基于NPAPI接口的windows平台安全控件开发（二）
通过前一篇博客，已经实现了基本的功能和图形界面 。本篇主要介绍如何实现插件与JS交互。交互功能主要是通过NPObject对象来实现的。
上面提到我们重写了NPP_GetValue函数，使NPP_GetValue去调用CPlugin中的GetScriptObject，而不是按默认流程调用GetValue（其实无所谓，改个名称而已）。所以，当插件加载完成后，浏览器会调用NPP_GetValue并将variable参数设置为NPPVpluginScriptableNPObject来查询浏览器是否支持与脚本语言的交互功能，如果插件支持交互功能，则NPP_GetValue会返回一个NPOject对象给浏览器，此时浏览器就可以通过这个NPObject对象与插件建立联系。所以在CPlugin::GetScriptObject函数中，我们要实现NPObject对象。实现如下：
NPObject *CPlugin::GetScriptableObject()
{
if (!m_pScriptableObject) {
m_pScriptableObject = NPN_CreateObject(m_pNPInstance,GET_NPOBJECT_CLASS(CScriptObject));
}
if (m_pScriptableObject) {
NPN_RetainObject(m_pScriptableObject);
}
return m_pScriptableObject;
}
当存在NPObject对象时，直接使用NPN_RetainObject获取并返回。若不存在NPObject对象时，使用NPN_CreateObject创建一个NPObject对象。GET_NPOBJECT_CLASS宏定义如下：
#define DECLARE_NPOBJECT_CLASS_WITH_BASE(_class, ctor) \
static NPClass s##_class##_NPClass = { \
NP_CLASS_STRUCT_VERSION_CTOR, \
ctor, \
ScriptablePluginObjectBase::_deallocate, \
ScriptablePluginObjectBase::_invalidate, \
ScriptablePluginObjectBase::_hasMethod, \
ScriptablePluginObjectBase::_invoke, \
ScriptablePluginObjectBase::_invokeDefault, \
ScriptablePluginObjectBase::_hasProperty, \
ScriptablePluginObjectBase::_getProperty, \
ScriptablePluginObjectBase::_setProperty, \
ScriptablePluginObjectBase::_removeProperty, \
ScriptablePluginObjectBase::_enumerate, \
ScriptablePluginObjectBase::_construct \
}
宏中的ScriptablePluginObjectBase定义如下：
class ScriptablePluginObjectBase : public NPObject
{
public:
ScriptablePluginObjectBase(NPP npp)
: mNpp(npp)
{
}
virtual ~ScriptablePluginObjectBase()
{
}
// Virtual NPObject hooks called through this base class. Override
// as you see fit.
//virtual NPObject *allocate(NPP npp, NPClass *aClass){}
virtual void invalidate();
virtual bool hasMethod(NPIdentifier name);
virtual bool invoke(NPIdentifier name, const NPVariant *args,uint32_t argCount, NPVariant *result);
virtual bool invokeDefault(const NPVariant *args, uint32_t argCount,NPVariant *result);
virtual bool hasProperty(NPIdentifier name);
virtual bool getProperty(NPIdentifier name, NPVariant *result);
virtual bool setProperty(NPIdentifier name, const NPVariant *value);
virtual bool removeProperty(NPIdentifier name);
virtual bool enumerate(NPIdentifier **identifier, uint32_t *count);
virtual bool construct(const NPVariant *args, uint32_t argCount,NPVariant *result);
public:
static NPObject *_allocate(NPP npp, NPClass *aClass);
static void _deallocate(NPObject *npobj);
static void _invalidate(NPObject *npobj);
static bool _hasMethod(NPObject *npobj, NPIdentifier name);
static bool _invoke(NPObject *npobj, NPIdentifier name,const NPVariant *args, uint32_t argCount,NPVariant *result);
static bool _invokeDefault(NPObject *npobj, const NPVariant *args,uint32_t argCount, NPVariant *result);
static bool _hasProperty(NPObject * npobj, NPIdentifier name);
static bool _getProperty(NPObject *npobj, NPIdentifier name,NPVariant *result);
static bool _setProperty(NPObject *npobj, NPIdentifier name,const NPVariant *value);
