xpcom/ds/nsAtom.h
author Petru Lingurar <petru.lingurar@softvision.ro>
Fri, 13 Jul 2018 17:16:37 +0300
changeset 426733 c2b1f1b52866d2c58f5e23fe2df97c9127ebcacf
parent 425702 ed26ab52032ea0a2f1420236e50b6f37824e9c8b
child 430008 2d7701c11a218faaaddb1acc9dff6ad12cafe7ae
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 nsAtom_h
#define nsAtom_h

#include "nsISupportsImpl.h"
#include "nsString.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/UniquePtr.h"

namespace mozilla {
struct AtomsSizes;
}

class nsStaticAtom;
class nsDynamicAtom;

// This class encompasses both static and dynamic atoms.
//
// - In places where static and dynamic atoms can be used, use RefPtr<nsAtom>.
//   This is by far the most common case. (The exception to this is the HTML5
//   parser, which does its own weird thing, and uses non-refcounted dynamic
//   atoms.)
//
// - In places where only static atoms can appear, use nsStaticAtom* to avoid
//   unnecessary refcounting. This is a moderately common case.
//
// - In places where only dynamic atoms can appear, it doesn't matter much
//   whether you use RefPtr<nsAtom> or RefPtr<nsDynamicAtom>. This is an
//   extremely rare case.
//
class nsAtom
{
public:
  void AddSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf,
                              mozilla::AtomsSizes& aSizes) const;

  // Dynamic HTML5 atoms are just like vanilla dynamic atoms, but we disallow
  // various operations, the most important of which is AddRef/Release.
  // XXX: we'd like to get rid of dynamic HTML5 atoms. See bug 1392185 for
  // details.
  enum class AtomKind : uint8_t {
    Static = 0,
    DynamicNormal = 1,
    DynamicHTML5 = 2,
  };

  bool Equals(char16ptr_t aString, uint32_t aLength) const
  {
    return mLength == aLength &&
           memcmp(GetUTF16String(), aString, mLength * sizeof(char16_t)) == 0;
  }

  bool Equals(const nsAString& aString) const
  {
    return Equals(aString.BeginReading(), aString.Length());
  }

  AtomKind Kind() const { return static_cast<AtomKind>(mKind); }

  bool IsStatic() const { return Kind() == AtomKind::Static; }
  bool IsDynamic() const
  {
    return Kind() == AtomKind::DynamicNormal ||
           Kind() == AtomKind::DynamicHTML5;
  }
  bool IsDynamicHTML5() const
  {
    return Kind() == AtomKind::DynamicHTML5;
  }

  const nsStaticAtom* AsStatic() const;
  const nsDynamicAtom* AsDynamic() const;
  nsDynamicAtom* AsDynamic();

  char16ptr_t GetUTF16String() const;

  uint32_t GetLength() const { return mLength; }

  void ToString(nsAString& aString) const;
  void ToUTF8String(nsACString& aString) const;

  // A hashcode that is better distributed than the actual atom pointer, for
  // use in situations that need a well-distributed hashcode. It's called hash()
  // rather than Hash() so we can use mozilla::BloomFilter<N, nsAtom>, because
  // BloomFilter requires elements to implement a function called hash().
  //
  uint32_t hash() const
  {
    MOZ_ASSERT(!IsDynamicHTML5());
    return mHash;
  }

  // We can't use NS_INLINE_DECL_THREADSAFE_REFCOUNTING because the refcounting
  // of this type is special.
  MozExternalRefCountType AddRef();
  MozExternalRefCountType Release();

  typedef mozilla::TrueType HasThreadSafeRefCnt;

protected:
  // Used by nsStaticAtom.
  constexpr nsAtom(const char16_t* aStr, uint32_t aLength)
    : mLength(aLength)
    , mKind(static_cast<uint32_t>(nsAtom::AtomKind::Static))
    , mHash(mozilla::ConstExprHashString(aStr))
  {}

  // Used by nsDynamicAtom.
  nsAtom(AtomKind aKind, const nsAString& aString, uint32_t aHash)
    : mLength(aString.Length())
    , mKind(static_cast<uint32_t>(aKind))
    , mHash(aHash)
  {
    MOZ_ASSERT(aKind == AtomKind::DynamicNormal ||
               aKind == AtomKind::DynamicHTML5);
  }

  ~nsAtom() = default;

  const uint32_t mLength:30;
  const uint32_t mKind:2; // nsAtom::AtomKind
  const uint32_t mHash;
};

