fft_base2

代码说明：

  本程序用于实现快速傅里叶变换的快速算法 ％ 为代码简便所有*2操作均直接实现，实际应采用二进制左移实现 (This procedure used to realize fast Fourier transform fast algorithm of all the code is simple to operate* 2 are referred directly to realize the actual binary left should be used to achieve)