web idl 接口定义语言数据类型与 C++绑定关系

web idl 接口定义语言数据类型与 C++绑定关系

Modules

Every IDL module corresponds to a C++ namespace. The name of that namespace is based on module's prefixed name.

IDL

module dom { };

C++

namespace org { namespace w3c { namespace dom {

IDL

[Prefix=::com] module getfirebug {

C++

namespace com { namespace getfirebug {

Note: Historically each W3C specification introduced its own module name. However, the recent specifications tend to omit the module specification in the IDL definition. At least it seems one module name per spec doesn't make sense any more.

cf.  ​​types

Any

The any type is the union of all other possible types.

IDL

any

C++

class Any { public: Any(); Any(const Any& value); template Any(const T& x); Any& operator=(const Any& x); template Any& operator=(const T& x); template operator T() const; // snip };

Example

IDL

interface CanvasRenderingContext2D { attribute any fillStyle; };

C++

class CanvasRenderingContext2D : public Object { public: Any getFillStyle(); void setFillStyle(Any fillStyle); }; canvasRenderingContext2D->setFillStyle("black");

DOMString

The DOMString type corresponds to the set of all possible sequences of 16 bit unsigned integer code units to be interpreted as UTF-16 encoded strings.

Date

The Date type corresponds to a 64 bit unsigned integer value. In C++ DOM API, the DOMTimeStamp type is defined as Date following Chrome's implementation as specified in DOM Level3 Core (*).

(*) It appears currently Chrome is the only browser that treats the DOMTimeStamp type as the Date object in ECMAScript.

Object

The object type corresponds to the set of all possible object references, plus the special value null, which indicates no object reference.

Interfaces

An interface is a specification of a set of interface members, which are the constants, attributes and operations.

IDL

interface CanvasRenderingContext2D { };

C++

class CanvasRenderingContext2D : public Object { };

Nullable types - T?

A nullable type is an IDL type that can represent an existing type (called the inner type) values, plus an additional value null.

C++

template class Nullable { public: bool hasValue() const; T value() const; Nullable(); Nullable(const T& value); Nullable(const Nullable& nullable); Nullable(const Any& any); // snip };

Example

IDL

attribute DOMString? background;

C++

Nullable getBackground(); void setBackground(Nullable background);

Sequences - sequence

The sequence

C++

template class Sequence { public: Sequence(); Sequence(const T* array, unsigned int size); Sequence(std::initializer_list list); Sequence(const Sequence& value); ~Sequence(); T operator[](int index) const; T& operator[](int index); unsigned int getLength() const; // snip };

IDL

typedef stylesheets::StyleSheetList StyleSheetList; readonly attribute StyleSheetList styleSheets;

C++

typedef Sequence StyleSheetList; StyleSheetList getStyleSheets();

Constants

Constants can be defined in interfaces and exceptions.

IDL

interface MediaError { const unsigned short MEDIA_ERR_ABORTED = 1; const unsigned short MEDIA_ERR_NETWORK = 2; const unsigned short MEDIA_ERR_DECODE = 3; const unsigned short MEDIA_ERR_NONE_SUPPORTED = 4; };

C++

class MediaError : public Object { public: static const unsigned short MEDIA_ERR_ABORTED = 1; static const unsigned short MEDIA_ERR_NETWORK = 2; static const unsigned short MEDIA_ERR_DECODE = 3; static const unsigned short MEDIA_ERR_NONE_SUPPORTED = 4; };

Operations

Each operation defined in the IDL interface will be mapped to one or more member functions in the C++ interface class.

IDL

interface CanvasRenderingContext2D { void fillRect(float x, float y, float w, float h); };

C++

class CanvasRenderingContext2D : public Object { public: void fillRect(float x, float y, float w, float h); };

Optional argument

If the "optional" keyword appears on an operation argument, it indicates that the operation can be invoked by passing values only for the those arguments appearing before the optional argument in the operation’s argument list.

