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diff --git a/xdelta3/cpp-btree/btree_test.h b/xdelta3/cpp-btree/btree_test.h
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+++ b/xdelta3/cpp-btree/btree_test.h
@@ -0,0 +1,940 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef UTIL_BTREE_BTREE_TEST_H__
+#define UTIL_BTREE_BTREE_TEST_H__
+
+#include <stdio.h>
+#include <algorithm>
+#include <functional>
+#include <type_traits>
+#include <iosfwd>
+#include <map>
+#include <set>
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "gflags/gflags.h"
+#include "btree_container.h"
+
+DECLARE_int32(test_values);
+DECLARE_int32(benchmark_values);
+
+namespace std {
+
+// Provide operator<< support for std::pair<T, U>.
+template <typename T, typename U>
+ostream& operator<<(ostream &os, const std::pair<T, U> &p) {
+  os << "(" << p.first << "," << p.second << ")";
+  return os;
+}
+
+// Provide pair equality testing that works as long as x.first is comparable to
+// y.first and x.second is comparable to y.second. Needed in the test for
+// comparing std::pair<T, U> to std::pair<const T, U>.
+template <typename T, typename U, typename V, typename W>
+bool operator==(const std::pair<T, U> &x, const std::pair<V, W> &y) {
+  return x.first == y.first && x.second == y.second;
+}
+
+// Partial specialization of remove_const that propagates the removal through
+// std::pair.
+template <typename T, typename U>
+struct remove_const<pair<T, U> > {
+  typedef pair<typename remove_const<T>::type,
+               typename remove_const<U>::type> type;
+};
+
+} // namespace std
+
+namespace btree {
+
+// Select the first member of a pair.
+template <class _Pair>
+struct select1st : public std::unary_function<_Pair, typename _Pair::first_type> {
+  const typename _Pair::first_type& operator()(const _Pair& __x) const {
+    return __x.first;
+  }
+};
+
+// Utility class to provide an accessor for a key given a value. The default
+// behavior is to treat the value as a pair and return the first element.
+template <typename K, typename V>
+struct KeyOfValue {
+  typedef select1st<V> type;
+};
+
+template <typename T>
+struct identity {
+  inline const T& operator()(const T& t) const { return t; }
+};
+
+// Partial specialization of KeyOfValue class for when the key and value are
+// the same type such as in set<> and btree_set<>.
+template <typename K>
+struct KeyOfValue<K, K> {
+  typedef identity<K> type;
+};
+
+// Counts the number of occurances of "c" in a buffer.
+inline ptrdiff_t strcount(const char* buf_begin, const char* buf_end, char c) {
+  if (buf_begin == NULL)
+    return 0;
+  if (buf_end <= buf_begin)
+    return 0;
+  ptrdiff_t num = 0;
+  for (const char* bp = buf_begin; bp != buf_end; bp++) {
+    if (*bp == c)
+      num++;
+  }
+  return num;
+}
+
+// for when the string is not null-terminated.
+inline ptrdiff_t strcount(const char* buf, size_t len, char c) {
+  return strcount(buf, buf + len, c);
+}
+
+inline ptrdiff_t strcount(const std::string& buf, char c) {
+  return strcount(buf.c_str(), buf.size(), c);
+}
+
+// The base class for a sorted associative container checker. TreeType is the
+// container type to check and CheckerType is the container type to check
+// against. TreeType is expected to be btree_{set,map,multiset,multimap} and
+// CheckerType is expected to be {set,map,multiset,multimap}.
+template <typename TreeType, typename CheckerType>
+class base_checker {
+  typedef base_checker<TreeType, CheckerType> self_type;
+
+ public:
+  typedef typename TreeType::key_type key_type;
+  typedef typename TreeType::value_type value_type;
+  typedef typename TreeType::key_compare key_compare;
+  typedef typename TreeType::pointer pointer;
+  typedef typename TreeType::const_pointer const_pointer;
+  typedef typename TreeType::reference reference;
+  typedef typename TreeType::const_reference const_reference;
+  typedef typename TreeType::size_type size_type;
+  typedef typename TreeType::difference_type difference_type;
+  typedef typename TreeType::iterator iterator;
+  typedef typename TreeType::const_iterator const_iterator;
+  typedef typename TreeType::reverse_iterator reverse_iterator;
+  typedef typename TreeType::const_reverse_iterator const_reverse_iterator;
+
+ public:
+  // Default constructor.
+  base_checker()
+      : const_tree_(tree_) {
+  }
+  // Copy constructor.
