mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Samuel Susla
5fa6c5a941
Summary: changelog: [internal] You can read more about this rule on https://clang.llvm.org/extra/clang-tidy/checks/modernize-pass-by-value.html # Isn't it wasteful to copy? Isn't reference more efficient? This rule of thumb is no longer true since C++11 with move semantics. Let's look at some examples. # Option one ``` class TextHolder { public: TextBox(std::string const &text) : text_(text) {} private: std::string text_; }; ``` By using reference here, we prevent the caller from using rvalue to and avoiding copy. Regardless of what the caller passes in, copy always happens. # Option two ``` class TextHolder { public: TextBox(std::string const &text) : text_(text) {} TextBox(std::string &&text) : text_(std::move(text)) {} private: std::string text_; }; ``` Here, we provide two constructors, one for const reference and one for rvalue reference. This gives the caller option to avoid copy. But now we have two constructors, which is not ideal. # Option three (what we do in this diff) ``` class TextHolder { public: TextBox(std::string text) : text_(std::move(text)) {} private: std::string text_; }; ``` Here, the caller has option to avoid copy and we only have single constructor. Reviewed By: fkgozali, JoshuaGross Differential Revision: D33276841 fbshipit-source-id: 619d5123d2e28937b22874650366629f24f20a63
91 lines
2.6 KiB
C++
91 lines
2.6 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its 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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#include "AttributedStringBox.h"
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#include <react/debug/react_native_assert.h>
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#include <utility>
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namespace facebook {
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namespace react {
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AttributedStringBox::AttributedStringBox()
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: mode_(Mode::Value),
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value_(std::make_shared<AttributedString const>(AttributedString{})),
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opaquePointer_({}){};
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AttributedStringBox::AttributedStringBox(AttributedString const &value)
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: mode_(Mode::Value),
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value_(std::make_shared<AttributedString const>(value)),
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opaquePointer_({}){};
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AttributedStringBox::AttributedStringBox(std::shared_ptr<void> opaquePointer)
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: mode_(Mode::OpaquePointer),
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value_({}),
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opaquePointer_(std::move(opaquePointer)) {}
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AttributedStringBox::AttributedStringBox(AttributedStringBox &&other) noexcept
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: mode_(other.mode_),
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value_(std::move(other.value_)),
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opaquePointer_(std::move(other.opaquePointer_)) {
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other.mode_ = AttributedStringBox::Mode::Value;
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other.value_ = std::make_shared<AttributedString const>(AttributedString{});
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}
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AttributedStringBox::Mode AttributedStringBox::getMode() const {
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return mode_;
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}
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AttributedString const &AttributedStringBox::getValue() const {
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react_native_assert(mode_ == AttributedStringBox::Mode::Value);
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react_native_assert(value_);
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return *value_;
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}
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std::shared_ptr<void> AttributedStringBox::getOpaquePointer() const {
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react_native_assert(mode_ == AttributedStringBox::Mode::OpaquePointer);
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react_native_assert(opaquePointer_);
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return opaquePointer_;
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}
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AttributedStringBox &AttributedStringBox::operator=(
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AttributedStringBox &&other) {
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if (this != &other) {
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mode_ = other.mode_;
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value_ = std::move(other.value_);
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opaquePointer_ = std::move(other.opaquePointer_);
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other.mode_ = AttributedStringBox::Mode::Value;
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other.value_ = std::make_shared<AttributedString const>(AttributedString{});
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}
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return *this;
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}
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bool operator==(
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AttributedStringBox const &lhs,
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AttributedStringBox const &rhs) {
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if (lhs.getMode() != rhs.getMode()) {
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return false;
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}
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switch (lhs.getMode()) {
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case AttributedStringBox::Mode::Value:
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return lhs.getValue() == rhs.getValue();
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case AttributedStringBox::Mode::OpaquePointer:
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return lhs.getOpaquePointer() == rhs.getOpaquePointer();
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}
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}
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bool operator!=(
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AttributedStringBox const &lhs,
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AttributedStringBox const &rhs) {
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return !(lhs == rhs);
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}
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} // namespace react
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} // namespace facebook
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