Source/WTF/wtf/Forward.h - WebKit - Git at Google

 /*
  *  Copyright (C) 2006-2018 Apple Inc. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  *  Library General Public License for more details.
  *
  *  You should have received a copy of the GNU Library General Public License
  *  along with this library; see the file COPYING.LIB.  If not, write to
  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  *  Boston, MA 02110-1301, USA.
  *
  */

 #pragma once

 #include <stddef.h>

 namespace WTF {

 class AtomString;
 class AtomStringImpl;
 class BinarySemaphore;
 class CString;
 class CrashOnOverflow;
 class FunctionDispatcher;
 class Hasher;
 class MonotonicTime;
 class OrdinalNumber;
 class PrintStream;
 class SHA1;
 class Seconds;
 class String;
 class StringBuilder;
 class StringImpl;
 class StringView;
 class TextPosition;
 class TextStream;
 class UniquedStringImpl;
 class URL;
 class WallTime;

 struct FastMalloc;

 template<typename> class CompletionHandler;
 template<typename T> struct DumbPtrTraits;
 template<typename T> struct DumbValueTraits;
 template<typename> class Function;
 template<typename> class LazyNeverDestroyed;
 template<typename> class NeverDestroyed;
 template<typename> class OptionSet;
 template<typename> class Optional;
 template<typename T, typename = DumbPtrTraits<T>> class Ref;
 template<typename T, typename = DumbPtrTraits<T>> class RefPtr;
 template<typename> class StringBuffer;
 template<typename, typename = void> class StringTypeAdapter;
 template<typename T> class WeakPtr;

 template<typename> struct DefaultHash { using Hash = void; };
 template<typename> struct HashTraits;

 template<typename> struct EnumTraits;
 template<typename E, E...> struct EnumValues;

 template<typename...> class Variant;
 template<typename, size_t = 0, typename = CrashOnOverflow, size_t = 16> class Vector;
 template<typename Value, typename = typename DefaultHash<Value>::Hash, typename = HashTraits<Value>> class HashCountedSet;
 template<typename KeyArg, typename MappedArg, typename = typename DefaultHash<KeyArg>::Hash, typename = HashTraits<KeyArg>, typename = HashTraits<MappedArg>> class HashMap;
 template<typename ValueArg, typename = typename DefaultHash<ValueArg>::Hash, typename = HashTraits<ValueArg>> class HashSet;

 template<size_t, typename> struct variant_alternative;
 template<ptrdiff_t, typename...> struct __indexed_type;
 template<ptrdiff_t _Index, typename... _Types> constexpr typename __indexed_type<_Index, _Types...>::__type const& get(Variant<_Types...> const&);

 }

 namespace std {
 namespace experimental {
 inline namespace fundamentals_v3 {
 template<class, class> class expected;
 template<class> class unexpected;
 }}} // namespace std::experimental::fundamentals_v3

 using WTF::AtomString;
 using WTF::AtomStringImpl;
 using WTF::BinarySemaphore;
 using WTF::CString;
 using WTF::CompletionHandler;
 using WTF::DumbPtrTraits;
 using WTF::DumbValueTraits;
 using WTF::Function;
 using WTF::FunctionDispatcher;
 using WTF::HashCountedSet;
 using WTF::HashMap;
 using WTF::HashSet;
 using WTF::Hasher;
 using WTF::LazyNeverDestroyed;
 using WTF::NeverDestroyed;
 using WTF::OptionSet;
 using WTF::Optional;
 using WTF::OrdinalNumber;
 using WTF::PrintStream;
 using WTF::Ref;
 using WTF::RefPtr;
 using WTF::SHA1;
 using WTF::String;
 using WTF::StringBuffer;
 using WTF::StringBuilder;
 using WTF::StringImpl;
 using WTF::StringView;
 using WTF::TextPosition;
 using WTF::TextStream;
 using WTF::URL;
 using WTF::Variant;
 using WTF::Vector;

 template<class T, class E> using Expected = std::experimental::expected<T, E>;
 template<class E> using Unexpected = std::experimental::unexpected<E>;