+  base_checker(const self_type &x)
+      : tree_(x.tree_),
+        const_tree_(tree_),
+        checker_(x.checker_) {
+  }
+  // Range constructor.
+  template <typename InputIterator>
+  base_checker(InputIterator b, InputIterator e)
+      : tree_(b, e),
+        const_tree_(tree_),
+        checker_(b, e) {
+  }
+
+  // Iterator routines.
+  iterator begin() { return tree_.begin(); }
+  const_iterator begin() const { return tree_.begin(); }
+  iterator end() { return tree_.end(); }
+  const_iterator end() const { return tree_.end(); }
+  reverse_iterator rbegin() { return tree_.rbegin(); }
+  const_reverse_iterator rbegin() const { return tree_.rbegin(); }
+  reverse_iterator rend() { return tree_.rend(); }
+  const_reverse_iterator rend() const { return tree_.rend(); }
+
+  // Helper routines.
+  template <typename IterType, typename CheckerIterType>
+  IterType iter_check(
+      IterType tree_iter, CheckerIterType checker_iter) const {
+    if (tree_iter == tree_.end()) {
+      EXPECT_EQ(checker_iter, checker_.end());
+    } else {
+      EXPECT_EQ(*tree_iter, *checker_iter);
+    }
+    return tree_iter;
+  }
+  template <typename IterType, typename CheckerIterType>
+  IterType riter_check(
+      IterType tree_iter, CheckerIterType checker_iter) const {
+    if (tree_iter == tree_.rend()) {
+      EXPECT_EQ(checker_iter, checker_.rend());
+    } else {
+      EXPECT_EQ(*tree_iter, *checker_iter);
+    }
+    return tree_iter;
+  }
+  void value_check(const value_type &x) {
+    typename KeyOfValue<typename TreeType::key_type,
+        typename TreeType::value_type>::type key_of_value;
+    const key_type &key = key_of_value(x);
+    EXPECT_EQ(*find(key), x);
+    lower_bound(key);
+    upper_bound(key);
+    equal_range(key);
+    count(key);
+  }
+  void erase_check(const key_type &key) {
+    EXPECT_TRUE(tree_.find(key) == const_tree_.end());
+    EXPECT_TRUE(const_tree_.find(key) == tree_.end());
+    EXPECT_TRUE(tree_.equal_range(key).first ==
+                const_tree_.equal_range(key).second);
+  }
+
+  // Lookup routines.
+  iterator lower_bound(const key_type &key) {
+    return iter_check(tree_.lower_bound(key), checker_.lower_bound(key));
+  }
+  const_iterator lower_bound(const key_type &key) const {
+    return iter_check(tree_.lower_bound(key), checker_.lower_bound(key));
+  }
+  iterator upper_bound(const key_type &key) {
+    return iter_check(tree_.upper_bound(key), checker_.upper_bound(key));
+  }
+  const_iterator upper_bound(const key_type &key) const {
+    return iter_check(tree_.upper_bound(key), checker_.upper_bound(key));
+  }
+  std::pair<iterator,iterator> equal_range(const key_type &key) {
+    std::pair<typename CheckerType::iterator,
+        typename CheckerType::iterator> checker_res =
+        checker_.equal_range(key);
+    std::pair<iterator, iterator> tree_res = tree_.equal_range(key);
+    iter_check(tree_res.first, checker_res.first);
+    iter_check(tree_res.second, checker_res.second);
+    return tree_res;
+  }
+  std::pair<const_iterator,const_iterator> equal_range(const key_type &key) const {
+    std::pair<typename CheckerType::const_iterator,
+        typename CheckerType::const_iterator> checker_res =
+        checker_.equal_range(key);
+    std::pair<const_iterator, const_iterator> tree_res = tree_.equal_range(key);
+    iter_check(tree_res.first, checker_res.first);
+    iter_check(tree_res.second, checker_res.second);
+    return tree_res;
+  }
+  iterator find(const key_type &key) {
+    return iter_check(tree_.find(key), checker_.find(key));
+  }
+  const_iterator find(const key_type &key) const {
+    return iter_check(tree_.find(key), checker_.find(key));
+  }
+  size_type count(const key_type &key) const {
+    size_type res = checker_.count(key);
+    EXPECT_EQ(res, tree_.count(key));
+    return res;
+  }
+
+  // Assignment operator.
+  self_type& operator=(const self_type &x) {
+    tree_ = x.tree_;
+    checker_ = x.checker_;
+    return *this;
+  }
+
+  // Deletion routines.
