// Copyright 2019 The Dawn Authors
//
// 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 SRC_DAWN_NATIVE_BUDDYMEMORYALLOCATOR_H_
#define SRC_DAWN_NATIVE_BUDDYMEMORYALLOCATOR_H_

#include "dawn/native/BuddyAllocator.h"
#include "dawn/native/Error.h"
#include "dawn/native/ResourceMemoryAllocation.h"

#include <memory>
#include <vector>

namespace dawn::native {

    class ResourceHeapAllocator;

    // BuddyMemoryAllocator uses the buddy allocator to sub-allocate blocks of device
    // memory created by MemoryAllocator clients. It creates a very large buddy system
    // where backing device memory blocks equal a specified level in the system.
    //
    // Upon sub-allocating, the offset gets mapped to device memory by computing the corresponding
    // memory index and should the memory not exist, it is created. If two sub-allocations share the
    // same memory index, the memory refcount is incremented to ensure de-allocating one doesn't
    // release the other prematurely.
    //
    // The MemoryAllocator should return ResourceHeaps that are all compatible with each other.
    // It should also outlive all the resources that are in the buddy allocator.
    class BuddyMemoryAllocator {
      public:
        BuddyMemoryAllocator(uint64_t maxSystemSize,
                             uint64_t memoryBlockSize,
                             ResourceHeapAllocator* heapAllocator);
        ~BuddyMemoryAllocator() = default;

        ResultOrError<ResourceMemoryAllocation> Allocate(uint64_t allocationSize,
                                                         uint64_t alignment);
        void Deallocate(const ResourceMemoryAllocation& allocation);

        uint64_t GetMemoryBlockSize() const;

        // For testing purposes.
        uint64_t ComputeTotalNumOfHeapsForTesting() const;

      private:
        uint64_t GetMemoryIndex(uint64_t offset) const;

        uint64_t mMemoryBlockSize = 0;

        BuddyAllocator mBuddyBlockAllocator;
        ResourceHeapAllocator* mHeapAllocator;

        struct TrackedSubAllocations {
            size_t refcount = 0;
            std::unique_ptr<ResourceHeapBase> mMemoryAllocation;
        };

        std::vector<TrackedSubAllocations> mTrackedSubAllocations;
    };

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_BUDDYMEMORYALLOCATOR_H_