preload 系列API的具体用法

ekiji120

如题，请教下列AIP的具体含义及其用法
native PreloadStart takes nothing returns nothing
native PreloadEnd takes real timeout returns nothing
native PreloadEndEx takes nothing returns nothing
native Preloader takes string filename returns nothing
native PreloadGenClear takes nothing returns nothing
native PreloadGenEnd takes string filename returns nothing
native PreloadGenStart takes nothing returns nothing
native PreloadRefresh takes nothing returns nothing
native PreloadStart takes nothing returns nothing