From 93c80f191056073b403f60bab7ee0084c810d2ee Mon Sep 17 00:00:00 2001
From: Niklas Mischkulnig <mischnic@users.noreply.github.com>
Date: Tue, 25 Feb 2020 15:01:34 +0100
Subject: [PATCH] Fix Buffer.from for SharedArrayBuffer

---
 index.js                       | 5 +++++
 package.json                   | 3 +++
 test/node/test-buffer-alloc.js | 8 ++++++++
 3 files changed, 16 insertions(+)

diff --git a/index.js b/index.js
index 19b0468..8f8b708 100644
--- a/index.js
+++ b/index.js
@@ -142,6 +142,11 @@ function from (value, encodingOrOffset, length) {
     return fromArrayBuffer(value, encodingOrOffset, length)
   }
 
+  if (isInstance(value, SharedArrayBuffer) ||
+      (value && isInstance(value.buffer, SharedArrayBuffer))) {
+    return fromArrayBuffer(value, encodingOrOffset, length)
+  }
+
   if (typeof value === 'number') {
     throw new TypeError(
       'The "value" argument must not be of type number. Received type number'
diff --git a/package.json b/package.json
index 9d9c6e0..494c282 100644
--- a/package.json
+++ b/package.json
@@ -74,6 +74,9 @@
       "test/common.js",
       "test/_polyfill.js",
       "perf/**/*.js"
+    ],
+    "globals": [
+      "SharedArrayBuffer"
     ]
   }
 }
diff --git a/test/node/test-buffer-alloc.js b/test/node/test-buffer-alloc.js
index 030bad3..5d96e0a 100644
--- a/test/node/test-buffer-alloc.js
+++ b/test/node/test-buffer-alloc.js
@@ -51,6 +51,14 @@ assert.strictEqual(0, d.length);
     assert.deepStrictEqual(value, ui32[key]);
   }
 }
+{
+  const sab = new SharedArrayBuffer(Uint8Array.BYTES_PER_ELEMENT * 4);
+  const ui32 = new Uint8Array(sab).fill(42);
+  const e = Buffer(sab);
+  for (const [key, value] of e.entries()) {
+    assert.deepStrictEqual(value, ui32[key]);
+  }
+}
 
 // Test invalid encoding for Buffer.toString
 assert.throws(() => b.toString('invalid'),
-- 
2.34.1