add stringToNumber to utils;ts

common/src/utils/utils.ts

@@ -363,3 +363,30 @@ export function BigintToArray(n: number, k: number, x: bigint) {
   }
   return ret;
 }
+
+
+/**
+ * Converts a string of maximum 30 characters to a single BigInt.
+ * Each byte is represented by three digits in the resulting BigInt.
+ * @param str The input string (max 30 characters)
+ * @returns A BigInt representing the concatenated byte values
+ */
+export function stringToNumber(str: string): bigint {
+  if (str.length > 30) {
+    throw new Error("Input string must not exceed 30 characters");
+  }
+  return BigInt('1' + Array.from(str)
+    .map(char => char.charCodeAt(0).toString().padStart(3, '0'))
+    .join(''));
+}
+
+/**
+* Converts a BigInt (representing concatenated byte values) back to a string.
+* @param num The input BigInt
+* @returns The reconstructed string
+*/
+export function numberToString(num: bigint): string {
+  const str = num.toString().slice(1); // Remove leading '1'
+  const charCodes = str.match(/.{1,3}/g) || [];
+  return String.fromCharCode(...charCodes.map(code => parseInt(code, 10)));
+}