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Add checksum recalculation to the utilities (#12)
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@marcelrv
marcelrv authored Jun 3, 2020
1 parent 553eb32 commit 0425ca5
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Showing 4 changed files with 140 additions and 71 deletions.
145 changes: 78 additions & 67 deletions index.js
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
'use strict';

(function() {
(function () {

var utils = {};

Expand Down Expand Up @@ -33,7 +33,15 @@
CELCIUS_IN_KELVIN: 273.15,
};

exports.valid = function(sentence, validateChecksum) {
function checksum(sentencePart) {
let check = 0;
for (let i = 1; i < sentencePart.length; i++) {
check = check ^ sentencePart.charCodeAt(i);
};
return check;
}

exports.valid = function (sentence, validateChecksum) {
sentence = String(sentence).trim();

if (sentence === "") {
Expand All @@ -43,117 +51,120 @@
var validateChecksum = typeof validateChecksum === 'undefined' || validateChecksum

if ((sentence.charAt(0) == '$' || sentence.charAt(0) == '!') && (validateChecksum == false || sentence.charAt(sentence.length - 3) == '*')) {
if ( validateChecksum ) {
var check = 0;
var split = sentence.split('*');

for (var i = 1; i < split[0].length; i++) {
check = check ^ split[0].charCodeAt(i);
};

return (parseInt(split[1], 16) == check);
if (validateChecksum) {
let split = sentence.split('*');
return (parseInt(split[1], 16) == checksum(split[0]));
} else {
return true
}
}

return false;
};

exports.source = function(sentence) {
exports.appendChecksum = function (sentence) {
let split = String(sentence).trim().split('*');
if (split.length === 1) {
if (split[0].charAt(0) == '$' || split[0].charAt(0) == '!') {
return split[0].concat('*').concat(checksum(split[0]).toString(16).padStart(2, '0').toUpperCase());
}
}
return sentence;
};

exports.source = function (sentence) {
return {
type: 'NMEA0183',
label: 'signalk-parser-nmea0183',
sentence: sentence || ''
};
};

exports.transform = function(value, inputFormat, outputFormat) {
exports.transform = function (value, inputFormat, outputFormat) {
value = exports.float(value);

inputFormat = inputFormat.toLowerCase();
inputFormat = inputFormat.toLowerCase();
outputFormat = outputFormat.toLowerCase();

if(inputFormat === outputFormat) {
if (inputFormat === outputFormat) {
return value;
}

// KM
if(inputFormat == 'km') {
if(outputFormat == 'nm') return value / utils.RATIOS.NM_IN_KM;
if (inputFormat == 'km') {
if (outputFormat == 'nm') return value / utils.RATIOS.NM_IN_KM;
}

// NM
if(inputFormat == 'nm') {
if(outputFormat == 'km') return value / utils.RATIOS.KM_IN_NM;
if(outputFormat == 'm') return value * 1000 / utils.RATIOS.KM_IN_NM ;
if (inputFormat == 'nm') {
if (outputFormat == 'km') return value / utils.RATIOS.KM_IN_NM;
if (outputFormat == 'm') return value * 1000 / utils.RATIOS.KM_IN_NM;
}

// KNOTS
if(inputFormat == 'knots') {
if(outputFormat == 'kph') return value / utils.RATIOS.KPH_IN_KNOTS;
if(outputFormat == 'ms') return value / utils.RATIOS.MS_IN_KNOTS;
if(outputFormat == 'mph') return value / utils.RATIOS.MPH_IN_KNOTS;
if (inputFormat == 'knots') {
if (outputFormat == 'kph') return value / utils.RATIOS.KPH_IN_KNOTS;
if (outputFormat == 'ms') return value / utils.RATIOS.MS_IN_KNOTS;
if (outputFormat == 'mph') return value / utils.RATIOS.MPH_IN_KNOTS;
}

