NPClass

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Summary

NPClass is a structure that holds a set of pointers to functions that make up the behavior of an instance of an NPClass (i.e. an NPObject).

Syntax

struct NPClass
{
  uint32_t structVersion;
  NPAllocateFunctionPtr allocate;
  NPDeallocateFunctionPtr deallocate;
  NPInvalidateFunctionPtr invalidate;
  NPHasMethodFunctionPtr hasMethod;
  NPInvokeFunctionPtr invoke;
  NPInvokeDefaultFunctionPtr invokeDefault;
  NPHasPropertyFunctionPtr hasProperty;
  NPGetPropertyFunctionPtr getProperty;
  NPSetPropertyFunctionPtr setProperty;
  NPRemovePropertyFunctionPtr removeProperty;
  NPEnumerationFunctionPtr enumerate;
  NPConstructFunctionPtr construct;
};

Fields

structVersion

The version number of the structure. This is set to NP_CLASS_STRUCT_VERSION, which is 1 in Mozilla 1.8.*, 2 since Mozilla 1.9a1, and 3 since Firefox 3.0b1.

allocate

Returns a pointer to a newly allocated NPObject. Called by NPN_CreateObject() if non-NULL, otherwise the browser calls malloc(). This function is expected to allocate and return enough storage to hold the NPObject that is being created.

deallocate

Called by NPN_ReleaseObject() when an object's reference count reaches zero. If this field is NULL, free() is called isntead.

invalidate

Called on live objects that belong to a plugin instance that is being destroyed. This call is always followed by a call to the deallocate function, or free(). Any attempt to use an invalidated object will result in undefined behavior.

hasMethod

Called by NPN_HasMethod() to determine whether or not a specified method exists on a given NPObject. Returns true if the method exists, otherwise returns false.

invoke

Called by NPN_Invoke() to invoke a specific method on a given NPObject. Returns true if invocation succeeded or false if an error occurred.

invokeDefault

Called by NPN_InvokeDefault() to invoke the default method (if available) on a given NPObject. Returns true if invocation succeeded or false if an error occurred.

hasProperty

Called by NPN_HasProperty() to check whether a given property exists on a given NPObject. Returns true if the specified property exists, otherwise returns false.

getProperty

Called by NPN_GetProperty() to get the value of the specified property on a given NPObject. Returns true if the value was successfully retrieved, otherwise returns false.

setProperty

Called by NPN_SetProperty() to set the value of the specified property on a given NPObject. Returns true if the value was successfully set, otherwise returns false.

removeProperty

Called by NPN_RemoveProperty() to remove a given property from a specified NPObject. Returns true if the property was successfully removed, otherwise returns false.

enumerate

Called by NPN_Enumerate. This field is available only if structVersion is NP_CLASS_STRUCT_VERSION_ENUM (2) or greater.

construct

Called by NPN_Construct. This field is available only if structVersion is NP_CLASS_STRUCT_VERSION_CTOR (3) or greater.

Function pointer syntax

typedef NPObject *(*NPAllocateFunctionPtr)(NPP npp, NPClass *aClass);
typedef void (*NPDeallocateFunctionPtr)(NPObject *npobj);
typedef void (*NPInvalidateFunctionPtr)(NPObject *npobj);
typedef bool (*NPHasMethodFunctionPtr)(NPObject *npobj, NPIdentifier name);
typedef bool (*NPInvokeFunctionPtr)(NPObject *npobj, NPIdentifier name,
                                    const NPVariant *args, uint32_t argCount,
                                    NPVariant *result);
typedef bool (*NPInvokeDefaultFunctionPtr)(NPObject *npobj,
                                           const NPVariant *args,
                                           uint32_t argCount,
                                           NPVariant *result);
typedef bool (*NPHasPropertyFunctionPtr)(NPObject *npobj, NPIdentifier name);
typedef bool (*NPGetPropertyFunctionPtr)(NPObject *npobj, NPIdentifier name,
                                         NPVariant *result);
typedef bool (*NPSetPropertyFunctionPtr)(NPObject *npobj, NPIdentifier name,
                                         const NPVariant *value);
typedef bool (*NPRemovePropertyFunctionPtr)(NPObject *npobj,
                                            NPIdentifier name);
typedef bool (*NPEnumerationFunctionPtr)(NPObject *npobj, NPIdentifier **value,
                                         uint32_t *count);
typedef bool (*NPConstructFunctionPtr)(NPObject *npobj,
                                       const NPVariant *args,
                                       uint32_t argCount,
                                       NPVariant *result);

See also

• NPObject