Validate additional font-dictionary properties

src/core/core_utils.js

@@ -218,6 +218,21 @@ function isWhiteSpace(ch) {
   return ch === 0x20 || ch === 0x09 || ch === 0x0d || ch === 0x0a;
 }
 
+/**
+ * Checks if something is an Array containing only numbers,
+ * and (optionally) checks its length.
+ * @param {any} arr
+ * @param {number | null} len
+ * @returns {boolean}
+ */
+function isNumberArray(arr, len) {
+  return (
+    Array.isArray(arr) &&
+    (len === null || arr.length === len) &&
+    arr.every(x => typeof x === "number")
+  );
+}
+
 /**
  * AcroForm field names use an array like notation to refer to
  * repeated XFA elements e.g. foo.bar[nnn].
@@ -637,6 +652,7 @@ export {
   getRotationMatrix,
   getSizeInBytes,
   isAscii,
+  isNumberArray,
   isWhiteSpace,
   log2,
   MissingDataException,