+  int erase(const key_type &key) {
+    int size = tree_.size();
+    int res = checker_.erase(key);
+    EXPECT_EQ(res, tree_.count(key));
+    EXPECT_EQ(res, tree_.erase(key));
+    EXPECT_EQ(tree_.count(key), 0);
+    EXPECT_EQ(tree_.size(), size - res);
+    erase_check(key);
+    return res;
+  }
+  iterator erase(iterator iter) {
+    key_type key = iter.key();
+    int size = tree_.size();
+    int count = tree_.count(key);
+    typename CheckerType::iterator checker_iter = checker_.find(key);
+    for (iterator tmp(tree_.find(key)); tmp != iter; ++tmp) {
+      ++checker_iter;
+    }
+    typename CheckerType::iterator checker_next = checker_iter;
+    ++checker_next;
+    checker_.erase(checker_iter);
+    iter = tree_.erase(iter);
+    EXPECT_EQ(tree_.size(), checker_.size());
+    EXPECT_EQ(tree_.size(), size - 1);
+    EXPECT_EQ(tree_.count(key), count - 1);
+    if (count == 1) {
+      erase_check(key);
+    }
+    return iter_check(iter, checker_next);
+  }
+
+  void erase(iterator begin, iterator end) {
+    int size = tree_.size();
+    int count = distance(begin, end);
+    typename CheckerType::iterator checker_begin = checker_.find(begin.key());
+    for (iterator tmp(tree_.find(begin.key())); tmp != begin; ++tmp) {
+      ++checker_begin;
+    }
+    typename CheckerType::iterator checker_end =
+        end == tree_.end() ? checker_.end() : checker_.find(end.key());
+    if (end != tree_.end()) {
+      for (iterator tmp(tree_.find(end.key())); tmp != end; ++tmp) {
+        ++checker_end;
+      }
+    }
+    checker_.erase(checker_begin, checker_end);
+    tree_.erase(begin, end);
+    EXPECT_EQ(tree_.size(), checker_.size());
+    EXPECT_EQ(tree_.size(), size - count);
+  }
+
+  // Utility routines.
+  void clear() {
+    tree_.clear();
+    checker_.clear();
+  }
+  void swap(self_type &x) {
+    tree_.swap(x.tree_);
+    checker_.swap(x.checker_);
+  }
+
+  void verify() const {
+    tree_.verify();
+    EXPECT_EQ(tree_.size(), checker_.size());
+
+    // Move through the forward iterators using increment.
+    typename CheckerType::const_iterator
+        checker_iter(checker_.begin());
+    const_iterator tree_iter(tree_.begin());
+    for (; tree_iter != tree_.end();
+         ++tree_iter, ++checker_iter) {
+      EXPECT_EQ(*tree_iter, *checker_iter);
+    }
+
+    // Move through the forward iterators using decrement.
+    for (int n = tree_.size() - 1; n >= 0; --n) {
+      iter_check(tree_iter, checker_iter);
+      --tree_iter;
+      --checker_iter;
+    }
+    EXPECT_TRUE(tree_iter == tree_.begin());
+    EXPECT_TRUE(checker_iter == checker_.begin());
+
+    // Move through the reverse iterators using increment.
+    typename CheckerType::const_reverse_iterator
+        checker_riter(checker_.rbegin());
+    const_reverse_iterator tree_riter(tree_.rbegin());
+    for (; tree_riter != tree_.rend();
+         ++tree_riter, ++checker_riter) {
+      EXPECT_EQ(*tree_riter, *checker_riter);
+    }
+
+    // Move through the reverse iterators using decrement.
+    for (int n = tree_.size() - 1; n >= 0; --n) {
+      riter_check(tree_riter, checker_riter);
+      --tree_riter;
+      --checker_riter;
+    }
+    EXPECT_EQ(tree_riter, tree_.rbegin());
+    EXPECT_EQ(checker_riter, checker_.rbegin());
+  }
+
+  // Access to the underlying btree.
+  const TreeType& tree() const { return tree_; }
+
+  // Size routines.
+  size_type size() const {
+    EXPECT_EQ(tree_.size(), checker_.size());
+    return tree_.size();
+  }
+  size_type max_size() const { return tree_.max_size(); }
+  bool empty() const {
+    EXPECT_EQ(tree_.empty(), checker_.empty());
+    return tree_.empty();
+  }
+  size_type height() const { return tree_.height(); }
+  size_type internal_nodes() const { return tree_.internal_nodes(); }
+  size_type leaf_nodes() const { return tree_.leaf_nodes(); }
+  size_type nodes() const { return tree_.nodes(); }
+  size_type bytes_used() const { return tree_.bytes_used(); }
+  double fullness() const { return tree_.fullness(); }
+  double overhead() const { return tree_.overhead(); }
+
+ protected:
+  TreeType tree_;
+  const TreeType &const_tree_;
+  CheckerType checker_;
+};
+
+// A checker for unique sorted associative containers. TreeType is expected to
+// be btree_{set,map} and CheckerType is expected to be {set,map}.
