gecko-dev/dom/bindings/BindingDeclarations.h

386 lines
9.5 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
/* vim: set ts=2 sw=2 et tw=79: */
/* 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 "nsStringGlue.h"
#include "jsapi.h"
#include "mozilla/Util.h"
#include "nsCOMPtr.h"
#include "nsDOMString.h"
#include "nsStringBuffer.h"
#include "nsTArray.h"
namespace mozilla {
namespace dom {
struct MainThreadDictionaryBase
{
protected:
JSContext* ParseJSON(const nsAString& aJSON,
mozilla::Maybe<JSAutoRequest>& aAr,
mozilla::Maybe<JSAutoCompartment>& aAc,
JS::Value& aVal);
};
struct EnumEntry {
const char* value;
size_t length;
};
class NS_STACK_CLASS GlobalObject
{
public:
GlobalObject(JSContext* aCx, JSObject* aObject);
nsISupports* Get() const
{
return mGlobalObject;
}
bool Failed() const
{
return !Get();
}
private:
js::RootedObject mGlobalJSObject;
nsISupports* mGlobalObject;
nsCOMPtr<nsISupports> mGlobalObjectRef;
};
class NS_STACK_CLASS WorkerGlobalObject
{
public:
WorkerGlobalObject(JSContext* aCx, JSObject* aObject);
JSObject* Get() const
{
return mGlobalJSObject;
}
// 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* GetContext() const
{
return mCx;
}
bool Failed() const
{
return !Get();
}
private:
js::RootedObject mGlobalJSObject;
JSContext* mCx;
};
/**
* A class for representing string return values. This can be either passed to
* callees that have an nsString or nsAString out param or passed to a callee
* that actually knows about this class and can work with it. Such a callee may
* call SetStringBuffer on this object, but only if it plans to keep holding a
* strong ref to the stringbuffer!
*
* The proper way to store a value in this class is to either to do nothing
* (which leaves this as an empty string), to call SetStringBuffer with a
* non-null stringbuffer, to call SetNull(), or to call AsAString() and set the
* value in the resulting nsString. These options are mutually exclusive!
* Don't do more than one of them.
*
* The proper way to extract a value is to check IsNull(). If not null, then
* check HasStringBuffer(). If that's true, check for a zero length, and if the
* length is nonzero call StringBuffer(). If the length is zero this is the
* empty string. If HasStringBuffer() returns false, call AsAString() and get
* the value from that.
*/
class NS_STACK_CLASS DOMString {
public:
DOMString()
: mStringBuffer(nullptr)
, mLength(0)
, mIsNull(false)
{}
~DOMString()
{
MOZ_ASSERT(mString.empty() || !mStringBuffer,
"Shouldn't have both present!");
}
operator nsString&()
{
return AsAString();
}
nsString& AsAString()
{
MOZ_ASSERT(!mStringBuffer, "We already have a stringbuffer?");
MOZ_ASSERT(!mIsNull, "We're already set as null");
if (mString.empty()) {
mString.construct();
}
return mString.ref();
}
bool HasStringBuffer() const
{
MOZ_ASSERT(mString.empty() || !mStringBuffer,
"Shouldn't have both present!");
MOZ_ASSERT(!mIsNull, "Caller should have checked IsNull() first");
return mString.empty();
}
// Get the stringbuffer. This can only be called if HasStringBuffer()
// returned true and StringBufferLength() is nonzero. If that's true, it will
// never return null.
nsStringBuffer* StringBuffer() const
{
MOZ_ASSERT(!mIsNull, "Caller should have checked IsNull() first");
MOZ_ASSERT(HasStringBuffer(),
"Don't ask for the stringbuffer if we don't have it");
MOZ_ASSERT(StringBufferLength() != 0, "Why are you asking for this?");
MOZ_ASSERT(mStringBuffer,
"If our length is nonzero, we better have a stringbuffer.");
return mStringBuffer;
}
// Get the length of the stringbuffer. Can only be called if
// HasStringBuffer().
