Add method for calculating the K&R hash code of a CP-1252-encoded string

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

util/src/main/java/dev/openrs2/util/StringUtils.kt

@@ -1,5 +1,7 @@
 package dev.openrs2.util
 
+import dev.openrs2.util.charset.Cp1252Charset
+
 fun CharSequence.indefiniteArticle(): String {
     require(isNotEmpty())
 
@@ -8,3 +10,11 @@ fun CharSequence.indefiniteArticle(): String {
         else -> "a"
     }
 }
+
+fun CharSequence.krHashCode(): Int {
+    var hash = 0
+    for (c in this) {
+        hash = ((hash shl 5) - hash) + Cp1252Charset.encode(c)
+    }
+    return hash
+}

util/src/test/java/dev/openrs2/util/StringUtilsTest.kt

@@ -13,4 +13,11 @@ object StringUtilsTest {
             "".indefiniteArticle()
         }
     }
+
+    @Test
+    fun testKrHashCode() {
+        assertEquals(0, "".krHashCode())
+        assertEquals(99162322, "hello".krHashCode())
+        assertEquals(92340183, "h€llo".krHashCode())
+    }
 }