+template <typename TreeType, typename CheckerType>
+class unique_checker : public base_checker<TreeType, CheckerType> {
+  typedef base_checker<TreeType, CheckerType> super_type;
+  typedef unique_checker<TreeType, CheckerType> self_type;
+
+ public:
+  typedef typename super_type::iterator iterator;
+  typedef typename super_type::value_type value_type;
+
+ public:
+  // Default constructor.
+  unique_checker()
+      : super_type() {
+  }
+  // Copy constructor.
+  unique_checker(const self_type &x)
+      : super_type(x) {
+  }
+  // Range constructor.
+  template <class InputIterator>
+  unique_checker(InputIterator b, InputIterator e)
+      : super_type(b, e) {
+  }
+
+  // Insertion routines.
+  std::pair<iterator,bool> insert(const value_type &x) {
+    int size = this->tree_.size();
+    std::pair<typename CheckerType::iterator,bool> checker_res =
+        this->checker_.insert(x);
+    std::pair<iterator,bool> tree_res = this->tree_.insert(x);
+    EXPECT_EQ(*tree_res.first, *checker_res.first);
+    EXPECT_EQ(tree_res.second, checker_res.second);
+    EXPECT_EQ(this->tree_.size(), this->checker_.size());
+    EXPECT_EQ(this->tree_.size(), size + tree_res.second);
+    return tree_res;
+  }
+  iterator insert(iterator position, const value_type &x) {
+    int size = this->tree_.size();
+    std::pair<typename CheckerType::iterator,bool> checker_res =
+        this->checker_.insert(x);
+    iterator tree_res = this->tree_.insert(position, x);
+    EXPECT_EQ(*tree_res, *checker_res.first);
+    EXPECT_EQ(this->tree_.size(), this->checker_.size());
+    EXPECT_EQ(this->tree_.size(), size + checker_res.second);
+    return tree_res;
+  }
+  template <typename InputIterator>
+  void insert(InputIterator b, InputIterator e) {
+    for (; b != e; ++b) {
+      insert(*b);
+    }
+  }
+};
+
+// A checker for multiple sorted associative containers. TreeType is expected
+// to be btree_{multiset,multimap} and CheckerType is expected to be
+// {multiset,multimap}.
+template <typename TreeType, typename CheckerType>
+class multi_checker : public base_checker<TreeType, CheckerType> {
+  typedef base_checker<TreeType, CheckerType> super_type;
+  typedef multi_checker<TreeType, CheckerType> self_type;
+
+ public:
+  typedef typename super_type::iterator iterator;
+  typedef typename super_type::value_type value_type;
+
+ public:
+  // Default constructor.
+  multi_checker()
+      : super_type() {
+  }
+  // Copy constructor.
+  multi_checker(const self_type &x)
+      : super_type(x) {
+  }
+  // Range constructor.
+  template <class InputIterator>
+  multi_checker(InputIterator b, InputIterator e)
+      : super_type(b, e) {
+  }
+
+  // Insertion routines.
