mojo/edk/system/awakable_list.cc

// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "mojo/edk/system/awakable_list.h"

#include <algorithm>

#include "base/logging.h"
#include "mojo/edk/system/awakable.h"
#include "mojo/edk/system/handle_signals_state.h"

namespace mojo {
namespace system {

AwakableList::AwakableList() {}

AwakableList::~AwakableList() {
  DCHECK(awakables_.empty());
}

void AwakableList::OnStateChange(const HandleSignalsState& old_state,
                                 const HandleSignalsState& new_state) {
  // Instead of deleting elements in-place, swap them with the last element and
  // erase the elements from the end.
  auto last = awakables_.end();
  for (auto it = awakables_.begin(); it != last;) {
    bool awoken = false;
    if (it->persistent) {
      // Persistent awakables are called for all changes on watched signals.
      if ((new_state.satisfied_signals & it->signals) !=
              (old_state.satisfied_signals & it->signals) ||
          (new_state.satisfiable_signals & it->signals) !=
              (old_state.satisfiable_signals & it->signals)) {
        awoken = true;
        it->awakable->Awake(it->context, Awakable::AwakeReason::CHANGED,
                            new_state);
      }
    } else {
      // One-shot awakables are only called on "leading edge" changes in overall
      // satisfied-ness or never-satisfiable-ness. (That is, if a one-shot
      // awakable was previously satisfied and is still satisfied, but for
      // different reasons, it will not be called.)
      if (new_state.satisfies(it->signals) &&
          !old_state.satisfies(it->signals)) {
        awoken = true;
        it->awakable->Awake(it->context, Awakable::AwakeReason::SATISFIED,
                            new_state);
      } else if (!new_state.can_satisfy(it->signals) &&
                 old_state.can_satisfy(it->signals)) {
        awoken = true;
        it->awakable->Awake(it->context, Awakable::AwakeReason::UNSATISFIABLE,
                            new_state);
      }
    }

    // Remove if the awakable was awoken and one-shot.
    if (awoken && !it->persistent) {
      --last;
      std::swap(*it, *last);
    } else {
      ++it;
    }
  }
  awakables_.erase(last, awakables_.end());
}

void AwakableList::CancelAndRemoveAll() {
  for (auto it = awakables_.begin(); it != awakables_.end(); ++it) {
    it->awakable->Awake(it->context, Awakable::AwakeReason::CANCELLED,
                        HandleSignalsState());
  }
  awakables_.clear();
}

void AwakableList::Add(Awakable* awakable,
                       uint64_t context,
                       bool persistent,
                       MojoHandleSignals signals,
                       const HandleSignalsState& current_state) {
  awakables_.push_back(AwakeInfo(awakable, context, persistent, signals));
  if (persistent)
    awakable->Awake(context, Awakable::AwakeReason::INITIALIZE, current_state);
}

void AwakableList::Remove(bool match_context,
                          Awakable* awakable,
                          uint64_t context) {
  // We allow a thread to wait on the same handle multiple times simultaneously,
  // so we need to scan the entire list and remove all occurrences of |waiter|.
  auto last = awakables_.end();
  for (AwakeInfoList::iterator it = awakables_.begin(); it != last;) {
    if (it->awakable == awakable &&
        (!match_context || it->context == context)) {
      --last;
      std::swap(*it, *last);
    } else {
      ++it;
    }
  }
  awakables_.erase(last, awakables_.end());
}

}  // namespace system
}  // namespace mojo