Add support for overriding the charset in readString/writeString

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

buffer/src/main/kotlin/org/openrs2/buffer/ByteBufExtensions.kt

@@ -95,7 +95,7 @@ public fun ByteBuf.writeUnsignedIntSmart(v: Int): ByteBuf {
     return this
 }
 
-public fun ByteBuf.readString(): String {
+public fun ByteBuf.readString(charset: Charset = Cp1252Charset): String {
     val start = readerIndex()
 
     val end = forEachByte(ByteProcessor.FIND_NUL)
@@ -103,13 +103,13 @@ public fun ByteBuf.readString(): String {
         "Unterminated string"
     }
 
-    val s = toString(start, end - start, Cp1252Charset)
+    val s = toString(start, end - start, charset)
     readerIndex(end + 1)
     return s
 }
 
-public fun ByteBuf.writeString(s: CharSequence): ByteBuf {
-    writeCharSequence(s, Cp1252Charset)
+public fun ByteBuf.writeString(s: CharSequence, charset: Charset = Cp1252Charset): ByteBuf {
+    writeCharSequence(s, charset)
     writeByte(0)
     return this
 }

buffer/src/test/kotlin/org/openrs2/buffer/ByteBufExtensionsTest.kt

@@ -2,6 +2,7 @@ package org.openrs2.buffer
 
 import io.netty.buffer.ByteBufAllocator
 import io.netty.buffer.Unpooled
+import org.openrs2.util.charset.ModifiedUtf8Charset
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
@@ -433,6 +434,33 @@ class ByteBufExtensionsTest {
         }
     }
 
+    @Test
+    fun testReadStringCharset() {
+        wrappedBuffer(0).use { buf ->
+            assertEquals("", buf.readString(ModifiedUtf8Charset))
+            assertFalse(buf.isReadable)
+        }
+
+        wrappedBuffer(
+            0xC3.toByte(),
+            0x96.toByte(),
+            'p'.code.toByte(),
+            'e'.code.toByte(),
+            'n'.code.toByte(),
+            'R'.code.toByte(),
+            'S'.code.toByte(),
+            '2'.code.toByte(),
+            0
+        ).use { buf ->
+            assertEquals("ÖpenRS2", buf.readString(ModifiedUtf8Charset))
+            assertFalse(buf.isReadable)
+        }
+
+        assertFailsWith<IllegalArgumentException> {
+            Unpooled.EMPTY_BUFFER.readString(ModifiedUtf8Charset)
+        }
+    }
+
     @Test
     fun testWriteString() {
         ByteBufAllocator.DEFAULT.buffer().use { actual ->
@@ -461,6 +489,35 @@ class ByteBufExtensionsTest {
         }
     }
 
+    @Test
+    fun testWriteStringCharset() {
+        ByteBufAllocator.DEFAULT.buffer().use { actual ->
+            actual.writeString("", ModifiedUtf8Charset)
+
+            wrappedBuffer(0).use { expected ->
+                assertEquals(expected, actual)
+            }
+        }
+
+        ByteBufAllocator.DEFAULT.buffer().use { actual ->
+            actual.writeString("ÖpenRS2", ModifiedUtf8Charset)
+
+            wrappedBuffer(
+                0xC3.toByte(),
+                0x96.toByte(),
+                'p'.code.toByte(),
+                'e'.code.toByte(),
+                'n'.code.toByte(),
+                'R'.code.toByte(),
+                'S'.code.toByte(),
+                '2'.code.toByte(),
+                0
+            ).use { expected ->
+                assertEquals(expected, actual)
+            }
+        }
+    }
+
     @Test
     fun testReadVersionedString() {
         wrappedBuffer(0, 0).use { buf ->