在此页

• 描述
• 构造函数
• 实例特性
• 实例方法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

SharedArrayBuffer object is used to represent a generic, fixed-length raw binary data buffer, similar to the ArrayBuffer object, but in a way that they can be used to create views on shared memory. Unlike an ArrayBuffer ， SharedArrayBuffer cannot become detached.

描述

Allocating and sharing memory

To share memory using SharedArrayBuffer objects from one agent in the cluster to another (an agent is either the web page’s main program or one of its web workers), postMessage and structured cloning 被使用。

The structured clone algorithm accepts SharedArrayBuffers and TypedArrays mapped onto SharedArrayBuffers . In both cases, the SharedArrayBuffer object is transmitted to the receiver resulting in a new, private SharedArrayBuffer object in the receiving agent (just as for ArrayBuffer ). However, the shared data block referenced by the two SharedArrayBuffer objects is the same data block, and a side effect to the block in one agent will eventually become visible in the other agent.

var sab = new SharedArrayBuffer(1024);
worker.postMessage(sab);
					

Updating and synchronizing shared memory with atomic operations

Shared memory can be created and updated simultaneously in workers or the main thread. Depending on the system (the CPU, the OS, the Browser) it can take a while until the change is propagated to all contexts. To synchronize, atomic operations are needed.

APIs which use SharedArrayBuffer objects

• WebGLRenderingContext.bufferData()
• WebGLRenderingContext.bufferSubData()
• WebGL2RenderingContext.getBufferSubData()

Security requirements

Shared memory and high-resolution timers were effectively disabled at the start of 2018 in light of Spectre . In 2020, a new, secure approach has been standardized to re-enable shared memory. With a few security measures, postMessage() will no longer throw for SharedArrayBuffer objects and shared memory across threads will be available:

As a baseline requirement, your document needs to be in a secure context .

For top-level documents, two headers will need to be set to cross-origin isolate your site:

• Cross-Origin-Opener-Policy with same-origin as value (protects your origin from attackers)
• Cross-Origin-Embedder-Policy with require-corp as value (protects victims from your origin)

Cross-Origin-Opener-Policy: same-origin
Cross-Origin-Embedder-Policy: require-corp
					

To check if cross origin isolation has been successful, you can test against the crossOriginIsolated property available to window and worker contexts:

if (crossOriginIsolated) {
  // Post SharedArrayBuffer
} else {
  // Do something else
}
					

另请参阅 Planned changes to shared memory which is starting to roll out to browsers (Firefox 79, for example.)

Always use the new operator to create a SharedArrayBuffer

SharedArrayBuffer constructors are required to be constructed with a new operator. Calling a SharedArrayBuffer constructor as a function without new will throw a TypeError .

var sab = SharedArrayBuffer(1024);
// TypeError: calling a builtin SharedArrayBuffer constructor
// without new is forbidden
					

var sab = new SharedArrayBuffer(1024);
					

构造函数

SharedArrayBuffer()

创建新的 SharedArrayBuffer 对象。

实例特性

SharedArrayBuffer.prototype.byteLength

The size, in bytes, of the array. This is established when the array is constructed and cannot be changed. Read only.

实例方法

SharedArrayBuffer.prototype.slice(begin, end)

返回新的 SharedArrayBuffer whose contents are a copy of this SharedArrayBuffer 's bytes from begin , inclusive, up to end , exclusive. If either begin or end is negative, it refers to an index from the end of the array, as opposed to from the beginning.

范例

Creating a new SharedArrayBuffer

var sab = new SharedArrayBuffer(1024);
					

Slicing the SharedArrayBuffer

sab.slice();    // SharedArrayBuffer { byteLength: 1024 }
sab.slice(2);   // SharedArrayBuffer { byteLength: 1022 }
sab.slice(-2);  // SharedArrayBuffer { byteLength: 2 }
sab.slice(0, 1); // SharedArrayBuffer { byteLength: 1 }
					

Using it in a WebGL buffer

const canvas = document.querySelector('canvas');
const gl = canvas.getContext('webgl');
const buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, sab, gl.STATIC_DRAW);
					

规范

规范
ECMAScript (ECMA-262) The definition of 'SharedArrayBuffer' in that specification.

