本程序是用于处理端点效应时的信号延拓方法，次程序是用于前段延拓，对于后端延拓的话直接把原信号进行翻转后再进行延拓，延拓后将信号再翻转回来就行。-This program is a signal extension methods for processing when the end effect, sub-program for front extension, extension to the rear end, then flip directly to the original sign