xpcom/threads/CondVar.h
author Henri Sivonen <hsivonen@hsivonen.fi>
Fri, 06 Jul 2018 10:44:43 +0300
changeset 489140 4ef0f163fdeb9afeddd87b37bfd987298c038542
parent 485701 ce33d2c68119f450cd888e8dca12d9a23361e5dd
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
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 mozilla_CondVar_h
#define mozilla_CondVar_h

#include "mozilla/BlockingResourceBase.h"
#include "mozilla/PlatformConditionVariable.h"
#include "mozilla/Mutex.h"

#ifdef MOZILLA_INTERNAL_API
#include "GeckoProfiler.h"
#endif //MOZILLA_INTERNAL_API

namespace mozilla {

/**
 * Similarly to OffTheBooksMutex, OffTheBooksCondvar is identical to CondVar,
 * except that OffTheBooksCondVar doesn't include leak checking.  Sometimes
 * you want to intentionally "leak" a CondVar until shutdown; in these cases,
 * OffTheBooksCondVar is for you.
 */
class OffTheBooksCondVar : BlockingResourceBase
{
public:
  /**
   * OffTheBooksCondVar
   *
   * The CALLER owns |aLock|.
   *
   * @param aLock A Mutex to associate with this condition variable.
   * @param aName A name which can reference this monitor
   * @returns If failure, nullptr.
   *          If success, a valid Monitor* which must be destroyed
   *          by Monitor::DestroyMonitor()
   **/
  OffTheBooksCondVar(OffTheBooksMutex& aLock, const char* aName)
    : BlockingResourceBase(aName, eCondVar)
    , mLock(&aLock)
  {
  }

  /**
   * ~OffTheBooksCondVar
   * Clean up after this OffTheBooksCondVar, but NOT its associated Mutex.
   **/
  ~OffTheBooksCondVar()
  {
  }

  /**
   * Wait
   * @see prcvar.h
   **/
#ifndef DEBUG
  void Wait()
  {
#ifdef MOZILLA_INTERNAL_API
    AUTO_PROFILER_THREAD_SLEEP;
#endif //MOZILLA_INTERNAL_API
    mImpl.wait(*mLock);
  }

  CVStatus Wait(TimeDuration aDuration)
  {
#ifdef MOZILLA_INTERNAL_API
    AUTO_PROFILER_THREAD_SLEEP;
#endif //MOZILLA_INTERNAL_API
    return mImpl.wait_for(*mLock, aDuration);
  }
#else
  // NOTE: debug impl is in BlockingResourceBase.cpp
  void Wait();
  CVStatus Wait(TimeDuration aDuration);
#endif

  /**
   * Notify
   * @see prcvar.h
   **/
  nsresult Notify()
  {
    mImpl.notify_one();
    return NS_OK;
  }

  /**
   * NotifyAll
   * @see prcvar.h
   **/
  nsresult NotifyAll()
  {
    mImpl.notify_all();
    return NS_OK;
  }

#ifdef DEBUG
  /**
   * AssertCurrentThreadOwnsMutex
   * @see Mutex::AssertCurrentThreadOwns
   **/
  void AssertCurrentThreadOwnsMutex()
  {
    mLock->AssertCurrentThreadOwns();
  }

  /**
   * AssertNotCurrentThreadOwnsMutex
   * @see Mutex::AssertNotCurrentThreadOwns
   **/
  void AssertNotCurrentThreadOwnsMutex()
  {
    mLock->AssertNotCurrentThreadOwns();
  }

#else
  void AssertCurrentThreadOwnsMutex() {}
  void AssertNotCurrentThreadOwnsMutex() {}

#endif  // ifdef DEBUG

private:
  OffTheBooksCondVar();
  OffTheBooksCondVar(const OffTheBooksCondVar&) = delete;
  OffTheBooksCondVar& operator=(const OffTheBooksCondVar&) = delete;

  OffTheBooksMutex* mLock;
  detail::ConditionVariableImpl mImpl;
};

/**
 * CondVar
 * Vanilla condition variable.  Please don't use this unless you have a
 * compelling reason --- Monitor provides a simpler API.
 */
class CondVar : public OffTheBooksCondVar
{
public:
  CondVar(OffTheBooksMutex& aLock, const char* aName)
    : OffTheBooksCondVar(aLock, aName)
  {
    MOZ_COUNT_CTOR(CondVar);
  }

  ~CondVar()
  {
    MOZ_COUNT_DTOR(CondVar);
  }

private:
  CondVar();
  CondVar(const CondVar&);
  CondVar& operator=(const CondVar&);
};

} // namespace mozilla


#endif  // ifndef mozilla_CondVar_h