Added librarys and test application

include/entityx/3rdparty/simplesignal.h

@@ -0,0 +1,580 @@
+// CC0 Public Domain: http://creativecommons.org/publicdomain/zero/1.0/
+#ifndef SIMPLE_SIGNAL_H__
+#define SIMPLE_SIGNAL_H__
+
+#include <assert.h>
+#include <stdint.h>
+#include <vector>
+#include <functional>
+
+namespace Simple {
+
+namespace Lib {
+
+/// ProtoSignal is the template implementation for callback list.
+template <typename, typename>
+class ProtoSignal;  // undefined
+
+/// CollectorInvocation invokes signal handlers differently depending on return
+/// type.
+template <typename, typename>
+struct CollectorInvocation;
+
+/// CollectorLast returns the result of the last signal handler from a signal
+/// emission.
+template <typename Result>
+struct CollectorLast {
+  typedef Result CollectorResult;
+  explicit CollectorLast() : last_() {}
+  inline bool operator()(Result r) {
+    last_ = r;
+    return true;
+  }
+  CollectorResult result() { return last_; }
+
+ private:
+  Result last_;
+};
+
+/// CollectorDefault implements the default signal handler collection behaviour.
+template <typename Result>
+struct CollectorDefault : CollectorLast<Result> {};
+
+/// CollectorDefault specialisation for signals with void return type.
+template <>
+struct CollectorDefault<void> {
+  typedef void CollectorResult;
+  void result() {}
+  inline bool operator()(void) { return true; }
+};
+
+/// CollectorInvocation specialisation for regular signals.
+template <class Collector, class R, class... Args>
+struct CollectorInvocation<Collector, R(Args...)> {
+  inline bool invoke(Collector &collector, const std::function<R(Args...)> &cbf,
+                     Args... args) {
+    return collector(cbf(args...));
+  }
+};
+
+/// CollectorInvocation specialisation for signals with void return type.
+template <class Collector, class... Args>
+struct CollectorInvocation<Collector, void(Args...)> {
+  inline bool invoke(Collector &collector,
+                     const std::function<void(Args...)> &cbf, Args... args) {
+    cbf(args...);
+    return collector();
+  }
+};
+
+/// ProtoSignal template specialised for the callback signature and collector.
+template <class Collector, class R, class... Args>
+class ProtoSignal<R(Args...), Collector> : private CollectorInvocation<
+                                               Collector, R(Args...)> {
+ protected:
+  typedef std::function<R(Args...)> CbFunction;
+  typedef typename CbFunction::result_type Result;
+  typedef typename Collector::CollectorResult CollectorResult;
+
+ private:
+  /// SignalLink implements a doubly-linked ring with ref-counted nodes
+  /// containing the signal handlers.
+  struct SignalLink {
+    SignalLink *next, *prev;
+    CbFunction function;
+    int ref_count;
+    explicit SignalLink(const CbFunction &cbf)
+        : next(0), prev(0), function(cbf), ref_count(1) {}
+    /*dtor*/ ~SignalLink() { assert(ref_count == 0); }
+    void incref() {
+      ref_count += 1;
+      assert(ref_count > 0);
+    }
+    void decref() {
+      ref_count -= 1;
+      if (!ref_count)
+        delete this;
+      else
+        assert(ref_count > 0);
+    }
+    void unlink() {
+      function = nullptr;
+      if (next) next->prev = prev;
+      if (prev) prev->next = next;
+      decref();
+      // leave intact ->next, ->prev for stale iterators
+    }
+    size_t add_before(const CbFunction &cb) {
+      SignalLink *link = new SignalLink(cb);
+      link->prev = prev;  // link to last
+      link->next = this;
+      prev->next = link;  // link from last
+      prev = link;
+      static_assert(sizeof(link) == sizeof(size_t), "sizeof size_t");
+      return size_t(link);
+    }
+    bool deactivate(const CbFunction &cbf) {
+      if (cbf == function) {
+        function = 0;  // deactivate static head
+        return true;
+      }
+      for (SignalLink *link = this->next ? this->next : this; link != this;
+           link = link->next)
+        if (cbf == link->function) {
+          link->unlink();  // deactivate and unlink sibling
+          return true;
+        }
+      return false;
+    }
+    bool remove_sibling(size_t id) {
+      for (SignalLink *link = this->next ? this->next : this; link != this;
+           link = link->next)
+        if (id == size_t(link)) {
+          link->unlink();  // deactivate and unlink sibling
+          return true;
+        }
+      return false;
+    }
+  };
+  SignalLink *callback_ring_;  // linked ring of callback nodes
+  /*copy-ctor*/ ProtoSignal(const ProtoSignal &) = delete;
+  ProtoSignal &operator=(const ProtoSignal &) = delete;
+  void ensure_ring() {
+    if (!callback_ring_) {
+      callback_ring_ = new SignalLink(CbFunction());  // ref_count = 1
+      callback_ring_->incref();  // ref_count = 2, head of ring, can be
+                                 // deactivated but not removed
+      callback_ring_->next = callback_ring_;  // ring head initialization
+      callback_ring_->prev = callback_ring_;  // ring tail initialization
+    }
+  }
+
+ public:
+  /// ProtoSignal constructor, connects default callback if non-0.
+  ProtoSignal(const CbFunction &method) : callback_ring_(0) {
+    if (method != 0) {
+      ensure_ring();
+      callback_ring_->function = method;
+    }
+  }
+  /// ProtoSignal destructor releases all resources associated with this signal.
+  ~ProtoSignal() {
+    if (callback_ring_) {
+      while (callback_ring_->next != callback_ring_)
+        callback_ring_->next->unlink();
+      assert(callback_ring_->ref_count >= 2);
+      callback_ring_->decref();
+      callback_ring_->decref();
+    }
+  }
+  /// Operator to add a new function or lambda as signal handler, returns a
+  /// handler connection ID.
+  size_t connect(const CbFunction &cb) {
+    ensure_ring();
+    return callback_ring_->add_before(cb);
+  }
+  /// Operator to remove a signal handler through it connection ID, returns if a
+  /// handler was removed.
+  bool disconnect(size_t connection) {
+    return callback_ring_ ? callback_ring_->remove_sibling(connection) : false;
+  }
+  /// Emit a signal, i.e. invoke all its callbacks and collect return types with
+  /// the Collector.
+  CollectorResult emit(Args... args) {
+    Collector collector;
+    if (!callback_ring_) return collector.result();
+    SignalLink *link = callback_ring_;
+    link->incref();
+    do {
+      if (link->function != 0) {
+        const bool continue_emission =
+            this->invoke(collector, link->function, args...);
+        if (!continue_emission) break;
+      }
+      SignalLink *old = link;
+      link = old->next;
+      link->incref();
+      old->decref();
+    } while (link != callback_ring_);
+    link->decref();
+    return collector.result();
+  }
+  // Number of connected slots.
+  std::size_t size() {
+    std::size_t size = 0;
+    SignalLink *link = callback_ring_;
+    link->incref();
+    do {
+      if (link->function != 0) {
+        size++;
+      }
+      SignalLink *old = link;
+      link = old->next;
+      link->incref();
+      old->decref();
+    } while (link != callback_ring_);
+    return size;
+  }
+};
+
+}  // Lib
+   // namespace Simple
+
+/**
+ * Signal is a template type providing an interface for arbitrary callback
+ * lists.
+ * A signal type needs to be declared with the function signature of its
+ * callbacks,
+ * and optionally a return result collector class type.
+ * Signal callbacks can be added with operator+= to a signal and removed with
+ * operator-=, using
+ * a callback connection ID return by operator+= as argument.
+ * The callbacks of a signal are invoked with the emit() method and arguments
+ * according to the signature.
+ * The result returned by emit() depends on the signal collector class. By
+ * default, the result of
+ * the last callback is returned from emit(). Collectors can be implemented to
+ * accumulate callback
+ * results or to halt a running emissions in correspondance to callback results.
+ * The signal implementation is safe against recursion, so callbacks may be
+ * removed and
+ * added during a signal emission and recursive emit() calls are also safe.
+ * The overhead of an unused signal is intentionally kept very low, around the
+ * size of a single pointer.
+ * Note that the Signal template types is non-copyable.
+ */
+template <typename SignalSignature,
+          class Collector = Lib::CollectorDefault<
+              typename std::function<SignalSignature>::result_type>>
+struct Signal /*final*/ : Lib::ProtoSignal<SignalSignature, Collector> {
+  typedef Lib::ProtoSignal<SignalSignature, Collector> ProtoSignal;
+  typedef typename ProtoSignal::CbFunction CbFunction;
+  /// Signal constructor, supports a default callback as argument.
+  Signal(const CbFunction &method = CbFunction()) : ProtoSignal(method) {}
+};
+
+/// This function creates a std::function by binding @a object to the member
+/// function pointer @a method.
+template <class Instance, class Class, class R, class... Args>
+std::function<R(Args...)> slot(Instance &object, R (Class::*method)(Args...)) {
+  return [&object, method](Args... args) { return (object.*method)(args...); };
+}
+
+/// This function creates a std::function by binding @a object to the member
