mfbt/TypedEnumBits.h
author Masayuki Nakano <masayuki@d-toybox.com>
Thu, 16 Mar 2017 16:26:43 +0900
changeset 398554 8e72178c3893c377972209cccd2e561e1ec06c7d
parent 369712 0dfe466e790f39710ce553a9a858f92da6a095a6
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1339331 TextEventDispatcher should replace \r in composition string with \n and TextComposition should allow to input \n with composition events r=m_kato According to ATOK's behavior, IME may send different line breaker from its platform's standard. Therefore, we should treat \r as \n too. Additionally, currently, TextComposition doesn't allow to input \n with composition. However, this was added for preventing to see odd control characters as boxes with code point. Therefore, we should allow \n for IMEs. (It was allowed, this limitation is unexpected when I reviewed the patch to reject control characters in TextComposition.) MozReview-Commit-ID: DzGSMgp89Av

/* -*- 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/. */

/*
 * MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS allows using a typed enum as bit flags.
 */

#ifndef mozilla_TypedEnumBits_h
#define mozilla_TypedEnumBits_h

#include "mozilla/Attributes.h"
#include "mozilla/IntegerTypeTraits.h"

namespace mozilla {

/*
 * The problem that CastableTypedEnumResult aims to solve is that
 * typed enums are not convertible to bool, and there is no way to make them
 * be, yet user code wants to be able to write
 *
 *   if (myFlags & Flags::SOME_PARTICULAR_FLAG)              (1)
 *
 * There are different approaches to solving this. Most of them require
 * adapting user code. For example, we could implement operator! and have
 * the user write
 *
 *   if (!!(myFlags & Flags::SOME_PARTICULAR_FLAG))          (2)
 *
 * Or we could supply a IsNonZero() or Any() function returning whether
 * an enum value is nonzero, and have the user write
 *
 *   if (Any(Flags & Flags::SOME_PARTICULAR_FLAG))           (3)
 *
 * But instead, we choose to preserve the original user syntax (1) as it
 * is inherently more readable, and to ease porting existing code to typed
 * enums. We achieve this by having operator& and other binary bitwise
 * operators have as return type a class, CastableTypedEnumResult,
 * that wraps a typed enum but adds bool convertibility.
 */
template<typename E>
class CastableTypedEnumResult
{
private:
  const E mValue;

public:
  explicit constexpr CastableTypedEnumResult(E aValue)
    : mValue(aValue)
  {}

  constexpr operator E() const { return mValue; }

  template<typename DestinationType>
  explicit constexpr
  operator DestinationType() const { return DestinationType(mValue); }

  constexpr bool operator !() const { return !bool(mValue); }
};

#define MOZ_CASTABLETYPEDENUMRESULT_BINOP(Op, OtherType, ReturnType) \
template<typename E> \
constexpr ReturnType \
operator Op(const OtherType& aE, const CastableTypedEnumResult<E>& aR) \
{ \
  return ReturnType(aE Op OtherType(aR)); \
} \
template<typename E> \
constexpr ReturnType \
operator Op(const CastableTypedEnumResult<E>& aR, const OtherType& aE) \
{ \
  return ReturnType(OtherType(aR) Op aE); \
} \
template<typename E> \
constexpr ReturnType \
operator Op(const CastableTypedEnumResult<E>& aR1, \
            const CastableTypedEnumResult<E>& aR2) \
{ \
  return ReturnType(OtherType(aR1) Op OtherType(aR2)); \
}

MOZ_CASTABLETYPEDENUMRESULT_BINOP(|, E, CastableTypedEnumResult<E>)
MOZ_CASTABLETYPEDENUMRESULT_BINOP(&, E, CastableTypedEnumResult<E>)
MOZ_CASTABLETYPEDENUMRESULT_BINOP(^, E, CastableTypedEnumResult<E>)
MOZ_CASTABLETYPEDENUMRESULT_BINOP(==, E, bool)
MOZ_CASTABLETYPEDENUMRESULT_BINOP(!=, E, bool)

template <typename E>
constexpr CastableTypedEnumResult<E>
operator ~(const CastableTypedEnumResult<E>& aR)
{
  return CastableTypedEnumResult<E>(~(E(aR)));
}

#define MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP(Op) \
template<typename E> \
E& \
operator Op(E& aR1, \
            const CastableTypedEnumResult<E>& aR2) \
{ \
  return aR1 Op E(aR2); \
}

MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP(&=)
MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP(|=)
MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP(^=)

#undef MOZ_CASTABLETYPEDENUMRESULT_COMPOUND_ASSIGN_OP

#undef MOZ_CASTABLETYPEDENUMRESULT_BINOP

namespace detail {
template<typename E>
struct UnsignedIntegerTypeForEnum
  : UnsignedStdintTypeForSize<sizeof(E)>
{};
} // namespace detail

} // namespace mozilla

#define MOZ_MAKE_ENUM_CLASS_BINOP_IMPL(Name, Op) \
   inline constexpr mozilla::CastableTypedEnumResult<Name> \
   operator Op(Name a, Name b) \
   { \
     typedef mozilla::CastableTypedEnumResult<Name> Result; \
     typedef mozilla::detail::UnsignedIntegerTypeForEnum<Name>::Type U; \
     return Result(Name(U(a) Op U(b))); \
   } \
 \
   inline Name& \
   operator Op##=(Name& a, Name b) \
   { \
     return a = a Op b; \
   }

/**
 * MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS generates standard bitwise operators
 * for the given enum type. Use this to enable using an enum type as bit-field.
 */
#define MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(Name) \
   MOZ_MAKE_ENUM_CLASS_BINOP_IMPL(Name, |) \
   MOZ_MAKE_ENUM_CLASS_BINOP_IMPL(Name, &) \
   MOZ_MAKE_ENUM_CLASS_BINOP_IMPL(Name, ^) \
   inline constexpr mozilla::CastableTypedEnumResult<Name> \
   operator~(Name a) \
   { \
     typedef mozilla::CastableTypedEnumResult<Name> Result; \
     typedef mozilla::detail::UnsignedIntegerTypeForEnum<Name>::Type U; \
     return Result(Name(~(U(a)))); \
   }

#endif // mozilla_TypedEnumBits_h