 // Sometimes an inline method simply forwards to another one and does nothing else. If it were
 // just a forward declaration of that method then you would only need a forward declaration of
 // its return types and parameter types too, but because it's inline and it actually needs to
 // return / pass these types (even though it's just passing through whatever it called) you
 // now find yourself having to actually have a full declaration of these types. That might be
 // an include you'd rather avoid.
 //
 // No more. Enter template magic to lazily instantiate that method!
 //
 // This macro makes the method work as if you'd declared the return / parameter types as normal,
 // but forces lazy instantiation of the method at the call site, at which point the caller (not
 // the declaration) had better have a full declaration of the return / parameter types.
 //
 // Simply pass the forward-declared types to the macro, with an alias for each, and then define
 // your function as you otherwise would have but using the aliased name. Why the alias? So you
 // can be lazy on templated types! Sample usage:
 //
 // struct Foo; // No need to define Foo!
 // template<typename T>
 // struct A {
 //     Foo declared(Bar); // Forward declarations of Foo and Bar are sufficient here.
 //     // The below code would normally require a definition of Foo and Bar.
 //     WTF_LAZY_INSTANTIATE(Foo=Foo, Bar=Bar) Foo forwarder(Bar b) { return declared(b); }
 // };
 #define WTF_LAZY_JOIN_UNLAZE(A, B) A##B
 #define WTF_LAZY_JOIN(A, B) WTF_LAZY_JOIN_UNLAZE(A, B)
 #define WTF_LAZY_ARGUMENT_NUMBER(_1, _2, _3, _4, _5, _6, _7, _8, N, ...) N
 #define WTF_LAZY_AUGMENT(...) unused, __VA_ARGS__
 #define WTF_LAZY_EXPAND(x) x
 #define WTF_LAZY_NUM_ARGS_(...) WTF_LAZY_EXPAND(WTF_LAZY_ARGUMENT_NUMBER(__VA_ARGS__, 7, 6, 5, 4, 3, 2, 1, 0))
 #define WTF_LAZY_NUM_ARGS(...) WTF_LAZY_NUM_ARGS_(WTF_LAZY_AUGMENT(__VA_ARGS__))
 #define WTF_LAZY_FOR_EACH_TERM(F, ...) \
     WTF_LAZY_JOIN(WTF_LAZY_FOR_EACH_TERM_, WTF_LAZY_NUM_ARGS(__VA_ARGS__))(F, (__VA_ARGS__))
 #define WTF_LAZY_FIRST(_1, ...) _1
 #define WTF_LAZY_REST(_1, ...) (__VA_ARGS__)
 #define WTF_LAZY_REST_(_1, ...) __VA_ARGS__
 #define WTF_LAZY_CALL(F, ARG) F(ARG)
 #define WTF_LAZY_FOR_EACH_TERM_0(...)
 #define WTF_LAZY_FOR_EACH_TERM_1(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_0(F, WTF_LAZY_REST ARGS)
 #define WTF_LAZY_FOR_EACH_TERM_2(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_1(F, WTF_LAZY_REST ARGS)
 #define WTF_LAZY_FOR_EACH_TERM_3(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_2(F, WTF_LAZY_REST ARGS)
 #define WTF_LAZY_FOR_EACH_TERM_4(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_3(F, WTF_LAZY_REST ARGS)
 #define WTF_LAZY_FOR_EACH_TERM_5(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_4(F, WTF_LAZY_REST ARGS)
 #define WTF_LAZY_FOR_EACH_TERM_6(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_5(F, WTF_LAZY_REST ARGS)
 #define WTF_LAZY_FOR_EACH_TERM_7(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_6(F, WTF_LAZY_REST ARGS)
 #define WTF_LAZY_DECLARE_ALIAS_AND_TYPE(ALIAS_AND_TYPE) typename ALIAS_AND_TYPE,
 #define WTF_LAZY_INSTANTIATE(...)                                        \
     template<                                                            \
     WTF_LAZY_FOR_EACH_TERM(WTF_LAZY_DECLARE_ALIAS_AND_TYPE, __VA_ARGS__) \
     typename = void>

 #define WTF_LAZY_HAS_REST_0(...)
 #define WTF_LAZY_HAS_REST_1(...)
 #define WTF_LAZY_HAS_REST_2 WTF_LAZY_EXPAND
 #define WTF_LAZY_HAS_REST_3 WTF_LAZY_EXPAND
 #define WTF_LAZY_HAS_REST_4 WTF_LAZY_EXPAND
 #define WTF_LAZY_HAS_REST_5 WTF_LAZY_EXPAND
 #define WTF_LAZY_HAS_REST_6 WTF_LAZY_EXPAND
 #define WTF_LAZY_HAS_REST_7 WTF_LAZY_EXPAND
 #define WTF_LAZY_HAS_REST_8 WTF_LAZY_EXPAND
 #define WTF_LAZY_HAS_REST(...) \
     WTF_LAZY_JOIN(WTF_LAZY_HAS_REST_, WTF_LAZY_NUM_ARGS(__VA_ARGS__))
	/*
	* Copyright (C) 2006-2018 Apple Inc. All rights reserved.
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Library General Public
	* License as published by the Free Software Foundation; either
	* version 2 of the License, or (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Library General Public License for more details.
	*
	* You should have received a copy of the GNU Library General Public License
	* along with this library; see the file COPYING.LIB. If not, write to
	* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
	* Boston, MA 02110-1301, USA.
	*
	*/