+  iterator insert(const value_type &x) {
+    int size = this->tree_.size();
+    typename CheckerType::iterator checker_res = this->checker_.insert(x);
+    iterator tree_res = this->tree_.insert(x);
+    EXPECT_EQ(*tree_res, *checker_res);
+    EXPECT_EQ(this->tree_.size(), this->checker_.size());
+    EXPECT_EQ(this->tree_.size(), size + 1);
+    return tree_res;
+  }
+  iterator insert(iterator position, const value_type &x) {
+    int size = this->tree_.size();
+    typename CheckerType::iterator checker_res = this->checker_.insert(x);
+    iterator tree_res = this->tree_.insert(position, x);
+    EXPECT_EQ(*tree_res, *checker_res);
+    EXPECT_EQ(this->tree_.size(), this->checker_.size());
+    EXPECT_EQ(this->tree_.size(), size + 1);
+    return tree_res;
+  }
+  template <typename InputIterator>
+  void insert(InputIterator b, InputIterator e) {
+    for (; b != e; ++b) {
+      insert(*b);
+    }
+  }
+};
+
+char* GenerateDigits(char buf[16], int val, int maxval) {
+  EXPECT_LE(val, maxval);
+  int p = 15;
+  buf[p--] = 0;
+  while (maxval > 0) {
+    buf[p--] = '0' + (val % 10);
+    val /= 10;
+    maxval /= 10;
+  }
+  return buf + p + 1;
+}
+
+template <typename K>
+struct Generator {
+  int maxval;
+  Generator(int m)
+      : maxval(m) {
+  }
+  K operator()(int i) const {
+    EXPECT_LE(i, maxval);
+    return i;
+  }
+};
+
+template <>
+struct Generator<std::string> {
+  int maxval;
+  Generator(int m)
+      : maxval(m) {
+  }
+  std::string operator()(int i) const {
+    char buf[16];
+    return GenerateDigits(buf, i, maxval);
+  }
+};
+
+template <typename T, typename U>
+struct Generator<std::pair<T, U> > {
+  Generator<typename std::remove_const<T>::type> tgen;
+  Generator<typename std::remove_const<U>::type> ugen;
+
+  Generator(int m)
+      : tgen(m),
+        ugen(m) {
+  }
+  std::pair<T, U> operator()(int i) const {
+    return std::make_pair(tgen(i), ugen(i));
+  }
+};
+
+// Generate values for our tests and benchmarks. Value range is [0, maxval].
+const std::vector<int>& GenerateNumbers(int n, int maxval) {
+  static std::vector<int> values;
+  static std::set<int> unique_values;
+
+  if (values.size() < n) {
+
+    for (int i = values.size(); i < n; i++) {
+      int value;
+      do {
+        value = rand() % (maxval + 1);
+      } while (unique_values.find(value) != unique_values.end());
+
+      values.push_back(value);
+      unique_values.insert(value);
+    }
+  }
+
+  return values;
+}
+
+// Generates values in the range
+// [0, 4 * min(FLAGS_benchmark_values, FLAGS_test_values)]
+template <typename V>
+std::vector<V> GenerateValues(int n) {
+  int two_times_max = 2 * std::max(FLAGS_benchmark_values, FLAGS_test_values);
+  int four_times_max = 2 * two_times_max;
+  EXPECT_LE(n, two_times_max);
+  const std::vector<int> &nums = GenerateNumbers(n, four_times_max);
+  Generator<V> gen(four_times_max);
+  std::vector<V> vec;
+
+  for (int i = 0; i < n; i++) {
+    vec.push_back(gen(nums[i]));
+  }
+
+  return vec;
+}
+
+template <typename T, typename V>
+void DoTest(const char *name, T *b, const std::vector<V> &values) {
+  typename KeyOfValue<typename T::key_type, V>::type key_of_value;
+
+  T &mutable_b = *b;
+  const T &const_b = *b;
+
+  // Test insert.
+  for (int i = 0; i < values.size(); ++i) {
+    mutable_b.insert(values[i]);
+    mutable_b.value_check(values[i]);
+  }
+  assert(mutable_b.size() == values.size());
+
+  const_b.verify();
+  printf("    %s fullness=%0.2f  overhead=%0.2f  bytes-per-value=%0.2f\n",
+         name, const_b.fullness(), const_b.overhead(),
+         double(const_b.bytes_used()) / const_b.size());
+
+  // Test copy constructor.
+  T b_copy(const_b);
+  EXPECT_EQ(b_copy.size(), const_b.size());
+  EXPECT_LE(b_copy.height(), const_b.height());
+  EXPECT_LE(b_copy.internal_nodes(), const_b.internal_nodes());
+  EXPECT_LE(b_copy.leaf_nodes(), const_b.leaf_nodes());
+  for (int i = 0; i < values.size(); ++i) {
+    EXPECT_EQ(*b_copy.find(key_of_value(values[i])), values[i]);
+  }
+
+  // Test range constructor.
+  T b_range(const_b.begin(), const_b.end());
+  EXPECT_EQ(b_range.size(), const_b.size());
+  EXPECT_LE(b_range.height(), const_b.height());
+  EXPECT_LE(b_range.internal_nodes(), const_b.internal_nodes());
+  EXPECT_LE(b_range.leaf_nodes(), const_b.leaf_nodes());
+  for (int i = 0; i < values.size(); ++i) {
+    EXPECT_EQ(*b_range.find(key_of_value(values[i])), values[i]);
+  }
+
+  // Test range insertion for values that already exist.
+  b_range.insert(b_copy.begin(), b_copy.end());
+  b_range.verify();
+
+  // Test range insertion for new values.
