src/tint/utils/containers/const_propagating_ptr.h

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#ifndef SRC_TINT_UTILS_CONTAINERS_CONST_PROPAGATING_PTR_H_
#define SRC_TINT_UTILS_CONTAINERS_CONST_PROPAGATING_PTR_H_

namespace tint {

/// ConstPropagatingPtr is a `const` propagating pointer - if the ConstPropagatingPtr is const, then
/// you will only be able to obtain a const pointee pointer.
template <typename T>
class ConstPropagatingPtr {
  public:
    /// Constructor.
    /// The pointer is initialized to null.
    ConstPropagatingPtr() : ptr_(nullptr) {}

    /// Constructor.
    /// @param ptr the pointer value.
    ConstPropagatingPtr(T* ptr) : ptr_(ptr) {}  // NOLINT(runtime/explicit)

    /// Move constructor.
    /// @param other the ConstPropagatingPtr to move.
    ConstPropagatingPtr(ConstPropagatingPtr&& other) = default;

    /// Copy (non-const) constructor.
    /// @param other the ConstPropagatingPtr to move.
    ConstPropagatingPtr(ConstPropagatingPtr& other) : ptr_(other.ptr_) {}

    /// Assignment operator
    /// @param ptr the new pointer value
    /// @return this ConstPropagatingPtr
    ConstPropagatingPtr& operator=(T* ptr) {
        ptr_ = ptr;
        return *this;
    }

    /// Move assignment operator.
    /// @param other the ConstPropagatingPtr to move.
    /// @return this ConstPropagatingPtr
    ConstPropagatingPtr& operator=(ConstPropagatingPtr&& other) = default;

    /// Copy (non-const) assignment operator.
    /// @param other the ConstPropagatingPtr to move.
    /// @return this ConstPropagatingPtr
    ConstPropagatingPtr& operator=(ConstPropagatingPtr& other) {
        ptr_ = other.ptr_;
        return *this;
    }

    /// @returns the pointer
    operator T*() { return ptr_; }

    /// @returns the const pointer
    operator const T*() const { return ptr_; }

    /// @returns the pointer
    T* operator->() { return ptr_; }

    /// @returns the const pointer
    const T* operator->() const { return ptr_; }

    /// @returns the pointer
    T* Get() { return ptr_; }

    /// @returns the const pointer
    const T* Get() const { return ptr_; }

    /// Equality operator
    /// @param ptr the pointer to compare against
    /// @return true if the pointers are equal
    bool operator==(T* ptr) const { return ptr_ == ptr; }

    /// Inequality operator
    /// @param ptr the pointer to compare against
    /// @return true if the pointers are not equal
    bool operator!=(T* ptr) const { return ptr_ != ptr; }

  private:
    // Delete copy constructor and copy-assignment to prevent making a copy of the
    // ConstPropagatingPtr to break const propagation.
    ConstPropagatingPtr(const ConstPropagatingPtr&) = delete;
    ConstPropagatingPtr& operator=(const ConstPropagatingPtr&) = delete;

    T* ptr_ = nullptr;
};

}  // namespace tint

#endif  // SRC_TINT_UTILS_CONTAINERS_CONST_PROPAGATING_PTR_H_