Optimise uncompression of encrypted groups with invalid keys

Creating the InputStream first allows us to immediately fail if a key is
invalid, without having the chance of allocating a huge ByteBuf based on
an incorrect length.

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

cache/src/main/kotlin/org/openrs2/cache/Js5Compression.kt

@@ -147,8 +147,8 @@ public object Js5Compression {
                 throw IOException("Uncompressed length is negative: $uncompressedLen")
             }
 
-            plaintext.alloc().buffer(uncompressedLen, uncompressedLen).use { output ->
             type.createInputStream(ByteBufInputStream(plaintext, len), uncompressedLen).use { inputStream ->
+                plaintext.alloc().buffer(uncompressedLen, uncompressedLen).use { output ->
                     var remaining = uncompressedLen
                     while (remaining > 0) {
                         val n = output.writeBytes(inputStream, remaining)
@@ -161,12 +161,12 @@ public object Js5Compression {
                     if (inputStream.read() != -1) {
                         throw IOException("Uncompressed data overflow")
                     }
-                }
 
                     return output.retain()
                 }
             }
         }
+    }
 
     public fun uncompressUnlessEncrypted(input: ByteBuf): ByteBuf? {
         return uncompressIfKeyValid(input, XteaKey.ZERO)
@@ -317,6 +317,8 @@ public object Js5Compression {
             val uncompressedLen = plaintext.readInt()
             check(uncompressedLen >= 0)
 
+            try {
+                type.createInputStream(ByteBufInputStream(plaintext, len), uncompressedLen).use { inputStream ->
                     /**
                      * We don't pass uncompressedLen to the buffer here: in some cases,
                      * an incorrect key can produce a valid header (particularly for
@@ -330,8 +332,6 @@ public object Js5Compression {
                      * We therefore allow the buffer to grow dynamically.
                      */
                     plaintext.alloc().buffer().use { output ->
-                try {
-                    type.createInputStream(ByteBufInputStream(plaintext, len), uncompressedLen).use { inputStream ->
                         var remaining = uncompressedLen
                         while (remaining > 0) {
                             val n = output.writeBytes(inputStream, remaining)
@@ -346,13 +346,13 @@ public object Js5Compression {
                             // uncompressed data overflow
                             return null
                         }
+
+                        return output.retain()
+                    }
                 }
             } catch (ex: IOException) {
                 return null
             }
-
-                return output.retain()
-            }
         }
     }