Move the encodeToXmlString helper function to src/core/core_utils.js

With the previous patch this function is now *only* accessed on the worker-thread, hence it's no longer necessary to include it in the *built* `pdf.js` file.

src/core/core_utils.js

@@ -316,8 +316,54 @@ function collectActions(xref, dict, eventType) {
   return objectSize(actions) > 0 ? actions : null;
 }
 
+const XMLEntities = {
+  /* < */ 0x3c: "&lt;",
+  /* > */ 0x3e: "&gt;",
+  /* & */ 0x26: "&amp;",
+  /* " */ 0x22: "&quot;",
+  /* ' */ 0x27: "&apos;",
+};
+
+function encodeToXmlString(str) {
+  const buffer = [];
+  let start = 0;
+  for (let i = 0, ii = str.length; i < ii; i++) {
+    const char = str.codePointAt(i);
+    if (0x20 <= char && char <= 0x7e) {
+      // ascii
+      const entity = XMLEntities[char];
+      if (entity) {
+        if (start < i) {
+          buffer.push(str.substring(start, i));
+        }
+        buffer.push(entity);
+        start = i + 1;
+      }
+    } else {
+      if (start < i) {
+        buffer.push(str.substring(start, i));
+      }
+      buffer.push(`&#x${char.toString(16).toUpperCase()};`);
+      if (char > 0xd7ff && (char < 0xe000 || char > 0xfffd)) {
+        // char is represented by two u16
+        i++;
+      }
+      start = i + 1;
+    }
+  }
+
+  if (buffer.length === 0) {
+    return str;
+  }
+  if (start < str.length) {
+    buffer.push(str.substring(start, str.length));
+  }
+  return buffer.join("");
+}
+
 export {
   collectActions,
+  encodeToXmlString,
   escapePDFName,
   getArrayLookupTableFactory,
   getInheritableProperty,