+/// function pointer @a method.
+template <class Class, class R, class... Args>
+std::function<R(Args...)> slot(Class *object, R (Class::*method)(Args...)) {
+  return [object, method](Args... args) { return (object->*method)(args...); };
+}
+
+/// Keep signal emissions going while all handlers return !0 (true).
+template <typename Result>
+struct CollectorUntil0 {
+  typedef Result CollectorResult;
+  explicit CollectorUntil0() : result_() {}
+  const CollectorResult &result() { return result_; }
+  inline bool operator()(Result r) {
+    result_ = r;
+    return result_ ? true : false;
+  }
+
+ private:
+  CollectorResult result_;
+};
+
+/// Keep signal emissions going while all handlers return 0 (false).
+template <typename Result>
+struct CollectorWhile0 {
+  typedef Result CollectorResult;
+  explicit CollectorWhile0() : result_() {}
+  const CollectorResult &result() { return result_; }
+  inline bool operator()(Result r) {
+    result_ = r;
+    return result_ ? false : true;
+  }
+
+ private:
+  CollectorResult result_;
+};
+
+/// CollectorVector returns the result of the all signal handlers from a signal
+/// emission in a std::vector.
+template <typename Result>
+struct CollectorVector {
+  typedef std::vector<Result> CollectorResult;
+  const CollectorResult &result() { return result_; }
+  inline bool operator()(Result r) {
+    result_.push_back(r);
+    return true;
+  }
+
+ private:
+  CollectorResult result_;
+};
+
+}  // Simple
+
+#endif  // SIMPLE_SIGNAL_H__
+
+#ifdef ENABLE_SIMPLE_SIGNAL_TESTS
+
+#include <string>
+#include <stdarg.h>
+#include <time.h>
+#include <sys/time.h>
+
+#ifdef __MACH__
+#include <mach/clock.h>
+#include <mach/mach.h>
+#endif
+
+static std::string string_printf(const char *format, ...)
+    __attribute__((__format__(__printf__, 1, 2)));
+static std::string string_printf(const char *format, ...) {
+  std::string result;
+  char *str = 0;
+  va_list args;
+  va_start(args, format);
+  if (vasprintf(&str, format, args) >= 0) result = str;
+  va_end(args);
+  if (str) free(str);
+  return result;
+}
+
+static uint64_t timestamp_benchmark() {
+  struct timespec tp = {0, 0};
+
+#ifdef __MACH__  // OS X does not have clock_gettime, use clock_get_time
+  clock_serv_t cclock;
+  mach_timespec_t mts;
+  host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock);
+  clock_get_time(cclock, &mts);
+  mach_port_deallocate(mach_task_self(), cclock);
+  tp.tv_sec = mts.tv_sec;
+  tp.tv_nsec = mts.tv_nsec;
+#else
+  clock_gettime(CLOCK_REALTIME, &tp);
+#endif
+  uint64_t stamp = tp.tv_sec * 1000000000ULL + tp.tv_nsec;
+  return stamp;
+}
+
+struct TestCounter {
+  static uint64_t get();
+  static void set(uint64_t);
+  static void add2(void *, uint64_t);
+};
+
+namespace {  // Anon
+void (*test_counter_add2)(void *, uint64_t) =
+    TestCounter::add2;  // external symbol to prevent easy inlining
+static uint64_t test_counter_var = 0;
+}  // Anon
+
+class BasicSignalTests {
+  static std::string accu;
+  struct Foo {
+    char foo_bool(float f, int i, std::string s) {
+      accu += string_printf("Foo: %.2f\n", f + i + s.size());
+      return true;
+    }
+  };
+  static char float_callback(float f, int, std::string) {
+    accu += string_printf("float: %.2f\n", f);
+    return 0;
+  }
+
+ public:
+  static void run() {
+    accu = "";
+    Simple::Signal<char(float, int, std::string)> sig1;
+    size_t id1 = sig1.connect(float_callback);
+    size_t id2 = sig1.connect([](float, int i, std::string) {
+      accu += string_printf("int: %d\n", i);
+      return 0;
+    });
+    size_t id3 = sig1.connect([](float, int, const std::string &s) {
+      accu += string_printf("string: %s\n", s.c_str());
+      return 0;
+    });
+    sig1.emit(.3, 4, "huhu");
+    bool success;
+    success = sig1.disconnect(id1);
+    assert(success == true);
+    success = sig1.disconnect(id1);
+    assert(success == false);
+    success = sig1.disconnect(id2);
+    assert(success == true);
+    success = sig1.disconnect(id3);
+    assert(success == true);
+    success = sig1.disconnect(id3);
+    assert(success == false);
+    success = sig1.disconnect(id2);
+    assert(success == false);
+    Foo foo;
+    sig1.connect(Simple::slot(foo, &Foo::foo_bool));
+    sig1.connect(Simple::slot(&foo, &Foo::foo_bool));
+    sig1.emit(.5, 1, "12");
+
+    Simple::Signal<void(std::string, int)> sig2;
+    sig2.connect([](std::string msg,
+                    int) { accu += string_printf("msg: %s", msg.c_str()); });
+    sig2.connect([](std::string,
+                    int d) { accu += string_printf(" *%d*\n", d); });
+    sig2.emit("in sig2", 17);
+
+    accu += "DONE";
+
+    const char *expected =
+        "float: 0.30\n"
+        "int: 4\n"
+        "string: huhu\n"
+        "Foo: 3.50\n"
+        "Foo: 3.50\n"
+        "msg: in sig2 *17*\n"
+        "DONE";
+    assert(accu == expected);
+  }
+};
+std::string BasicSignalTests::accu;
+
+class TestCollectorVector {
+  static int handler1() { return 1; }
+  static int handler42() { return 42; }
+  static int handler777() { return 777; }
+
+ public:
+  static void run() {
+    Simple::Signal<int(), Simple::CollectorVector<int>> sig_vector;
+    sig_vector.connect(handler777);
+    sig_vector.connect(handler42);
+    sig_vector.connect(handler1);
+    sig_vector.connect(handler42);
+    sig_vector.connect(handler777);
+    std::vector<int> results = sig_vector.emit();
+    const std::vector<int> reference = {777, 42, 1, 42, 777, };
+    assert(results == reference);
+  }
+};
+
+class TestCollectorUntil0 {
+  bool check1, check2;
+  TestCollectorUntil0() : check1(0), check2(0) {}
+  bool handler_true() {
+    check1 = true;
+    return true;
+  }
+  bool handler_false() {
+    check2 = true;
+    return false;
+  }
+  bool handler_abort() { abort(); }
+
+ public:
+  static void run() {
+    TestCollectorUntil0 self;
+    Simple::Signal<bool(), Simple::CollectorUntil0<bool>> sig_until0;
+    sig_until0.connect(Simple::slot(self, &TestCollectorUntil0::handler_true));
+    sig_until0.connect(Simple::slot(self, &TestCollectorUntil0::handler_false));
+    sig_until0.connect(Simple::slot(self, &TestCollectorUntil0::handler_abort));
+    assert(!self.check1 && !self.check2);
+    const bool result = sig_until0.emit();
+    assert(!result && self.check1 && self.check2);
+  }
+};
+
+class TestCollectorWhile0 {
+  bool check1, check2;
+  TestCollectorWhile0() : check1(0), check2(0) {}
+  bool handler_0() {
+    check1 = true;
+    return false;
+  }
+  bool handler_1() {
+    check2 = true;
+    return true;
+  }
+  bool handler_abort() { abort(); }
+
+ public:
+  static void run() {
+    TestCollectorWhile0 self;
+    Simple::Signal<bool(), Simple::CollectorWhile0<bool>> sig_while0;
+    sig_while0.connect(Simple::slot(self, &TestCollectorWhile0::handler_0));
+    sig_while0.connect(Simple::slot(self, &TestCollectorWhile0::handler_1));
+    sig_while0.connect(Simple::slot(self, &TestCollectorWhile0::handler_abort));
+    assert(!self.check1 && !self.check2);
+    const bool result = sig_while0.emit();
+    assert(result == true && self.check1 && self.check2);
+  }
+};
+
+static void bench_simple_signal() {
+  Simple::Signal<void(void *, uint64_t)> sig_increment;
+  sig_increment.connect(test_counter_add2);
+  const uint64_t start_counter = TestCounter::get();
+  const uint64_t benchstart = timestamp_benchmark();
+  uint64_t i;
+  for (i = 0; i < 999999; i++) {
+    sig_increment.emit(0, 1);
+  }
+  const uint64_t benchdone = timestamp_benchmark();
+  const uint64_t end_counter = TestCounter::get();
+  assert(end_counter - start_counter == i);
+  printf("OK\n  Benchmark: Simple::Signal: %fns per emission (size=%zu): ",
+         size_t(benchdone - benchstart) * 1.0 / size_t(i),
+         sizeof(sig_increment));
+}
+
+static void bench_callback_loop() {
+  void (*counter_increment)(void *, uint64_t) = test_counter_add2;
+  const uint64_t start_counter = TestCounter::get();
+  const uint64_t benchstart = timestamp_benchmark();
+  uint64_t i;
+  for (i = 0; i < 999999; i++) {
+    counter_increment(0, 1);
+  }
+  const uint64_t benchdone = timestamp_benchmark();
+  const uint64_t end_counter = TestCounter::get();
+  assert(end_counter - start_counter == i);
+  printf("OK\n  Benchmark: callback loop: %fns per round: ",
+         size_t(benchdone - benchstart) * 1.0 / size_t(i));
+}
+
+uint64_t TestCounter::get() { return test_counter_var; }
+
+void TestCounter::set(uint64_t v) { test_counter_var = v; }
+
+void TestCounter::add2(void *, uint64_t v) { test_counter_var += v; }
+
+int main(int argc, char *argv[]) {
+  printf("Signal/Basic Tests: ");
+  BasicSignalTests::run();
+  printf("OK\n");
+
+  printf("Signal/CollectorVector: ");
+  TestCollectorVector::run();
+  printf("OK\n");
+
+  printf("Signal/CollectorUntil0: ");
+  TestCollectorUntil0::run();
+  printf("OK\n");
+
+  printf("Signal/CollectorWhile0: ");
+  TestCollectorWhile0::run();
+  printf("OK\n");
+
+  printf("Signal/Benchmark: Simple::Signal: ");
+  bench_simple_signal();
+  printf("OK\n");
+
+  printf("Signal/Benchmark: callback loop: ");
+  bench_callback_loop();
+  printf("OK\n");
+
+  return 0;
+}
+
+#endif  // DISABLE_TESTS
+
+// g++ -Wall -O2 -std=gnu++0x -pthread simplesignal.cc -lrt && ./a.out

