Fixes an issue where Buffer.from was not supporting SharedArrayBuffer

lib/buffer.js

@@ -2,7 +2,7 @@
 'use strict';
 
 const binding = process.binding('buffer');
-const { isArrayBuffer } = process.binding('util');
+const { isArrayBuffer, isSharedArrayBuffer } = process.binding('util');
 const bindingObj = {};
 const internalUtil = require('internal/util');
 
@@ -103,7 +103,7 @@ Buffer.from = function(value, encodingOrOffset, length) {
   if (typeof value === 'number')
     throw new TypeError('"value" argument must not be a number');
 
-  if (isArrayBuffer(value))
+  if (isArrayBuffer(value) || isSharedArrayBuffer(value))
     return fromArrayBuffer(value, encodingOrOffset, length);
 
   if (typeof value === 'string')

src/node_util.cc

@@ -20,6 +20,7 @@ using v8::Value;
 
 #define VALUE_METHOD_MAP(V)                                                   \
   V(isArrayBuffer, IsArrayBuffer)                                             \
+  V(isSharedArrayBuffer, IsSharedArrayBuffer)                                 \
   V(isDataView, IsDataView)                                                   \
   V(isDate, IsDate)                                                           \
   V(isMap, IsMap)                                                             \

test/parallel/test-buffer-sharedarraybuffer.js

@@ -0,0 +1,25 @@
+/*global SharedArrayBuffer*/
+'use strict';
+// Flags: --harmony-sharedarraybuffer
+
+require('../common');
+const assert = require('assert');
+const Buffer = require('buffer').Buffer;
+
+const sab = new SharedArrayBuffer(24);
+const arr = new Uint16Array(sab);
+const ar = new Uint16Array(12);
+ar[0] = 5000;
+arr[0] = 5000;
+arr[1] = 4000;
+ar[1] = 4000;
+
+var arr_buf = Buffer.from(arr.buffer);
+var ar_buf = Buffer.from(ar.buffer);
+
+assert.deepStrictEqual(arr_buf, ar_buf, 0);
+
+arr[1] = 6000;
+ar[1] = 6000;
+
+assert.deepStrictEqual(arr_buf, ar_buf, 0);