uran.c

用dsp解压mp3程序的算法

/****************************************************************
*  uran.c - This function generates pseudo-random numbers       
****************************************************************/

static  long  xn = (long)12357; // seed x(0) = 12357
float uran()

{
  float ran;                    // random number r(n)
  xn = (long)2045*xn + 1L;      // x(n+1)=2045*x(n)+1
  xn -= (xn/1048576L)*1048576L; // x(n+1) mod M
  ran = (float)(xn + 1L)/(float)1048577; // normalization
  return(ran);                  // return r(n) to main function
}