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/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   void Run();
  22
  23  private:
  24   AtomicRefCount num_callbacks_left_;
  25   OnceClosure done_closure_;
  26 };
  27
  28 BarrierInfo::BarrierInfo(size_t num_callbacks, OnceClosure done_closure)
  29     : num_callbacks_left_(checked_cast<int>(num_callbacks)),
  30       done_closure_(std::move(done_closure)) {}
  31
  32 void BarrierInfo::Run() {
  33   DCHECK(!num_callbacks_left_.IsZero());
  34   if (!num_callbacks_left_.Decrement())
  35     std::move(done_closure_).Run();
  36 }
  37
  38 void ShouldNeverRun() {
  39   CHECK(false);
  40 }
  41
  42 }  // namespace
  43
  44 RepeatingClosure BarrierClosure(size_t num_callbacks_left,
  45                                 OnceClosure done_closure) {
  46   if (num_callbacks_left == 0) {
  47     std::move(done_closure).Run();
  48     return BindRepeating(&ShouldNeverRun);
  49   }
  50
  51   return BindRepeating(&BarrierInfo::Run,
  52                        std::make_unique<BarrierInfo>(num_callbacks_left,
  53                                                      std::move(done_closure)));
  54 }
  55
  56 }  // namespace base