1 //===--- Cancellation.cpp -----------------------------------------*-C++-*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "support/Cancellation.h"
10 #include <atomic>
11 
12 namespace clang {
13 namespace clangd {
14 
15 char CancelledError::ID = 0;
16 
17 // We don't want a cancelable scope to "shadow" an enclosing one.
18 struct CancelState {
19   std::shared_ptr<std::atomic<int>> Cancelled;
20   const CancelState *Parent;
21 };
22 static Key<CancelState> StateKey;
23 
cancelableTask(int Reason)24 std::pair<Context, Canceler> cancelableTask(int Reason) {
25   assert(Reason != 0 && "Can't detect cancellation if Reason is zero");
26   CancelState State;
27   State.Cancelled = std::make_shared<std::atomic<int>>();
28   State.Parent = Context::current().get(StateKey);
29   return {
30       Context::current().derive(StateKey, State),
31       [Reason, Flag(State.Cancelled)] { *Flag = Reason; },
32   };
33 }
34 
isCancelled(const Context & Ctx)35 int isCancelled(const Context &Ctx) {
36   for (const CancelState *State = Ctx.get(StateKey); State != nullptr;
37        State = State->Parent)
38     if (int Reason = State->Cancelled->load())
39       return Reason;
40   return 0;
41 }
42 
43 } // namespace clangd
44 } // namespace clang
45