BSONObj S2CellIdToIndexKey(const S2CellId& cellId, S2IndexVersion indexVersion) {
// The range of an unsigned long long is
// |-----------------|------------------|
// 0 2^32 2^64 - 1
// 000... 100... 111...
// The range of a signed long long is
// |-----------------|------------------|
// -2^63 0 2^63 - 1
// 100... 000... 011...
// S2 gives us an unsigned long long, and we need
// to use signed long longs for the index.
//
// The relative ordering may be changed with unsigned
// numbers around 2^32 being converted to signed
//
// However, because a single cell cannot span over
// more than once face, individual intervals will
// never cross that threshold. Thus, scans will still
// produce the same results.
BSONObjBuilder b;
if (indexVersion >= S2_INDEX_VERSION_3) {
b.append("", static_cast<long long>(cellId.id()));
} else {
b.append("", cellId.ToString());
}
return b.obj();
}
BSONObj S2CellIdToIndexKey(const S2CellId& cellId, S2IndexVersion indexVersion) {
// The range of an unsigned long long is
// |-----------------|------------------|
// 0 2^32 2^64 - 1
// 000... 100... 111...
// The range of a signed long long is
// |-----------------|------------------|
// -2^63 0 2^63 - 1
// 100... 000... 011...
// S2 gives us an unsigned long long, and we need
// to use signed long longs for the index.
//
// The relative ordering may be changed with unsigned
// numbers around 2^32 being converted to signed
//
// However, because a single cell cannot span over
// more than once face, individual intervals will
// never cross that threshold. Thus, scans will still
// produce the same results.
if (indexVersion >= S2_INDEX_VERSION_3) {
// The size of an index BSONObj in S2 index version 3 is 15 bytes.
// total size (4 bytes) | type code 0x12 (1) | field name "" 0x00 (1) |
// long long cell id (8) | EOO (1)
BSONObjBuilder b(15);
b.append("", static_cast<long long>(cellId.id()));
return b.obj();
}
// The size of an index BSONObj in older versions is 10 ~ 40 bytes.
// total size (4 bytes) | type code 0x12 (1) | field name "" 0x00 (1) |
// cell id string (2 ~ 32) 0x00 (1) | EOO (1)
BSONObjBuilder b;
b.append("", cellId.ToString());
// Return a copy so its buffer size fits the object size.
return b.obj().copy();
}
