/**************************************************                                                **  Runs test                                     **  This is same math as NIST.                    **  Enter with source pointer, endianness, and    **   number of bits to scan.                      **  Returns p-value as explained in section 3.3   **   of NIST docs.  Note that frequency tests out **  of range give 0.0 p-value (if prob > 2/(n)^.5 **  NIST says this math breaks down)              **                                                **************************************************/#include <math.h>#include "randtest.h"double runs( SRCPTR *src, int endian, int numbits){  double freq, Vn, chi;  unsigned char mask, nxtbit, thsbit;  int count;  count = numbits;  Vn = 1.0;  freq = 0.0;  mask = 1 << src->bitpos;  while( count)  {    thsbit = (mask & *src->byteptr) ? 1 : 0;    if( endian)    {      src->bitpos--;      mask >>= 1;      if( !(mask & 0xff))      {	mask = 0x80;	src->byteptr++;	src->bitpos = 7;      }    }    else    {      src->bitpos++;      mask <<= 1;      if( !(mask & 0xff))      {	mask = 1;	src->byteptr++;	src->bitpos = 0;      }    }    nxtbit = (mask & *src->byteptr) ? 1 : 0;    if( thsbit) freq += 1.0;    if( (count>1) && (thsbit ^ nxtbit)) Vn += 1.0;    count--;  }  freq /= numbits;  if( fabs( freq - 0.5) > 2.0/sqrt(numbits))     return (0.0);  chi = fabs( Vn - 2.0*numbits*freq*(1.0 - freq));  chi /= 2.0*sqrt( 2.0*numbits)*freq*(1.0 - freq);  chi = erfc(chi);  return(chi);}