modules/libpref/nsPrefBranch.h
author Michael Comella <michael.l.comella@gmail.com>
Thu, 28 Sep 2017 14:09:48 -0700
changeset 672179 24a1c13c077ff73b0699219074d5b7c7e97041ef
parent 642125 e405ea7e39436fcaf07ae2c2961f20f6faf702b4
child 648192 c236dfe7dc98c387219d7cb45d0693560db708fd
child 675884 6c3283cc10aef15b3e85b8e81054f5e8ea2b0793
child 677122 014f84dbd970d28beb9ee89e385a764b814916e4
permissions -rw-r--r--
Bug 1403755: Rm code to insert blanks into top sites. r=liuche This code was being mistakenly activated when getting top sites for Activity Stream. This is the first removal of old top sites code and will mean we can't go back to old top sites by flipping the `ActivityStream.isEnabled` flag. Since we're planning to ship AS, this shouldn't matter. If we wanted to preserve support, we could create a branch but deleting the code is much simpler. MozReview-Commit-ID: 9VB0RqNHmE0

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 nsPrefBranch_h
#define nsPrefBranch_h

#include "nsCOMPtr.h"
#include "nsIObserver.h"
#include "nsIPrefBranch.h"
#include "nsIPrefLocalizedString.h"
#include "nsXPCOM.h"
#include "nsISupportsPrimitives.h"
#include "nsIRelativeFilePref.h"
#include "nsIFile.h"
#include "nsString.h"
#include "nsTArray.h"
#include "nsWeakReference.h"
#include "nsClassHashtable.h"
#include "nsCRT.h"
#include "nsISupportsImpl.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/Variant.h"

namespace mozilla {
class PreferenceServiceReporter;
} // namespace mozilla

class nsPrefBranch;

class PrefCallback : public PLDHashEntryHdr {
  friend class mozilla::PreferenceServiceReporter;

  public:
    typedef PrefCallback* KeyType;
    typedef const PrefCallback* KeyTypePointer;

    static const PrefCallback* KeyToPointer(PrefCallback *aKey)
    {
      return aKey;
    }

    static PLDHashNumber HashKey(const PrefCallback *aKey)
    {
      uint32_t hash = mozilla::HashString(aKey->mDomain);
      return mozilla::AddToHash(hash, aKey->mCanonical);
    }


  public:
    // Create a PrefCallback with a strong reference to its observer.
    PrefCallback(const char *aDomain, nsIObserver *aObserver,
                 nsPrefBranch *aBranch)
      : mDomain(aDomain),
        mBranch(aBranch),
        mWeakRef(nullptr),
        mStrongRef(aObserver)
    {
      MOZ_COUNT_CTOR(PrefCallback);
      nsCOMPtr<nsISupports> canonical = do_QueryInterface(aObserver);
      mCanonical = canonical;
    }

    // Create a PrefCallback with a weak reference to its observer.
    PrefCallback(const char *aDomain,
                 nsISupportsWeakReference *aObserver,
                 nsPrefBranch *aBranch)
      : mDomain(aDomain),
        mBranch(aBranch),
        mWeakRef(do_GetWeakReference(aObserver)),
        mStrongRef(nullptr)
    {
      MOZ_COUNT_CTOR(PrefCallback);
      nsCOMPtr<nsISupports> canonical = do_QueryInterface(aObserver);
      mCanonical = canonical;
    }

    // Copy constructor needs to be explicit or the linker complains.
    explicit PrefCallback(const PrefCallback *&aCopy)
      : mDomain(aCopy->mDomain),
        mBranch(aCopy->mBranch),
        mWeakRef(aCopy->mWeakRef),
        mStrongRef(aCopy->mStrongRef),
        mCanonical(aCopy->mCanonical)
    {
      MOZ_COUNT_CTOR(PrefCallback);
    }

    ~PrefCallback()
    {
      MOZ_COUNT_DTOR(PrefCallback);
    }

    bool KeyEquals(const PrefCallback *aKey) const
    {
      // We want to be able to look up a weakly-referencing PrefCallback after
      // its observer has died so we can remove it from the table.  Once the
      // callback's observer dies, its canonical pointer is stale -- in
      // particular, we may have allocated a new observer in the same spot in
      // memory!  So we can't just compare canonical pointers to determine
      // whether aKey refers to the same observer as this.
      //
      // Our workaround is based on the way we use this hashtable: When we ask
      // the hashtable to remove a PrefCallback whose weak reference has
      // expired, we use as the key for removal the same object as was inserted
      // into the hashtable.  Thus we can say that if one of the keys' weak
      // references has expired, the two keys are equal iff they're the same
      // object.

      if (IsExpired() || aKey->IsExpired())
        return this == aKey;

      if (mCanonical != aKey->mCanonical)
        return false;

      return mDomain.Equals(aKey->mDomain);
    }

    PrefCallback *GetKey() const
    {
      return const_cast<PrefCallback*>(this);
    }