	#pragma once

	#include <stddef.h>

	namespace WTF {

	class AtomString;
	class AtomStringImpl;
	class BinarySemaphore;
	class CString;
	class CrashOnOverflow;
	class FunctionDispatcher;
	class Hasher;
	class MonotonicTime;
	class OrdinalNumber;
	class PrintStream;
	class SHA1;
	class Seconds;
	class String;
	class StringBuilder;
	class StringImpl;
	class StringView;
	class TextPosition;
	class TextStream;
	class UniquedStringImpl;
	class URL;
	class WallTime;

	struct FastMalloc;

	template<typename> class CompletionHandler;
	template<typename T> struct DumbPtrTraits;
	template<typename T> struct DumbValueTraits;
	template<typename> class Function;
	template<typename> class LazyNeverDestroyed;
	template<typename> class NeverDestroyed;
	template<typename> class OptionSet;
	template<typename> class Optional;
	template<typename T, typename = DumbPtrTraits<T>> class Ref;
	template<typename T, typename = DumbPtrTraits<T>> class RefPtr;
	template<typename> class StringBuffer;
	template<typename, typename = void> class StringTypeAdapter;
	template<typename T> class WeakPtr;

	template<typename> struct DefaultHash { using Hash = void; };
	template<typename> struct HashTraits;

	template<typename> struct EnumTraits;
	template<typename E, E...> struct EnumValues;

	template<typename...> class Variant;
	template<typename, size_t = 0, typename = CrashOnOverflow, size_t = 16> class Vector;
	template<typename Value, typename = typename DefaultHash<Value>::Hash, typename = HashTraits<Value>> class HashCountedSet;
	template<typename KeyArg, typename MappedArg, typename = typename DefaultHash<KeyArg>::Hash, typename = HashTraits<KeyArg>, typename = HashTraits<MappedArg>> class HashMap;
	template<typename ValueArg, typename = typename DefaultHash<ValueArg>::Hash, typename = HashTraits<ValueArg>> class HashSet;

	template<size_t, typename> struct variant_alternative;
	template<ptrdiff_t, typename...> struct __indexed_type;
	template<ptrdiff_t _Index, typename... _Types> constexpr typename __indexed_type<_Index, _Types...>::__type const& get(Variant<_Types...> const&);

	}

	namespace std {
	namespace experimental {
	inline namespace fundamentals_v3 {
	template<class, class> class expected;
	template<class> class unexpected;
	}}} // namespace std::experimental::fundamentals_v3

	using WTF::AtomString;
	using WTF::AtomStringImpl;
	using WTF::BinarySemaphore;
	using WTF::CString;
	using WTF::CompletionHandler;
	using WTF::DumbPtrTraits;
	using WTF::DumbValueTraits;
	using WTF::Function;
	using WTF::FunctionDispatcher;
	using WTF::HashCountedSet;
	using WTF::HashMap;
	using WTF::HashSet;
	using WTF::Hasher;
	using WTF::LazyNeverDestroyed;
	using WTF::NeverDestroyed;
	using WTF::OptionSet;
	using WTF::Optional;
	using WTF::OrdinalNumber;
	using WTF::PrintStream;
	using WTF::Ref;
	using WTF::RefPtr;
	using WTF::SHA1;
	using WTF::String;
	using WTF::StringBuffer;
	using WTF::StringBuilder;
	using WTF::StringImpl;
	using WTF::StringView;
	using WTF::TextPosition;
	using WTF::TextStream;
	using WTF::URL;
	using WTF::Variant;
	using WTF::Vector;

	template<class T, class E> using Expected = std::experimental::expected<T, E>;
	template<class E> using Unexpected = std::experimental::unexpected<E>;

