base/barrier_closure.cc

   1 // Copyright 2013 The Chromium Authors
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/barrier_closure.h"
   6
   7 #include <utility>
   8
   9 #include "base/atomic_ref_count.h"
  10 #include "base/functional/bind.h"
  11 #include "base/memory/ptr_util.h"
  12 #include "base/numerics/safe_conversions.h"
  13
  14 namespace base {
  15 namespace {
  16
  17 // Maintains state for a BarrierClosure.
  18 class BarrierInfo {
  19  public:
  20   BarrierInfo(size_t num_callbacks_left, OnceClosure done_closure);
  21   BarrierInfo(const BarrierInfo&) = delete;
  22   BarrierInfo& operator=(const BarrierInfo&) = delete;
  23   void Run();
  24
  25  private:
  26   AtomicRefCount num_callbacks_left_;
  27   OnceClosure done_closure_;
  28 };
  29
  30 BarrierInfo::BarrierInfo(size_t num_callbacks, OnceClosure done_closure)
  31     : num_callbacks_left_(checked_cast<int>(num_callbacks)),
  32       done_closure_(std::move(done_closure)) {}
  33
  34 void BarrierInfo::Run() {
  35   DCHECK(!num_callbacks_left_.IsZero());
  36   if (!num_callbacks_left_.Decrement())
  37     std::move(done_closure_).Run();
  38 }
  39
  40 void ShouldNeverRun() {
  41   CHECK(false);
  42 }
  43
  44 }  // namespace
  45
  46 RepeatingClosure BarrierClosure(size_t num_callbacks_left,
  47                                 OnceClosure done_closure) {
  48   if (num_callbacks_left == 0) {
  49     std::move(done_closure).Run();
  50     return BindRepeating(&ShouldNeverRun);
  51   }
  52
  53   return BindRepeating(&BarrierInfo::Run,
  54                        std::make_unique<BarrierInfo>(num_callbacks_left,
  55                                                      std::move(done_closure)));
  56 }
  57
  58 }  // namespace base