include/entityx/Benchmarks_test.cc

@@ -0,0 +1,154 @@
+#define CATCH_CONFIG_MAIN
+
+#include <iostream>
+#include <vector>
+#include "entityx/3rdparty/catch.hpp"
+#include "entityx/help/Timer.h"
+#include "entityx/Entity.h"
+
+using std::uint64_t;
+using std::cout;
+using std::endl;
+using std::vector;
+
+using entityx::Receiver;
+using entityx::Component;
+using entityx::ComponentHandle;
+using entityx::Entity;
+using entityx::EntityCreatedEvent;
+using entityx::EntityDestroyedEvent;
+using entityx::EventManager;
+using entityx::EntityManager;
+
+struct AutoTimer {
+  ~AutoTimer() {
+    cout << timer_.elapsed() << " seconds elapsed" << endl;
+  }
+
+private:
+  entityx::help::Timer timer_;
+};
+
+struct Listener : public Receiver<Listener> {
+  void receive(const EntityCreatedEvent &event) { ++created; }
+  void receive(const EntityDestroyedEvent &event) { ++destroyed; }
+
+  int created = 0;
+  int destroyed = 0;
+};
+
+struct Position : public Component<Position> {
+};
+
+
+struct Direction : public Component<Direction> {
+};
+
+
+struct BenchmarkFixture {
+  BenchmarkFixture() : em(ev) {}
+
+  EventManager ev;
+  EntityManager em;
+};
+
+
+TEST_CASE_METHOD(BenchmarkFixture, "TestCreateEntities") {
+  AutoTimer t;
+
+  uint64_t count = 10000000L;
+  cout << "creating " << count << " entities" << endl;
+
+  for (uint64_t i = 0; i < count; i++) {
+    em.create();
+  }
+}
+
+
+TEST_CASE_METHOD(BenchmarkFixture, "TestDestroyEntities") {
+  uint64_t count = 10000000L;
+  vector<Entity> entities;
+  for (uint64_t i = 0; i < count; i++) {
+    entities.push_back(em.create());
+  }
+
+  AutoTimer t;
+  cout << "destroying " << count << " entities" << endl;
+
+  for (auto e : entities) {
+    e.destroy();
+  }
+}
+
+TEST_CASE_METHOD(BenchmarkFixture, "TestCreateEntitiesWithListener") {
+  Listener listen;
+  ev.subscribe<EntityCreatedEvent>(listen);
+
+  int count = 10000000L;
+
+  AutoTimer t;
+  cout << "creating " << count << " entities while notifying a single EntityCreatedEvent listener" << endl;
+
+  vector<Entity> entities;
+  for (int i = 0; i < count; i++) {
+    entities.push_back(em.create());
+  }
+
+  REQUIRE(entities.size() == count);
+  REQUIRE(listen.created == count);
+}
+
+TEST_CASE_METHOD(BenchmarkFixture, "TestDestroyEntitiesWithListener") {
+  int count = 10000000;
+  vector<Entity> entities;
+  for (int i = 0; i < count; i++) {
+    entities.push_back(em.create());
+  }
+
+  Listener listen;
+  ev.subscribe<EntityDestroyedEvent>(listen);
+
+  AutoTimer t;
+  cout << "destroying " << count << " entities while notifying a single EntityDestroyedEvent listener" << endl;
+
+  for (auto &e : entities) {
+    e.destroy();
+  }
+
+  REQUIRE(entities.size() == count);
+  REQUIRE(listen.destroyed == count);
+}
+
+TEST_CASE_METHOD(BenchmarkFixture, "TestEntityIteration") {
+  int count = 10000000;
+  for (int i = 0; i < count; i++) {
+    auto e = em.create();
+    e.assign<Position>();
+  }
+
+  AutoTimer t;
+  cout << "iterating over " << count << " entities, unpacking one component" << endl;
+
+  ComponentHandle<Position> position;
+  for (auto e : em.entities_with_components(position)) {
+    (void)e;
+  }
+}
+
+TEST_CASE_METHOD(BenchmarkFixture, "TestEntityIterationUnpackTwo") {
+  int count = 10000000;
+  for (int i = 0; i < count; i++) {
+    auto e = em.create();
+    e.assign<Position>();
+    e.assign<Direction>();
+  }
+
+  AutoTimer t;
+  cout << "iterating over " << count << " entities, unpacking two components" << endl;
+
+  ComponentHandle<Position> position;
+  ComponentHandle<Direction> direction;
+  for (auto e : em.entities_with_components(position, direction)) {
+    (void)e;
+  }
+}

include/entityx/Entity.cc

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#include <algorithm>
+#include "entityx/Entity.h"
+
+namespace entityx {
+
+const Entity::Id Entity::INVALID;
+BaseComponent::Family BaseComponent::family_counter_ = 0;
+
+void Entity::invalidate() {
+  id_ = INVALID;
+  manager_ = nullptr;
+}
+
+void Entity::destroy() {
+  assert(valid());
+  manager_->destroy(id_);
+  invalidate();
+}
+
+std::bitset<entityx::MAX_COMPONENTS> Entity::component_mask() const {
+  return manager_->component_mask(id_);
+}
+
+EntityManager::EntityManager(EventManager &event_manager) : event_manager_(event_manager) {
+}
+
+EntityManager::~EntityManager() {
+  reset();
+}
+
+void EntityManager::reset() {
+  for (Entity entity : entities_for_debugging()) entity.destroy();
+  for (BasePool *pool : component_pools_) {
+    if (pool) delete pool;
+  }
+  for (BaseComponentHelper *helper : component_helpers_) {
+    if (helper) delete helper;
+  }
+  component_pools_.clear();
+  component_helpers_.clear();
+  entity_component_mask_.clear();
+  entity_version_.clear();
+  free_list_.clear();
+  index_counter_ = 0;
+}
+
+EntityCreatedEvent::~EntityCreatedEvent() {}
+EntityDestroyedEvent::~EntityDestroyedEvent() {}
+
+
+}  // namespace entityx

