xpcom/threads/IdleTaskRunner.h
author Henri Sivonen <hsivonen@hsivonen.fi>
Fri, 06 Jul 2018 10:44:43 +0300
changeset 489140 4ef0f163fdeb9afeddd87b37bfd987298c038542
parent 479074 1d80ff31f25a7b113b51738590187b9b0acafa34
child 501569 7b36a8c21a150097364be7d4642904bc2051e93c
permissions -rw-r--r--
Bug 1402247 - Use encoding_rs for XPCOM string encoding conversions. r=Nika,erahm,froydnj. Correctness improvements: * UTF errors are handled safely per spec instead of dangerously truncating strings. * There are fewer converter implementations. Performance improvements: * The old code did exact buffer length math, which meant doing UTF math twice on each input string (once for length calculation and another time for conversion). Exact length math is more complicated when handling errors properly, which the old code didn't do. The new code does UTF math on the string content only once (when converting) but risks allocating more than once. There are heuristics in place to lower the probability of reallocation in cases where the double math avoidance isn't enough of a saving to absorb an allocation and memcpy. * Previously, in UTF-16 <-> UTF-8 conversions, an ASCII prefix was optimized but a single non-ASCII code point pessimized the rest of the string. The new code tries to get back on the fast ASCII path. * UTF-16 to Latin1 conversion guarantees less about handling of out-of-range input to eliminate an operation from the inner loop on x86/x86_64. * When assigning to a pre-existing string, the new code tries to reuse the old buffer instead of first releasing the old buffer and then allocating a new one. * When reallocating from the new code, the memcpy covers only the data that is part of the logical length of the old string instead of memcpying the whole capacity. (For old callers old excess memcpy behavior is preserved due to bogus callers. See bug 1472113.) * UTF-8 strings in XPConnect that are in the Latin1 range are passed to SpiderMonkey as Latin1. New features: * Conversion between UTF-8 and Latin1 is added in order to enable faster future interop between Rust code (or otherwise UTF-8-using code) and text node and SpiderMonkey code that uses Latin1. MozReview-Commit-ID: JaJuExfILM9

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef IdleTaskRunner_h
#define IdleTaskRunner_h

#include "mozilla/TimeStamp.h"
#include "mozilla/TaskCategory.h"
#include "nsThreadUtils.h"
#include <functional>

namespace mozilla {

// A general purpose repeating callback runner (it can be configured
// to a one-time runner, too.) If it is running repeatedly,
// one has to either explicitly Cancel() the runner or have
// MayContinueProcessing() callback return false to completely remove
// the runner.
class IdleTaskRunner final : public IdleRunnable
{
public:
  // Return true if some meaningful work was done.
  using CallbackType = std::function<bool(TimeStamp aDeadline)>;

  // A callback for "stop processing" decision. Return true to
  // stop processing. This can be an alternative to Cancel() or
  // work together in different way.
  using MayStopProcessingCallbackType = std::function<bool()>;

public:
  static already_AddRefed<IdleTaskRunner>
  Create(const CallbackType& aCallback,
         const char* aRunnableName, uint32_t aDelay,
         int64_t aBudget, bool aRepeating,
         const MayStopProcessingCallbackType& aMayStopProcessing,
         TaskCategory aTaskCategory = TaskCategory::Count);

  NS_IMETHOD Run() override;

  void SetDeadline(mozilla::TimeStamp aDeadline) override;
  void SetTimer(uint32_t aDelay, nsIEventTarget* aTarget) override;

  nsresult Cancel() override;
  void Schedule(bool aAllowIdleDispatch);

private:
  explicit IdleTaskRunner(const CallbackType& aCallback,
                          const char* aRunnableName,
                          uint32_t aDelay, int64_t aBudget,
                          bool aRepeating,
                          const MayStopProcessingCallbackType& aMayStopProcessing,
                          TaskCategory aTaskCategory);
  ~IdleTaskRunner();
  void CancelTimer();
  void SetTimerInternal(uint32_t aDelay);

  nsCOMPtr<nsITimer> mTimer;
  nsCOMPtr<nsITimer> mScheduleTimer;
  CallbackType mCallback;
  uint32_t mDelay;
  TimeStamp mDeadline;
  TimeDuration mBudget;
  bool mRepeating;
  bool mTimerActive;
  MayStopProcessingCallbackType mMayStopProcessing;
  TaskCategory mTaskCategory;
  const char* mName;
};

} // end of namespace mozilla.

#endif