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RuntimeTarget refactor - introduce WeakList for Target→Agent refs
Summary: Changelog: [Internal] Replaces the copypasta'd `PageTarget::forEachSession`, `InstanceTarget::forEachAgent` and `RuntimeTarget::forEachAgent` with a shared utility class for managing a list of `weak_ptr`s. In a `WeakList`, elements can only be added (`insert`), iterated over (`forEach`), and counted (`size`, `empty`). Conceptually, elements are automatically removed from the list as soon as they're destroyed, but internally, space is reclaimed *lazily*: the next time we have a reason to iterate over the underlying list, we delete any pointers that are found to be null. ## Naming This is almost a WeakSet, but we don't bother checking for duplicates, hence "WeakList". Reviewed By: hoxyq Differential Revision: D53671483 fbshipit-source-id: 460bfbaa2b8e821281dc352fed0946f99352c9fc
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79 changes: 79 additions & 0 deletions
79
packages/react-native/ReactCommon/jsinspector-modern/WeakList.h
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,79 @@ | ||
| /* | ||
| * Copyright (c) Meta Platforms, Inc. and affiliates. | ||
| * | ||
| * This source code is licensed under the MIT license found in the | ||
| * LICENSE file in the root directory of this source tree. | ||
| */ | ||
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| #pragma once | ||
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| #include <list> | ||
| #include <memory> | ||
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| namespace facebook::react::jsinspector_modern { | ||
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| /** | ||
| * A list that holds weak pointers to objects of type `T`. Null pointers are not | ||
| * considered to be in the list. | ||
| * | ||
| * The list is not thread-safe! The caller is responsible for synchronization. | ||
| */ | ||
| template <typename T> | ||
| class WeakList { | ||
| public: | ||
| /** | ||
| * Call the given function for every element in the list, ensuring the element | ||
| * is not destroyed for the duration of the call. Elements are visited in the | ||
| * order they were inserted. | ||
| * | ||
| * As a side effect, any null pointers in the underlying list (corresponding | ||
| * to destroyed elements) will be removed during iteration. | ||
| */ | ||
| template <typename Fn> | ||
| void forEach(Fn&& fn) const { | ||
| for (auto it = ptrs_.begin(); it != ptrs_.end();) { | ||
| if (auto ptr = it->lock()) { | ||
| fn(*ptr); | ||
| ++it; | ||
| } else { | ||
| it = ptrs_.erase(it); | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * Returns the number of (non-null) elements in the list. The count will only | ||
| * remain accurate as long as the list is not modified and elements are | ||
| * not destroyed. | ||
| * | ||
| * As a side effect, any null pointers in the underlying list (corresponding | ||
| * to destroyed elements) will be removed during this method. | ||
| */ | ||
| size_t size() const { | ||
| size_t count{0}; | ||
| forEach([&count](const auto&) { ++count; }); | ||
| return count; | ||
| } | ||
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| /** | ||
| * Returns true if there are no elements in the list. | ||
| * | ||
| * As a side effect, any null pointers in the underlying list (corresponding | ||
| * to destroyed elements) will be removed during this method. | ||
| */ | ||
| bool empty() const { | ||
| return !size(); | ||
| } | ||
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| /** | ||
| * Inserts an element into the list. | ||
| */ | ||
| void insert(std::weak_ptr<T> ptr) { | ||
| ptrs_.push_back(ptr); | ||
| } | ||
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| private: | ||
| mutable std::list<std::weak_ptr<T>> ptrs_; | ||
| }; | ||
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| } // namespace facebook::react::jsinspector_modern |
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packages/react-native/ReactCommon/jsinspector-modern/tests/WeakListTest.cpp
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| /* | ||
| * Copyright (c) Meta Platforms, Inc. and affiliates. | ||
| * | ||
| * This source code is licensed under the MIT license found in the | ||
| * LICENSE file in the root directory of this source tree. | ||
| */ | ||
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| #include <jsinspector-modern/WeakList.h> | ||
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| #include <gmock/gmock.h> | ||
| #include <gtest/gtest.h> | ||
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| #include <vector> | ||
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| using namespace ::testing; | ||
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| namespace facebook::react::jsinspector_modern { | ||
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| TEST(WeakListTest, Size) { | ||
| WeakList<int> list; | ||
| EXPECT_EQ(list.size(), 0); | ||
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| auto p1 = std::make_shared<int>(1); | ||
| list.insert(p1); | ||
| EXPECT_EQ(list.size(), 1); | ||
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| auto p2 = std::make_shared<int>(2); | ||
| list.insert(p2); | ||
| EXPECT_EQ(list.size(), 2); | ||
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| p1.reset(); | ||
| EXPECT_EQ(list.size(), 1); | ||
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| p2.reset(); | ||
| EXPECT_EQ(list.size(), 0); | ||
| } | ||
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| TEST(WeakListTest, Empty) { | ||
| WeakList<int> list; | ||
| EXPECT_EQ(list.empty(), true); | ||
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| auto p1 = std::make_shared<int>(1); | ||
| list.insert(p1); | ||
| EXPECT_EQ(list.empty(), false); | ||
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| auto p2 = std::make_shared<int>(2); | ||
| list.insert(p2); | ||
| EXPECT_EQ(list.empty(), false); | ||
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| p1.reset(); | ||
| EXPECT_EQ(list.empty(), false); | ||
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| p2.reset(); | ||
| EXPECT_EQ(list.empty(), true); | ||
| } | ||
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| TEST(WeakListTest, ForEach) { | ||
| WeakList<int> list; | ||
| auto p1 = std::make_shared<int>(1); | ||
| list.insert(p1); | ||
| auto p2 = std::make_shared<int>(2); | ||
| list.insert(p2); | ||
| auto p3 = std::make_shared<int>(3); | ||
| list.insert(p3); | ||
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| p2.reset(); | ||
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| std::vector<int> visited; | ||
| list.forEach([&visited](const int& value) { visited.push_back(value); }); | ||
| EXPECT_THAT(visited, ElementsAre(1, 3)); | ||
| } | ||
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| TEST(WeakListTest, ElementsAreAliveDuringCallback) { | ||
| WeakList<int> list; | ||
| auto p1 = std::make_shared<int>(1); | ||
| // A separate weak_ptr to observe the lifetime of `p1`. | ||
| std::weak_ptr wp1 = p1; | ||
| list.insert(p1); | ||
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| std::vector<int> visited; | ||
| list.forEach([&](const int& value) { | ||
| p1.reset(); | ||
| EXPECT_FALSE(wp1.expired()); | ||
| visited.push_back(value); | ||
| }); | ||
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| EXPECT_TRUE(wp1.expired()); | ||
| EXPECT_THAT(visited, ElementsAre(1)); | ||
| } | ||
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| } // namespace facebook::react::jsinspector_modern |