// This class would be |final| if it wasn't for nsICSSAnonBoxPseudo and
// nsICSSPseudoElement, which are trivial subclasses used to ensure only
// certain static atoms are passed to certain functions.
class nsStaticAtom : public nsAtom
{
public:
  // These are deleted so it's impossible to RefPtr<nsStaticAtom>. Raw
  // nsStaticAtom pointers should be used instead.
  MozExternalRefCountType AddRef() = delete;
  MozExternalRefCountType Release() = delete;

  constexpr nsStaticAtom(const char16_t* aStr, uint32_t aLength,
                         uint32_t aStringOffset)
    : nsAtom(aStr, aLength)
    , mStringOffset(aStringOffset)
  {}

  const char16_t* String() const
  {
    return reinterpret_cast<const char16_t*>(uintptr_t(this) - mStringOffset);
  }

  already_AddRefed<nsAtom> ToAddRefed() {
    return already_AddRefed<nsAtom>(static_cast<nsAtom*>(this));
  }

private:
  // This is an offset to the string chars, which must be at a lower address in
  // memory. This should be achieved by using the macros in nsStaticAtom.h.
  uint32_t mStringOffset;
};

class nsDynamicAtom : public nsAtom
{
public:
  // We can't use NS_INLINE_DECL_THREADSAFE_REFCOUNTING because the refcounting
  // of this type is special.
  MozExternalRefCountType AddRef();
  MozExternalRefCountType Release();

  const char16_t* String() const
  {
    return reinterpret_cast<const char16_t*>(this + 1);
  }

  static nsDynamicAtom* FromChars(char16_t* chars)
  {
    return reinterpret_cast<nsDynamicAtom*>(chars) - 1;
  }

private:
  friend class nsAtomTable;
  friend class nsAtomSubTable;
  // XXX: we'd like to remove nsHtml5AtomEntry. See bug 1392185.
  friend class nsHtml5AtomEntry;

  // These shouldn't be used directly, even by friend classes. The
  // Create()/Destroy() methods use them.
  static nsDynamicAtom* CreateInner(const nsAString& aString, uint32_t aHash);
  nsDynamicAtom(const nsAString& aString, uint32_t aHash);
  ~nsDynamicAtom() {}

  // Creation/destruction is done by friend classes. The first Create() is for
  // dynamic normal atoms, the second is for dynamic HTML5 atoms.
  static nsDynamicAtom* Create(const nsAString& aString, uint32_t aHash);
  static nsDynamicAtom* Create(const nsAString& aString);
  static void Destroy(nsDynamicAtom* aAtom);

  mozilla::ThreadSafeAutoRefCnt mRefCnt;

  // The atom's chars are stored at the end of the struct.
};

// The four forms of NS_Atomize (for use with |RefPtr<nsAtom>|) return the
// atom for the string given. At any given time there will always be one atom
// representing a given string. Atoms are intended to make string comparison
// cheaper by simplifying it to pointer equality. A pointer to the atom that
// does not own a reference is not guaranteed to be valid.

// Find an atom that matches the given UTF-8 string. The string is assumed to
// be zero terminated. Never returns null.
already_AddRefed<nsAtom> NS_Atomize(const char* aUTF8String);

// Find an atom that matches the given UTF-8 string. Never returns null.
already_AddRefed<nsAtom> NS_Atomize(const nsACString& aUTF8String);

// Find an atom that matches the given UTF-16 string. The string is assumed to
// be zero terminated. Never returns null.
already_AddRefed<nsAtom> NS_Atomize(const char16_t* aUTF16String);

// Find an atom that matches the given UTF-16 string. Never returns null.
already_AddRefed<nsAtom> NS_Atomize(const nsAString& aUTF16String);

// An optimized version of the method above for the main thread.
already_AddRefed<nsAtom> NS_AtomizeMainThread(const nsAString& aUTF16String);

// Return a count of the total number of atoms currently alive in the system.
//
// Note that the result is imprecise and racy if other threads are currently
// operating on atoms. It's also slow, since it triggers a GC before counting.
// Currently this function is only used in tests, which should probably remain
// the case.
nsrefcnt NS_GetNumberOfAtoms();

// Return a pointer for a static atom for the string or null if there's no
// static atom for this string.
nsStaticAtom* NS_GetStaticAtom(const nsAString& aUTF16String);

// Record that all static atoms have been inserted.
void NS_SetStaticAtomsDone();

class nsAtomString : public nsString
{
public:
  explicit nsAtomString(const nsAtom* aAtom) { aAtom->ToString(*this); }
};

class nsAtomCString : public nsCString
{
public:
  explicit nsAtomCString(nsAtom* aAtom) { aAtom->ToUTF8String(*this); }
};

class nsDependentAtomString : public nsDependentString
{
public:
  explicit nsDependentAtomString(const nsAtom* aAtom)
    : nsDependentString(aAtom->GetUTF16String(), aAtom->GetLength())
  {}
};

// Checks if the ascii chars in a given atom are already lowercase.
// If they are, no-op. Otherwise, converts all the ascii uppercase
// chars to lowercase and atomizes, storing the result in the inout
// param.
void ToLowerCaseASCII(RefPtr<nsAtom>& aAtom);

#endif  // nsAtom_h