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#ifndef GMX_PBCUTIL_ISHIFT_H
#define GMX_PBCUTIL_ISHIFT_H

namespace gmx
{
//! Maximum dimensions of grid expressing shifts across PBC
//! \{
constexpr int c_dBoxZ = 1;
constexpr int c_dBoxY = 1;
constexpr int c_dBoxX = 2;
//! \}
namespace detail
{
constexpr int c_nBoxZ    = 2 * gmx::c_dBoxZ + 1;
constexpr int c_nBoxY    = 2 * gmx::c_dBoxY + 1;
constexpr int c_nBoxX    = 2 * gmx::c_dBoxX + 1;
constexpr int c_numIvecs = detail::c_nBoxZ * detail::c_nBoxY * detail::c_nBoxX;
} // namespace detail

constexpr int c_centralShiftIndex = detail::c_numIvecs / 2;
constexpr int c_numShiftVectors   = detail::c_numIvecs;

//! Convert grid coordinates to shift index
static inline int xyzToShiftIndex(int x, int y, int z)
{
    return (detail::c_nBoxX * (detail::c_nBoxY * ((z) + gmx::c_dBoxZ) + (y) + gmx::c_dBoxY) + (x)
            + gmx::c_dBoxX);
}

//! Convert grid coordinates to shift index
static inline int ivecToShiftIndex(ivec iv)
{
    return (xyzToShiftIndex((iv)[XX], (iv)[YY], (iv)[ZZ]));
}

//! Return the shift in the X dimension of grid space corresponding to \c iv
static inline int shiftIndexToXDim(int iv)
{
    return (((iv) % detail::c_nBoxX) - gmx::c_dBoxX);
}
} // namespace gmx
#endif