IDL

interface ColorCreator { object createColor(float v1, optional float v2, float v3, optional float alpha); };

C++

class ColorCreator { public: Object createColor(float v1); Object createColor(float v1, float v2, float v3); Object createColor(float v1, float v2, float v3, float alpha); };

Variadic operation

If the final argument uses the "..." terminal, it indicates that the operation is variadic, and can be passed zero or more arguments after the regular arguments. In C++, a varying number of arguments are represent as a Variadic value.

Example

IDL

interface IntegerSet { readonly attribute unsigned long cardinality; void union(long... ints); void intersection(long... ints); };

C++

class IntegerSet { public: unsigned int getCardinality(); void union(Variadic ints = Variadic()); void intersection(Variadic ints = Variadic()); }; template class Variadic {public: Variadic(); Variadic(const Any* variadic, size_t length); Variadic(std::initializer_list list); T operator[](int index) const; size_t size() const; };

Operations with no identifier

While it has been agreed to remove unnamed getters/setters at W3C WebApps WG (*), operations with no identifier are still in use in several W3C specifications. In C++, the default operation name as shown in the following table is used for operations with no identifier.

Example

IDL

interface CanvasPixelArray { readonly attribute unsigned long length; getter octet (in unsigned long index); setter void (in unsigned long index, in octet value); };

C++

class CanvasPixelArray : public Object { public: // CanvasPixelArray unsigned int getLength(); unsigned char getElement(unsigned int index); void setElement(unsigned int index, unsigned char value); // snip };(*) each attribute defined on the IDL interface, a getter method is declared. For each attribute defined on the IDL interface that is not read only, a corresponding setter method is also declared.

IDL

interface CanvasRenderingContext2D { attribute float globalAlpha; };

C++

class CanvasRenderingContext2D : public Object { public: float getGlobalAlpha(); void setGlobalAlpha(float globalAlpha); };

Note: A getter is prefixed with "get", and the setter is prefixed with "set" following the Web IDL Java binding.

Exceptions

An exception is used to declare a type of exception that can be thrown by implementation.

IDL

exception DOMException { const unsigned short INDEX_SIZE_ERR = 1; const unsigned short DOMSTRING_SIZE_ERR = 2; unsigned short code; };

C++

struct DOMException { const unsigned short INDEX_SIZE_ERR = 1; const unsigned short DOMSTRING_SIZE_ERR = 2; unsigned short code; };

Note: The use of exceptions can be turned off with esidl.

Implements statements

An implements statement declares the all objects implementing an interface A (the first name) MUST also implement interface B (the second name). In C++, interface members in the mixin interface B are mixed into the primary interface A.

Example

IDL

interface ElementTraversal { readonly attribute Element firstElementChild; readonly attribute Element lastElementChild; readonly attribute Element previousElementSibling; readonly attribute Element nextElementSibling; }; Element implements ElementTraversal; interface Element : Node { // snip };

C++

class Element : public Node { public: // snip Element getFirstElementChild(); Element getLastElementChild(); Element getPreviousElementSibling(); Element getNextElementSibling(); // snip

cf.  ​​attributes

[Constructor], [NamedConstructor]

If the [Constructor]

IDL

[Constructor, Constructor(HTMLFormElement form)] interface FormData { void append(DOMString name, Blob value); void append(DOMString name, DOMString value); };

C++

class FormData : public Object { public: // FormData void append(std::u16string name, file::Blob value); void append(std::u16string name, std::u16string value); // [Constructor] FormData(); FormData(html::HTMLFormElement form); // snip };

Note: Unlike ECMAScript, you do not have to use the "new" operator to create an instance of the interface with the [Constructor]

[PutForwards]

If the [PutForwards]

IDL

interface Name { attribute DOMString full; attribute DOMString family; attribute DOMString given; }; interface Person { [PutForwards=full] readonly attribute Name name; };

C++

class Person { public: Name* getName(); void setName(std::string name); // snip };

[Prefix]

See Modules.

[Supplemental]

cf. ​​Element : Node { readonly attribute DOMString tagName; // snip }; [Supplemental] interface Element { ClientRectList getClientRects(); ClientRect getBoundingClientRect(); };

C++

class Element : public Node { public: std::string getTagName(); // snip ClientRectList getClientRects(); ClientRect getBoundingClientRect(); };

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