coords util

db/coords.go

@@ -0,0 +1,42 @@
+package db
+
+//https://bitbucket.org/s_l_teichmann/mtsatellite/src/e1bf980a2b278c570b3f44f9452c9c087558acb3/common/coords.go?at=default&fileviewer=file-view-default
+const (
+	numBitsPerComponent = 12
+	modulo              = 1 << numBitsPerComponent
+	maxPositive         = modulo / 2
+	minValue            = -1 << (numBitsPerComponent - 1)
+	maxValue            = 1<<(numBitsPerComponent-1) - 1
+)
+
+
+func CoordToPlain(x, y, z int) int64 {
+	return int64(z)<<(2*numBitsPerComponent) +
+		int64(y)<<numBitsPerComponent +
+		int64(x)
+}
+
+func unsignedToSigned(i int16) int16 {
+	if i < maxPositive {
+		return i
+	}
+	return i - maxPositive*2
+}
+
+// To match C++ code.
+func pythonModulo(i int16) int16 {
+	const mask = modulo - 1
+	if i >= 0 {
+		return i & mask
+	}
+	return modulo - -i&mask
+}
+
+func PlainToCoord(i int64) (int, int, int) {
+	x := unsignedToSigned(pythonModulo(int16(i)))
+	i = (i - int64(x)) >> numBitsPerComponent
+	y := unsignedToSigned(pythonModulo(int16(i)))
+	i = (i - int64(x)) >> numBitsPerComponent
+	z := unsignedToSigned(pythonModulo(int16(i)))
+	return int(x), int(y), int(z)
+}