    shrink_threshold = static_cast<size_type>(num_buckets
+                                              * shrink_resize_percent);
+    consider_shrink = false;   // whatever caused us to reset already considered
+  }
+};
+
+// We need a global swap as well
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+inline void swap(dense_hashtable<V,K,HF,ExK,SetK,EqK,A> &x,
+                 dense_hashtable<V,K,HF,ExK,SetK,EqK,A> &y) {
+  x.swap(y);
+}
+
+#undef JUMP_
+
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+const typename dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::size_type
+dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::ILLEGAL_BUCKET;
+
+// How full we let the table get before we resize.  Knuth says .8 is
+// good -- higher causes us to probe too much, though saves memory.
+// However, we go with .5, getting better performance at the cost of
+// more space (a trade-off densehashtable explicitly chooses to make).
+// Feel free to play around with different values, though.
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+const float dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_FLT = 0.5f;
+
+// How empty we let the table get before we resize lower.
+// It should be less than OCCUPANCY_FLT / 2 or we thrash resizing
+template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
+const float dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_EMPTY_FLT
+    = 0.4f * dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_FLT;
+
+_END_GOOGLE_NAMESPACE_
+
+#endif /* _DENSEHASHTABLE_H_ */
diff --git a/ext/sparsehash/google/sparsehash/sparseconfig.h b/ext/sparsehash/google/sparsehash/sparseconfig.h
new file mode 100644
index 000000000..29e0bf867
--- /dev/null
+++ b/ext/sparsehash/google/sparsehash/sparseconfig.h
@@ -0,0 +1,28 @@
+/*
+ * NOTE: This file is for internal use only.
+ *       Do not use these #defines in your own program!
+ */
+
+/* Namespace for Google classes */
+#define GOOGLE_NAMESPACE ::google
+
+/* the location of the header defining hash functions */
+#define HASH_FUN_H <tr1/functional>
+
+/* the namespace of the hash<> function */
+#define HASH_NAMESPACE std::tr1
+
+/* Define to 1 if the system has the type `long long'. */
+#define HAVE_LONG_LONG 1
+
+/* The system-provided hash function including the namespace. */
+#define SPARSEHASH_HASH HASH_NAMESPACE::hash
+
+/* the namespace where STL code like vector<> is defined */
+#define STL_NAMESPACE std
+
+/* Stops putting the code inside the Google namespace */
+#define _END_GOOGLE_NAMESPACE_ }
+
+/* Puts following code inside the Google namespace */
+#define _START_GOOGLE_NAMESPACE_ namespace google {
diff --git a/ext/sparsehash/google/type_traits.h b/ext/sparsehash/google/type_traits.h
new file mode 100644
index 000000000..d9d4faf83
--- /dev/null
+++ b/ext/sparsehash/google/type_traits.h
@@ -0,0 +1,250 @@
+// Copyright (c) 2006, Google Inc.
+// All rights reserved.
+//
+// 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: Matt Austern
+//
+// Define a small subset of tr1 type traits. The traits we define are:
+//   is_integral
+//   is_floating_point
+//   is_pointer
+//   is_reference
+//   is_pod
+//   has_trivial_constructor
+//   has_trivial_copy
+//   has_trivial_assign
+//   has_trivial_destructor
+//   remove_const
+//   remove_volatile
+//   remove_cv
+//   remove_reference
+//   remove_pointer
+//   is_convertible
+// We can add more type traits as required.
+
+#ifndef BASE_TYPE_TRAITS_H_
+#define BASE_TYPE_TRAITS_H_
+
+#include "google/sparsehash/sparseconfig.h"
+#include <utility>                  // For pair
+
+_START_GOOGLE_NAMESPACE_
+
+// integral_constant, defined in tr1, is a wrapper for an integer
+// value. We don't really need this generality; we could get away
+// with hardcoding the integer type to bool. We use the fully
+// general integer_constant for compatibility with tr1.