include/entityx/Entity_test.cc

@@ -0,0 +1,680 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#define CATCH_CONFIG_MAIN
+
+#include <algorithm>
+#include <iterator>
+#include <string>
+#include <utility>
+#include <vector>
+#include <set>
+#include <map>
+#include "entityx/3rdparty/catch.hpp"
+#include "entityx/entityx.h"
+
+// using namespace std;
+using namespace entityx;
+
+using std::ostream;
+using std::vector;
+using std::set;
+using std::map;
+using std::pair;
+using std::string;
+
+template <typename T>
+int size(const T &t) {
+  int n = 0;
+  for (auto i : t) {
+    ++n;
+    (void)i;  // Unused on purpose, suppress warning
+  }
+  return n;
+}
+
+struct Position {
+  Position(float x = 0.0f, float y = 0.0f) : x(x), y(y) {}
+
+  bool operator==(const Position &other) const {
+    return x == other.x && y == other.y;
+  }
+
+  float x, y;
+};
+
+ostream &operator<<(ostream &out, const Position &position) {
+  out << "Position(" << position.x << ", " << position.y << ")";
+  return out;
+}
+
+struct Direction {
+  Direction(float x = 0.0f, float y = 0.0f) : x(x), y(y) {}
+
+  bool operator==(const Direction &other) const {
+    return x == other.x && y == other.y;
+  }
+
+  float x, y;
+};
+
+ostream &operator<<(ostream &out, const Direction &direction) {
+  out << "Direction(" << direction.x << ", " << direction.y << ")";
+  return out;
+}
+
+struct Tag : Component<Tag> {
+  explicit Tag(string tag) : tag(tag) {}
+
+  bool operator==(const Tag &other) const { return tag == other.tag; }
+
+  string tag;
+};
+
+ostream &operator<<(ostream &out, const Tag &tag) {
+  out << "Tag(" << tag.tag << ")";
+  return out;
+}
+
+
+struct EntityManagerFixture {
+  EntityManagerFixture() : em(ev) {}
+
+  EventManager ev;
+  EntityManager em;
+};
+
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestCreateEntity") {
+  REQUIRE(em.size() ==  0UL);
+
+  Entity e2;
+  REQUIRE(!(e2.valid()));
+
+  Entity e = em.create();
+  REQUIRE(e.valid());
+  REQUIRE(em.size() ==  1UL);
+
+  e2 = e;
+  REQUIRE(e2.valid());
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityAsBoolean") {
+  REQUIRE(em.size() ==  0UL);
+  Entity e = em.create();
+  REQUIRE(e.valid());
+  REQUIRE(em.size() ==  1UL);
+  REQUIRE(!(!e));
+
+  e.destroy();
+
+  REQUIRE(em.size() ==  0UL);
+
+  REQUIRE(!e);
+
+  Entity e2;  // Not initialized
+  REQUIRE(!e2);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityReuse") {
+  Entity e1 = em.create();
+  Entity e2 = e1;
+  auto id = e1.id();
+  REQUIRE(e1.valid());
+  REQUIRE(e2.valid());
+  e1.destroy();
+  REQUIRE(!e1.valid());
+  REQUIRE(!e2.valid());
+  Entity e3 = em.create();
+  // It is assumed that the allocation will reuse the same entity id, though
+  // the version will change.
+  auto new_id = e3.id();
+  REQUIRE(new_id !=  id);
+  REQUIRE((new_id.id() & 0xffffffffUL) == (id.id() & 0xffffffffUL));
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentConstruction") {
+  auto e = em.create();
+  auto p = e.assign<Position>(1, 2);
+  auto cp = e.component<Position>();
+  REQUIRE(p ==  cp);
+  REQUIRE(1.0 == Approx(cp->x));
+  REQUIRE(2.0 == Approx(cp->y));
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestDestroyEntity") {
+  Entity e = em.create();
+  Entity f = em.create();
+  e.assign<Position>();
+  f.assign<Position>();
+  e.assign<Direction>();
+  f.assign<Direction>();
+
+  REQUIRE(e.valid());
+  REQUIRE(f.valid());
+  REQUIRE(static_cast<bool>(e.component<Position>()));
+  REQUIRE(static_cast<bool>(e.component<Direction>()));
+  REQUIRE(static_cast<bool>(f.component<Position>()));
+  REQUIRE(static_cast<bool>(f.component<Direction>()));
+
+  e.destroy();
+
+  REQUIRE(!(e.valid()));
+  REQUIRE(f.valid());
+  REQUIRE(static_cast<bool>(f.component<Position>()));
+  REQUIRE(static_cast<bool>(f.component<Direction>()));
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestGetEntitiesWithComponent") {
+  Entity e = em.create();
+  Entity f = em.create();
+  Entity g = em.create();
+  e.assign<Position>();
+  e.assign<Direction>();
+  f.assign<Position>();
+  g.assign<Position>();
+  REQUIRE(3 ==  size(em.entities_with_components<Position>()));
+  REQUIRE(1 ==  size(em.entities_with_components<Direction>()));
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestGetEntitiesWithIntersectionOfComponents") {
+  vector<Entity> entities;
+  for (int i = 0; i < 150; ++i) {
+    Entity e = em.create();
+    entities.push_back(e);
+    if (i % 2 == 0) e.assign<Position>();
+    if (i % 3 == 0) e.assign<Direction>();
+  }
+  REQUIRE(50 ==  size(em.entities_with_components<Direction>()));
+  REQUIRE(75 ==  size(em.entities_with_components<Position>()));
+  REQUIRE(25 ==  size(em.entities_with_components<Direction, Position>()));
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestGetEntitiesWithComponentAndUnpacking") {
+  vector<Entity::Id> entities;
+  Entity e = em.create();
+  Entity f = em.create();
+  Entity g = em.create();
+  std::vector<std::pair<ComponentHandle<Position>, ComponentHandle<Direction>>> position_directions;
+  position_directions.push_back(std::make_pair(
+      e.assign<Position>(1.0f, 2.0f), e.assign<Direction>(3.0f, 4.0f)));
+  position_directions.push_back(std::make_pair(
+      f.assign<Position>(7.0f, 8.0f), f.assign<Direction>(9.0f, 10.0f)));
+  auto thetag = f.assign<Tag>("tag");
+  g.assign<Position>(5.0f, 6.0f);
+  int i = 0;
+
+  ComponentHandle<Position> position;
+  REQUIRE(3 ==  size(em.entities_with_components(position)));
+
+  ComponentHandle<Direction> direction;
+  for (auto unused_entity : em.entities_with_components(position, direction)) {
+    (void)unused_entity;
+    REQUIRE(position);
+    REQUIRE(direction);
+    auto pd = position_directions.at(i);
+    REQUIRE(position ==  pd.first);
+    REQUIRE(direction ==  pd.second);
+    ++i;
+  }
+  REQUIRE(2 ==  i);
+  ComponentHandle<Tag> tag;
+  i = 0;
+  for (auto unused_entity :
+       em.entities_with_components(position, direction, tag)) {
+    (void)unused_entity;
+    REQUIRE(static_cast<bool>(position));
+    REQUIRE(static_cast<bool>(direction));
+    REQUIRE(static_cast<bool>(tag));
+    auto pd = position_directions.at(1);
+    REQUIRE(position ==  pd.first);
+    REQUIRE(direction ==  pd.second);
+    REQUIRE(tag ==  thetag);
+    i++;
+  }
+  REQUIRE(1 ==  i);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestIterateAllEntitiesSkipsDestroyed") {
+  Entity a = em.create();
+  Entity b = em.create();
+  Entity c = em.create();
+
+  b.destroy();
+
+  auto it = em.entities_for_debugging().begin();
+  REQUIRE(a.id() == (*it).id());
+  ++it;
+  REQUIRE(c.id() == (*it).id());
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestUnpack") {
+  Entity e = em.create();
+  auto p = e.assign<Position>(1.0, 2.0);
+  auto d = e.assign<Direction>(3.0, 4.0);
+  auto t = e.assign<Tag>("tag");
+
+  ComponentHandle<Position> up;
+  ComponentHandle<Direction> ud;
+  ComponentHandle<Tag> ut;
+  e.unpack(up);
+  REQUIRE(p ==  up);
+  e.unpack(up, ud);
+  REQUIRE(p ==  up);
+  REQUIRE(d ==  ud);
+  e.unpack(up, ud, ut);
+  REQUIRE(p ==  up);
+  REQUIRE(d ==  ud);
+  REQUIRE(t ==  ut);
+}
+
+// gcc 4.7.2 does not allow this struct to be declared locally inside the
+// TEST_CASE_METHOD.EntityManagerFixture, " //" TEST_CASE_METHOD(EntityManagerFixture, "TestUnpackNullMissing") {
+//   Entity e = em.create();
+//   auto p = e.assign<Position>();
+
+//   std::shared_ptr<Position> up(reinterpret_cast<Position*>(0Xdeadbeef),
+// NullDeleter());
+//   std::shared_ptr<Direction> ud(reinterpret_cast<Direction*>(0Xdeadbeef),
+// NullDeleter());
+//   e.unpack<Position, Direction>(up, ud);
+//   REQUIRE(p ==  up);
+//   REQUIRE(std::shared_ptr<Direction>() ==  ud);
+// }
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentIdsDiffer") {
+  REQUIRE(EntityManager::component_family<Position>() !=  EntityManager::component_family<Direction>());
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityCreatedEvent") {
+  struct EntityCreatedEventReceiver
+      : public Receiver<EntityCreatedEventReceiver> {
+    void receive(const EntityCreatedEvent &event) {
+      created.push_back(event.entity);
+    }
+
+    vector<Entity> created;
+  };
+
+  EntityCreatedEventReceiver receiver;
+  ev.subscribe<EntityCreatedEvent>(receiver);
+
+  REQUIRE(0UL ==  receiver.created.size());
+  for (int i = 0; i < 10; ++i) {
+    em.create();
+  }
+  REQUIRE(10UL ==  receiver.created.size());
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityDestroyedEvent") {
+  struct EntityDestroyedEventReceiver
+      : public Receiver<EntityDestroyedEventReceiver> {
+    void receive(const EntityDestroyedEvent &event) {
+      destroyed.push_back(event.entity);
+    }
+
+    vector<Entity> destroyed;
+  };
+
+  EntityDestroyedEventReceiver receiver;
+  ev.subscribe<EntityDestroyedEvent>(receiver);
+
+  REQUIRE(0UL ==  receiver.destroyed.size());
+  vector<Entity> entities;
+  for (int i = 0; i < 10; ++i) {
+    entities.push_back(em.create());
+  }
+  REQUIRE(0UL ==  receiver.destroyed.size());
+  for (auto e : entities) {
+    e.destroy();
+  }
+  REQUIRE(10UL == receiver.destroyed.size());
+  REQUIRE(entities ==  receiver.destroyed);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentAddedEvent") {
+  struct ComponentAddedEventReceiver
+      : public Receiver<ComponentAddedEventReceiver> {
+
+    ComponentAddedEventReceiver()
+      : position_events(0), direction_events(0) {}
+
