xpcom/ds/nsCheapSets.h
author Petru Lingurar <petru.lingurar@softvision.ro>
Fri, 13 Jul 2018 17:16:37 +0300
changeset 426733 c2b1f1b52866d2c58f5e23fe2df97c9127ebcacf
parent 423666 33346f699996421fc8bf22a25f574de470142a41
child 448947 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1385464 - Start using support library v. 26; r=nalexander This patch also: Resolves missing resources and api changes - LeanplumActionBarActivity was removed because Support Library 26 deprecated ActionBarActivity. Class was already not in use. - CustomTabsService added two new methods which we need to override. Tested to make sure that previous functionality was maintained but with the addition of the two new methods maybe that feature could be improved. - For checking layout direction we'll use our own new method from ViewUtil which mimics what the now restricted method from the support library would do. - Upgraded to use AppCompatResources#getDrawable(..) in place of the now restricted AppCompatDrawableManager.get().getDrawable(..). Resolves obscure leaks and crashes after the upgrade - LoaderManager.destroyLoader(..) was added before the existing call to LoaderManager.restartLoader(..) to prevent potential Cursor leaks - Disable website suggestions depending on the address bar inputs when running in automation to avoid Robocop tests failing (they were entering serially maybe 100 characters in <5 ms which created around that many new Threads, operation that could cause the Executor to throw a RejectedExecutionException) At the moment this functionality is not covered by tests anyway and it was the only fix I could find that would not involve changing the whole implemenation for address bar suggestions, implementation which in the real world works ok. MozReview-Commit-ID: 2fX1SBHiSh0

/* -*- 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 __nsCheapSets_h__
#define __nsCheapSets_h__

#include "nsTHashtable.h"
#include <stdint.h>

enum nsCheapSetOperator
{
  OpNext = 0,   // enumerator says continue
  OpRemove = 1, // enumerator says remove and continue
};

/**
 * A set that takes up minimal size when there are 0 or 1 entries in the set.
 * Use for cases where sizes of 0 and 1 are even slightly common.
 */
template<typename EntryType>
class nsCheapSet
{
public:
  typedef typename EntryType::KeyType KeyType;
  typedef nsCheapSetOperator (*Enumerator)(EntryType* aEntry, void* userArg);

  nsCheapSet()
    : mState(ZERO)
  {
    mUnion.table = nullptr;
  }
  ~nsCheapSet() { Clear(); }

  /**
   * Remove all entries.
   */
  void Clear()
  {
    switch (mState) {
      case ZERO:
        break;
      case ONE:
        GetSingleEntry()->~EntryType();
        break;
      case MANY:
        delete mUnion.table;
        break;
      default:
        MOZ_ASSERT_UNREACHABLE("bogus state");
        break;
    }
    mState = ZERO;
  }

  void Put(const KeyType aVal);

  void Remove(const KeyType aVal);

  bool Contains(const KeyType aVal)
  {
    switch (mState) {
      case ZERO:
        return false;
      case ONE:
        return GetSingleEntry()->KeyEquals(EntryType::KeyToPointer(aVal));
      case MANY:
        return !!mUnion.table->GetEntry(aVal);
      default:
        MOZ_ASSERT_UNREACHABLE("bogus state");
        return false;
    }
  }

  uint32_t EnumerateEntries(Enumerator aEnumFunc, void* aUserArg)
  {
    switch (mState) {
      case ZERO:
        return 0;
      case ONE:
        if (aEnumFunc(GetSingleEntry(), aUserArg) == OpRemove) {
          GetSingleEntry()->~EntryType();
          mState = ZERO;
        }
        return 1;
      case MANY: {
        uint32_t n = mUnion.table->Count();
        for (auto iter = mUnion.table->Iter(); !iter.Done(); iter.Next()) {
          auto entry = static_cast<EntryType*>(iter.Get());
          if (aEnumFunc(entry, aUserArg) == OpRemove) {
            iter.Remove();
          }
        }
        return n;
      }
      default:
        MOZ_ASSERT_UNREACHABLE("bogus state");
        return 0;
    }
  }

private:
  EntryType* GetSingleEntry()
  {
    return reinterpret_cast<EntryType*>(&mUnion.singleEntry[0]);
  }

  enum SetState
  {
    ZERO,
    ONE,
    MANY
  };

  union
  {
    nsTHashtable<EntryType>* table;
    char singleEntry[sizeof(EntryType)];
  } mUnion;
  enum SetState mState;
};

template<typename EntryType>
void
nsCheapSet<EntryType>::Put(const KeyType aVal)
{
  switch (mState) {
    case ZERO:
      new (GetSingleEntry()) EntryType(EntryType::KeyToPointer(aVal));
      mState = ONE;
      return;
    case ONE: {
      nsTHashtable<EntryType>* table = new nsTHashtable<EntryType>();
      EntryType* entry = GetSingleEntry();
      table->PutEntry(entry->GetKey());
      entry->~EntryType();
      mUnion.table = table;
      mState = MANY;
    }
    MOZ_FALLTHROUGH;

    case MANY:
      mUnion.table->PutEntry(aVal);
      return;
    default:
      MOZ_ASSERT_UNREACHABLE("bogus state");
      return;
  }
}

template<typename EntryType>
void
nsCheapSet<EntryType>::Remove(const KeyType aVal)
{
  switch (mState) {
    case ZERO:
      break;
    case ONE:
      if (Contains(aVal)) {
        GetSingleEntry()->~EntryType();
        mState = ZERO;
      }
      break;
    case MANY:
      mUnion.table->RemoveEntry(aVal);
      break;
    default:
      MOZ_ASSERT_UNREACHABLE("bogus state");
      break;
  }
}

#endif