From ada493f607f3e55603e266f5d7d50b4a354b7259 Mon Sep 17 00:00:00 2001
From: Justin Starry <justin@solana.com>
Date: Mon, 29 Aug 2022 22:20:16 +0200
Subject: [PATCH] feat: add VersionedMessage.deserializeMessageVersion utility
 function (#27415)

---
 web3.js/src/message/versioned.ts             | 15 ++++++++---
 web3.js/test/message-tests/versioned.test.ts | 28 ++++++++++++++++++++
 2 files changed, 40 insertions(+), 3 deletions(-)
 create mode 100644 web3.js/test/message-tests/versioned.test.ts

diff --git a/web3.js/src/message/versioned.ts b/web3.js/src/message/versioned.ts
index 042fc1c72fcebb..92b4d888bdbf67 100644
--- a/web3.js/src/message/versioned.ts
+++ b/web3.js/src/message/versioned.ts
@@ -5,17 +5,26 @@ import {MessageV0} from './v0';
 export type VersionedMessage = Message | MessageV0;
 // eslint-disable-next-line no-redeclare
 export const VersionedMessage = {
-  deserialize: (serializedMessage: Uint8Array): VersionedMessage => {
+  deserializeMessageVersion(serializedMessage: Uint8Array): 'legacy' | number {
     const prefix = serializedMessage[0];
     const maskedPrefix = prefix & VERSION_PREFIX_MASK;
 
     // if the highest bit of the prefix is not set, the message is not versioned
     if (maskedPrefix === prefix) {
-      return Message.from(serializedMessage);
+      return 'legacy';
     }
 
     // the lower 7 bits of the prefix indicate the message version
-    const version = maskedPrefix;
+    return maskedPrefix;
+  },
+
+  deserialize: (serializedMessage: Uint8Array): VersionedMessage => {
+    const version =
+      VersionedMessage.deserializeMessageVersion(serializedMessage);
+    if (version === 'legacy') {
+      return Message.from(serializedMessage);
+    }
+
     if (version === 0) {
       return MessageV0.deserialize(serializedMessage);
     } else {
diff --git a/web3.js/test/message-tests/versioned.test.ts b/web3.js/test/message-tests/versioned.test.ts
new file mode 100644
index 00000000000000..1acaf7823b1443
--- /dev/null
+++ b/web3.js/test/message-tests/versioned.test.ts
@@ -0,0 +1,28 @@
+import {expect} from 'chai';
+
+import {VersionedMessage} from '../../src/message';
+
+describe('VersionedMessage', () => {
+  it('deserializeMessageVersion', () => {
+    const bufferWithLegacyPrefix = new Uint8Array([1]);
+    expect(
+      VersionedMessage.deserializeMessageVersion(bufferWithLegacyPrefix),
+    ).to.eq('legacy');
+
+    for (const version of [0, 1, 127]) {
+      const bufferWithVersionPrefix = new Uint8Array([(1 << 7) + version]);
+      expect(
+        VersionedMessage.deserializeMessageVersion(bufferWithVersionPrefix),
+      ).to.eq(version);
+    }
+  });
+
+  it('deserialize failure', () => {
+    const bufferWithV1Prefix = new Uint8Array([(1 << 7) + 1]);
+    expect(() => {
+      VersionedMessage.deserialize(bufferWithV1Prefix);
+    }).to.throw(
+      'Transaction message version 1 deserialization is not supported',
+    );
+  });
+});