+    void receive(const ComponentAddedEvent<Position> &event) {
+      auto p = event.component;
+      float n = static_cast<float>(position_events);
+      REQUIRE(p->x ==  n);
+      REQUIRE(p->y ==  n);
+      position_events++;
+    }
+
+    void receive(const ComponentAddedEvent<Direction> &event) {
+      auto p = event.component;
+      float n = static_cast<float>(direction_events);
+      REQUIRE(p->x ==  -n);
+      REQUIRE(p->y ==  -n);
+      direction_events++;
+    }
+
+    int position_events;
+    int direction_events;
+  };
+
+  ComponentAddedEventReceiver receiver;
+  ev.subscribe<ComponentAddedEvent<Position>>(receiver);
+  ev.subscribe<ComponentAddedEvent<Direction>>(receiver);
+
+  REQUIRE(ComponentAddedEvent<Position>::family() !=
+            ComponentAddedEvent<Direction>::family());
+
+  REQUIRE(0 ==  receiver.position_events);
+  REQUIRE(0 ==  receiver.direction_events);
+  for (int i = 0; i < 10; ++i) {
+    Entity e = em.create();
+    e.assign<Position>(static_cast<float>(i), static_cast<float>(i));
+    e.assign<Direction>(static_cast<float>(-i), static_cast<float>(-i));
+  }
+  REQUIRE(10 ==  receiver.position_events);
+  REQUIRE(10 ==  receiver.direction_events);
+}
+
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentRemovedEvent") {
+  struct ComponentRemovedReceiver : public Receiver<ComponentRemovedReceiver> {
+    void receive(const ComponentRemovedEvent<Direction> &event) {
+      removed = event.component;
+    }
+
+    ComponentHandle<Direction> removed;
+  };
+
+  ComponentRemovedReceiver receiver;
+  ev.subscribe<ComponentRemovedEvent<Direction>>(receiver);
+
+  REQUIRE(!(receiver.removed));
+  Entity e = em.create();
+  ComponentHandle<Direction> p = e.assign<Direction>(1.0, 2.0);
+  e.remove<Direction>();
+  REQUIRE(receiver.removed ==  p);
+  REQUIRE(!(e.component<Direction>()));
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentRemovedEventOnEntityDestroyed") {
+  struct ComponentRemovedReceiver : public Receiver<ComponentRemovedReceiver> {
+    void receive(const ComponentRemovedEvent<Direction> &event) {
+      removed = true;
+    }
+
+    bool removed = false;
+  };
+
+  ComponentRemovedReceiver receiver;
+  ev.subscribe<ComponentRemovedEvent<Direction>>(receiver);
+
+  REQUIRE(!(receiver.removed));
+
+  Entity e = em.create();
+  e.assign<Direction>(1.0, 2.0);
+  e.destroy();
+
+  REQUIRE(receiver.removed);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityAssignment") {
+  Entity a, b;
+  a = em.create();
+  REQUIRE(a !=  b);
+  b = a;
+  REQUIRE(a ==  b);
+  a.invalidate();
+  REQUIRE(a !=  b);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityDestroyAll") {
+  Entity a = em.create(), b = em.create();
+  em.reset();
+  REQUIRE(!(a.valid()));
+  REQUIRE(!(b.valid()));
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityDestroyHole") {
+  std::vector<Entity> entities;
+
+  auto count = [this]()->int {
+    auto e = em.entities_with_components<Position>();
+    return std::count_if(e.begin(), e.end(),
+                         [](const Entity &) { return true; });
+  };
+
+  for (int i = 0; i < 5000; i++) {
+    auto e = em.create();
+    e.assign<Position>();
+    entities.push_back(e);
+  }
+
+  REQUIRE(count() ==  5000);
+
+  entities[2500].destroy();
+
+  REQUIRE(count() ==  4999);
+}
+
+// TODO(alec): Disable this on OSX - it doesn't seem to be possible to catch it?!?
+// TEST_CASE_METHOD(EntityManagerFixture, "DeleteComponentThrowsBadAlloc") {
+//   Position *position = new Position();
+//   REQUIRE_THROWS_AS(delete position, std::bad_alloc);
+// }
+
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentHandleInvalidatedWhenEntityDestroyed") {
+  Entity a = em.create();
+  ComponentHandle<Position> position = a.assign<Position>(1, 2);
+  REQUIRE(position);
+  REQUIRE(position->x == 1);
+  REQUIRE(position->y == 2);
+  a.destroy();
+  REQUIRE(!position);
+}
+
+struct CopyVerifier : Component<CopyVerifier> {
+  CopyVerifier() : copied(false) {}
+  CopyVerifier(const CopyVerifier &other) {
+    copied = other.copied + 1;
+  }
+
+  int copied;
+};
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentAssignmentFromCopy") {
+  Entity a = em.create();
+  CopyVerifier original;
+  ComponentHandle<CopyVerifier> copy = a.assign_from_copy(original);
+  REQUIRE(copy);
+  REQUIRE(copy->copied == 1);
+  a.destroy();
+  REQUIRE(!copy);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityCreateFromCopy") {
+  Entity a = em.create();
+  a.assign<CopyVerifier>();
+  ComponentHandle<CopyVerifier> original = a.component<CopyVerifier>();
+  ComponentHandle<Position> aPosition = a.assign<Position>(1, 2);
+  Entity b = em.create_from_copy(a);
+  ComponentHandle<CopyVerifier> copy = b.component<CopyVerifier>();
+  ComponentHandle<Position> bPosition = b.component<Position>();
+  REQUIRE(original);
+  REQUIRE(original->copied == false);
+  REQUIRE(copy);
+  REQUIRE(copy->copied == 1);
+  REQUIRE(aPosition->x == bPosition->x);
+  REQUIRE(aPosition->y == bPosition->y);
+  REQUIRE(aPosition.get() != bPosition.get());
+  REQUIRE(a.component_mask() == b.component_mask());
+  REQUIRE(a != b);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentHandleInvalidatedWhenComponentDestroyed") {
+  Entity a = em.create();
+  ComponentHandle<Position> position = a.assign<Position>(1, 2);
+  REQUIRE(position);
+  REQUIRE(position->x == 1);
+  REQUIRE(position->y == 2);
+  a.remove<Position>();
+  REQUIRE(!position);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestDeleteEntityWithNoComponents") {
+  Entity a = em.create();
+  a.assign<Position>(1, 2);
+  Entity b = em.create();
+  b.destroy();
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityInStdSet") {
+  Entity a = em.create();
+  Entity b = em.create();
+  Entity c = em.create();
+  set<Entity> entitySet;
+  REQUIRE(entitySet.insert(a).second);
+  REQUIRE(entitySet.insert(b).second);
+  REQUIRE(entitySet.insert(c).second);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityInStdMap") {
+  Entity a = em.create();
+  Entity b = em.create();
+  Entity c = em.create();
+  map<Entity, int> entityMap;
+  REQUIRE(entityMap.insert(pair<Entity, int>(a, 1)).second);
+  REQUIRE(entityMap.insert(pair<Entity, int>(b, 2)).second);
+  REQUIRE(entityMap.insert(pair<Entity, int>(c, 3)).second);
+  REQUIRE(entityMap[a] == 1);
+  REQUIRE(entityMap[b] == 2);
+  REQUIRE(entityMap[c] == 3);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityComponentsFromTuple") {
+  Entity e = em.create();
+  e.assign<Position>(1, 2);
+  e.assign<Direction>(3, 4);
+
+  std::tuple<ComponentHandle<Position>, ComponentHandle<Direction>> components = e.components<Position, Direction>();
+
+  REQUIRE(std::get<0>(components)->x == 1);
+  REQUIRE(std::get<0>(components)->y == 2);
+  REQUIRE(std::get<1>(components)->x == 3);
+  REQUIRE(std::get<1>(components)->y == 4);
+}
+
+TEST_CASE("TestComponentDestructorCalledWhenManagerDestroyed") {
+  struct Freed {
+    explicit Freed(bool &yes) : yes(yes) {}
+    ~Freed() { yes = true; }
+
+    bool &yes;
+  };
+
+  struct Test : Component<Test> {
+    explicit Test(bool &yes) : freed(yes) {}
+
+    Freed freed;
+  };
+
+  bool freed = false;
+  {
+    EntityX e;
+    auto test = e.entities.create();
+    test.assign<Test>(freed);
+  }
+  REQUIRE(freed == true);
+}
+
+TEST_CASE("TestComponentDestructorCalledWhenEntityDestroyed") {
+  struct Freed {
+    explicit Freed(bool &yes) : yes(yes) {}
+    ~Freed() { yes = true; }
+
+    bool &yes;
+  };
+
+  struct Test : Component<Test> {
+    explicit Test(bool &yes) : freed(yes) {}
+
+    Freed freed;
+  };
+
+  bool freed = false;
+  EntityX e;
+  auto test = e.entities.create();
+  test.assign<Test>(freed);
+  REQUIRE(freed == false);
+  test.destroy();
+  REQUIRE(freed == true);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentsRemovedFromReusedEntities") {
+  Entity a = em.create();
+  Entity::Id aid = a.id();
+  a.assign<Position>(1, 2);
+  a.destroy();
+
+  Entity b = em.create();
+  Entity::Id bid = b.id();
+
+  REQUIRE(aid.index() == bid.index());
+  REQUIRE(!b.has_component<Position>());
+  b.assign<Position>(3, 4);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestConstComponentsNotInstantiatedTwice") {
+  Entity a = em.create();
+  a.assign<Position>(1, 2);
+
+  const Entity b = a;
+
+  REQUIRE(a.component<Position>().valid());
+  REQUIRE(b.component<const Position>().valid());
+  REQUIRE(b.component<const Position>()->x == 1);
+  REQUIRE(b.component<const Position>()->y == 2);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestEntityManagerEach") {
+  Entity a = em.create();
+  a.assign<Position>(1, 2);
+  int count = 0;
+  em.each<Position>([&count](Entity entity, Position &position) {
+    count++;
+    REQUIRE(position.x == 1);
+    REQUIRE(position.y == 2);
+  });
+  REQUIRE(count == 1);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestViewEach") {
+  Entity a = em.create();
+  a.assign<Position>(1, 2);
+  int count = 0;
+  em.entities_with_components<Position>().each([&count](Entity entity, Position &position) {
+    count++;
+    REQUIRE(position.x == 1);
+    REQUIRE(position.y == 2);
+  });
+  REQUIRE(count == 1);
+}
+
+TEST_CASE_METHOD(EntityManagerFixture, "TestComponentDereference") {
+  Entity a = em.create();
+  a.assign<Position>(10, 5);
+  auto& positionRef = *a.component<Position>();
+  REQUIRE(positionRef.x == 10);
+  REQUIRE(positionRef.y == 5);
+  positionRef.y = 20;
+  REQUIRE(a.component<Position>()->y == 20);
+}

