From 3b62145392e7fe0b1589ad8fb055fba58d5e3b83 Mon Sep 17 00:00:00 2001
From: FUJI Goro <g.psy.va@gmail.com>
Date: Wed, 5 Feb 2025 20:31:43 +0900
Subject: [PATCH] fix index of built-in encoders/decoders (close #241)

---
 src/ExtensionCodec.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ExtensionCodec.ts b/src/ExtensionCodec.ts
index e36ed0e..5bd2200 100644
--- a/src/ExtensionCodec.ts
+++ b/src/ExtensionCodec.ts
@@ -57,7 +57,7 @@ export class ExtensionCodec<ContextType = undefined> implements ExtensionCodecTy
       this.decoders[type] = decode;
     } else {
       // built-in extensions
-      const index = 1 + type;
+      const index = -1 - type;
       this.builtInEncoders[index] = encode;
       this.builtInDecoders[index] = decode;
     }