Set writerIndex correctly in ByteBufBodyHandler

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

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

@@ -19,6 +19,7 @@ public class ByteBufBodyHandler @Inject constructor(
         return object : HttpResponse.BodySubscriber<ByteBuf> {
             private val buf = alloc.compositeBuffer()
             private val future = CompletableFuture<ByteBuf>()
+            private var len = 0
 
             override fun onSubscribe(subscription: Flow.Subscription) {
                 subscription.request(Long.MAX_VALUE)
@@ -26,7 +27,11 @@ public class ByteBufBodyHandler @Inject constructor(
 
             override fun onNext(item: List<ByteBuffer>) {
                 for (b in item) {
-                    buf.addComponent(Unpooled.wrappedBuffer(b))
+                    val component = Unpooled.wrappedBuffer(b)
+                    buf.addComponent(component)
+
+                    len += component.readableBytes()
+                    check(len >= 0)
                 }
             }
 
@@ -36,6 +41,7 @@ public class ByteBufBodyHandler @Inject constructor(
             }
 
             override fun onComplete() {
+                buf.writerIndex(len)
                 future.complete(buf)
             }