cocos_lib/cocos/renderer/frame-graph/ResourceAllocator.h

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 Copyright (c) 2021-2023 Xiamen Yaji Software Co., Ltd.

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#pragma once

#include <algorithm>
#include "base/RefVector.h"
#include "base/memory/Memory.h"
#include "base/std/container/unordered_map.h"
#include "gfx-base/GFXDef.h"

namespace cc {
namespace framegraph {

template <typename DeviceResourceType, typename DescriptorType, typename DeviceResourceCreatorType>
class ResourceAllocator final {
public:
    using DeviceResourceCreator = DeviceResourceCreatorType;

    ResourceAllocator(const ResourceAllocator &) = delete;
    ResourceAllocator(ResourceAllocator &&) noexcept = delete;
    ResourceAllocator &operator=(const ResourceAllocator &) = delete;
    ResourceAllocator &operator=(ResourceAllocator &&) noexcept = delete;

    static ResourceAllocator &getInstance() noexcept;
    DeviceResourceType *alloc(const DescriptorType &desc) noexcept;
    void free(DeviceResourceType *resource) noexcept;
    inline void tick() noexcept;
    void gc(uint32_t unusedFrameCount) noexcept;

private:
    using DeviceResourcePool = RefVector<DeviceResourceType *>;

    ResourceAllocator() noexcept = default;
    ~ResourceAllocator() = default;

    ccstd::unordered_map<DescriptorType, DeviceResourcePool, gfx::Hasher<DescriptorType>> _pool{};
    ccstd::unordered_map<DeviceResourceType *, int64_t> _ages{};
    uint64_t _age{0};
};

//////////////////////////////////////////////////////////////////////////

template <typename DeviceResourceType, typename DescriptorType, typename DeviceResourceCreatorType>
ResourceAllocator<DeviceResourceType, DescriptorType, DeviceResourceCreatorType> &
ResourceAllocator<DeviceResourceType, DescriptorType, DeviceResourceCreatorType>::getInstance() noexcept {
    static ResourceAllocator instance;
    return instance;
}

template <typename DeviceResourceType, typename DescriptorType, typename DeviceResourceCreatorType>
DeviceResourceType *ResourceAllocator<DeviceResourceType, DescriptorType, DeviceResourceCreatorType>::alloc(const DescriptorType &desc) noexcept {
    DeviceResourcePool &pool{_pool[desc]};

    DeviceResourceType *resource{nullptr};
    for (DeviceResourceType *res : pool) {
        if (_ages[res] >= 0) {
            resource = res;
            break;
        }
    }
    if (!resource) {
        DeviceResourceCreator creator;
        resource = creator(desc);
        pool.pushBack(resource);
    }

    _ages[resource] = -1;
    return resource;
}

template <typename DeviceResourceType, typename DescriptorType, typename DeviceResourceCreatorType>
void ResourceAllocator<DeviceResourceType, DescriptorType, DeviceResourceCreatorType>::free(DeviceResourceType *const resource) noexcept {
    CC_ASSERT(_ages.count(resource) && _ages[resource] < 0);
    _ages[resource] = _age;
}

template <typename DeviceResourceType, typename DescriptorType, typename DeviceResourceCreatorType>
void ResourceAllocator<DeviceResourceType, DescriptorType, DeviceResourceCreatorType>::tick() noexcept {
    ++_age;
}

template <typename DeviceResourceType, typename DescriptorType, typename DeviceResourceCreatorType>
void ResourceAllocator<DeviceResourceType, DescriptorType, DeviceResourceCreatorType>::gc(uint32_t const unusedFrameCount) noexcept {
    for (auto &pair : _pool) {
        DeviceResourcePool &pool = pair.second;

        auto count = static_cast<int>(pool.size());

        if (!count) {
            continue;
        }

        int destroyBegin = count - 1;

        for (int i = 0; i < count; ++i) {
            int64_t ageI = _ages[pool.at(i)];
            if (ageI < 0 || _age - ageI < unusedFrameCount) {
                continue;
            }

            int j = destroyBegin;

            for (; j > i; --j) {
                int64_t ageJ = _ages[pool.at(j)];
                if (ageJ < 0 || _age - ageJ < unusedFrameCount) {
                    std::swap(pool.at(i), pool.at(j));
                    destroyBegin = j - 1;
                    break;
                }
            }

            if (i >= j) {
                destroyBegin = i - 1;
            }

            if (i >= destroyBegin) {
                break;
            }
        }

        while (++destroyBegin < count) {
            auto *resource = pool.back();
            _ages.erase(resource);
            pool.popBack();
        }
    }
}

template <typename DeviceResourceType, typename DeviceResourceCreatorType>
class ResourceAllocator<DeviceResourceType, gfx::FramebufferInfo, DeviceResourceCreatorType> final {
public:
    using DeviceResourceCreator = DeviceResourceCreatorType;

