proj/globalhs/apps/calversfunctions.c

char *cvsinfo = "cvsinfo: $Header: /home/cvsuser/cvsroot/JSOC/proj/globalhs/apps/calversfunctions.c,v 1.3 2013/04/28 07:58:43 tplarson Exp $";

/* 
the following function is taken directly from chapter 2 of Kernighan and Ritchie
getbits: get n bits from position p
*/
unsigned long long getbits(unsigned long long x, int p, int n)
{
  return (x >> (p+1-n)) & ~(~0ull << n);
}

/*
Richard Heathfield's solution to exercise 2-6 of K&R 
*/
unsigned long long setbits(unsigned long long x, int p, int n, unsigned long long y)
{
  return (x & ((~0ull << (p + 1)) | (~(~0ull << (p + 1 - n))))) | ((y & ~(~0ull << n)) << (p + 1 - n));
// another solution (untested):
//return (x & ~(~(~0<<n)<<(p+1)) | (y&~(~0<<n)) << (p+1));
}

unsigned long long fixcalver64(unsigned long long x)
{
  int firstnibble = getbits(x,3,4);
  if (firstnibble == 0)
    return setbits(x,3,4,2);
  else
    return x;
}

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