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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
This file contains the declaration for CppVariant, a type used by C++ classes
that are to be bound to JavaScript objects.
CppVariant exists primarily as an interface between C++ callers and the
corresponding NPVariant type. CppVariant also provides a number of
convenience constructors and accessors, so that the NPVariantType values
don't need to be exposed, and a destructor to free any memory allocated for
string values.
For a usage example, see cpp_binding_example.{h|cc}.
#include <string>
#include <vector>
#include "base/basictypes.h"
#include "third_party/npapi/bindings/npruntime.h"
#include "webkit/renderer/webkit_renderer_export.h"
namespace webkit_glue {
class WEBKIT_RENDERER_EXPORT CppVariant : public NPVariant {
void SetNull();
void Set(bool value);
void Set(int32_t value);
void Set(double value);
// Note that setting a CppVariant to a string value involves copying the
// string data, which must be freed with a call to FreeData() when the
// CppVariant is set to a different value or is no longer needed. Normally
// this is handled by the other Set() methods and by the destructor.
void Set(const char* value); // Must be a null-terminated string.
void Set(const std::string& value);
void Set(const NPString& new_value);
void Set(const NPVariant& new_value);
// Note that setting a CppVariant to an NPObject involves ref-counting
// the actual object. FreeData() should only be called if the CppVariant
// is no longer needed. The other Set() methods handle this internally.
// Also, the object's NPClass is expected to be a static object: neither
// the NP runtime nor CPPVariant will ever free it.
void Set(NPObject* new_value);
// These three methods all perform deep copies of any string data. This
// allows local CppVariants to be released by the destructor without
// corrupting their sources. In performance-critical code, or when strings
// are very long, avoid creating new CppVariants.
// In case of NPObject as the data, the copying involves ref-counting
// as opposed to deep-copying. The ref-counting ensures that sources don't
// get corrupted when the copies get destroyed.
void CopyToNPVariant(NPVariant* result) const;
CppVariant& operator=(const CppVariant& original);
CppVariant(const CppVariant& original);
// Calls NPN_ReleaseVariantValue, which frees any string data
// held by the object and sets its type to null.
// In case of NPObject, the NPN_ReleaseVariantValue decrements
// the ref-count (releases when ref-count becomes 0)
void FreeData();
// Compares this CppVariant's type and value to another's. They must be
// identical in both type and value to be considered equal. For string and
// object types, a deep comparison is performed; that is, the contents of the
// strings, or the classes and refcounts of the objects, must be the same,
// but they need not be the same pointers.
bool isEqual(const CppVariant& other) const;
// The value of a CppVariant may be read directly from its NPVariant (but
// should only be set using one of the Set() methods above). Although the
// type of a CppVariant is likewise public, it can be accessed through these
// functions rather than directly if a caller wishes to avoid dependence on
// the NPVariantType values.
bool isBool() const { return (type == NPVariantType_Bool); }
bool isInt32() const { return (type == NPVariantType_Int32); }
bool isDouble() const { return (type == NPVariantType_Double); }
bool isNumber() const { return (isInt32() || isDouble()); }
bool isString() const { return (type == NPVariantType_String); }
bool isVoid() const { return (type == NPVariantType_Void); }
bool isNull() const { return (type == NPVariantType_Null); }
bool isEmpty() const { return (isVoid() || isNull()); }
bool isObject() const { return (type == NPVariantType_Object); }
// Converters. The CppVariant must be of a type convertible to these values.
// For example, ToInt32() works only if isNumber() is true.
std::string ToString() const;
int32_t ToInt32() const;
double ToDouble() const;
bool ToBoolean() const;
// Returns a vector of CppVariant for the specified variant. This should only
// be called on an Object. If the object has no "length" property an empty
// vector is returned.
std::vector<CppVariant> ToVector() const;
// Invoke method of the given name on an object with the supplied arguments.
// The first argument should be the object on which the method is to be
// invoked. Returns whether the method was successfully invoked. If the
// method was invoked successfully, any return value is stored in the
// CppVariant specified by result.
bool Invoke(const std::string& method, const CppVariant* args,
uint32 arg_count, CppVariant& result) const;
} // namespace webkit_glue