// KPH
if(inputFormat == 'kph') {
if(outputFormat == 'knots') return value / utils.RATIOS.KNOTS_IN_KPH;
if(outputFormat == 'ms') return value / utils.RATIOS.MS_IN_KPH;
if(outputFormat == 'mph') return value / utils.RATIOS.MPH_IN_KPH;
if (inputFormat == 'kph') {
if (outputFormat == 'knots') return value / utils.RATIOS.KNOTS_IN_KPH;
if (outputFormat == 'ms') return value / utils.RATIOS.MS_IN_KPH;
if (outputFormat == 'mph') return value / utils.RATIOS.MPH_IN_KPH;
}

// MPH
if(inputFormat == 'mph') {
if(outputFormat == 'knots') return value / utils.RATIOS.KNOTS_IN_MPH;
if(outputFormat == 'ms') return value / utils.RATIOS.MS_IN_MPH;
if(outputFormat == 'kph') return value / utils.RATIOS.KPH_IN_MPH;
if (inputFormat == 'mph') {
if (outputFormat == 'knots') return value / utils.RATIOS.KNOTS_IN_MPH;
if (outputFormat == 'ms') return value / utils.RATIOS.MS_IN_MPH;
if (outputFormat == 'kph') return value / utils.RATIOS.KPH_IN_MPH;
}

// MS
if(inputFormat == 'ms') {
if(outputFormat == 'knots') return value / utils.RATIOS.KNOTS_IN_MS;
if(outputFormat == 'mph') return value / utils.RATIOS.MPH_IN_MS;
if(outputFormat == 'kph') return value / utils.RATIOS.KPH_IN_MS;
if (inputFormat == 'ms') {
if (outputFormat == 'knots') return value / utils.RATIOS.KNOTS_IN_MS;
if (outputFormat == 'mph') return value / utils.RATIOS.MPH_IN_MS;
if (outputFormat == 'kph') return value / utils.RATIOS.KPH_IN_MS;
}

// ANGLES
if(inputFormat == 'deg') {
if(outputFormat == 'rad') return value / utils.RATIOS.RAD_IN_DEG;
if (inputFormat == 'deg') {
if (outputFormat == 'rad') return value / utils.RATIOS.RAD_IN_DEG;
}

if(inputFormat == 'rad') {
if(outputFormat == 'deg') return value / utils.RATIOS.DEG_IN_RAD;
if (inputFormat == 'rad') {
if (outputFormat == 'deg') return value / utils.RATIOS.DEG_IN_RAD;
}
if(inputFormat == 'c') {
if(outputFormat == 'k') return value + utils.RATIOS.CELCIUS_IN_KELVIN;

if (inputFormat == 'c') {
if (outputFormat == 'k') return value + utils.RATIOS.CELCIUS_IN_KELVIN;
}
if(inputFormat == 'k') {
if(outputFormat == 'c') return value - utils.RATIOS.CELCIUS_IN_KELVIN;

if (inputFormat == 'k') {
if (outputFormat == 'c') return value - utils.RATIOS.CELCIUS_IN_KELVIN;
}

// Just return input if input/output formats are not recognised.
return value;
};

exports.magneticVariaton = function(degrees, pole) {
exports.magneticVariaton = function (degrees, pole) {
pole = pole.toUpperCase();
degrees = this.float(degrees);

if(pole == "S" || pole == "W") {
if (pole == "S" || pole == "W") {
degrees *= -1;
}

return degrees;
};

exports.timestamp = function(time, date) {
exports.timestamp = function (time, date) {
/* TIME (UTC) */
var hours, minutes, seconds, year, month, day;

if(time) {
if (time) {
hours = this.int(time.slice(0, 2), true);
minutes = this.int(time.slice(2, 4), true);
seconds = this.int(time.slice(4, 6), true);
Expand All @@ -165,16 +176,16 @@
}

/* DATE (UTC) */
if(date) {
if (date) {
var year, month, day;
day = this.int(date.slice(0, 2), true);
month = this.int(date.slice(2, 4), true);
year = this.int(date.slice(-2));

