gecko-dev/dom/bindings/BindingDeclarations.h

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/* -*- 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/. */
/**
* A header for declaring various things that binding implementation headers
* might need. The idea is to make binding implementation headers safe to
* include anywhere without running into include hell like we do with
* BindingUtils.h
*/
#ifndef mozilla_dom_BindingDeclarations_h__
#define mozilla_dom_BindingDeclarations_h__
#include "js/RootingAPI.h"
#include "js/Value.h"
#include "mozilla/Maybe.h"
#include "mozilla/OwningNonNull.h"
#include "mozilla/dom/DOMString.h"
#include "nsAutoPtr.h" // for nsRefPtr member variables
#include "nsCOMPtr.h"
#include "nsStringGlue.h"
#include "nsTArray.h"
class nsWrapperCache;
namespace mozilla {
namespace dom {
// Struct that serves as a base class for all dictionaries. Particularly useful
// so we can use IsBaseOf to detect dictionary template arguments.
struct DictionaryBase
{
protected:
bool ParseJSON(JSContext* aCx, const nsAString& aJSON,
JS::MutableHandle<JS::Value> aVal);
bool StringifyToJSON(JSContext* aCx,
JS::MutableHandle<JS::Value> aValue,
nsAString& aJSON) const;
// Struct used as a way to force a dictionary constructor to not init the
// dictionary (via constructing from a pointer to this class). We're putting
// it here so that all the dictionaries will have access to it, but outside
// code will not.
struct FastDictionaryInitializer {
};
private:
// aString is expected to actually be an nsAString*. Should only be
// called from StringifyToJSON.
static bool AppendJSONToString(const char16_t* aJSONData,
uint32_t aDataLength, void* aString);
};
// Struct that serves as a base class for all typed arrays and array buffers and
// array buffer views. Particularly useful so we can use IsBaseOf to detect
// typed array/buffer/view template arguments.
struct AllTypedArraysBase {
};
// Struct that serves as a base class for all owning unions.
// Particularly useful so we can use IsBaseOf to detect owning union
// template arguments.
struct AllOwningUnionBase {
};
struct EnumEntry {
const char* value;
size_t length;
};
class MOZ_STACK_CLASS GlobalObject
{
public:
GlobalObject(JSContext* aCx, JSObject* aObject);
JSObject* Get() const
{
return mGlobalJSObject;
}
nsISupports* GetAsSupports() const;
// The context that this returns is not guaranteed to be in the compartment of
// the object returned from Get(), in fact it's generally in the caller's
// compartment.
JSContext* Context() const
{
return mCx;
}
bool Failed() const
{
return !Get();
}
protected:
JS::Rooted<JSObject*> mGlobalJSObject;
JSContext* mCx;
mutable nsISupports* MOZ_UNSAFE_REF("Valid because GlobalObject is a stack "
"class, and mGlobalObject points to the "
"global, so it won't be destroyed as long "
"as GlobalObject lives on the stack") mGlobalObject;
};
// Class for representing optional arguments.
template<typename T, typename InternalType>
class Optional_base
{
public:
Optional_base()
{}
explicit Optional_base(const T& aValue)
{
mImpl.emplace(aValue);
}
bool operator==(const Optional_base<T, InternalType>& aOther) const
{
return mImpl == aOther.mImpl;
}
template<typename T1, typename T2>
explicit Optional_base(const T1& aValue1, const T2& aValue2)
{
mImpl.emplace(aValue1, aValue2);
}
bool WasPassed() const
{
return mImpl.isSome();
}
// Return InternalType here so we can work with it usefully.
template<typename... Args>
InternalType& Construct(Args&&... aArgs)
{
mImpl.emplace(Forward<Args>(aArgs)...);
return *mImpl;
}
void Reset()
{
mImpl.reset();
}
const T& Value() const
{
return *mImpl;
}
// Return InternalType here so we can work with it usefully.