	// Sometimes an inline method simply forwards to another one and does nothing else. If it were
	// just a forward declaration of that method then you would only need a forward declaration of
	// its return types and parameter types too, but because it's inline and it actually needs to
	// return / pass these types (even though it's just passing through whatever it called) you
	// now find yourself having to actually have a full declaration of these types. That might be
	// an include you'd rather avoid.
	//
	// No more. Enter template magic to lazily instantiate that method!
	//
	// This macro makes the method work as if you'd declared the return / parameter types as normal,
	// but forces lazy instantiation of the method at the call site, at which point the caller (not
	// the declaration) had better have a full declaration of the return / parameter types.
	//
	// Simply pass the forward-declared types to the macro, with an alias for each, and then define
	// your function as you otherwise would have but using the aliased name. Why the alias? So you
	// can be lazy on templated types! Sample usage:
	//
	// struct Foo; // No need to define Foo!
	// template<typename T>
	// struct A {
	// Foo declared(Bar); // Forward declarations of Foo and Bar are sufficient here.
	// // The below code would normally require a definition of Foo and Bar.
	// WTF_LAZY_INSTANTIATE(Foo=Foo, Bar=Bar) Foo forwarder(Bar b) { return declared(b); }
	// };
	#define WTF_LAZY_JOIN_UNLAZE(A, B) A##B
	#define WTF_LAZY_JOIN(A, B) WTF_LAZY_JOIN_UNLAZE(A, B)
	#define WTF_LAZY_ARGUMENT_NUMBER(_1, _2, _3, _4, _5, _6, _7, _8, N, ...) N
	#define WTF_LAZY_AUGMENT(...) unused, __VA_ARGS__
	#define WTF_LAZY_EXPAND(x) x
	#define WTF_LAZY_NUM_ARGS_(...) WTF_LAZY_EXPAND(WTF_LAZY_ARGUMENT_NUMBER(__VA_ARGS__, 7, 6, 5, 4, 3, 2, 1, 0))
	#define WTF_LAZY_NUM_ARGS(...) WTF_LAZY_NUM_ARGS_(WTF_LAZY_AUGMENT(__VA_ARGS__))
	#define WTF_LAZY_FOR_EACH_TERM(F, ...) \
	WTF_LAZY_JOIN(WTF_LAZY_FOR_EACH_TERM_, WTF_LAZY_NUM_ARGS(__VA_ARGS__))(F, (__VA_ARGS__))
	#define WTF_LAZY_FIRST(_1, ...) _1
	#define WTF_LAZY_REST(_1, ...) (__VA_ARGS__)
	#define WTF_LAZY_REST_(_1, ...) __VA_ARGS__
	#define WTF_LAZY_CALL(F, ARG) F(ARG)
	#define WTF_LAZY_FOR_EACH_TERM_0(...)
	#define WTF_LAZY_FOR_EACH_TERM_1(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_0(F, WTF_LAZY_REST ARGS)
	#define WTF_LAZY_FOR_EACH_TERM_2(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_1(F, WTF_LAZY_REST ARGS)
	#define WTF_LAZY_FOR_EACH_TERM_3(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_2(F, WTF_LAZY_REST ARGS)
	#define WTF_LAZY_FOR_EACH_TERM_4(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_3(F, WTF_LAZY_REST ARGS)
	#define WTF_LAZY_FOR_EACH_TERM_5(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_4(F, WTF_LAZY_REST ARGS)
	#define WTF_LAZY_FOR_EACH_TERM_6(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_5(F, WTF_LAZY_REST ARGS)
	#define WTF_LAZY_FOR_EACH_TERM_7(F, ARGS) WTF_LAZY_CALL(F, WTF_LAZY_FIRST ARGS) WTF_LAZY_FOR_EACH_TERM_6(F, WTF_LAZY_REST ARGS)
	#define WTF_LAZY_DECLARE_ALIAS_AND_TYPE(ALIAS_AND_TYPE) typename ALIAS_AND_TYPE,
	#define WTF_LAZY_INSTANTIATE(...) \
	template< \
	WTF_LAZY_FOR_EACH_TERM(WTF_LAZY_DECLARE_ALIAS_AND_TYPE, __VA_ARGS__) \
	typename = void>

	#define WTF_LAZY_HAS_REST_0(...)
	#define WTF_LAZY_HAS_REST_1(...)
	#define WTF_LAZY_HAS_REST_2 WTF_LAZY_EXPAND
	#define WTF_LAZY_HAS_REST_3 WTF_LAZY_EXPAND
	#define WTF_LAZY_HAS_REST_4 WTF_LAZY_EXPAND
	#define WTF_LAZY_HAS_REST_5 WTF_LAZY_EXPAND
	#define WTF_LAZY_HAS_REST_6 WTF_LAZY_EXPAND
	#define WTF_LAZY_HAS_REST_7 WTF_LAZY_EXPAND
	#define WTF_LAZY_HAS_REST_8 WTF_LAZY_EXPAND
	#define WTF_LAZY_HAS_REST(...) \
	WTF_LAZY_JOIN(WTF_LAZY_HAS_REST_, WTF_LAZY_NUM_ARGS(__VA_ARGS__))