[New] add support for SharedArrayBuffer

Author: ljharb

.eslintrc

@@ -25,7 +25,7 @@
       "files": "example/**",
       "rules": {
         "no-console": 0,
-		"no-magic-numbers": 0,
+        "no-magic-numbers": 0,
       }
     },
     {

index.js

@@ -1,24 +1,26 @@
 'use strict';
 
-var objectKeys = require('object-keys');
-var isArguments = require('is-arguments');
-var is = require('object-is');
-var isRegex = require('is-regex');
+var assign = require('object.assign');
+var callBound = require('call-bind/callBound');
 var flags = require('regexp.prototype.flags');
+var GetIntrinsic = require('get-intrinsic');
+var getIterator = require('es-get-iterator');
+var getSideChannel = require('side-channel');
+var is = require('object-is');
+var isArguments = require('is-arguments');
 var isArray = require('isarray');
+var isArrayBuffer = require('is-array-buffer');
 var isDate = require('is-date-object');
+var isRegex = require('is-regex');
+var isSharedArrayBuffer = require('is-shared-array-buffer');
+var objectKeys = require('object-keys');
 var whichBoxedPrimitive = require('which-boxed-primitive');
-var GetIntrinsic = require('get-intrinsic');
-var callBound = require('call-bind/callBound');
 var whichCollection = require('which-collection');
-var getIterator = require('es-get-iterator');
-var getSideChannel = require('side-channel');
 var whichTypedArray = require('which-typed-array');
-var assign = require('object.assign');
-var isArrayBuffer = require('is-array-buffer');
 
-var byteLength = callBound('%ArrayBuffer.prototype.byteLength%', true)
+var byteLength = callBound('ArrayBuffer.prototype.byteLength', true)
 	|| function byteLength(ab) { return ab.byteLength; }; // in node < 0.11, byteLength is an own nonconfigurable property
+var sabByteLength = callBound('SharedArrayBuffer.prototype.byteLength', true);
 
 var $getTime = callBound('Date.prototype.getTime');
 var gPO = Object.getPrototypeOf;
@@ -335,6 +337,14 @@ function objEquiv(a, b, opts, channel) {
     return typeof Uint8Array === 'function' && internalDeepEqual(new Uint8Array(a), new Uint8Array(b), opts, channel);
   }
 
+  var aIsSAB = isSharedArrayBuffer(a);
+  var bIsSAB = isSharedArrayBuffer(b);
+  if (aIsSAB !== bIsSAB) { return false; }
+  if (aIsSAB || bIsSAB) { // && would work too, because both are true or both false here
+    if (sabByteLength(a) !== sabByteLength(b)) { return false; }
+    return typeof Uint8Array === 'function' && internalDeepEqual(new Uint8Array(a), new Uint8Array(b), opts, channel);
+  }
+
   if (typeof a !== typeof b) { return false; }
 
   var ka = objectKeys(a);

package.json

@@ -38,6 +38,7 @@
     "is-array-buffer": "^3.0.1",
     "is-date-object": "^1.0.5",
     "is-regex": "^1.1.4",
+    "is-shared-array-buffer": "^1.0.2",
     "isarray": "^2.0.5",
     "object-is": "^1.1.5",
     "object-keys": "^1.1.1",

test/cmp.js

@@ -1236,5 +1236,66 @@ test('TypedArrays', { skip: !hasTypedArrays }, function (t) {
     st.end();
   });
 
+  t.test('SharedArrayBuffers', { skip: typeof SharedArrayBuffer !== 'function' }, function (st) {
+    var buffer1 = new SharedArrayBuffer(8); // initial value of 0's
+    var buffer2 = new SharedArrayBuffer(8); // initial value of 0's
+
+    var view1 = new Int8Array(buffer1);
+    var view2 = new Int8Array(buffer2);
+
+    st.deepEqualTest(
+      view1,
+      view2,
+      'Int8Arrays of similar SharedArrayBuffers',
+      true,
+      true
+    );
+
+    st.deepEqualTest(
+      buffer1,
+      buffer2,
+      'similar SharedArrayBuffers',
+      true,
+      true
+    );
+
+    for (var i = 0; i < view1.byteLength; i += 1) {
+      view1[i] = 9; // change all values to 9's
+    }
+
+    st.deepEqualTest(
+      view1,
+      view2,
+      'Int8Arrays of different SharedArrayBuffers',
+      false,
+      false
+    );
+
+    st.deepEqualTest(
+      buffer1,
+      buffer2,
+      'different SharedArrayBuffers',
+      false,
+      false
+    );
+
+    t.test('lies about byteLength', { skip: !('byteLength' in SharedArrayBuffer.prototype) }, function (s2t) {
+      var empty4 = new SharedArrayBuffer(4);
+      var empty6 = new SharedArrayBuffer(6);
+      Object.defineProperty(empty6, 'byteLength', { value: 4 });
+
+      s2t.deepEqualTest(
+        empty4,
+        empty6,
+        'different-length SharedArrayBuffers, one lying',
+        false,
+        false
+      );
+      s2t.end();
+    });
+
+    st.end();
+  });
+
   t.end();
 });