The static Atomics
.xor()
method computes a bitwise XOR with a given value at a given position in the array, and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.
Atomics.xor(typedArray, index, value)
typedArray
Int8Array
, Uint8Array
, Int16Array
, Uint16Array
, Int32Array
, or Uint32Array
.index
typedArray
to compute the bitwise XOR.value
The old value at the given position (typedArray[index]
).
TypeError
, if typedArray
is not one of the allowed integer types.TypeError
, if typedArray
is not a shared typed array type.RangeError
, if index
is out of bounds in the typedArray
.The bitwise XOR operation yields 1, if a
and b
are different. The truth table for the XOR operation is:
a | b | a ^ b |
---|---|---|
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 0 |
For example, a bitwise XOR of 5 & 1
results in 0100
which is 4 in decimal.
5 0101 1 0001 ---- 4 0100
var sab = new SharedArrayBuffer(1024); var ta = new Uint8Array(sab); ta[0] = 5; Atomics.xor(ta, 0, 1); // returns 5, the old value Atomics.load(ta, 0); // 4
Specification | Status | Comment |
---|---|---|
ECMAScript Latest Draft (ECMA-262) The definition of 'Atomics.xor' in that specification. | Draft | Initial definition in ES2017. |
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 601 | No2 |
55 — 57 46 — 555 |
No | No | 10.1 —? |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | Opera Android | iOS Safari | Samsung Internet |
---|---|---|---|---|---|---|---|
Basic support | 601 | 601 | ? |
55 — 57 46 — 555 |
No | No | ? |
1. Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.
2. Support was removed to mitigate speculative execution side-channel attacks (Windows blog).
3. Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
4. From version 57: this feature is behind the javascript.options.shared_memory
preference (needs to be set to true
). To change preferences in Firefox, visit about:config.
5. From version 46 until version 55 (exclusive): this feature is behind the javascript.options.shared_memory
preference (needs to be set to true
). To change preferences in Firefox, visit about:config.
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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics/xor