include/entityx/Event.cc

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#include "entityx/Event.h"
+
+namespace entityx {
+
+BaseEvent::Family BaseEvent::family_counter_ = 0;
+
+BaseEvent::~BaseEvent() {
+}
+
+EventManager::EventManager() {
+}
+
+EventManager::~EventManager() {
+}
+
+}  // namespace entityx

include/entityx/Event.h

@@ -0,0 +1,216 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#pragma once
+
+#include <cstdint>
+#include <cstddef>
+#include <vector>
+#include <list>
+#include <unordered_map>
+#include <memory>
+#include <utility>
+#include "entityx/config.h"
+#include "entityx/3rdparty/simplesignal.h"
+#include "entityx/help/NonCopyable.h"
+
+
+namespace entityx {
+
+
+/// Used internally by the EventManager.
+class BaseEvent {
+ public:
+  typedef std::size_t Family;
+
+  virtual ~BaseEvent();
+
+ protected:
+  static Family family_counter_;
+};
+
+
+typedef Simple::Signal<void (const void*)> EventSignal;
+typedef std::shared_ptr<EventSignal> EventSignalPtr;
+typedef std::weak_ptr<EventSignal> EventSignalWeakPtr;
+
+
+/**
+ * Event types should subclass from this.
+ *
+ * struct Explosion : public Event<Explosion> {
+ *   Explosion(int damage) : damage(damage) {}
+ *   int damage;
+ * };
+ */
+template <typename Derived>
+class Event : public BaseEvent {
+ public:
+  /// Used internally for registration.
+  static Family family() {
+    static Family family = family_counter_++;
+    return family;
+  }
+};
+
+
+class BaseReceiver {
+ public:
+  virtual ~BaseReceiver() {
+    for (auto connection : connections_) {
+      auto &ptr = connection.second.first;
+      if (!ptr.expired()) {
+        ptr.lock()->disconnect(connection.second.second);
+      }
+    }
+  }
+
+  // Return number of signals connected to this receiver.
+  std::size_t connected_signals() const {
+    std::size_t size = 0;
+    for (auto connection : connections_) {
+      if (!connection.second.first.expired()) {
+        size++;
+      }
+    }
+    return size;
+  }
+
+ private:
+  friend class EventManager;
+  std::unordered_map<BaseEvent::Family, std::pair<EventSignalWeakPtr, std::size_t>> connections_;
+};
+
+
+template <typename Derived>
+class Receiver : public BaseReceiver {
+ public:
+  virtual ~Receiver() {}
+};
+
+
+/**
+ * Handles event subscription and delivery.
+ *
+ * Subscriptions are automatically removed when receivers are destroyed..
+ */
+class EventManager : entityx::help::NonCopyable {
+ public:
+  EventManager();
+  virtual ~EventManager();
+
+  /**
+   * Subscribe an object to receive events of type E.
+   *
+   * Receivers must be subclasses of Receiver and must implement a receive() method accepting the given event type.
+   *
+   * eg.
+   *
+   *     struct ExplosionReceiver : public Receiver<ExplosionReceiver> {
+   *       void receive(const Explosion &explosion) {
+   *       }
+   *     };
+   *
+   *     ExplosionReceiver receiver;
+   *     em.subscribe<Explosion>(receiver);
+   */
+  template <typename E, typename Receiver>
+  void subscribe(Receiver &receiver) {
+    void (Receiver::*receive)(const E &) = &Receiver::receive;
+    auto sig = signal_for(Event<E>::family());
+    auto wrapper = EventCallbackWrapper<E>(std::bind(receive, &receiver, std::placeholders::_1));
+    auto connection = sig->connect(wrapper);
+    BaseReceiver &base = receiver;
+    base.connections_.insert(std::make_pair(Event<E>::family(), std::make_pair(EventSignalWeakPtr(sig), connection)));
+  }
+
+  /**
+   * Unsubscribe an object in order to not receive events of type E anymore.
+   *
+   * Receivers must have subscribed for event E before unsubscribing from event E.
+   *
+   */
+  template <typename E, typename Receiver>
+  void unsubscribe(Receiver &receiver) {
+    BaseReceiver &base = receiver;
+    // Assert that it has been subscribed before
+    assert(base.connections_.find(Event<E>::family()) != base.connections_.end());
+    auto pair = base.connections_[Event<E>::family()];
+    auto connection = pair.second;
+    auto &ptr = pair.first;
+    if (!ptr.expired()) {
+      ptr.lock()->disconnect(connection);
+    }
+    base.connections_.erase(Event<E>::family());
+  }
+
+  template <typename E>
+  void emit(const E &event) {
+    auto sig = signal_for(Event<E>::family());
+    sig->emit(&event);
+  }
+
+  /**
+   * Emit an already constructed event.
+   */
+  template <typename E>
+  void emit(std::unique_ptr<E> event) {
+    auto sig = signal_for(Event<E>::family());
+    sig->emit(event.get());
+  }
+
+  /**
+   * Emit an event to receivers.
+   *
+   * This method constructs a new event object of type E with the provided arguments, then delivers it to all receivers.
+   *
+   * eg.
+   *
+   * std::shared_ptr<EventManager> em = new EventManager();
+   * em->emit<Explosion>(10);
+   *
+   */
+  template <typename E, typename ... Args>
+  void emit(Args && ... args) {
+    // Using 'E event(std::forward...)' causes VS to fail with an internal error. Hack around it.
+    E event = E(std::forward<Args>(args) ...);
+    auto sig = signal_for(std::size_t(Event<E>::family()));
+    sig->emit(&event);
+  }
+
+  std::size_t connected_receivers() const {
+    std::size_t size = 0;
+    for (EventSignalPtr handler : handlers_) {
+      if (handler) size += handler->size();
+    }
+    return size;
+  }
+
+ private:
+  EventSignalPtr &signal_for(std::size_t id) {
+    if (id >= handlers_.size())
+      handlers_.resize(id + 1);
+    if (!handlers_[id])
+      handlers_[id] = std::make_shared<EventSignal>();
+    return handlers_[id];
+  }
+
+  // Functor used as an event signal callback that casts to E.
+  template <typename E>
+  struct EventCallbackWrapper {
+    explicit EventCallbackWrapper(std::function<void(const E &)> callback) : callback(callback) {}
+    void operator()(const void *event) { callback(*(static_cast<const E*>(event))); }
+    std::function<void(const E &)> callback;
+  };
+
+  std::vector<EventSignalPtr> handlers_;
+};
+
+}  // namespace entityx

include/entityx/Event_test.cc

@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#define CATCH_CONFIG_MAIN
+
+#include <string>
+#include <vector>
+#include "entityx/3rdparty/catch.hpp"
+#include "entityx/Event.h"
+
+
+using entityx::EventManager;
+using entityx::Event;
+using entityx::Receiver;
+
+
+struct Explosion {
+  explicit Explosion(int damage) : damage(damage) {}
+  int damage;
+};
+
+
+struct Collision {
+  explicit Collision(int damage) : damage(damage) {}
+  int damage;
+};
+
+struct ExplosionSystem : public Receiver<ExplosionSystem> {
+  void receive(const Explosion &explosion) {
+    damage_received += explosion.damage;
+    received_count++;
+  }
+
+  void receive(const Collision &collision) {
+    damage_received += collision.damage;
+    received_count++;
+  }
+
+  int received_count = 0;
+  int damage_received = 0;
+};
+
+TEST_CASE("TestEmitReceive") {
+  EventManager em;
+  ExplosionSystem explosion_system;
+  em.subscribe<Explosion>(explosion_system);
+  em.subscribe<Collision>(explosion_system);
+  REQUIRE(0 == explosion_system.damage_received);
+  em.emit<Explosion>(10);
+  REQUIRE(1 == explosion_system.received_count);
+  REQUIRE(10 == explosion_system.damage_received);
+  em.emit<Collision>(10);
+  REQUIRE(20 == explosion_system.damage_received);
+  REQUIRE(2 == explosion_system.received_count);
+}
+
+TEST_CASE("TestUntypedEmitReceive") {
+  EventManager em;
+  ExplosionSystem explosion_system;
+  em.subscribe<Explosion>(explosion_system);
+  REQUIRE(0 == explosion_system.damage_received);
+  Explosion explosion(10);
+  em.emit(explosion);
+  REQUIRE(1 == explosion_system.received_count);
+  REQUIRE(10 == explosion_system.damage_received);
+}
+
+
+TEST_CASE("TestReceiverExpired") {
+  EventManager em;
+  {
+    ExplosionSystem explosion_system;
+    em.subscribe<Explosion>(explosion_system);
+    em.emit<Explosion>(10);
+    REQUIRE(10 == explosion_system.damage_received);
+    REQUIRE(1 == explosion_system.connected_signals());
+    REQUIRE(1 == em.connected_receivers());
+  }
+  REQUIRE(0 == em.connected_receivers());
+}
+
+
+TEST_CASE("TestSenderExpired") {
+  ExplosionSystem explosion_system;
+  {
+    EventManager em;
+    em.subscribe<Explosion>(explosion_system);
+    em.emit<Explosion>(10);
+    REQUIRE(10 == explosion_system.damage_received);
+    REQUIRE(1 == explosion_system.connected_signals());
+    REQUIRE(1 == em.connected_receivers());
+  }
+  REQUIRE(0 == explosion_system.connected_signals());
+}
+
+TEST_CASE("TestUnsubscription") {
+  ExplosionSystem explosion_system;
+  {
+    EventManager em;
+    em.subscribe<Explosion>(explosion_system);
+    REQUIRE(explosion_system.damage_received == 0);
+    em.emit<Explosion>(1);
+    REQUIRE(explosion_system.damage_received == 1);
+    em.unsubscribe<Explosion>(explosion_system);
+    em.emit<Explosion>(1);
+    REQUIRE(explosion_system.damage_received == 1);
+  }
+}

include/entityx/System.cc

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#include "entityx/System.h"
+
+namespace entityx {
+
+BaseSystem::Family BaseSystem::family_counter_;
+
+BaseSystem::~BaseSystem() {
+}
+
+void SystemManager::update_all(TimeDelta dt) {
+  assert(initialized_ && "SystemManager::configure() not called");
+  for (auto &pair : systems_) {
+    pair.second->update(entity_manager_, event_manager_, dt);
+  }
+}
+
+void SystemManager::configure() {
+  for (auto &pair : systems_) {
+    pair.second->configure(entity_manager_, event_manager_);
+  }
+  initialized_ = true;
+}
+
+}  // namespace entityx

include/entityx/System.h

@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#pragma once
+
+
+#include <cstdint>
+#include <unordered_map>
+#include <utility>
+#include <cassert>
+#include "entityx/config.h"
+#include "entityx/Entity.h"
+#include "entityx/Event.h"
+#include "entityx/help/NonCopyable.h"
+
+
+namespace entityx {
+
+
+class SystemManager;
+
+
+/**
+ * Base System class. Generally should not be directly used, instead see System<Derived>.
+ */
+class BaseSystem : entityx::help::NonCopyable {
+ public:
+  typedef size_t Family;
+
+  virtual ~BaseSystem();
+
+  /**
+   * Called once all Systems have been added to the SystemManager.
+   *
+   * Typically used to set up event handlers.
+   */
+  virtual void configure(EntityManager &entities, EventManager &events) {
+    configure(events);
+  }
+
+  /**
+   * Legacy configure(). Called by default implementation of configure(EntityManager&, EventManager&).
+   */
+  virtual void configure(EventManager &events) {}
+
+  /**
+   * Apply System behavior.
+   *
+   * Called every game step.
+   */
+  virtual void update(EntityManager &entities, EventManager &events, TimeDelta dt) = 0;
+
+  static Family family_counter_;
+
+ protected:
+};
+
+
+/**
+ * Use this class when implementing Systems.
+ *
+ * struct MovementSystem : public System<MovementSystem> {
+ *   void update(EntityManager &entities, EventManager &events, TimeDelta dt) {
+ *     // Do stuff to/with entities...
+ *   }
+ * }
+ */
+template <typename Derived>
+class System : public BaseSystem {
+ public:
+  virtual ~System() {}
+
+private:
+  friend class SystemManager;
+
+  static Family family() {
+    static Family family = family_counter_++;
+    return family;
+  }
+};
+
+
+class SystemManager : entityx::help::NonCopyable {
+ public:
+  SystemManager(EntityManager &entity_manager,
+                EventManager &event_manager) :
+                entity_manager_(entity_manager),
+                event_manager_(event_manager) {}
+
+  /**
+   * Add a System to the SystemManager.
+   *
+   * Must be called before Systems can be used.
+   *
+   * eg.
+   * std::shared_ptr<MovementSystem> movement = entityx::make_shared<MovementSystem>();
+   * system.add(movement);
+   */
+  template <typename S>
+  void add(std::shared_ptr<S> system) {
+    systems_.insert(std::make_pair(S::family(), system));
+  }
+
+  /**
+   * Add a System to the SystemManager.
+   *
+   * Must be called before Systems can be used.
+   *
+   * eg.
+   * auto movement = system.add<MovementSystem>();
+   */
+  template <typename S, typename ... Args>
+  std::shared_ptr<S> add(Args && ... args) {
+    std::shared_ptr<S> s(new S(std::forward<Args>(args) ...));
+    add(s);
+    return s;
+  }
+
+  /**
+   * Retrieve the registered System instance, if any.
+   *
+   *   std::shared_ptr<CollisionSystem> collisions = systems.system<CollisionSystem>();
+   *
+   * @return System instance or empty shared_std::shared_ptr<S>.
+   */
+  template <typename S>
+  std::shared_ptr<S> system() {
+    auto it = systems_.find(S::family());
+    assert(it != systems_.end());
+    return it == systems_.end()
+        ? std::shared_ptr<S>()
+        : std::shared_ptr<S>(std::static_pointer_cast<S>(it->second));
+  }
+
+  /**
+   * Call the System::update() method for a registered system.
+   */
+  template <typename S>
+  void update(TimeDelta dt) {
+    assert(initialized_ && "SystemManager::configure() not called");
+    std::shared_ptr<S> s = system<S>();
+    s->update(entity_manager_, event_manager_, dt);
+  }
+
+  /**
+   * Call System::update() on all registered systems.
+   *
+   * The order which the registered systems are updated is arbitrary but consistent,
+   * meaning the order which they will be updated cannot be specified, but that order
+   * will stay the same as long no systems are added or removed.
+   *
+   * If the order in which systems update is important, use SystemManager::update()
+   * to manually specify the update order. EntityX does not yet support a way of
+   * specifying priority for update_all().
+   */
+  void update_all(TimeDelta dt);
+
+  /**
+   * Configure the system. Call after adding all Systems.
+   *
+   * This is typically used to set up event handlers.
+   */
+  void configure();
+
+ private:
+  bool initialized_ = false;
+  EntityManager &entity_manager_;
+  EventManager &event_manager_;
+  std::unordered_map<BaseSystem::Family, std::shared_ptr<BaseSystem>> systems_;
+};
+
+}  // namespace entityx

