Bootstrap ASN methods

src/bootstrap.ts

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+/**
+ * Compares a given range to the value, returning the relative position.
+ *
+ * If the returned value is 1, the value sits AFTER the range.
+ * If the returned value is 0, the value sits WITHIN the range.
+ * If the returned value is -1, the value sits BEFORE the range.
+ * The range given is considered to be inclusive (e.g. 6 sits WITHIN 6-10).
+ *
+ * @param value The value.
+ * @param range The range, two positive numbers split by a single dash.
+ * @returns {number} The relative position of the value to the range as -1, 0 or 1.
+ */
+function compareASN(value: number, range: string): number {
+    const [start, end] = range.split('-', 2) as [string, string];
+    if (value < parseInt(start)) return -1;
+    if (value > parseInt(end)) return 1;
+    return 0;
+}
+
+/**
+ * Find the range in which a given ASN exists via binary search. If not found, -1 is used.
+ */
+export function findASN(asn: number, ranges: string[]) {
+    let start = 0;
+    let end = ranges.length - 1;
+
+    while (start <= end) {
+        const mid = Math.floor((start + end) / 2);
+        const comparison = compareASN(asn, ranges[mid] as string);
+        if (comparison == 0) return mid; // Success case
+        if (comparison == -1) end = mid - 1;
+        else start = mid + 1;
+    }
+    return -1; // Failure case
+}