InternalType& Value()
{
return *mImpl;
}
// And an explicit way to get the InternalType even if we're const.
const InternalType& InternalValue() const
{
return *mImpl;
}
// If we ever decide to add conversion operators for optional arrays
// like the ones Nullable has, we'll need to ensure that Maybe<> has
// the boolean before the actual data.
private:
// Forbid copy-construction and assignment
Optional_base(const Optional_base& other) = delete;
const Optional_base &operator=(const Optional_base &other) = delete;
protected:
Maybe<InternalType> mImpl;
};
template<typename T>
class Optional : public Optional_base<T, T>
{
public:
Optional() :
Optional_base<T, T>()
{}
explicit Optional(const T& aValue) :
Optional_base<T, T>(aValue)
{}
};
template<typename T>
class Optional<JS::Handle<T> > :
public Optional_base<JS::Handle<T>, JS::Rooted<T> >
{
public:
Optional() :
Optional_base<JS::Handle<T>, JS::Rooted<T> >()
{}
explicit Optional(JSContext* cx) :
Optional_base<JS::Handle<T>, JS::Rooted<T> >()
{
this->Construct(cx);
}
Optional(JSContext* cx, const T& aValue) :
Optional_base<JS::Handle<T>, JS::Rooted<T> >(cx, aValue)
{}
// Override the const Value() to return the right thing so we're not
// returning references to temporaries.
JS::Handle<T> Value() const
{
return *this->mImpl;
}
// And we have to override the non-const one too, since we're
// shadowing the one on the superclass.
JS::Rooted<T>& Value()
{
return *this->mImpl;
}
};
// A specialization of Optional for JSObject* to make sure that when someone
// calls Construct() on it we will pre-initialized the JSObject* to nullptr so
// it can be traced safely.
template<>
class Optional<JSObject*> : public Optional_base<JSObject*, JSObject*>
{
public:
Optional() :
Optional_base<JSObject*, JSObject*>()
{}
explicit Optional(JSObject* aValue) :
Optional_base<JSObject*, JSObject*>(aValue)
{}
// Don't allow us to have an uninitialized JSObject*
JSObject*& Construct()
{
// The Android compiler sucks and thinks we're trying to construct
// a JSObject* from an int if we don't cast here. :(
return Optional_base<JSObject*, JSObject*>::Construct(
static_cast<JSObject*>(nullptr));
}
template <class T1>
JSObject*& Construct(const T1& t1)
{
return Optional_base<JSObject*, JSObject*>::Construct(t1);
}
};
// A specialization of Optional for JS::Value to make sure no one ever uses it.
template<>
class Optional<JS::Value>
{
private:
Optional() = delete;
explicit Optional(JS::Value aValue) = delete;
};
// A specialization of Optional for NonNull that lets us get a T& from Value()
template<typename U> class NonNull;
template<typename T>
class Optional<NonNull<T> > : public Optional_base<T, NonNull<T> >
{
public:
// We want our Value to actually return a non-const reference, even
// if we're const. At least for things that are normally pointer
// types...
T& Value() const
{
return *this->mImpl->get();
}
// And we have to override the non-const one too, since we're
// shadowing the one on the superclass.
NonNull<T>& Value()
{
return *this->mImpl;
}
};
// A specialization of Optional for OwningNonNull that lets us get a
// T& from Value()
template<typename T>
class Optional<OwningNonNull<T> > : public Optional_base<T, OwningNonNull<T> >
{
public:
// We want our Value to actually return a non-const reference, even
// if we're const. At least for things that are normally pointer
// types...
T& Value() const
{
return *this->mImpl->get();
}
// And we have to override the non-const one too, since we're
// shadowing the one on the superclass.
OwningNonNull<T>& Value()
{
return *this->mImpl;
}
};
// Specialization for strings.
