Class for allocating a chunk of memory for RenderPass

cc/quads/list_container.h

Index: cc/quads/list_container.h
diff --git a/cc/quads/list_container.h b/cc/quads/list_container.h
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+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CC_QUADS_LIST_CONTAINER_H_
+#define CC_QUADS_LIST_CONTAINER_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "cc/base/cc_export.h"
+
+namespace cc {
+class SharedQuadState;
+class DrawQuad;
+
+// This class is a container type that handles allocating contiguous memory for
+// new elements and traversing through elements with either iterator or reverse
+// iterator. Since this container hands out raw pointers of its elements, it is
+// very important that this container never reallocate its memory so those raw
+// pointer will continue to be valid.  This class is used to contain
+// SharedQuadState or DrawQuad. Since the size of each DrawQuad varies, to hold
+// DrawQuads, the allocations size of each element in this class is
+// kLargestDrawQuad while BaseElementType is DrawQuad.
+template <class BaseElementType>
+class CC_EXPORT ListContainer {
+ public:
+  // BaseElementType is the type of raw pointers this class hands out; however,
+  // its derived classes might require different memory sizes.
+  // max_size_for_derived_class the largest memory size required for all the
+  // derived classes to use for allocation.
+  explicit ListContainer(size_t max_size_for_derived_class);
+  // This constructor omits input variable for max_size_for_derived_class. This
+  // is used when there is no derived classes from BaseElementType we need to
+  // worry about, and allocation size is just sizeof(BaseElementType).
+  ListContainer();
+  // This constructor reserves the requested memory up front so only a single
+  // allocation is needed.
+  ListContainer(size_t max_size_for_derived_class,
+                size_t num_of_elements_to_reserve_for);
+
+  ~ListContainer();
+
+  // This class deals only with char* and void*. It does allocation and passing
+  // out raw pointers, as well as memory deallocation when being destroyed.
+  class CC_EXPORT ListContainerCharAllocator;
+
+  // This class points to a certain position inside memory of
+  // ListContainerCharAllocator. It is a base class for ListContainer iterators.
+  struct CC_EXPORT PositionInListContainerCharAllocator {
+    ListContainerCharAllocator* ptr_to_container;
+    size_t vector_index;
+    char* item_iterator;
+
+    PositionInListContainerCharAllocator(
+        const PositionInListContainerCharAllocator& other);
+
+    PositionInListContainerCharAllocator(ListContainerCharAllocator* container,
+                                         size_t vector_ind,
+                                         char* item_iter);
+
+    bool operator==(const PositionInListContainerCharAllocator& other) const;
+    bool operator!=(const PositionInListContainerCharAllocator& other) const;
+
+    PositionInListContainerCharAllocator Increment();
+    PositionInListContainerCharAllocator ReverseIncrement();
+  };
+
+  // Iterator classes that can be used to access data.
+  /////////////////////////////////////////////////////////////////
+  class CC_EXPORT Iterator : public PositionInListContainerCharAllocator {
+    // This class is only defined to forward iterate through
+    // ListContainerCharAllocator.
+   public:
+    Iterator(ListContainerCharAllocator* container,
+             size_t vector_ind,
+             char* item_iter);
+    ~Iterator();
+    BaseElementType* operator->() const;
+    BaseElementType& operator*() const;
+    Iterator operator++(int unused_post_increment);
+    Iterator operator++();
+  };
+
+  class CC_EXPORT ConstIterator : public PositionInListContainerCharAllocator {
+    // This class is only defined to forward iterate through
+    // ListContainerCharAllocator.
+   public:
+    ConstIterator(ListContainerCharAllocator* container,
+                  size_t vector_ind,
+                  char* item_iter);
+    ConstIterator(const Iterator& other);  // NOLINT
+    ~ConstIterator();
+    const BaseElementType* operator->() const;
+    const BaseElementType& operator*() const;
+    ConstIterator operator++(int unused_post_increment);
+    ConstIterator operator++();
+  };
+
+  class CC_EXPORT ReverseIterator
+      : public PositionInListContainerCharAllocator {
+    // This class is only defined to reverse iterate through
+    // ListContainerCharAllocator.
+   public:
+    ReverseIterator(ListContainerCharAllocator* container,
+                    size_t vector_ind,
+                    char* item_iter);
+    ~ReverseIterator();
+    BaseElementType* operator->() const;
+    BaseElementType& operator*() const;
+    ReverseIterator operator++(int unused_post_increment);
+    ReverseIterator operator++();
+  };
+
+  class CC_EXPORT ConstReverseIterator
+      : public PositionInListContainerCharAllocator {
+    // This class is only defined to reverse iterate through
+    // ListContainerCharAllocator.
+   public:
+    ConstReverseIterator(ListContainerCharAllocator* container,
+                         size_t vector_ind,
+                         char* item_iter);
+    ConstReverseIterator(const ReverseIterator& other);  // NOLINT
+    ~ConstReverseIterator();
+    const BaseElementType* operator->() const;
+    const BaseElementType& operator*() const;
+    ConstReverseIterator operator++(int unused_post_increment);
+    ConstReverseIterator operator++();
+  };
+
+  // When called, all raw pointers that have been handed out are no longer
+  // valid. Use with caution.
+  // This function does not deallocate memory.
+  void EraseAndInvalidateAllPointers(Iterator position);
+
+  ConstReverseIterator rbegin() const;
+  ConstReverseIterator rend() const;
+  ReverseIterator rbegin();
+  ReverseIterator rend();
+  ConstIterator begin() const;
+  ConstIterator end() const;
+  Iterator begin();
+  Iterator end();
+
+  BaseElementType* front();
+  BaseElementType* back();
+  const BaseElementType* front() const;
+  const BaseElementType* back() const;
+
+  // Take in derived element type and construct it at location generated by
+  // Allocate().
+  template <typename DerivedElementType>
+  DerivedElementType* AllocateAndConstruct() {
+    DerivedElementType* result =
+        new (Allocate(sizeof(DerivedElementType))) DerivedElementType;
+    return result;
+  }
+
+  size_t size() const;
+  bool empty() const;
+  void clear();
+
+  size_t AvailableSizeWithoutAnotherAllocationForTesting() const;
+
+ private:
+  // Hands out memory location for an element at the end of data structure.
+  BaseElementType* Allocate(size_t size_of_actual_element_in_bytes);
+
+  scoped_ptr<ListContainerCharAllocator> data_;
+
+  DISALLOW_COPY_AND_ASSIGN(ListContainer);
+};
+
+#if !defined(COMPILER_MSVC)
+extern template class ListContainer<SharedQuadState>;
+extern template class ListContainer<DrawQuad>;
+#endif
+}  // namespace cc
+
+#endif  // CC_QUADS_LIST_CONTAINER_H_