From 9d2fd7e45e018defa1d65fb47a4e155ce617f413 Mon Sep 17 00:00:00 2001
From: HDegroote <75906619+HDegroote@users.noreply.github.com>
Date: Fri, 18 Oct 2024 13:38:45 +0200
Subject: [PATCH] Error when encoding fixed-length buffers of incorrect size
 (#30)

---
 index.js |  1 +
 test.js  | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/index.js b/index.js
index 027f059..af95f3e 100644
--- a/index.js
+++ b/index.js
@@ -420,6 +420,7 @@ exports.bool = {
 const fixed = exports.fixed = function fixed (n) {
   return {
     preencode (state, s) {
+      if (s.byteLength !== n) throw new Error('Incorrect buffer size')
       state.end += n
     },
     encode (state, s) {
diff --git a/test.js b/test.js
index f21a4e5..371046d 100644
--- a/test.js
+++ b/test.js
@@ -565,6 +565,19 @@ test('fixed n', function (t) {
   t.exception(() => fixed.decode(state))
 })
 
+test('error for incorrect buffer sizes when encoding fixed-length buffers', function (t) {
+  const smallbuf = b4a.from('aa', 'hex')
+  const bigBuf = b4a.from('aa'.repeat(500), 'hex')
+
+  t.exception(() => enc.encode(enc.fixed32, smallbuf), /Incorrect buffer size/)
+  t.exception(() => enc.encode(enc.fixed64, smallbuf), /Incorrect buffer size/)
+  t.exception(() => enc.encode(enc.fixed(100), smallbuf), /Incorrect buffer size/)
+
+  t.exception(() => enc.encode(enc.fixed32, bigBuf), /Incorrect buffer size/)
+  t.exception(() => enc.encode(enc.fixed64, bigBuf), /Incorrect buffer size/)
+  t.exception(() => enc.encode(enc.fixed(100), bigBuf), /Incorrect buffer size/)
+})
+
 test('array', function (t) {
   const state = enc.state()
   const arr = enc.array(enc.bool)