static bool _removeProperty(NPObject *npobj, NPIdentifier name);
static bool _enumerate(NPObject *npobj, NPIdentifier **identifier,uint32_t *count);
static bool _construct(NPObject *npobj, const NPVariant *args,uint32_t argCount, NPVariant *result);
static NPObject *AllocateCScriptObject(NPP npp, NPClass *aClass);
protected:
NPP mNpp;
};
该类需要继承自NPObject，因为插件需要给浏览器返回一个NPObject对象。随后再定一个类CScriptObject。
class CScriptObject:
public ScriptablePluginObjectBase
{
public:
NPUTF8 *utf8_chars1,*utf8_chars2,*utf8_chars3,*utf8_chars4;//缓冲区
static NPObject *sWindowObj;
static NPIdentifier s_idGetPasswd;
static NPIdentifier s_idGetMacAddress;
static NPIdentifier s_idGetHardwareInfo;
static NPIdentifier s_idSetEditSize;
static NPIdentifier s_idGetVersion;
//int result_size;
//NPString str1;
//NPUTF8 utf8_chars1[INVOKE_STRING_LENGTH];
CScriptObject(NPP npp);
~CScriptObject();
virtual bool hasProperty(NPIdentifier name);
virtual bool hasMethod(NPIdentifier name);
virtual bool getProperty(NPIdentifier name, NPVariant *result);
virtual bool setProperty(NPIdentifier name, const NPVariant *value);
virtual bool invoke(NPIdentifier name, const NPVariant *args, uint32_t argCount, NPVariant *result);
virtual bool invokeDefault(const NPVariant *args, uint32_t argCount, NPVariant *result);
virtual bool enumerate(NPIdentifier **identifier, uint32_t *count);
virtual bool construct(const NPVariant *args, uint32_t argCount,NPVariant *result);
};
CScriptObject对象继承ScriptablePluginObjectBase类，随后就是实现CScriptObject中的虚函数，以下为部分实现：
CScriptObject::CScriptObject(NPP npp):ScriptablePluginObjectBase(npp)
{
s_idGetPasswd = NPN_GetStringIdentifier("GetPasswd");
s_idGetMacAddress = NPN_GetStringIdentifier("GetMacAddress");
s_idGetHardwareInfo = NPN_GetStringIdentifier("GetHardwareInfo");
s_idSetEditSize = NPN_GetStringIdentifier("SetEditSize");
s_idGetVersion = NPN_GetStringIdentifier("GetVersion");
utf8_chars1 = static_cast<NPUTF8 *>(NPN_MemAlloc(INVOKE_STRING_LENGTH));
utf8_chars2 = static_cast<NPUTF8 *>(NPN_MemAlloc(INVOKE_STRING_LENGTH));
utf8_chars3 = static_cast<NPUTF8 *>(NPN_MemAlloc(INVOKE_STRING_LENGTH));
utf8_chars4 = static_cast<NPUTF8 *>(NPN_MemAlloc(INVOKE_STRING_LENGTH));
}
CScriptObject::~CScriptObject()
{
//NPN_MemAlloc分配的内存不需要手动释放，浏览器会自动释放
//NPN_MemFree(utf8_chars1);
//NPN_MemFree(utf8_chars2);
//NPN_MemFree(utf8_chars3);
//MessageBox(NULL,"CScriptobject delete","Plugin GetMacAddress",MB_ICONERROR|MB_OK);
}
bool CScriptObject::hasMethod(NPIdentifier name)
{
//MessageBox(NULL,"HashMethod Successful","HashMethod",MB_ICONERROR|MB_OK);
return name == s_idGetPasswd || name == s_idGetMacAddress || name == s_idGetHardwareInfo || name == s_idSetEditSize || name == s_idGetVersion;
}
bool CScriptObject::hasProperty(NPIdentifier name)
{
//return name == s_idSetEditSize;
return false;
}
bool CScriptObject::getProperty(NPIdentifier name, NPVariant *result)
{
return false;
}
bool CScriptObject::setProperty(NPIdentifier name, const NPVariant *value)
