67 lines
2.3 KiB
JavaScript
67 lines
2.3 KiB
JavaScript
class PositionUtil {
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/**
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* Obfuscates the provided latitude or longitude down to the provided precision in bits.
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* This is based on the same logic in the official meshtastic firmware.
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* https://github.com/meshtastic/firmware/blob/0a93261c0646f93aea518cc0599e547e9dc0e997/src/modules/PositionModule.cpp#L187
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*/
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static setPositionPrecision(latitudeOrLongitudeInteger, precision) {
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// check if we should use the provided precision
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if(precision > 0 && precision < 32){
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// apply bitmask to reduce precision of position to wanted bits
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latitudeOrLongitudeInteger = latitudeOrLongitudeInteger & (0xFFFFFFFF << (32 - precision));
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// we want the imprecise position to be the middle of the possible location
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latitudeOrLongitudeInteger += (1 << (31 - precision));
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}
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return latitudeOrLongitudeInteger;
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}
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/**
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* Truncates the provided latitude or longitude to a maximum of x decimal places
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* e.g: 12.3456789 with 2 decimal places would be 12.34
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* @param latitudeOrLongitudeString e.g: 12.3456789
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* @param numberOfDecimalPlaces how many decimal places to allow in the result
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* @returns {*|string|null}
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*/
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static truncateDecimalPlaces(latitudeOrLongitudeString, numberOfDecimalPlaces) {
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// ensure value not null
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if(latitudeOrLongitudeString == null){
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return null;
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}
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// split into left and right side of decimal point
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// e.g: -12.3456789 -> [-12, 3456789]
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var [ leftOfDecimalPoint, rightOfDecimalPoint ] = latitudeOrLongitudeString.split(".");
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// check if decimal places available
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if(rightOfDecimalPoint != null){
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// truncate decimal places to desired length
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rightOfDecimalPoint = rightOfDecimalPoint.substring(0, numberOfDecimalPlaces);
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// return modified position with decimal places, if available
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if(rightOfDecimalPoint.length > 0){
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return [ leftOfDecimalPoint, rightOfDecimalPoint ].join(".");
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}
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// no decimal places available anymore, return left side without dot
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return leftOfDecimalPoint;
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}
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// decimal places not available, return position as is
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return latitudeOrLongitudeString;
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}
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}
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module.exports = PositionUtil;
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