Struct std::hash< lsst::jointcal::CcdImageKey >

template<>
struct hash<lsst::jointcal::CcdImageKey>

Hash a ccdImage by its visit and ccd IDs.

ccdId and visitId are both 32-bit ints, hash() returns a size_t, so put the ccdId in the most-significant-bit, and the visitId in the least for a simple, unique, hash per ccdImage.