    ResourceAllocator(const ResourceAllocator &) = delete;
    ResourceAllocator(ResourceAllocator &&) noexcept = delete;
    ResourceAllocator &operator=(const ResourceAllocator &) = delete;
    ResourceAllocator &operator=(ResourceAllocator &&) noexcept = delete;

    static ResourceAllocator &getInstance() noexcept;
    DeviceResourceType *alloc(const gfx::FramebufferInfo &desc) noexcept;
    void free(DeviceResourceType *resource) noexcept;
    inline void tick() noexcept;
    void gc(uint32_t unusedFrameCount) noexcept;

private:
    using DeviceResourcePool = RefVector<DeviceResourceType *>;

    ResourceAllocator() noexcept = default;
    ~ResourceAllocator() = default;

    std::unordered_map<ccstd::hash_t, DeviceResourcePool> _pool{};
    std::unordered_map<DeviceResourceType *, int64_t> _ages{};
    uint64_t _age{0};
};

//////////////////////////////////////////////////////////////////////////

template <typename DeviceResourceType, typename DeviceResourceCreatorType>
ResourceAllocator<DeviceResourceType, gfx::FramebufferInfo, DeviceResourceCreatorType> &
ResourceAllocator<DeviceResourceType, gfx::FramebufferInfo, DeviceResourceCreatorType>::getInstance() noexcept {
    static ResourceAllocator instance;
    return instance;
}

template <typename DeviceResourceType, typename DeviceResourceCreatorType>
DeviceResourceType *ResourceAllocator<DeviceResourceType, gfx::FramebufferInfo, DeviceResourceCreatorType>::alloc(const gfx::FramebufferInfo &desc) noexcept {
    ccstd::hash_t hash = gfx::Hasher<gfx::FramebufferInfo>()(desc);
    DeviceResourcePool &pool{_pool[hash]};

    DeviceResourceType *resource{nullptr};
    for (DeviceResourceType *res : pool) {
        if (_ages[res] >= 0) {
            resource = res;
            break;
        }
    }
    if (!resource) {
        DeviceResourceCreator creator;
        resource = creator(desc);
        pool.pushBack(resource);
    }

    _ages[resource] = -1;
    return resource;
}

template <typename DeviceResourceType, typename DeviceResourceCreatorType>
void ResourceAllocator<DeviceResourceType, gfx::FramebufferInfo, DeviceResourceCreatorType>::free(DeviceResourceType *const resource) noexcept {
    CC_ASSERT(_ages.count(resource) && _ages[resource] < 0);
    _ages[resource] = _age;
}

template <typename DeviceResourceType, typename DeviceResourceCreatorType>
void ResourceAllocator<DeviceResourceType, gfx::FramebufferInfo, DeviceResourceCreatorType>::tick() noexcept {
    ++_age;
}

template <typename DeviceResourceType, typename DeviceResourceCreatorType>
void ResourceAllocator<DeviceResourceType, gfx::FramebufferInfo, DeviceResourceCreatorType>::gc(uint32_t const unusedFrameCount) noexcept {
    for (auto &pair : _pool) {
        DeviceResourcePool &pool = pair.second;

        auto count = static_cast<int>(pool.size());

        if (!count) {
            continue;
        }

        int destroyBegin = count - 1;

        for (int i = 0; i < count; ++i) {
            int64_t ageI = _ages[pool.at(i)];
            if (ageI < 0 || _age - ageI < unusedFrameCount) {
                continue;
            }

            int j = destroyBegin;

            for (; j > i; --j) {
                int64_t ageJ = _ages[pool.at(j)];
                if (ageJ < 0 || _age - ageJ < unusedFrameCount) {
                    std::swap(pool.at(i), pool.at(j));
                    destroyBegin = j - 1;
                    break;
                }
            }

            if (i >= j) {
                destroyBegin = i - 1;
            }

            if (i >= destroyBegin) {
                break;
            }
        }

        while (++destroyBegin < count) {
            auto *resource = pool.back();
            //            delete resource;
            _ages.erase(resource);
            pool.popBack();
        }
    }
}

} // namespace framegraph
} // namespace cc