Add hash function used by pre-JS5 caches

Signed-off-by: Graham <gpe@openrs2.org>

util/src/main/kotlin/org/openrs2/util/StringUtils.kt

@@ -19,6 +19,14 @@ public fun CharSequence.krHashCode(): Int {
     return hash
 }
 
+public fun CharSequence.jagHashCode(): Int {
+    var hash = 0
+    for (c in this) {
+        hash = (hash * 61) + (c.code - 32)
+    }
+    return hash
+}
+
 public fun String.capitalize(): String {
     return replaceFirstChar { it.titlecase() }
 }

util/src/test/kotlin/org/openrs2/util/StringUtilsTest.kt

@@ -21,6 +21,12 @@ class StringUtilsTest {
         assertEquals(92340183, "h€llo".krHashCode())
     }
 
+    @Test
+    fun testJagHashCode() {
+        assertEquals(0, "".jagHashCode())
+        assertEquals(1012849752, "hello".jagHashCode())
+    }
+
     @Test
     fun testCapitalize() {
         assertEquals("Hello", "hello".capitalize())