+
+template<class T, T v>
+struct integral_constant {
+  static const T value = v;
+  typedef T value_type;
+  typedef integral_constant<T, v> type;
+};
+
+template <class T, T v> const T integral_constant<T, v>::value;
+
+// Abbreviations: true_type and false_type are structs that represent
+// boolean true and false values.
+typedef integral_constant<bool, true>  true_type;
+typedef integral_constant<bool, false> false_type;
+
+// Types small_ and big_ are guaranteed such that sizeof(small_) <
+// sizeof(big_)
+typedef char small_;
+
+struct big_ {
+  char dummy[2];
+};
+
+// is_integral is false except for the built-in integer types.
+template <class T> struct is_integral : false_type { };
+template<> struct is_integral<bool> : true_type { };
+template<> struct is_integral<char> : true_type { };
+template<> struct is_integral<unsigned char> : true_type { };
+template<> struct is_integral<signed char> : true_type { };
+#if defined(_MSC_VER)
+// wchar_t is not by default a distinct type from unsigned short in
+// Microsoft C.
+// See http://msdn2.microsoft.com/en-us/library/dh8che7s(VS.80).aspx
+template<> struct is_integral<__wchar_t> : true_type { };
+#else
+template<> struct is_integral<wchar_t> : true_type { };
+#endif
+template<> struct is_integral<short> : true_type { };
+template<> struct is_integral<unsigned short> : true_type { };
+template<> struct is_integral<int> : true_type { };
+template<> struct is_integral<unsigned int> : true_type { };
+template<> struct is_integral<long> : true_type { };
+template<> struct is_integral<unsigned long> : true_type { };
+#ifdef HAVE_LONG_LONG
+template<> struct is_integral<long long> : true_type { };
+template<> struct is_integral<unsigned long long> : true_type { };
+#endif
+
+
+// is_floating_point is false except for the built-in floating-point types.
+template <class T> struct is_floating_point : false_type { };
+template<> struct is_floating_point<float> : true_type { };
+template<> struct is_floating_point<double> : true_type { };
+template<> struct is_floating_point<long double> : true_type { };
+
+
+// is_pointer is false except for pointer types.
+template <class T> struct is_pointer : false_type { };
+template <class T> struct is_pointer<T*> : true_type { };
+
+
+// is_reference is false except for reference types.
+template<typename T> struct is_reference : false_type {};
+template<typename T> struct is_reference<T&> : true_type {};
+
+
+// We can't get is_pod right without compiler help, so fail conservatively.
+// We will assume it's false except for arithmetic types and pointers,
+// and const versions thereof. Note that std::pair is not a POD.
+template <class T> struct is_pod
+ : integral_constant<bool, (is_integral<T>::value ||
+                            is_floating_point<T>::value ||
+                            is_pointer<T>::value)> { };
+template <class T> struct is_pod<const T> : is_pod<T> { };
+
+
+// We can't get has_trivial_constructor right without compiler help, so
+// fail conservatively. We will assume it's false except for: (1) types
+// for which is_pod is true. (2) std::pair of types with trivial
+// constructors. (3) array of a type with a trivial constructor.
+// (4) const versions thereof.
+template <class T> struct has_trivial_constructor : is_pod<T> { };
+template <class T, class U> struct has_trivial_constructor<std::pair<T, U> >
+  : integral_constant<bool,
+                      (has_trivial_constructor<T>::value &&
+                       has_trivial_constructor<U>::value)> { };
+template <class A, int N> struct has_trivial_constructor<A[N]>
+  : has_trivial_constructor<A> { };
+template <class T> struct has_trivial_constructor<const T>
+  : has_trivial_constructor<T> { };
+
+// We can't get has_trivial_copy right without compiler help, so fail
+// conservatively. We will assume it's false except for: (1) types
+// for which is_pod is true. (2) std::pair of types with trivial copy
+// constructors. (3) array of a type with a trivial copy constructor.
+// (4) const versions thereof.
