Initial release

src/parser.ts

@@ -0,0 +1,91 @@
+/**
+ * Decode a Base91 encoded string to a number.
+ * Base91 uses ASCII characters 33-123 (! to {) for encoding.
+ * Each character represents a digit in base 91.
+ *
+ * @param str Base91 encoded string (typically 4 characters for 32-bit values in APRS)
+ * @returns Decoded number value
+ */
+export const base91ToNumber = (str: string): number => {
+  let value = 0;
+  const base = 91;
+
+  for (let i = 0; i < str.length; i++) {
+    const charCode = str.charCodeAt(i);
+    const digit = charCode - 33; // Base91 uses chars 33-123 (! to {)
+
+    if (digit < 0 || digit >= base) {
+      throw new Error(`Invalid Base91 character: '${str[i]}' (code ${charCode})`);
+    }
+
+    value = value * base + digit;
+  }
+
+  return value;
+}
+
+/* Conversions from Freedom Units to whatever the rest of the world uses and understands. */
+
+const KNOTS_TO_KMH = 1.852;
+const FEET_TO_METERS = 0.3048;
+const FAHRENHEIT_TO_CELSIUS_OFFSET = 32;
+
+/**
+ * Convert speed from knots to kilometers per hour.
+ *
+ * @param knots number of knots
+ * @returns equivalent speed in kilometers per hour
+ */
+export const knotsToKmh = (knots: number): number => {
+  return knots * KNOTS_TO_KMH;
+}
+
+/**
+ * Convert speed from kilometers per hour to knots.
+ *
+ * @param kmh speed in kilometers per hour
+ * @returns equivalent speed in knots
+ */
+export const kmhToKnots = (kmh: number): number => {
+  return kmh / KNOTS_TO_KMH;
+}
+
+/**
+ * Convert altitude from feet to meters.
+ *
+ * @param feet altitude in feet
+ * @returns equivalent altitude in meters
+ */
+export const feetToMeters = (feet: number): number => {
+  return feet * FEET_TO_METERS;
+}
+
+/**
+ * Convert altitude from meters to feet.
+ *
+ * @param meters altitude in meters
+ * @returns equivalent altitude in feet
+ */
+export const metersToFeet = (meters: number): number => {
+  return meters / FEET_TO_METERS;
+}
+
+/**
+ * Convert temperature from Celsius to Fahrenheit.
+ *
+ * @param celsius temperature in Celsius
+ * @returns equivalent temperature in Fahrenheit
+ */
+export const celsiusToFahrenheit = (celsius: number): number => {
+  return (celsius * 9/5) + FAHRENHEIT_TO_CELSIUS_OFFSET;
+}
+
+/**
+ * Convert temperature from Fahrenheit to Celsius.
+ *
+ * @param fahrenheit temperature in Fahrenheit
+ * @returns equivalent temperature in Celsius
+ */
+export const fahrenheitToCelsius = (fahrenheit: number): number => {
+  return (fahrenheit - FAHRENHEIT_TO_CELSIUS_OFFSET) * 5/9;
+}