+  b_range.clear();
+  b_range.insert(b_copy.begin(), b_copy.end());
+  EXPECT_EQ(b_range.size(), b_copy.size());
+  EXPECT_EQ(b_range.height(), b_copy.height());
+  EXPECT_EQ(b_range.internal_nodes(), b_copy.internal_nodes());
+  EXPECT_EQ(b_range.leaf_nodes(), b_copy.leaf_nodes());
+  for (int i = 0; i < values.size(); ++i) {
+    EXPECT_EQ(*b_range.find(key_of_value(values[i])), values[i]);
+  }
+
+  // Test assignment to self. Nothing should change.
+  b_range.operator=(b_range);
+  EXPECT_EQ(b_range.size(), b_copy.size());
+  EXPECT_EQ(b_range.height(), b_copy.height());
+  EXPECT_EQ(b_range.internal_nodes(), b_copy.internal_nodes());
+  EXPECT_EQ(b_range.leaf_nodes(), b_copy.leaf_nodes());
+
+  // Test assignment of new values.
+  b_range.clear();
+  b_range = b_copy;
+  EXPECT_EQ(b_range.size(), b_copy.size());
+  EXPECT_EQ(b_range.height(), b_copy.height());
+  EXPECT_EQ(b_range.internal_nodes(), b_copy.internal_nodes());
+  EXPECT_EQ(b_range.leaf_nodes(), b_copy.leaf_nodes());
+
+  // Test swap.
+  b_range.clear();
+  b_range.swap(b_copy);
+  EXPECT_EQ(b_copy.size(), 0);
+  EXPECT_EQ(b_range.size(), const_b.size());
+  for (int i = 0; i < values.size(); ++i) {
+    EXPECT_EQ(*b_range.find(key_of_value(values[i])), values[i]);
+  }
+  b_range.swap(b_copy);
+
+  // Test erase via values.
+  for (int i = 0; i < values.size(); ++i) {
+    mutable_b.erase(key_of_value(values[i]));
+    // Erasing a non-existent key should have no effect.
+    EXPECT_EQ(mutable_b.erase(key_of_value(values[i])), 0);
+  }
+
+  const_b.verify();
+  EXPECT_EQ(const_b.internal_nodes(), 0);
+  EXPECT_EQ(const_b.leaf_nodes(), 0);
+  EXPECT_EQ(const_b.size(), 0);
+
+  // Test erase via iterators.
+  mutable_b = b_copy;
+  for (int i = 0; i < values.size(); ++i) {
+    mutable_b.erase(mutable_b.find(key_of_value(values[i])));
+  }
+
+  const_b.verify();
+  EXPECT_EQ(const_b.internal_nodes(), 0);
+  EXPECT_EQ(const_b.leaf_nodes(), 0);
+  EXPECT_EQ(const_b.size(), 0);
+
+  // Test insert with hint.
+  for (int i = 0; i < values.size(); i++) {
+    mutable_b.insert(mutable_b.upper_bound(key_of_value(values[i])), values[i]);
+  }
+
+  const_b.verify();
+
+  // Test dumping of the btree to an ostream. There should be 1 line for each
+  // value.
+  std::stringstream strm;
+  strm << mutable_b.tree();
+  EXPECT_EQ(mutable_b.size(), strcount(strm.str(), '\n'));
+
+  // Test range erase.
+  mutable_b.erase(mutable_b.begin(), mutable_b.end());
+  EXPECT_EQ(mutable_b.size(), 0);
+  const_b.verify();
+
+  // First half.
+  mutable_b = b_copy;
+  typename T::iterator mutable_iter_end = mutable_b.begin();
+  for (int i = 0; i < values.size() / 2; ++i) ++mutable_iter_end;
+  mutable_b.erase(mutable_b.begin(), mutable_iter_end);
+  EXPECT_EQ(mutable_b.size(), values.size() - values.size() / 2);
+  const_b.verify();
+
+  // Second half.
+  mutable_b = b_copy;
+  typename T::iterator mutable_iter_begin = mutable_b.begin();
+  for (int i = 0; i < values.size() / 2; ++i) ++mutable_iter_begin;
+  mutable_b.erase(mutable_iter_begin, mutable_b.end());
+  EXPECT_EQ(mutable_b.size(), values.size() / 2);
+  const_b.verify();
+
+  // Second quarter.
