/*          Frequency test within a block.  This is slightly different than the NIST test, but it does the  same thing using their suggestion of -1 for 0 bits and +1 for  1 bits in the block.  This moves the average from 1/2 as they   have, to zero.  This simplifies the computation of the chi^2  observed value to              chi^2(observed) = (sum(P_i)^2)/M  where M = number of bits in a block        N = number of blocks to do	P_i = sum( bits )  (+1 if bit set, -1 if bit clear)  Enter with source pointer, endianness, size of each block and    number of blocks to work on.  Returns chi^2 value and source pointer updated.*/#include "randtest.h"double freqtest( SRCPTR *src, int endian, int blocksize, int numblocks){  int sumeps, i;  unsigned char mask;  double sum = 0.0;  mask = 1 << src->bitpos;  while( numblocks)  {    sumeps = 0;    for( i=0; i<blocksize; i++)    {      if( *(src->byteptr) & mask) sumeps += 1;      else sumeps -= 1;      if( endian)      {	mask >>= 1;	src->bitpos--;	if (src->bitpos < 0)	{	  mask = 0x80;	  src->bitpos = 7;	  src->byteptr++;	}      }      else      {	mask <<= 1;	src->bitpos++;	if (src->bitpos > 7)	{	  mask = 1;	  src->bitpos = 0;	  src->byteptr++;	}      }    }    sum += sumeps*sumeps;    numblocks--;  }  sum /= blocksize;  return (sum);}/*  check math - ensure we get the same answer that theory says    we ought to.  It does work, exactly the same as expected :-)double freqtestck( SRCPTR *src, int endian, int blocksize, int numblocks){  int i;  unsigned char mask;  double sum = 0.0;  double sumeps;  mask = 1 << src->bitpos;  while( numblocks)  {    sumeps = 0.0;    for( i=0; i<blocksize; i++)    {      if( *(src->byteptr) & mask) sumeps += 1.0;      if( endian)      {	mask >>= 1;	src->bitpos--;	if (src->bitpos < 0)	{	  mask = 0x80;	  src->bitpos = 7;	  src->byteptr++;	}      }      else      {	mask <<= 1;	src->bitpos++;	if (src->bitpos > 7)	{	  mask = 1;	  src->bitpos = 0;	  src->byteptr++;	}      }    }    numblocks--;    sumeps = sumeps/blocksize - 0.5;    sum += sumeps*sumeps;  }  sum *= 4.0*blocksize;  return sum;}*/