+template <class T> struct has_trivial_copy : is_pod<T> { };
+template <class T, class U> struct has_trivial_copy<std::pair<T, U> >
+  : integral_constant<bool,
+                      (has_trivial_copy<T>::value &&
+                       has_trivial_copy<U>::value)> { };
+template <class A, int N> struct has_trivial_copy<A[N]>
+  : has_trivial_copy<A> { };
+template <class T> struct has_trivial_copy<const T> : has_trivial_copy<T> { };
+
+// We can't get has_trivial_assign right without compiler help, so fail
+// conservatively. We will assume it's false except for: (1) types
+// for which is_pod is true. (2) std::pair of types with trivial copy
+// constructors. (3) array of a type with a trivial assign constructor.
+template <class T> struct has_trivial_assign : is_pod<T> { };
+template <class T, class U> struct has_trivial_assign<std::pair<T, U> >
+  : integral_constant<bool,
+                      (has_trivial_assign<T>::value &&
+                       has_trivial_assign<U>::value)> { };
+template <class A, int N> struct has_trivial_assign<A[N]>
+  : has_trivial_assign<A> { };
+
+// We can't get has_trivial_destructor right without compiler help, so
+// fail conservatively. We will assume it's false except for: (1) types
+// for which is_pod is true. (2) std::pair of types with trivial
+// destructors. (3) array of a type with a trivial destructor.
+// (4) const versions thereof.
+template <class T> struct has_trivial_destructor : is_pod<T> { };
+template <class T, class U> struct has_trivial_destructor<std::pair<T, U> >
+  : integral_constant<bool,
+                      (has_trivial_destructor<T>::value &&
+                       has_trivial_destructor<U>::value)> { };
+template <class A, int N> struct has_trivial_destructor<A[N]>
+  : has_trivial_destructor<A> { };
+template <class T> struct has_trivial_destructor<const T>
+  : has_trivial_destructor<T> { };
+
+// Specified by TR1 [4.7.1]
+template<typename T> struct remove_const { typedef T type; };
+template<typename T> struct remove_const<T const> { typedef T type; };
+template<typename T> struct remove_volatile { typedef T type; };
+template<typename T> struct remove_volatile<T volatile> { typedef T type; };
+template<typename T> struct remove_cv {
+  typedef typename remove_const<typename remove_volatile<T>::type>::type type;
+};
+
+
+// Specified by TR1 [4.7.2]
+template<typename T> struct remove_reference { typedef T type; };
+template<typename T> struct remove_reference<T&> { typedef T type; };
+
+// Specified by TR1 [4.7.4] Pointer modifications.
+template<typename T> struct remove_pointer { typedef T type; };
+template<typename T> struct remove_pointer<T*> { typedef T type; };
+template<typename T> struct remove_pointer<T* const> { typedef T type; };
+template<typename T> struct remove_pointer<T* volatile> { typedef T type; };
+template<typename T> struct remove_pointer<T* const volatile> {
+  typedef T type; };
+
+// Specified by TR1 [4.6] Relationships between types
+#ifndef _MSC_VER
+namespace internal {
+
+// This class is an implementation detail for is_convertible, and you
+// don't need to know how it works to use is_convertible. For those
+// who care: we declare two different functions, one whose argument is
+// of type To and one with a variadic argument list. We give them
+// return types of different size, so we can use sizeof to trick the
+// compiler into telling us which function it would have chosen if we
+// had called it with an argument of type From.  See Alexandrescu's
+// _Modern C++ Design_ for more details on this sort of trick.
+
+template <typename From, typename To>
+struct ConvertHelper {
+  static small_ Test(To);
+  static big_ Test(...);
+  static From Create();
+};
+}  // namespace internal
+
+// Inherits from true_type if From is convertible to To, false_type otherwise.
+template <typename From, typename To>
+struct is_convertible
+    : integral_constant<bool,
+                        sizeof(internal::ConvertHelper<From, To>::Test(
+                                  internal::ConvertHelper<From, To>::Create()))
+                        == sizeof(small_)> {
+};
+#endif
+
+_END_GOOGLE_NAMESPACE_
+
+#endif  // BASE_TYPE_TRAITS_H_