Fix off-by-one erorr in the JS5 codecs

Excluding the 0xFF trailers, the first block is actually 512 bytes, and
the remaining blocks are all 511 bytes. I had mistakenly written the
code and tests on the basis of all blocks being 511 bytes.

The Js5ResponseDecoder now works with OSRS.

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

protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoder.kt

@@ -62,7 +62,7 @@ public class Js5ResponseDecoder : ByteToMessageDecoder() {
 
         if (state == State.READ_DATA) {
             while (data.isWritable) {
-                val blockLen = min(511 - ((data.readableBytes() + 3) % 511), data.writableBytes())
+                val blockLen = min(511 - ((data.readableBytes() + 2) % 511), data.writableBytes())
                 val last = data.writableBytes() <= blockLen
 
                 val blockLenIncludingTrailer = if (last) {

protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoder.kt

@@ -24,7 +24,7 @@ public object Js5ResponseEncoder : MessageToByteEncoder<Js5Response>(Js5Response
         }
         out.writeByte(compression)
 
-        out.writeBytes(msg.data, min(msg.data.readableBytes(), 507))
+        out.writeBytes(msg.data, min(msg.data.readableBytes(), 508))
 
         while (msg.data.isReadable) {
             out.writeByte(0xFF)
@@ -34,7 +34,7 @@ public object Js5ResponseEncoder : MessageToByteEncoder<Js5Response>(Js5Response
 
     override fun allocateBuffer(ctx: ChannelHandlerContext, msg: Js5Response, preferDirect: Boolean): ByteBuf {
         val dataLen = msg.data.readableBytes()
-        val len = 3 + dataLen + (3 + dataLen) / 511
+        val len = 3 + dataLen + (2 + dataLen) / 511
 
         return if (preferDirect) {
             ctx.alloc().ioBuffer(len, len)

protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoderTest.kt

@@ -14,23 +14,23 @@ import kotlin.test.assertEquals
 object Js5ResponseDecoderTest {
     @Test
     fun testDecode() {
-        testDecode("508.dat", "508-prefetch.dat", true)
-        testDecode("508.dat", "508-urgent.dat", false)
-
         testDecode("509.dat", "509-prefetch.dat", true)
         testDecode("509.dat", "509-urgent.dat", false)
 
-        testDecode("1019.dat", "1019-prefetch.dat", true)
-        testDecode("1019.dat", "1019-urgent.dat", false)
+        testDecode("510.dat", "510-prefetch.dat", true)
+        testDecode("510.dat", "510-urgent.dat", false)
 
         testDecode("1020.dat", "1020-prefetch.dat", true)
         testDecode("1020.dat", "1020-urgent.dat", false)
 
-        testDecode("1530.dat", "1530-prefetch.dat", true)
-        testDecode("1530.dat", "1530-urgent.dat", false)
+        testDecode("1021.dat", "1021-prefetch.dat", true)
+        testDecode("1021.dat", "1021-urgent.dat", false)
 
         testDecode("1531.dat", "1531-prefetch.dat", true)
         testDecode("1531.dat", "1531-urgent.dat", false)
+
+        testDecode("1532.dat", "1532-prefetch.dat", true)
+        testDecode("1532.dat", "1532-urgent.dat", false)
     }
 
     @Test

protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoderTest.kt

@@ -12,23 +12,23 @@ import kotlin.test.assertEquals
 object Js5ResponseEncoderTest {
     @Test
     fun testEncode() {
-        testEncode("508.dat", "508-prefetch.dat", true)
-        testEncode("508.dat", "508-urgent.dat", false)
-
         testEncode("509.dat", "509-prefetch.dat", true)
         testEncode("509.dat", "509-urgent.dat", false)
 
-        testEncode("1019.dat", "1019-prefetch.dat", true)
-        testEncode("1019.dat", "1019-urgent.dat", false)
+        testEncode("510.dat", "510-prefetch.dat", true)
+        testEncode("510.dat", "510-urgent.dat", false)
 
         testEncode("1020.dat", "1020-prefetch.dat", true)
         testEncode("1020.dat", "1020-urgent.dat", false)
 
-        testEncode("1530.dat", "1530-prefetch.dat", true)
-        testEncode("1530.dat", "1530-urgent.dat", false)
+        testEncode("1021.dat", "1021-prefetch.dat", true)
+        testEncode("1021.dat", "1021-urgent.dat", false)
 
         testEncode("1531.dat", "1531-prefetch.dat", true)
         testEncode("1531.dat", "1531-urgent.dat", false)
+
+        testEncode("1532.dat", "1532-prefetch.dat", true)
+        testEncode("1532.dat", "1532-urgent.dat", false)
     }
 
     @Test