Replace recursive regex in PhoneNumberUtil.normalize() with linear scan

java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberUtil.java

@@ -277,10 +277,6 @@ public class PhoneNumberUtil {
   private static final String UNWANTED_END_CHARS = "[[\\P{N}&&\\P{L}]&&[^#]]+$";
   static final Pattern UNWANTED_END_CHAR_PATTERN = Pattern.compile(UNWANTED_END_CHARS);
 
-  // We use this pattern to check if the phone number has at least three letters in it - if so, then
-  // we treat it as a number where some phone-number digits are represented by letters.
-  private static final Pattern VALID_ALPHA_PHONE_PATTERN = Pattern.compile("(?:.*?[A-Za-z]){3}.*");
-
   // Regular expression of viable phone numbers. This is location independent. Checks we have at
   // least three leading digits, and only valid punctuation, alpha characters and
   // digits in the phone number. Does not include extension data.
@@ -802,8 +798,7 @@ static boolean isViablePhoneNumber(CharSequence number) {
    *     normalized in place
    */
   static StringBuilder normalize(StringBuilder number) {
-    Matcher m = VALID_ALPHA_PHONE_PATTERN.matcher(number);
-    if (m.matches()) {
+    if (hasAtLeastThreeAlphaChars(number)) {
       number.replace(0, number.length(), normalizeHelper(number, ALPHA_PHONE_MAPPINGS, true));
     } else {
       number.replace(0, number.length(), normalizeDigitsOnly(number));

java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberUtilTest.java

@@ -476,6 +476,15 @@ public void testNormaliseOtherDigits() {
                  expectedOutput, PhoneNumberUtil.normalize(inputNumber).toString());
   }
 
+  public void testNormaliseLongNumericInputDoesNotThrow() {
+    StringBuilder inputNumber = new StringBuilder("+");
+    for (int i = 0; i < 5000; i++) {
+      inputNumber.append('1');
+    }
+    // Should not throw StackOverflowError and correctly normalize digits.
+    assertEquals(5000, PhoneNumberUtil.normalize(inputNumber).length());
+  }
+
   public void testNormaliseStripAlphaCharacters() {
     String inputNumber = "034-56&+a#234";
     String expectedOutput = "03456234";

pending_code_changes.txt

@@ -1 +1,2 @@
-
+Code changes:
+ - Fixed PhoneNumberUtil.normalize(StringBuilder) in Java to use a linear character scan instead of the recursive VALID_ALPHA_PHONE_PATTERN regex, preventing StackOverflowError on long inputs.