Added librarys and test application

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