+  mutable_b = b_copy;
+  mutable_iter_begin = mutable_b.begin();
+  for (int i = 0; i < values.size() / 4; ++i) ++mutable_iter_begin;
+  mutable_iter_end = mutable_iter_begin;
+  for (int i = 0; i < values.size() / 4; ++i) ++mutable_iter_end;
+  mutable_b.erase(mutable_iter_begin, mutable_iter_end);
+  EXPECT_EQ(mutable_b.size(), values.size() - values.size() / 4);
+  const_b.verify();
+
+  mutable_b.clear();
+}
+
+template <typename T>
+void ConstTest() {
+  typedef typename T::value_type value_type;
+  typename KeyOfValue<typename T::key_type, value_type>::type key_of_value;
+
+  T mutable_b;
+  const T &const_b = mutable_b;
+
+  // Insert a single value into the container and test looking it up.
+  value_type value = Generator<value_type>(2)(2);
+  mutable_b.insert(value);
+  EXPECT_TRUE(mutable_b.find(key_of_value(value)) != const_b.end());
+  EXPECT_TRUE(const_b.find(key_of_value(value)) != mutable_b.end());
+  EXPECT_EQ(*const_b.lower_bound(key_of_value(value)), value);
+  EXPECT_TRUE(const_b.upper_bound(key_of_value(value)) == const_b.end());
+  EXPECT_EQ(*const_b.equal_range(key_of_value(value)).first, value);
+
+  // We can only create a non-const iterator from a non-const container.
+  typename T::iterator mutable_iter(mutable_b.begin());
+  EXPECT_TRUE(mutable_iter == const_b.begin());
+  EXPECT_TRUE(mutable_iter != const_b.end());
+  EXPECT_TRUE(const_b.begin() == mutable_iter);
+  EXPECT_TRUE(const_b.end() != mutable_iter);
+  typename T::reverse_iterator mutable_riter(mutable_b.rbegin());
+  EXPECT_TRUE(mutable_riter == const_b.rbegin());
+  EXPECT_TRUE(mutable_riter != const_b.rend());
+  EXPECT_TRUE(const_b.rbegin() == mutable_riter);
+  EXPECT_TRUE(const_b.rend() != mutable_riter);
+
+  // We can create a const iterator from a non-const iterator.
+  typename T::const_iterator const_iter(mutable_iter);
+  EXPECT_TRUE(const_iter == mutable_b.begin());
+  EXPECT_TRUE(const_iter != mutable_b.end());
+  EXPECT_TRUE(mutable_b.begin() == const_iter);
+  EXPECT_TRUE(mutable_b.end() != const_iter);
+  typename T::const_reverse_iterator const_riter(mutable_riter);
+  EXPECT_EQ(const_riter, mutable_b.rbegin());
+  EXPECT_TRUE(const_riter != mutable_b.rend());
+  EXPECT_EQ(mutable_b.rbegin(), const_riter);
+  EXPECT_TRUE(mutable_b.rend() != const_riter);
+
+  // Make sure various methods can be invoked on a const container.
+  const_b.verify();
+  EXPECT_FALSE(const_b.empty());
+  EXPECT_EQ(const_b.size(), 1);
+  EXPECT_GT(const_b.max_size(), 0);
+  EXPECT_EQ(const_b.height(), 1);
+  EXPECT_EQ(const_b.count(key_of_value(value)), 1);
+  EXPECT_EQ(const_b.internal_nodes(), 0);
+  EXPECT_EQ(const_b.leaf_nodes(), 1);
+  EXPECT_EQ(const_b.nodes(), 1);
+  EXPECT_GT(const_b.bytes_used(), 0);
+  EXPECT_GT(const_b.fullness(), 0);
+  EXPECT_GT(const_b.overhead(), 0);
+}
+
+template <typename T, typename C>
+void BtreeTest() {
+  ConstTest<T>();
+
+  typedef typename std::remove_const<typename T::value_type>::type V;
+  std::vector<V> random_values = GenerateValues<V>(FLAGS_test_values);
+
+  unique_checker<T, C> container;
+
+  // Test key insertion/deletion in sorted order.
+  std::vector<V> sorted_values(random_values);
+  sort(sorted_values.begin(), sorted_values.end());
+  DoTest("sorted:    ", &container, sorted_values);
+
+  // Test key insertion/deletion in reverse sorted order.
+  reverse(sorted_values.begin(), sorted_values.end());
+  DoTest("rsorted:   ", &container, sorted_values);
+
+  // Test key insertion/deletion in random order.
+  DoTest("random:    ", &container, random_values);
+}
+
+template <typename T, typename C>
+void BtreeMultiTest() {
+  ConstTest<T>();
+
+  typedef typename std::remove_const<typename T::value_type>::type V;
+  const std::vector<V>& random_values = GenerateValues<V>(FLAGS_test_values);
+
+  multi_checker<T, C> container;
+
+  // Test keys in sorted order.