// HACK copied from jamesp/node-nmea
if(year < 73) {
if (year < 73) {
year = this.int("20" + year);
} else {
} else {
year = this.int("19" + year);
}
} else {
Expand All @@ -189,7 +200,7 @@
return d.toISOString();
};

exports.coordinate = function(value, pole) {
exports.coordinate = function (value, pole) {
// N 5222.3277 should be read as 52°22.3277'
// E 454.5824 should be read as 4°54.5824'
//
Expand All @@ -204,47 +215,47 @@

pole = pole.toUpperCase();

var split = value.split('.');
var split = value.split('.');
var degrees = this.float(split[0].slice(0, -2));
var minsec = this.float(split[0].slice(-2) + '.' + split[1]);
var minsec = this.float(split[0].slice(-2) + '.' + split[1]);
var decimal = this.float(degrees + (minsec / 60));

if (pole == "S" || pole == "W") {
decimal *= -1;
}

return exports.float(decimal);
};

exports.zero = function(n) {
if(this.float(n) < 10) {
exports.zero = function (n) {
if (this.float(n) < 10) {
return "0" + n;
} else {
return "" + n;
}
};

exports.int = function(n) {
if(("" + n).trim() === '') {
exports.int = function (n) {
if (("" + n).trim() === '') {
return 0;
} else {
return parseInt(n, 10);
}
};

exports.integer = function(n) {
exports.integer = function (n) {
return exports.int(n);
};

exports.float = function(n) {
if(("" + n).trim() === '') {
exports.float = function (n) {
if (("" + n).trim() === '') {
return 0.0;
} else {
return parseFloat(n);
}
};

exports.double = function(n) {
exports.double = function (n) {
return exports.float(n);
};

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8 changes: 4 additions & 4 deletions package-lock.json
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5 changes: 5 additions & 0 deletions package.json
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Expand Up @@ -21,6 +21,11 @@
"signalk"
],
"author": "Fabian Tollenaar <[email protected]>",
"contributors": [
{
"name": "Marcel Verpaalen",
"email": "[email protected]"
}],
"license": "Apache-2.0",
"bugs": {
"url": "https://github.com/SignalK/nmea0183-utilities/issues"
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53 changes: 53 additions & 0 deletions test/checksum.js
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@@ -0,0 +1,53 @@
var chai = require("chai");
var expect = chai.expect;
var utils = require('../index');

describe('CheckSum', function () {

var sentence1 = '$GPBOD,045.,T,023.,M,DEST,START';
it('Checksum should be added and equal *01', function (done) {
expect(utils.appendChecksum(sentence1)).to.equal('$GPBOD,045.,T,023.,M,DEST,START*01');
done();
});

var sentence2 = '!GPGGA,000000.00,5253.164,N,00539.655,E,0,00,99.9,,M,,M,,';
it('Checksum should be added and equal *6F', function (done) {
expect(utils.appendChecksum(sentence2)).to.equal('!GPGGA,000000.00,5253.164,N,00539.655,E,0,00,99.9,,M,,M,,*6F');
done();
});

var sentence3 = '#GPGGA,000000.00,5253.164,N,00539.655,E,0,00,99.9,,M,,M,,';
it('Checksum should not be appended', function (done) {
expect(utils.appendChecksum(sentence3)).to.equal('#GPGGA,000000.00,5253.164,N,00539.655,E,0,00,99.9,,M,,M,,');
done();
});

var sentence4 = '$GPGGA,000000.00,5253.164,N,00539.655,E,0,00,99.9,,M,,M,,*6A';
it('Checksum should not be recalculated to *6F', function (done) {
expect(utils.appendChecksum(sentence4)).to.equal('$GPGGA,000000.00,5253.164,N,00539.655,E,0,00,99.9,,M,,M,,*6A');
done();
});

var sentence5 = '$GPBOD,045.,T,023.,M,DEST*,START*';
it('Checksum should not be appended', function (done) {
expect(utils.appendChecksum(sentence5)).to.equal('$GPBOD,045.,T,023.,M,DEST*,START*');
done();
});


it('Checksum is valid', function (done) {
expect(utils.valid('!GPGGA,000000.00,5253.164,N,00539.655,E,0,00,99.9,,M,,M,,*6F',true)).to.equal(true);
done();
});

it('Checksum is invalid', function (done) {
expect(utils.valid(sentence4,true)).to.equal(false);
done();
});

it('Checksum is invalid but should not be checked', function (done) {
expect(utils.valid(sentence4,false)).to.equal(true);
done();
});

});

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