Geometry calculations

CeoCalc.swift

///Polygon decoder
public func decodePoly(encoded: String) -> [Location]? {
    
        var poly = [Location]()
        var index = 0
        let len = encoded.length
        var lat = 0.0, lng = 0.0
        var encodedData = encoded.unicodeScalars
        
        
        while (index < len) {
            
            var b = 0
            var shift = 0
            var result = 0
            
            repeat {
                
                b = Int(encodedData[encodedData.index(encodedData.startIndex, offsetBy: index)].value) - 63
                result |= (b & 0x1f) << shift
                shift += 5
                index = index + 1
                
            } while (b >= 0x20);
            
            let dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1))
            lat = lat + Double(dlat)
            shift = 0
            result = 0
            
            repeat {
                
                b = Int(encodedData[encodedData.index(encodedData.startIndex, offsetBy: index)].value) - 63
                result |= (b & 0x1f) << shift
                shift += 5
                index = index + 1
                
            } while (b >= 0x20)
            
            let dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1))
            lng = lng + Double(dlng)
            
            let location = Location.init(lat / 1E5, lng / 1E5)
            poly.append(location)
        }
        return poly;
    }
    
    
    public func isPointInPolygon(point: Location, polygon: [Location]) -> Bool {
    
        var j = polygon.count - 1
        var result = false
        
        for i in 0 ..< polygon.count {
            
            if  (polygon[i].latitude > point.latitude) != (polygon[j].latitude > point.latitude) &&
                (point.longitude < (polygon[j].longitude - polygon[i].longitude) * (point.latitude - polygon[i].latitude) / (polygon[j].latitude - polygon[i].latitude) + polygon[i].longitude) {
            
                result = !result
            }
            
            j = i 
        }
        return result;
    }