include/entityx/System_test.cc

@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#define CATCH_CONFIG_MAIN
+
+#include <string>
+#include <vector>
+#include "entityx/3rdparty/catch.hpp"
+#include "entityx/System.h"
+#include "entityx/quick.h"
+
+// using namespace std;
+using namespace entityx;
+using std::string;
+
+struct Position : Component<Position> {
+  explicit Position(float x = 0.0f, float y = 0.0f) : x(x), y(y) {}
+
+  float x, y;
+};
+
+struct Direction : Component<Direction> {
+  explicit Direction(float x = 0.0f, float y = 0.0f) : x(x), y(y) {}
+
+  float x, y;
+};
+
+struct Counter : Component<Counter> {
+  explicit Counter(int counter = 0) : counter(counter) {}
+
+  int counter;
+};
+
+class MovementSystem : public System<MovementSystem> {
+ public:
+  explicit MovementSystem(string label = "") : label(label) {}
+
+  void update(EntityManager &es, EventManager &events, TimeDelta) override {
+    auto entities = es.entities_with_components<Position, Direction>();
+    ComponentHandle<Position> position;
+    ComponentHandle<Direction> direction;
+    for (auto entity : entities) {
+      entity.unpack<Position, Direction>(position, direction);
+      position->x += direction->x;
+      position->y += direction->y;
+    }
+  }
+
+  string label;
+};
+
+class CounterSystem : public System<CounterSystem> {
+public:
+  void update(EntityManager &es, EventManager &events, TimeDelta) override {
+    auto entities = es.entities_with_components<Counter>();
+    Counter::Handle counter;
+    for (auto entity : entities) {
+      entity.unpack<Counter>(counter);
+      counter->counter++;
+    }
+  }
+};
+
+class EntitiesFixture : public EntityX {
+ public:
+  std::vector<Entity> created_entities;
+
+  EntitiesFixture() {
+    for (int i = 0; i < 150; ++i) {
+      Entity e = entities.create();
+      created_entities.push_back(e);
+      if (i % 2 == 0) e.assign<Position>(1, 2);
+      if (i % 3 == 0) e.assign<Direction>(1, 1);
+
+      e.assign<Counter>(0);
+    }
+  }
+};
+
+TEST_CASE_METHOD(EntitiesFixture, "TestConstructSystemWithArgs") {
+  systems.add<MovementSystem>("movement");
+  systems.configure();
+
+  REQUIRE("movement" == systems.system<MovementSystem>()->label);
+}
+
+TEST_CASE_METHOD(EntitiesFixture, "TestApplySystem") {
+  systems.add<MovementSystem>();
+  systems.configure();
+
+  systems.update<MovementSystem>(0.0);
+  ComponentHandle<Position> position;
+  ComponentHandle<Direction> direction;
+  for (auto entity : created_entities) {
+    entity.unpack<Position, Direction>(position, direction);
+    if (position && direction) {
+      REQUIRE(2.0 == Approx(position->x));
+      REQUIRE(3.0 == Approx(position->y));
+    } else if (position) {
+      REQUIRE(1.0 == Approx(position->x));
+      REQUIRE(2.0 == Approx(position->y));
+    }
+  }
+}
+
+TEST_CASE_METHOD(EntitiesFixture, "TestApplyAllSystems") {
+  systems.add<MovementSystem>();
+  systems.add<CounterSystem>();
+  systems.configure();
+
+  systems.update_all(0.0);
+  Position::Handle position;
+  Direction::Handle direction;
+  Counter::Handle counter;
+  for (auto entity : created_entities) {
+    entity.unpack<Position, Direction, Counter>(position, direction, counter);
+    if (position && direction) {
+      REQUIRE(2.0 == Approx(position->x));
+      REQUIRE(3.0 == Approx(position->y));
+    } else if (position) {
+      REQUIRE(1.0 == Approx(position->x));
+      REQUIRE(2.0 == Approx(position->y));
+    }
+    REQUIRE(1 == counter->counter);
+  }
+}

include/entityx/config.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <cstdint>
+#include <cstddef>
+
+namespace entityx {
+
+static const size_t MAX_COMPONENTS = 64;
+typedef double TimeDelta;
+
+}  // namespace entityx

include/entityx/config.h.in

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <cstdint>
+#include <cstddef>
+
+namespace entityx {
+
+static const size_t MAX_COMPONENTS = @ENTITYX_MAX_COMPONENTS@;
+typedef @ENTITYX_DT_TYPE@ TimeDelta;
+
+}  // namespace entityx

include/entityx/deps/Dependencies.h

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2013 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+#pragma once
+
+#include "entityx/System.h"
+#include "entityx/Event.h"
+#include "entityx/Entity.h"
+
+namespace entityx {
+namespace deps {
+
+/**
+ * An entityx::System for declaring component dependencies.
+ *
+ * eg. To declare that a `Physics` component must always be paired with `Position`
+ * and `Direction` components:
+ *
+ *     system_manager->add<Dependency<Physics, Position, Direction>>();
+ */
+template <typename C, typename ... Deps>
+class Dependency : public System<Dependency<C, Deps...>>, public Receiver<Dependency<C, Deps...>> {
+public:
+  void receive(const ComponentAddedEvent<C> &event) {
+    assign<Deps...>(event.entity);
+  }
+
+  void configure(EventManager &events) override {
+    events.subscribe<ComponentAddedEvent<C>>(*this);
+  }
+
+  void update(EntityManager &entities, EventManager &events, TimeDelta dt) override {}
+
+private:
+  template <typename D>
+  void assign(Entity entity) {
+    if (!entity.component<D>()) entity.assign<D>();
+  }
+
+  template <typename D, typename D1, typename ... Ds>
+  void assign(Entity entity) {
+    assign<D>(entity);
+    assign<D1, Ds...>(entity);
+  }
+};
+
+}  // namespace deps
+}  // namespace entityx

include/entityx/deps/Dependencies_test.cc

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2013 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#define CATCH_CONFIG_MAIN
+
+#include "entityx/3rdparty/catch.hpp"
+#include "entityx/deps/Dependencies.h"
+#include "entityx/quick.h"
+
+
+namespace deps = entityx::deps;
+
+
+struct A : public entityx::Component<A> {};
+struct B : public entityx::Component<B> {
+  explicit B(bool b = false) : b(b) {}
+
+  bool b;
+};
+struct C : public entityx::Component<C> {};
+
+TEST_CASE_METHOD(entityx::EntityX, "TestSingleDependency") {
+  systems.add<deps::Dependency<A, B>>();
+  systems.configure();
+
+  entityx::Entity e = entities.create();
+  REQUIRE(!static_cast<bool>(e.component<A>()));
+  REQUIRE(!static_cast<bool>(e.component<B>()));
+  e.assign<A>();
+  REQUIRE(static_cast<bool>(e.component<A>()));
+  REQUIRE(static_cast<bool>(e.component<B>()));
+}
+
+TEST_CASE_METHOD(entityx::EntityX, "TestMultipleDependencies") {
+  systems.add<deps::Dependency<A, B, C>>();
+  systems.configure();
+
+  entityx::Entity e = entities.create();
+  REQUIRE(!static_cast<bool>(e.component<A>()));
+  REQUIRE(!static_cast<bool>(e.component<B>()));
+  REQUIRE(!static_cast<bool>(e.component<C>()));
+  e.assign<A>();
+  REQUIRE(static_cast<bool>(e.component<A>()));
+  REQUIRE(static_cast<bool>(e.component<B>()));
+  REQUIRE(static_cast<bool>(e.component<C>()));
+}
+
+TEST_CASE_METHOD(entityx::EntityX, "TestDependencyDoesNotRecreateComponent") {
+  systems.add<deps::Dependency<A, B>>();
+  systems.configure();
+
+  entityx::Entity e = entities.create();
+  e.assign<B>(true);
+  REQUIRE(e.component<B>()->b);
+  e.assign<A>();
+  REQUIRE(e.component<B>()->b);
+}

include/entityx/entityx.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include "entityx/config.h"
+#include "entityx/Event.h"
+#include "entityx/Entity.h"
+#include "entityx/System.h"
+#include "entityx/quick.h"

