source: python/vendor/Python-2.6.5/Parser/bitset.c

/* Bitset primitives used by the parser generator */

#include "pgenheaders.h"
#include "bitset.h"

bitset
newbitset(int nbits)
{
        int nbytes = NBYTES(nbits);
        bitset ss = (char *)PyObject_MALLOC(sizeof(BYTE) *  nbytes);
        
        if (ss == NULL)
                Py_FatalError("no mem for bitset");
        
        ss += nbytes;
        while (--nbytes >= 0)
                *--ss = 0;
        return ss;
}

void
delbitset(bitset ss)
{
        PyObject_FREE(ss);
}

int
addbit(bitset ss, int ibit)
{
        int ibyte = BIT2BYTE(ibit);
        BYTE mask = BIT2MASK(ibit);
        
        if (ss[ibyte] & mask)
                return 0; /* Bit already set */
        ss[ibyte] |= mask;
        return 1;
}

#if 0 /* Now a macro */
int
testbit(bitset ss, int ibit)
{
        return (ss[BIT2BYTE(ibit)] & BIT2MASK(ibit)) != 0;
}
#endif

int
samebitset(bitset ss1, bitset ss2, int nbits)
{
        int i;
        
        for (i = NBYTES(nbits); --i >= 0; )
                if (*ss1++ != *ss2++)
                        return 0;
        return 1;
}

void
mergebitset(bitset ss1, bitset ss2, int nbits)
{
        int i;
        
        for (i = NBYTES(nbits); --i >= 0; )
                *ss1++ |= *ss2++;
}