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
SharedArrayBuffer	Chrome 68 68 不支持 60 — 63 Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks . This was a temporary removal while mitigations were put in place.	Edge 79 79 不支持 16 — 17 Support was removed to mitigate speculative execution side-channel attacks (Windows blog) .	Firefox 79 79 57 Disabled Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog) . Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	IE No	Opera No	Safari 10.1 — 11	WebView Android 60 — 63 不支持 60 — 63 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.	Chrome Android 60 — 63 不支持 60 — 63 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.	Firefox Android 57 Disabled 57 Disabled Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog) . Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	Opera Android No	Safari iOS 10.3 — 11	Samsung Internet Android No 不支持 No 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.	nodejs 8.10.0
SharedArrayBuffer() 构造函数	Chrome 68 68 不支持 60 — 63 Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks . This was a temporary removal while mitigations were put in place.	Edge 79 79 不支持 16 — 17 Support was removed to mitigate speculative execution side-channel attacks (Windows blog) .	Firefox 79 79 57 Disabled Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog) . Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	IE No	Opera No	Safari 10.1 — 11	WebView Android 60 — 63 不支持 60 — 63 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.	Chrome Android 60 — 63 不支持 60 — 63 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.	Firefox Android 57 Disabled 57 Disabled Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog) . Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	Opera Android No	Safari iOS 10.3 — 11	Samsung Internet Android No 不支持 No 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.	nodejs 8.10.0
byteLength	Chrome 68 68 不支持 60 — 63 Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks . This was a temporary removal while mitigations were put in place.	Edge 79 79 不支持 16 — 17 Support was removed to mitigate speculative execution side-channel attacks (Windows blog) .	Firefox 79 79 57 Disabled Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog) . Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	IE No	Opera No	Safari 10.1 — 11	WebView Android 60 — 63 不支持 60 — 63 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.	Chrome Android 60 — 63 不支持 60 — 63 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.	Firefox Android 57 Disabled 57 Disabled Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog) . Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	Opera Android No	Safari iOS 10.3 — 11	Samsung Internet Android No 不支持 No 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.	nodejs 8.10.0
slice	Chrome 68 68 不支持 60 — 63 Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks . This was a temporary removal while mitigations were put in place.	Edge 79 79 不支持 16 — 17 Support was removed to mitigate speculative execution side-channel attacks (Windows blog) .	Firefox 79 79 57 Disabled Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog) . Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	IE No	Opera No	Safari 10.1 — 11	WebView Android 60 — 63 不支持 60 — 63 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.	Chrome Android 60 — 63 不支持 60 — 63 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.	Firefox Android 57 Disabled 57 Disabled Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog) . Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	Opera Android No	Safari iOS 10.3 — 11	Samsung Internet Android No 不支持 No 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.	nodejs 8.10.0

图例

完整支持

完整支持

不支持

不支持

见实现注意事项。

用户必须明确启用此特征。

用户必须明确启用此特征。

另请参阅

• Atomics
• ArrayBuffer
• JavaScript 类型数组
• Web 工作者
• parlib-simple – a simple library providing synchronization and work distribution abstractions.
• Shared Memory – a brief tutorial

• A Taste of JavaScript’s New Parallel Primitives – Mozilla Hacks

元数据

• 最后修改： Jul 23, 2020

相关话题

1. 标准内置对象
2. SharedArrayBuffer
3. 特性
   1. SharedArrayBuffer.prototype.byteLength
4. 方法
   1. SharedArrayBuffer.prototype.slice()
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
9. Object
10. 特性
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
11. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()