include/entityx/help/NonCopyable.h

@@ -0,0 +1,20 @@
+//  Inspired heavily by boost::noncopyable
+
+#pragma once
+
+namespace entityx {
+namespace help {
+
+class NonCopyable {
+protected:
+  NonCopyable() = default;
+  ~NonCopyable() = default;
+
+
+  NonCopyable(const NonCopyable&) = delete;
+  NonCopyable& operator = (const NonCopyable &) = delete;
+};
+
+
+}  // namespace help
+}  // namespace entityx

include/entityx/help/Pool.cc

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2012-2014 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#include "entityx/help/Pool.h"
+
+namespace entityx {
+
+BasePool::~BasePool() {
+  for (char *ptr : blocks_) {
+    delete[] ptr;
+  }
+}
+
+}  // namespace entityx

include/entityx/help/Pool.h

@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2012-2014 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#pragma once
+
+#include <cstddef>
+#include <cassert>
+#include <vector>
+
+namespace entityx {
+
+/**
+ * Provides a resizable, semi-contiguous pool of memory for constructing
+ * objects in. Pointers into the pool will be invalided only when the pool is
+ * destroyed.
+ *
+ * The semi-contiguous nature aims to provide cache-friendly iteration.
+ *
+ * Lookups are O(1).
+ * Appends are amortized O(1).
+ */
+class BasePool {
+ public:
+  explicit BasePool(std::size_t element_size, std::size_t chunk_size = 8192)
+      : element_size_(element_size), chunk_size_(chunk_size), capacity_(0) {}
+  virtual ~BasePool();
+
+  std::size_t size() const { return size_; }
+  std::size_t capacity() const { return capacity_; }
+  std::size_t chunks() const { return blocks_.size(); }
+
+  /// Ensure at least n elements will fit in the pool.
+  inline void expand(std::size_t n) {
+    if (n >= size_) {
+      if (n >= capacity_) reserve(n);
+      size_ = n;
+    }
+  }
+
+  inline void reserve(std::size_t n) {
+    while (capacity_ < n) {
+      char *chunk = new char[element_size_ * chunk_size_];
+      blocks_.push_back(chunk);
+      capacity_ += chunk_size_;
+    }
+  }
+
+  inline void *get(std::size_t n) {
+    assert(n < size_);
+    return blocks_[n / chunk_size_] + (n % chunk_size_) * element_size_;
+  }
+
+  inline const void *get(std::size_t n) const {
+    assert(n < size_);
+    return blocks_[n / chunk_size_] + (n % chunk_size_) * element_size_;
+  }
+
+  virtual void destroy(std::size_t n) = 0;
+
+ protected:
+  std::vector<char *> blocks_;
+  std::size_t element_size_;
+  std::size_t chunk_size_;
+  std::size_t size_ = 0;
+  std::size_t capacity_;
+};
+
+
+/**
+ * Implementation of BasePool that provides type-"safe" deconstruction of
+ * elements in the pool.
+ */
+template <typename T, std::size_t ChunkSize = 8192>
+class Pool : public BasePool {
+ public:
+  Pool() : BasePool(sizeof(T), ChunkSize) {}
+  virtual ~Pool() {
+    // Component destructors *must* be called by owner.
+  }
+
+  virtual void destroy(std::size_t n) override {
+    assert(n < size_);
+    T *ptr = static_cast<T*>(get(n));
+    ptr->~T();
+  }
+};
+
+}  // namespace entityx

include/entityx/help/Pool_test.cc

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2012-2014 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#define CATCH_CONFIG_MAIN
+
+#include <vector>
+#include "entityx/3rdparty/catch.hpp"
+#include "entityx/help/Pool.h"
+
+struct Position {
+  explicit Position(int *ptr = nullptr) : ptr(ptr) {
+    if (ptr) (*ptr)++;
+  }
+  ~Position() {
+    if (ptr) (*ptr)++;
+  }
+
+  float x, y;
+  int *ptr;
+};
+
+
+TEST_CASE("TestPoolReserve") {
+  entityx::Pool<Position, 8> pool;
+  REQUIRE(0 ==  pool.capacity());
+  REQUIRE(0 ==  pool.chunks());
+  pool.reserve(8);
+  REQUIRE(0 ==  pool.size());
+  REQUIRE(8 ==  pool.capacity());
+  REQUIRE(1 ==  pool.chunks());
+  pool.reserve(16);
+  REQUIRE(0 ==  pool.size());
+  REQUIRE(16 ==  pool.capacity());
+  REQUIRE(2 ==  pool.chunks());
+}
+
+TEST_CASE("TestPoolPointers") {
+  entityx::Pool<Position, 8> pool;
+  std::vector<char*> ptrs;
+  for (int i = 0; i < 4; i++) {
+    pool.expand(i * 8 + 8);
+    // NOTE: This is an attempt to ensure non-contiguous allocations from
+    // arena allocators.
+    ptrs.push_back(new char[8 * sizeof(Position)]);
+  }
+  char *p0 = static_cast<char*>(pool.get(0));
+  char *p7 = static_cast<char*>(pool.get(7));
+  char *p8 = static_cast<char*>(pool.get(8));
+  char *p16 = static_cast<char*>(pool.get(16));
+  char *p24 = static_cast<char*>(pool.get(24));
+
+  void *expected_p7 = p0 + 7 * sizeof(Position);
+  REQUIRE(expected_p7 == static_cast<void*>(p7));
+  void *extrapolated_p8 = p0 + 8 * sizeof(Position);
+  REQUIRE(extrapolated_p8 !=  static_cast<void*>(p8));
+  void *extrapolated_p16 = p8 + 8 * sizeof(Position);
+  REQUIRE(extrapolated_p16 !=  static_cast<void*>(p16));
+  void *extrapolated_p24 = p16 + 8 * sizeof(Position);
+  REQUIRE(extrapolated_p24 !=  static_cast<void*>(p24));
+}
+
+TEST_CASE("TestDeconstruct") {
+  entityx::Pool<Position, 8> pool;
+  pool.expand(8);
+
+  void *p0 = pool.get(0);
+
+  int counter = 0;
+  new(p0) Position(&counter);
+  REQUIRE(1 ==  counter);
+  pool.destroy(0);
+  REQUIRE(2 ==  counter);
+}

include/entityx/help/Timer.cc

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2013 Antony Woods <antony@teamwoods.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Antony Woods <antony@teamwoods.org>
+ */
+
+#include "entityx/help/Timer.h"
+
+namespace entityx {
+namespace help {
+
+Timer::Timer() {
+  _start = std::chrono::system_clock::now();
+}
+
+Timer::~Timer() {
+}
+
+void Timer::restart() {
+  _start = std::chrono::system_clock::now();
+}
+
+double Timer::elapsed() {
+  return std::chrono::duration<double>(std::chrono::system_clock::now() - _start).count();
+}
+
+}  // namespace help
+}  // namespace entityx

include/entityx/help/Timer.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2013 Antony Woods <antony@teamwoods.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Antony Woods <antony@teamwoods.org>
+ */
+#pragma once
+
+#include <chrono>
+
+namespace entityx {
+namespace help {
+
+class Timer {
+public:
+  Timer();
+  ~Timer();
+
+  void restart();
+  double elapsed();
+private:
+  std::chrono::time_point<std::chrono::system_clock> _start;
+};
+
+}  // namespace help
+}  // namespace entityx

include/entityx/quick.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2014 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#pragma once
+
+#include "entityx/Entity.h"
+#include "entityx/Event.h"
+#include "entityx/System.h"
+#include "entityx/config.h"
+
+namespace entityx {
+
+/**
+ * A convenience class for instantiating an EventManager, EntityManager and
+ * SystemManager.
+ */
+class EntityX {
+ public:
+  EntityX() : entities(events), systems(entities, events) {}
+
+  EventManager events;
+  EntityManager entities;
+  SystemManager systems;
+};
+
+}  // namespace entityx

include/entityx/tags/TagsComponent.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#pragma once
+
+#include <unordered_set>
+#include <string>
+#include "entityx/Entity.h"
+
+namespace entityx {
+namespace tags {
+
+/**
+ * Allow entities to be tagged with strings.
+ *
+ * entity.assign<TagsComponent>("tag1", "tag2");
+ *
+ * ComponentPtr<TagsComponent> tags;
+ * for (Entity entity : entity_manager.entities_with_components(tags))
+ */
+class TagsComponent : public Component<TagsComponent> {
+ public:
+  /**
+   * Construct a new TagsComponent with the given tags.
+   *
+   * eg. TagsComponent tags("a", "b", "c");
+   */
+  template <typename ... Args>
+  TagsComponent(const std::string &tag, const Args & ... tags) {
+    set_tags(tag, tags ...);
+  }
+
+  std::unordered_set<std::string> tags;
+
+ private:
+  template <typename ... Args>
+  void set_tags(const std::string &tag1, const std::string &tag2, const Args & ... tags) {
+    this->tags.insert(tag1);
+    set_tags(tag2, tags ...);
+  }
+
+  void set_tags(const std::string &tag) {
+    tags.insert(tag);
+  }
+};
+
+}  // namespace tags
+}  // namespace entityx

include/entityx/tags/TagsComponent_test.cc

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2012 Alec Thomas <alec@swapoff.org>
+ * All rights reserved.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution.
+ *
+ * Author: Alec Thomas <alec@swapoff.org>
+ */
+
+#define CATCH_CONFIG_MAIN
+
+#include <string>
+#include "entityx/3rdparty/catch.hpp"
+#include "entityx/tags/TagsComponent.h"
+
+using namespace std;
+using namespace entityx;
+using namespace entityx::tags;
+
+
+struct Position : public Component<Position> {};
+
+
+template <typename T>
+int size(const T &t) {
+  int n = 0;
+  for (auto i : t) {
+    ++n;
+    (void)i;  // Unused on purpose, suppress warning
+  }
+  return n;
+}
+
+
+TEST_CASE("TestVariadicConstruction", "TagsComponentTest") {
+  auto tags = TagsComponent("player", "indestructible");
+  unordered_set<string> expected;
+  expected.insert("player");
+  expected.insert("indestructible");
+  REQUIRE(expected == tags.tags);
+}