uint32_t StringBufferLength() const
{
MOZ_ASSERT(HasStringBuffer(), "Don't call this if there is no stringbuffer");
return mLength;
}
void SetStringBuffer(nsStringBuffer* aStringBuffer, uint32_t aLength)
{
MOZ_ASSERT(mString.empty(), "We already have a string?");
MOZ_ASSERT(!mIsNull, "We're already set as null");
MOZ_ASSERT(!mStringBuffer, "Setting stringbuffer twice?");
MOZ_ASSERT(aStringBuffer, "Why are we getting null?");
mStringBuffer = aStringBuffer;
mLength = aLength;
}
void SetNull()
{
MOZ_ASSERT(!mStringBuffer, "Should have no stringbuffer if null");
MOZ_ASSERT(mString.empty(), "Should have no string if null");
mIsNull = true;
}
bool IsNull() const
{
MOZ_ASSERT(!mStringBuffer || mString.empty(),
"How could we have a stringbuffer and a nonempty string?");
return mIsNull || (!mString.empty() && mString.ref().IsVoid());
}
void ToString(nsAString& aString)
{
if (IsNull()) {
SetDOMStringToNull(aString);
} else if (HasStringBuffer()) {
if (StringBufferLength() == 0) {
aString.Truncate();
} else {
StringBuffer()->ToString(StringBufferLength(), aString);
}
} else {
aString = AsAString();
}
}
private:
// We need to be able to act like a string as needed
Maybe<nsString> mString;
// For callees that know we exist, we can be a stringbuffer/length/null-flag
// triple.
nsStringBuffer* mStringBuffer;
uint32_t mLength;
bool mIsNull;
};
// Class for representing optional arguments.
template<typename T>
class Optional
{
public:
Optional()
{}
bool WasPassed() const
{
return !mImpl.empty();
}
void Construct()
{
mImpl.construct();
}
template <class T1>
void Construct(const T1 &t1)
{
mImpl.construct(t1);
}
template <class T1, class T2>
void Construct(const T1 &t1, const T2 &t2)
{
mImpl.construct(t1, t2);
}
const T& Value() const
{
return mImpl.ref();
}
T& Value()
{
return mImpl.ref();
}
// 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(const Optional& other) MOZ_DELETE;
const Optional &operator=(const Optional &other) MOZ_DELETE;
Maybe<T> mImpl;
};
// Specialization for strings.
// XXXbz we can't pull in FakeDependentString here, because it depends on
// internal strings. So we just have to forward-declare it and reimplement its
// ToAStringPtr.
struct FakeDependentString;
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
// FakeDependentString class in BindingUtils.h.
void operator=(const FakeDependentString* str)
{
MOZ_ASSERT(str);
mStr = reinterpret_cast<const nsDependentString*>(str);
mPassed = true;
}
const nsAString& Value() const
{
MOZ_ASSERT(WasPassed());
return *mStr;
}
private:
// Forbid copy-construction and assignment
Optional(const Optional& other) MOZ_DELETE;
const Optional &operator=(const Optional &other) MOZ_DELETE;
bool mPassed;
const nsAString* mStr;
};
// Class for representing sequences in arguments. We use an auto array that can
// hold 16 elements, to avoid having to allocate in common cases. 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 AutoFallibleTArray<T, 16>
{
public:
Sequence() : AutoFallibleTArray<T, 16>()
{}
};
class RootedJSValue
{
public:
RootedJSValue()
: mCx(nullptr)
{}
~RootedJSValue()
{
if (mCx) {
JS_RemoveValueRoot(mCx, &mValue);
}
}
bool SetValue(JSContext* aCx, JS::Value aValue)
{
// We don't go ahead and root if v is null, because we want to allow
// null-initialization even when there is no cx.
MOZ_ASSERT_IF(!aValue.isNull(), aCx);
// Be careful to not clobber mCx if it's already set, just in case we're
// being null-initialized (with a null cx for some reason) after we have
// already been initialized properly with a non-null value.
if (!aValue.isNull() && !mCx) {
if (!JS_AddNamedValueRoot(aCx, &mValue, "RootedJSValue::mValue")) {
return false;
}
mCx = aCx;
}
mValue = aValue;
return true;
}
operator JS::Value()
{
return mValue;
}
operator const JS::Value() const
{
return mValue;
}
private:
// Don't allow copy-construction of these objects, because it'll do the wrong
// thing with our flag mCx.
RootedJSValue(const RootedJSValue&) MOZ_DELETE;
JS::Value mValue;
JSContext* mCx;
};
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_BindingDeclarations_h__