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#ifndef CURVE_H
#define CURVE_H
#include <limits.h>
#define BIT_OF(X, I) (((X) >> (I)) & 1ULL)
static uintptr_t zorder(int x, int y) {
uintptr_t z = 0;
// interleaving bits results in a point on the z-order curve
for (int i = 0; i < sizeof(x) * CHAR_BIT; i++)
z |= (BIT_OF(x, i) << i*2) | (BIT_OF(y, i) << (i*2 + 1));
return z;
}
static void unzorder(uintptr_t z, int *x, int *y) {
*x = 0; *y = 0;
for (int i = 0; i < sizeof(z) * CHAR_BIT / 2; i++) {
*x |= BIT_OF(z, i*2) << i;
*y |= BIT_OF(z, i*2 + 1) << i;
}
}
#undef BIT_OF
#endif
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