170 lines
5.5 KiB
C++
170 lines
5.5 KiB
C++
/* SPDX-FileCopyrightText: 2023 Blender Authors
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*
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* SPDX-License-Identifier: GPL-2.0-or-later */
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/** \file
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* \ingroup bke
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*/
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#pragma once
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#include "DNA_node_types.h"
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#include "BLI_any.hh"
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#include "BLI_cpp_type.hh"
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#include "BLI_generic_pointer.hh"
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namespace blender::bke {
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/**
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* #SocketValueVariant is used by geometry nodes in the lazy-function evaluator to pass data
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* between nodes. Specifically, it is the container type for the following socket types: bool,
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* float, integer, vector, rotation, color and string.
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*
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* The data passed through e.g. an integer socket can be a single value or a field (and in the
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* future potentially grids, lists and images). Each of those is stored differently, but this
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* container can store them all.
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*
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* A key requirement for this container is that it is type-erased, i.e. not all code that uses it
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* has to include all the headers required to process the other storage types. This is achieved by
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* using the #Any type and by providing templated accessors that are implemented outside of a
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* header.
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*/
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class SocketValueVariant {
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private:
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/**
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* This allows faster lookup of the correct type in the #Any below. For example, when retrieving
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* the value of an integer socket, we'd usually have to check whether the #Any contains a single
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* `int` or a field. Doing that check by comparing an enum is cheaper.
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*
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* Also, to figure out if we currently store a single value we'd otherwise have to check whether
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* they #Any stored an integer or float or boolean etc.
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*/
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enum class Kind {
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/**
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* Used to indicate that there is no value currently. This is used by the default constructor.
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*/
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None,
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/**
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* Indicates that there is a single value like `int`, `float` or `std::string` stored.
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*/
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Single,
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/**
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* Indicates that there is a `GField` stored.
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*/
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Field,
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};
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/**
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* High level category of the stored type.
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*/
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Kind kind_ = Kind::None;
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/**
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* The socket type that corresponds to the stored value type, e.g. `SOCK_INT` for an `int` or
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* integer field.
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*/
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eNodeSocketDatatype socket_type_;
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/**
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* Contains the actual socket value. For single values this contains the value directly (e.g.
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* `int` or `float3`). For fields this always contains a #GField and not e.g. #Field<int>. This
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* simplifies generic code.
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*
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* Small types are embedded directly, while larger types are separately allocated.
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*/
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Any<void, 24> value_;
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public:
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/**
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* Create an empty variant. This is not valid for any socket type yet.
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*/
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SocketValueVariant() = default;
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/**
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* Create a variant based on the given value. This works for primitive types, #GField and
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* #Field<T>.
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*/
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template<typename T> explicit SocketValueVariant(T &&value);
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/**
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* \return True if the stored value is valid for a specific socket type. This is mainly meant to
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* be used by asserts.
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*/
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bool valid_for_socket(eNodeSocketDatatype socket_type) const;
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/**
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* Get the stored value as a specific type. For convenience this allows accessing the stored type
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* as a different type. For example, a stored single `int` can also be accessed as `GField` or
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* `Field<int>` (but not `float` or `Field<float>`).
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*
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* This method may leave the variant empty, in a moved from state or unchanged. Therefore, this
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* should only be called once.
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*/
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template<typename T> T extract();
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/**
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* Same as #extract, but always leaves the variant unchanged. So this method can be called
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* multiple times.
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*/
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template<typename T> T get() const;
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/**
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* Replaces the stored value with a new value of potentially a different type.
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*/
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template<typename T> void set(T &&value);
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/**
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* If true, the stored value cannot be converted to a single value without loss of information.
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*/
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bool is_context_dependent_field() const;
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/**
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* Convert the stored value into a single value. For simple value access, this is not necessary,
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* because #get` does the conversion implicitly. However, it is necessary if one wants to use
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* #get_single_ptr.
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*
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* The caller has to make sure that the stored value is a single value or a field.
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*/
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void convert_to_single();
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/**
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* Get a pointer to the embedded single value. The caller has to make sure that there actually is
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* a single value stored, e.g. by calling #convert_to_single.
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*/
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GPointer get_single_ptr() const;
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GMutablePointer get_single_ptr();
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/**
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* Replace the stored value with the given single value.
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*/
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void store_single(eNodeSocketDatatype socket_type, const void *value);
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/**
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* Replaces the stored value with a new value-initialized single value of the given type and
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* returns a pointer to the value. The caller can then write a different value of the same type
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* into its place.
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*/
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void *new_single_for_write(eNodeSocketDatatype socket_type);
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void *new_single_for_write(const CPPType &cpp_type);
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friend std::ostream &operator<<(std::ostream &stream, const SocketValueVariant &value_variant);
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private:
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/**
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* This exists so that only one instance of the underlying template has to be instantiated per
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* type. So only `store_impl<int>` is necessary, but not `store_impl<const int &>`.
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*/
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template<typename T> void store_impl(T value);
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};
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template<typename T> inline SocketValueVariant::SocketValueVariant(T &&value)
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{
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this->set(std::forward<T>(value));
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}
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template<typename T> inline void SocketValueVariant::set(T &&value)
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{
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this->store_impl<std::decay_t<T>>(std::forward<T>(value));
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}
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} // namespace blender::bke
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