mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Ruslan ShestopalyukandFacebook GitHub Bot
7252c66292
Summary: [Changelog][Internal] The diff changes underlying storage types used by different enums that are used in ViewProps data structure, together with some eventual field rearranging to reduce padding overhead. This **shaves off 128 bytes** from each `ViewProps` instance, which is **a ~10% improvement**. Given that an average RN app may have thousands of shadow tree nodes, and correspondingly `ViewProps` instances in flight (e.g. Oculus Store has 2-3K of them nominally), the overall memory win is about **300K+** for this change only. Plus slightly better cache locality, which never a bad thing either. Reviewed By: mdvacca Differential Revision: D42372127 fbshipit-source-id: d3a832af2b2e89f50a5b8e04d24d0df92869ea4d
96 lines
2.7 KiB
C++
96 lines
2.7 KiB
C++
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <atomic>
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#include <react/debug/flags.h>
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namespace facebook {
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namespace react {
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/*
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* Represents an object which can be *sealed* (imperatively marked as
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* immutable).
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*
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* The `sealed` flag is tight to a particular instance of the class and resets
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* to `false` for all newly created (by copy-constructor, assignment operator
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* and so on) derivative objects.
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*
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* Why do we need this? In Fabric, some objects are semi-immutable
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* even if they are explicitly marked as `const`. It means that in some special
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* cases those objects can be const-casted-away and then mutated. That comes
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* from the fact that we share some object's life-cycle responsibilities with
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* React and the immutability is guaranteed by some logic splitted between
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* native and JavaScript worlds (which makes it impossible to fully use
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* immutability enforcement at a language level). To detect possible errors as
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* early as possible we additionally mark objects as *sealed* after some stages
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* and then enforce this at run-time.
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*
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* How to use:
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* 1. Inherit your class from `Sealable`.
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* 2. Call `ensureUnsealed()` in all cases where the object might be mutated:
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* a. At the beginning of all *always* mutating `non-const` methods;
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* b. Right before the place where actual mutation happens in all
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* *possible* mutating `non-const` methods; c. Right after performing
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* `const_cast`. (Optionally. This is not strictly necessary but might help
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* detect problems earlier.)
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* 3. Call `seal()` at some point from which any modifications
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* must be prevented.
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*/
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#ifndef REACT_NATIVE_DEBUG
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// Release-mode, production version
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class Sealable {
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public:
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inline void seal() const {}
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inline bool getSealed() const {
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return true;
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}
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inline void ensureUnsealed() const {}
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};
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#else
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// Debug version
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class Sealable {
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public:
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Sealable();
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Sealable(const Sealable &other);
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Sealable(Sealable &&other) noexcept;
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~Sealable() noexcept;
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Sealable &operator=(const Sealable &other);
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Sealable &operator=(Sealable &&other) noexcept;
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/*
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* Seals the object. This operation is irreversible;
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* the object cannot be "unsealed" after being sealed.
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*/
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void seal() const;
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/*
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* Returns if the object already sealed or not.
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*/
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bool getSealed() const;
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/*
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* Throws an exception if the object is sealed.
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* Call this from all non-`const` methods.
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*/
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void ensureUnsealed() const;
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private:
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mutable std::atomic<bool> sealed_{false};
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};
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#endif
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} // namespace react
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} // namespace facebook
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