// XXXbz we can't pull in FakeString here, because it depends on internal
// strings. So we just have to forward-declare it and reimplement its
// ToAStringPtr.
namespace binding_detail {
struct FakeString;
} // namespace binding_detail
template<>
class Optional<nsAString>
{
public:
Optional() : mPassed(false) {}
bool WasPassed() const
{
return mPassed;
}
void operator=(const nsAString* str)
{
MOZ_ASSERT(str);
mStr = str;
mPassed = true;
}
// If this code ever goes away, remove the comment pointing to it in the
// FakeString class in BindingUtils.h.
void operator=(const binding_detail::FakeString* str)
{
MOZ_ASSERT(str);
mStr = reinterpret_cast<const nsString*>(str);
mPassed = true;
}
const nsAString& Value() const
{
MOZ_ASSERT(WasPassed());
return *mStr;
}
private:
// Forbid copy-construction and assignment
Optional(const Optional& other) = delete;
const Optional &operator=(const Optional &other) = delete;
bool mPassed;
const nsAString* mStr;
};
template<class T>
class NonNull
{
public:
NonNull()
#ifdef DEBUG
: inited(false)
#endif
{}
// This is no worse than get() in terms of const handling.
operator T&() const {
MOZ_ASSERT(inited);
MOZ_ASSERT(ptr, "NonNull<T> was set to null");
return *ptr;
}
operator T*() const {
MOZ_ASSERT(inited);
MOZ_ASSERT(ptr, "NonNull<T> was set to null");
return ptr;
}
void operator=(T* t) {
ptr = t;
MOZ_ASSERT(ptr);
#ifdef DEBUG
inited = true;
#endif
}
template<typename U>
void operator=(U* t) {
ptr = t->ToAStringPtr();
MOZ_ASSERT(ptr);
#ifdef DEBUG
inited = true;
#endif
}
T** Slot() {
#ifdef DEBUG
inited = true;
#endif
return &ptr;
}
T* Ptr() {
MOZ_ASSERT(inited);
MOZ_ASSERT(ptr, "NonNull<T> was set to null");
return ptr;
}
// Make us work with smart-ptr helpers that expect a get()
T* get() const {
MOZ_ASSERT(inited);
MOZ_ASSERT(ptr);
return ptr;
}
protected:
T* ptr;
#ifdef DEBUG
bool inited;
#endif
};
// Class for representing sequences in arguments. We use a non-auto array
// because that allows us to use sequences of sequences and the like. This
// needs to be fallible because web content controls the length of the array,
// and can easily try to create very large lengths.
template<typename T>
class Sequence : public FallibleTArray<T>
{
public:
Sequence() : FallibleTArray<T>()
{}
};
inline nsWrapperCache*
GetWrapperCache(nsWrapperCache* cache)
{
return cache;
}
inline nsWrapperCache*
GetWrapperCache(void* p)
{
return nullptr;
}
// Helper template for smart pointers to resolve ambiguity between
// GetWrappeCache(void*) and GetWrapperCache(const ParentObject&).
template <template <typename> class SmartPtr, typename T>
inline nsWrapperCache*
GetWrapperCache(const SmartPtr<T>& aObject)
{
return GetWrapperCache(aObject.get());
}
struct MOZ_STACK_CLASS ParentObject {
template<class T>
MOZ_IMPLICIT ParentObject(T* aObject) :
mObject(aObject),
mWrapperCache(GetWrapperCache(aObject)),
mUseXBLScope(false)
{}
template<class T, template<typename> class SmartPtr>
MOZ_IMPLICIT ParentObject(const SmartPtr<T>& aObject) :
mObject(aObject.get()),
mWrapperCache(GetWrapperCache(aObject.get())),
mUseXBLScope(false)
{}
ParentObject(nsISupports* aObject, nsWrapperCache* aCache) :
mObject(aObject),
mWrapperCache(aCache),
mUseXBLScope(false)
{}
// We don't want to make this an nsCOMPtr because of performance reasons, but
// it's safe because ParentObject is a stack class.
nsISupports* const MOZ_NON_OWNING_REF mObject;
nsWrapperCache* const mWrapperCache;
bool mUseXBLScope;
};
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_BindingDeclarations_h__