    // Get a reference to the callback's observer, or null if the observer was
    // weakly referenced and has been destroyed.
    already_AddRefed<nsIObserver> GetObserver() const
    {
      if (!IsWeak()) {
        nsCOMPtr<nsIObserver> copy = mStrongRef;
        return copy.forget();
      }

      nsCOMPtr<nsIObserver> observer = do_QueryReferent(mWeakRef);
      return observer.forget();
    }

    const nsCString& GetDomain() const
    {
      return mDomain;
    }

    nsPrefBranch* GetPrefBranch() const
    {
      return mBranch;
    }

    // Has this callback's weak reference died?
    bool IsExpired() const
    {
      if (!IsWeak())
        return false;

      nsCOMPtr<nsIObserver> observer(do_QueryReferent(mWeakRef));
      return !observer;
    }

    enum { ALLOW_MEMMOVE = true };

  private:
    nsCString             mDomain;
    nsPrefBranch         *mBranch;

    // Exactly one of mWeakRef and mStrongRef should be non-null.
    nsWeakPtr             mWeakRef;
    nsCOMPtr<nsIObserver> mStrongRef;

    // We need a canonical nsISupports pointer, per bug 578392.
    nsISupports          *mCanonical;

    bool IsWeak() const
    {
      return !!mWeakRef;
    }
};

class nsPrefBranch final : public nsIPrefBranch,
                           public nsIObserver,
                           public nsSupportsWeakReference
{
  friend class mozilla::PreferenceServiceReporter;
public:
  NS_DECL_ISUPPORTS
  NS_DECL_NSIPREFBRANCH
  NS_DECL_NSIOBSERVER

  nsPrefBranch(const char *aPrefRoot, bool aDefaultBranch);
  nsPrefBranch() = delete;

  int32_t GetRootLength() const { return mPrefRoot.Length(); }

  nsresult RemoveObserverFromMap(const char *aDomain, nsISupports *aObserver);

  static void NotifyObserver(const char *newpref, void *data);

  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf);

  static void ReportToConsole(const nsAString& aMessage);

protected:
  /**
   * Helper class for either returning a raw cstring or nsCString.
   */
  typedef mozilla::Variant<const char*, const nsCString> PrefNameBase;
  class PrefName : public PrefNameBase
  {
  public:
    explicit PrefName(const char* aName) : PrefNameBase(aName) {}
    explicit PrefName(const nsCString& aName) : PrefNameBase(aName) {}

    /**
     * Use default move constructors, disallow copy constructors.
     */
    PrefName(PrefName&& aOther) = default;
    PrefName& operator=(PrefName&& aOther) = default;
    PrefName(const PrefName&) = delete;
    PrefName& operator=(const PrefName&) = delete;

    struct PtrMatcher {
      static const char* match(const char* aVal) { return aVal; }
      static const char* match(const nsCString& aVal) { return aVal.get(); }
    };

    struct LenMatcher {
      static size_t match(const char* aVal) { return strlen(aVal); }
      static size_t match(const nsCString& aVal) { return aVal.Length(); }
    };

    const char* get() const {
      static PtrMatcher m;
      return match(m);
    }

    size_t Length() const {
      static LenMatcher m;
      return match(m);
    }
  };

  virtual ~nsPrefBranch();

  nsresult   GetDefaultFromPropertiesFile(const char *aPrefName, nsAString& aReturn);
  // As SetCharPref, but without any check on the length of |aValue|
  nsresult   SetCharPrefInternal(const char *aPrefName, const char *aValue);
  // Reject strings that are more than 1Mb, warn if strings are more than 16kb
  nsresult   CheckSanityOfStringLength(const char* aPrefName, const nsAString& aValue);
  nsresult   CheckSanityOfStringLength(const char* aPrefName, const nsACString& aValue);
  nsresult   CheckSanityOfStringLength(const char* aPrefName, const char* aValue);
  nsresult   CheckSanityOfStringLength(const char* aPrefName, const uint32_t aLength);
  void RemoveExpiredCallback(PrefCallback *aCallback);
  PrefName getPrefName(const char *aPrefName) const;
  void       freeObserverList(void);

private:
  const nsCString mPrefRoot;
  bool                  mIsDefault;

  bool                  mFreeingObserverList;
  nsClassHashtable<PrefCallback, PrefCallback> mObservers;
};


class nsPrefLocalizedString final : public nsIPrefLocalizedString,
                                    public nsISupportsString
{
public:
  nsPrefLocalizedString();

  NS_DECL_ISUPPORTS
  NS_FORWARD_NSISUPPORTSSTRING(mUnicodeString->)
  NS_FORWARD_NSISUPPORTSPRIMITIVE(mUnicodeString->)

  nsresult Init();

private:
  virtual ~nsPrefLocalizedString();

  NS_IMETHOD GetData(char16_t**) override;
  NS_IMETHOD SetData(const char16_t* aData) override;
  NS_IMETHOD SetDataWithLength(uint32_t aLength, const char16_t *aData) override;

  nsCOMPtr<nsISupportsString> mUnicodeString;
};


class nsRelativeFilePref : public nsIRelativeFilePref
{
public:
  NS_DECL_ISUPPORTS
  NS_DECL_NSIRELATIVEFILEPREF

  nsRelativeFilePref();

private:
  virtual ~nsRelativeFilePref();

  nsCOMPtr<nsIFile> mFile;
  nsCString mRelativeToKey;
};

#endif