{
return false;
}
bool CScriptObject::invoke(NPIdentifier name, const NPVariant *args, uint32_t argCount, NPVariant *result)
{
char *tmp;
CPlugin* plugin = (CPlugin*) mNpp->pdata;
if (name == s_idGetPasswd)
{
tmp = plugin->myedit->GetVal();
//*result = NPVARIANT_TO_STRING(tmp);
memset(utf8_chars1,'\0',INVOKE_STRING_LENGTH);
strcpy(utf8_chars1,tmp);
//STRINGZ_TO_NPVARIANT(utf8_chars1,*result);
//INT32_TO_NPVARIANT(10,*result);
result->type = NPVariantType_String;
NPString str1 = {utf8_chars1, uint32_t(strlen(utf8_chars1)) };
//str1.UTF8Characters = utf8_chars1;
//str1.UTF8Length = uint32_t(strlen(utf8_chars1));
result->value.stringValue = str1;
return true;
}
if(name == s_idGetMacAddress){
tmp = plugin->myedit->GetMacAddress();
memset(utf8_chars2,'\0',INVOKE_STRING_LENGTH);
strcpy(utf8_chars2,tmp);
//STRINGZ_TO_NPVARIANT(utf8_chars2,*result);
result->type = NPVariantType_String;
NPString str2 = { utf8_chars2, uint32_t(strlen(utf8_chars2)) };
result->value.stringValue = str2;
return true;
}
if(name == s_idGetHardwareInfo){
tmp = plugin->myedit->GetHardwareInfo();
memset(utf8_chars3,'\0',INVOKE_STRING_LENGTH);
strcpy(utf8_chars3,tmp);
//STRINGZ_TO_NPVARIANT(utf8_chars3,*result);
result->type = NPVariantType_String;
NPString str3 = { utf8_chars3, uint32_t(strlen(utf8_chars3)) };
result->value.stringValue = str3;
return true;
}
if(name == s_idSetEditSize){
//plugin->myedit->SetEditSize();
if(args[0].type == NPVariantType_Int32 && args[1].type == NPVariantType_Int32){
plugin->myedit->SetEditSize(NPVARIANT_TO_INT32(args[0]),NPVARIANT_TO_INT32(args[1]));
}else if (args[0].type == NPVariantType_Double && args[1].type == NPVariantType_Double){
plugin->myedit->SetEditSize((int)NPVARIANT_TO_DOUBLE(args[0]),(int)NPVARIANT_TO_DOUBLE(args[1]));
}
//INT32_TO_NPVARIANT(result_size,*result);
return true;
}
if(name == s_idGetVersion){
tmp = plugin->myedit->GetVersion();
memset(utf8_chars4,'\0',INVOKE_STRING_LENGTH);
strcpy(utf8_chars4,tmp);
result->type = NPVariantType_String;
NPString str4 = { utf8_chars4, uint32_t(strlen(utf8_chars4)) };
result->value.stringValue = str4;
return true;
}
return false;
}
其中最主要的是hasMethod和invoke两个函数。当浏览器中JS调用某个插件函数A时，浏览器会通过NPObject调用hasMethod函数，以判断插件是否提供函数A的调用，若插件存在函数A（即hasMethod返回true），随后浏览器将调用invoke函数。故，在hasMethod函数中，我们将插件对外提供的函数在此处列出。
return name == s_idGetPasswd || name == s_idGetMacAddress || name == s_idGetHardwareInfo || name == s_idSetEditSize || name == s_idGetVersion;
其中s_idGetPasswd等变量在CScriptObject进行了相应的初始化，以关联具体函数名。
CScriptObject::CScriptObject(NPP npp):ScriptablePluginObjectBase(npp)
{
s_idGetPasswd = NPN_GetStringIdentifier("GetPasswd");
s_idGetMacAddress = NPN_GetStringIdentifier("GetMacAddress");
s_idGetHardwareInfo = NPN_GetStringIdentifier("GetHardwareInfo");
s_idSetEditSize = NPN_GetStringIdentifier("SetEditSize");
s_idGetVersion = NPN_GetStringIdentifier("GetVersion");
........
}
当通过hasMethod返回true之后，浏览器讲会调用invoke函数，在invoke函数中，通过判断name参数，确定浏览器需要具体调用插件中的哪个函数，随后调用该函数即可，具体可参照invoke实现代码。插件提供的各种函数在CYKedit中详细定义。