src/dawn/native/DynamicArrayState.h

// Copyright 2025 The Dawn & Tint Authors
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#ifndef SRC_DAWN_NATIVE_DYNAMICARRAYSTATE_H_
#define SRC_DAWN_NATIVE_DYNAMICARRAYSTATE_H_

#include <vector>

#include "dawn/common/Ref.h"
#include "dawn/common/RefCounted.h"
#include "dawn/common/WeakRefSupport.h"
#include "dawn/common/ityp_span.h"
#include "dawn/common/ityp_vector.h"
#include "dawn/native/Error.h"
#include "dawn/native/Forward.h"
#include "dawn/native/IntegerTypes.h"
#include "dawn/native/dawn_platform.h"
#include "partition_alloc/pointers/raw_ptr.h"

namespace tint {
enum class ResourceType : uint32_t;
}  // namespace tint

namespace dawn::native {

// An optional component of a BindGroup that's used to track the resources that are in the dynamic
// binding array part. It helps maintain the metadata buffer that's used in shaders to know if it is
// valid to access an entry of the dynamic binding array with a given type (note that the writing of
// the updates to the buffer are done by the backends).
//
// DynamicArrayState has a single strong reference owned by the BindGroup that created it, however
// all resources contained in the dynamic array need WeakRefs to update it on Pin/Unpin. (They use
// WeakRef to avoid a reference cycle between the dynamic array and its bindings).
class DynamicArrayState : public RefCounted, public WeakRefSupport<DynamicArrayState> {
  public:
    explicit DynamicArrayState(BindingIndex size);

    MaybeError Initialize(DeviceBase* device);
    void Destroy();

    BindingIndex GetSize() const;
    ityp::span<BindingIndex, const Ref<TextureViewBase>> GetBindings() const;
    BufferBase* GetMetadataBuffer() const;
    bool IsDestroyed() const;

    // Methods that mutate the state of bindings in the dynamic array. They keep track of the
    // necessary metadata buffer updates required for dynamic type checks in the shader to match
    // what's in the binding array.
    void Update(BindingIndex i, TextureViewBase* view);
    void OnPinned(BindingIndex i, TextureBase* texture);
    void OnUnpinned(BindingIndex i, TextureBase* texture);

    // Returns the various type ids that need to be updated in the metadata buffer before the next
    // use of the binding array.
    struct BindingStateUpdate {
        uint32_t offset;
        uint32_t data;
    };
    bool HasDirtyBindings() const;
    std::vector<BindingStateUpdate> AcquireDirtyBindingUpdates();

  private:
    bool mDestroyed = false;

    ityp::vector<BindingIndex, Ref<TextureViewBase>> mBindings;
    // Buffer that contains a WGSL metadata struct of the following shape:
    //
    // struct Metadata {
    //     arrayLength: u32,  //  Doesn't include the default bindings
    //     bindings: array<u32>,  // `arrayLength` entries
    // }
    Ref<BufferBase> mMetadataBuffer;

    struct BindingState {
        // Matches the value of the Tint enum for type IDs but kept as u32 to keep usage of Tint
        // headers local.
        tint::ResourceType typeId = tint::ResourceType(0);
        bool dirty = false;
        bool pinned = false;
    };
    ityp::vector<BindingIndex, BindingState> mBindingState;

    // The list of bindings that need to be updated before the next use of the dynamic array.
    std::vector<BindingIndex> mDirtyBindings;
    void MarkStateDirty(BindingIndex i);
};

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_DYNAMICARRAYSTATE_H_