forked from OSchip/llvm-project
109 lines
3.6 KiB
C++
109 lines
3.6 KiB
C++
//===--- Function.h - Utility callable wrappers -----------------*- C++-*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file provides utilities for callable objects.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_SUPPORT_FUNCTION_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_SUPPORT_FUNCTION_H
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#include "llvm/ADT/FunctionExtras.h"
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#include "llvm/Support/Error.h"
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#include <mutex>
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#include <tuple>
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#include <utility>
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namespace clang {
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namespace clangd {
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/// A Callback<T> is a void function that accepts Expected<T>.
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/// This is accepted by ClangdServer functions that logically return T.
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template <typename T>
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using Callback = llvm::unique_function<void(llvm::Expected<T>)>;
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/// An Event<T> allows events of type T to be broadcast to listeners.
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template <typename T> class Event {
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public:
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// A Listener is the callback through which events are delivered.
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using Listener = std::function<void(const T &)>;
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// A subscription defines the scope of when a listener should receive events.
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// After destroying the subscription, no more events are received.
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class LLVM_NODISCARD Subscription {
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Event *Parent;
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unsigned ListenerID;
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Subscription(Event *Parent, unsigned ListenerID)
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: Parent(Parent), ListenerID(ListenerID) {}
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friend Event;
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public:
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Subscription() : Parent(nullptr) {}
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Subscription(Subscription &&Other) : Parent(nullptr) {
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*this = std::move(Other);
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}
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Subscription &operator=(Subscription &&Other) {
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// If *this is active, unsubscribe.
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if (Parent) {
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std::lock_guard<std::recursive_mutex> Lock(Parent->ListenersMu);
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llvm::erase_if(Parent->Listeners,
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[&](const std::pair<Listener, unsigned> &P) {
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return P.second == ListenerID;
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});
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}
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// Take over the other subscription, and mark it inactive.
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std::tie(Parent, ListenerID) = std::tie(Other.Parent, Other.ListenerID);
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Other.Parent = nullptr;
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return *this;
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}
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// Destroying a subscription may block if an event is being broadcast.
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~Subscription() {
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if (Parent)
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*this = Subscription(); // Unsubscribe.
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}
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};
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// Adds a listener that will observe all future events until the returned
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// subscription is destroyed.
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// May block if an event is currently being broadcast.
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Subscription observe(Listener L) {
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std::lock_guard<std::recursive_mutex> Lock(ListenersMu);
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Listeners.push_back({std::move(L), ++ListenerCount});
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return Subscription(this, ListenerCount);
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}
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// Synchronously sends an event to all registered listeners.
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// Must not be called from a listener to this event.
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void broadcast(const T &V) {
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// FIXME: it would be nice to dynamically check non-reentrancy here.
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std::lock_guard<std::recursive_mutex> Lock(ListenersMu);
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for (const auto &L : Listeners)
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L.first(V);
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}
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~Event() {
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std::lock_guard<std::recursive_mutex> Lock(ListenersMu);
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assert(Listeners.empty());
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}
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private:
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static_assert(std::is_same<typename std::decay<T>::type, T>::value,
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"use a plain type: event values are always passed by const&");
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std::recursive_mutex ListenersMu;
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bool IsBroadcasting = false;
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std::vector<std::pair<Listener, unsigned>> Listeners;
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unsigned ListenerCount = 0;
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};
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} // namespace clangd
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} // namespace clang
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#endif
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