From 022f51b36b7c4ae7e6bc3ab626d7636949479ace Mon Sep 17 00:00:00 2001
From: Matt Broadstone <mbroadst@mongodb.com>
Date: Tue, 12 Nov 2019 08:12:30 -0500
Subject: [PATCH] fix(compression): recalculate opcode after determine
 OP_COMPRESSED

---
 lib/core/cmap/message_stream.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/core/cmap/message_stream.js b/lib/core/cmap/message_stream.js
index ca952fc436..89c46fdb5f 100644
--- a/lib/core/cmap/message_stream.js
+++ b/lib/core/cmap/message_stream.js
@@ -131,7 +131,7 @@ function processMessage(stream, message, callback) {
     opCode: message.readInt32LE(12)
   };
 
-  const ResponseType = messageHeader.opCode === OP_MSG ? BinMsg : Response;
+  let ResponseType = messageHeader.opCode === OP_MSG ? BinMsg : Response;
   const responseOptions = stream.responseOptions;
   if (messageHeader.opCode !== OP_COMPRESSED) {
     const messageBody = message.slice(MESSAGE_HEADER_SIZE);
@@ -150,6 +150,8 @@ function processMessage(stream, message, callback) {
   const compressorID = message[MESSAGE_HEADER_SIZE + 8];
   const compressedBuffer = message.slice(MESSAGE_HEADER_SIZE + 9);
 
+  // recalculate based on wrapped opcode
+  ResponseType = messageHeader.opCode === OP_MSG ? BinMsg : Response;
   decompress(compressorID, compressedBuffer, (err, messageBody) => {
     if (err) {
       callback(err);