From b3b7271fbda1ef5fc5d2dbdbd473d6ea627a1aa8 Mon Sep 17 00:00:00 2001
From: Tooru Fujisawa <arai_a@mac.com>
Date: Tue, 17 Sep 2019 15:46:36 +0000
Subject: [PATCH] Bug 1581880 - Remove loop from
 BinASTTokenReaderBase::readByte. r=Yoric

Differential Revision: https://phabricator.services.mozilla.com/D46164

--HG--
extra : moz-landing-system : lando
---
 js/src/frontend/BinASTTokenReaderBase.cpp | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/js/src/frontend/BinASTTokenReaderBase.cpp b/js/src/frontend/BinASTTokenReaderBase.cpp
index f8456e8da75a..c64d8e08ab6c 100644
--- a/js/src/frontend/BinASTTokenReaderBase.cpp
+++ b/js/src/frontend/BinASTTokenReaderBase.cpp
@@ -98,9 +98,13 @@ JS::Result<Ok> BinASTTokenReaderBase::readBuf(uint8_t* bytes, uint32_t len) {
 }
 
 JS::Result<uint8_t> BinASTTokenReaderBase::readByte() {
-  uint8_t byte;
-  MOZ_TRY(readBuf(&byte, 1));
-  return byte;
+  MOZ_ASSERT(!hasRaisedError());
+
+  if (MOZ_UNLIKELY(stop_ == current_)) {
+    return raiseError("Buffer exceeds length");
+  }
+
+  return *current_++;
 }
 
 }  // namespace frontend