+  std::vector<V> sorted_values(random_values);
+  sort(sorted_values.begin(), sorted_values.end());
+  DoTest("sorted:    ", &container, sorted_values);
+
+  // Test keys in reverse sorted order.
+  reverse(sorted_values.begin(), sorted_values.end());
+  DoTest("rsorted:   ", &container, sorted_values);
+
+  // Test keys in random order.
+  DoTest("random:    ", &container, random_values);
+
+  // Test keys in random order w/ duplicates.
+  std::vector<V> duplicate_values(random_values);
+  duplicate_values.insert(
+      duplicate_values.end(), random_values.begin(), random_values.end());
+  DoTest("duplicates:", &container, duplicate_values);
+
+  // Test all identical keys.
+  std::vector<V> identical_values(100);
+  fill(identical_values.begin(), identical_values.end(), Generator<V>(2)(2));
+  DoTest("identical: ", &container, identical_values);
+}
+
+template <typename T, typename Alloc = std::allocator<T> >
+class TestAllocator : public Alloc {
+ public:
+  typedef typename Alloc::pointer pointer;
+  typedef typename Alloc::size_type size_type;
+
+  TestAllocator() : bytes_used_(NULL) { }
+  TestAllocator(int64_t *bytes_used) : bytes_used_(bytes_used) { }
+
+  // Constructor used for rebinding
+  template <class U>
+  TestAllocator(const TestAllocator<U>& x)
+      : Alloc(x),
+        bytes_used_(x.bytes_used()) {
+  }
+
+  pointer allocate(size_type n, std::allocator<void>::const_pointer hint = 0) {
+    EXPECT_TRUE(bytes_used_ != NULL);
+    *bytes_used_ += n * sizeof(T);
+    return Alloc::allocate(n, hint);
+  }
+
+  void deallocate(pointer p, size_type n) {
+    Alloc::deallocate(p, n);
+    EXPECT_TRUE(bytes_used_ != NULL);
+    *bytes_used_ -= n * sizeof(T);
+  }
+
+  // Rebind allows an allocator<T> to be used for a different type
+  template <class U> struct rebind {
+    typedef TestAllocator<U, typename Alloc::template rebind<U>::other> other;
+  };
+
+  int64_t* bytes_used() const { return bytes_used_; }
+
+ private:
+  int64_t *bytes_used_;
+};
+
+template <typename T>
+void BtreeAllocatorTest() {
+  typedef typename T::value_type value_type;
+
+  int64_t alloc1 = 0;
+  int64_t alloc2 = 0;
+  T b1(typename T::key_compare(), &alloc1);
+  T b2(typename T::key_compare(), &alloc2);
+
+  // This should swap the allocators!
+  swap(b1, b2);
+
+  for (int i = 0; i < 1000; i++) {
+    b1.insert(Generator<value_type>(1000)(i));
+  }
+
+  // We should have allocated out of alloc2!
+  EXPECT_LE(b1.bytes_used(), alloc2 + sizeof(b1));
+  EXPECT_GT(alloc2, alloc1);
+}
+
+template <typename T>
+void BtreeMapTest() {
+  typedef typename T::value_type value_type;
+  typedef typename T::mapped_type mapped_type;
+
+  mapped_type m = Generator<mapped_type>(0)(0);
+  (void) m;
+
+  T b;
+
+  // Verify we can insert using operator[].
+  for (int i = 0; i < 1000; i++) {
+    value_type v = Generator<value_type>(1000)(i);
+    b[v.first] = v.second;
+  }
+  EXPECT_EQ(b.size(), 1000);
+
+  // Test whether we can use the "->" operator on iterators and
+  // reverse_iterators. This stresses the btree_map_params::pair_pointer
+  // mechanism.
+  EXPECT_EQ(b.begin()->first, Generator<value_type>(1000)(0).first);
+  EXPECT_EQ(b.begin()->second, Generator<value_type>(1000)(0).second);
+  EXPECT_EQ(b.rbegin()->first, Generator<value_type>(1000)(999).first);
+  EXPECT_EQ(b.rbegin()->second, Generator<value_type>(1000)(999).second);
+}
+
+template <typename T>
+void BtreeMultiMapTest() {
+  typedef typename T::mapped_type mapped_type;
+  mapped_type m = Generator<mapped_type>(0)(0);
+  (void) m;
+}
+
+} // namespace btree
+
+#endif  // UTIL_BTREE_BTREE_TEST_H__