/
twkb.go
42 lines (34 loc) · 1.12 KB
/
twkb.go
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package geom
// Tiny Well Known Binary
// See spec https://github.com/TWKB/Specification/blob/master/twkb.md
type twkbGeometryType int
const (
twkbTypePoint twkbGeometryType = 1
twkbTypeLineString twkbGeometryType = 2
twkbTypePolygon twkbGeometryType = 3
twkbTypeMultiPoint twkbGeometryType = 4
twkbTypeMultiLineString twkbGeometryType = 5
twkbTypeMultiPolygon twkbGeometryType = 6
twkbTypeGeometryCollection twkbGeometryType = 7
)
const (
twkbMaxDimensions = 4
)
type twkbMetadataHeader int
const (
twkbHasBBox twkbMetadataHeader = 1
twkbHasSize twkbMetadataHeader = 2
twkbHasIDs twkbMetadataHeader = 4
twkbHasExtPrec twkbMetadataHeader = 8
twkbIsEmpty twkbMetadataHeader = 16
)
// decodeZigZagInt64 accepts a uint64 and reverses the zigzag encoding
// to produce the decoded signed int64 value.
func decodeZigZagInt64(z uint64) int64 {
return int64(z>>1) ^ -int64(z&1)
}
// encodeZigZagInt64 accepts a signed int64 and zigzag encodes
// it to produce an encoded uint64 value.
func encodeZigZagInt64(n int64) uint64 {
return uint64((n << 1) ^ (n >> 63))
}