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[#]: collector: (lujun9972)
[#]: translator: (laingke)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
[#]: subject: (Why everyone is talking about WebAssembly)
[#]: via: (https://opensource.com/article/20/1/webassembly)
[#]: author: (Mike Bursell https://opensource.com/users/mikecamel)
Why everyone is talking about WebAssembly
======
Learn more about the newest way to run any code in a web browser.
![Digital creative of a browser on the internet][1]
If you haven’t heard of [WebAssembly][2] yet, then you will soon. It’s one of the industry’s best-kept secrets, but it’s everywhere. It’s supported by all the major browsers, and it’s coming to the server-side, too. It’s fast. It’s being used for gaming. It’s an open World Wide Web Consortium (W3C), the main international standards organization for the web, standard. It’s platform-neutral and can run on Linux, Macs, and Windows.
"Wow," you may be saying, "this sounds like something I should learn to code in!" You’d be right, but you’d be wrong too; you don’t code in WebAssembly. Let’s take some time to learn about the technology that’s often fondly abbreviated to "Wasm."
### Where did it come from?
Going back about ten years, there was a growing recognition that the widely-used JavaScript wasn’t fast enough for many purposes. JavaScript was undoubtedly successful and convenient. It ran in any browser and enabled the type of dynamic web pages that we take for granted today. But it was a high-level language and wasn’t designed with compute-intensive workloads in mind.
However, although engineers responsible for the leading web browsers were generally in agreement about the performance problem, they weren’t aligned on what to do about it. Two camps emerged. Google began its Native Client project and, later, its Portable Native Client variation, to focus on allowing games and other software written in C/C++ to run in a secure compartment within Chrome. Mozilla, meanwhile, won the backing of Microsoft for asm.js, an approach that updated the browser so it can run a low-level subset of JavaScript instructions very quickly (another project enabled the conversion of C/C++ code into these instructions).
With neither camp gaining widespread adoption, the various parties agreed to join forces in 2015 around a new standard called WebAssembly that built on the basic approach taken by asm.js. [As CNET’s Stephen Shankland wrote at the time][3], "On today’s Web, the browser’s JavaScript translates those instructions into machine code. But with WebAssembly, the programmer does a lot of the work earlier in the process, producing a program that’s in between the two states. That frees the browser from a lot of the hard work of creating the machine code, but it also fulfills the promise of the Web—that software will run on any device with a browser regardless of the underlying hardware details."
In 2017, Mozilla declared it to be a minimum viable product and brought it out of preview. All the main browsers had adopted it by the end of that year. [In December 2019][4], the WebAssembly Working Group published the three WebAssembly specifications as W3C recommendations.
WebAssembly defines a portable binary code format for executable programs, a corresponding textual assembly language, and interfaces for facilitating interactions between such programs and their host environment. WebAssembly code runs within a low-level virtual machine that mimics the functionality of the many microprocessors upon which it can be run. Either through Just-In-Time (JIT) compilation or interpretation, the WebAssembly engine can perform at nearly the speed of code compiled for a native platform.
### Why the interest now?
Certainly, some of the recent interest in WebAssembly stems from that initial desire to run more compute-intensive code in browsers. Laptop users, in particular, are spending more and more of their time in a browser (or, in the case of Chromebooks, essentially all their time). This trend has created an urgency around removing barriers to running a broad range of applications within a browser. And one of those barriers is often some aspect of performance, which is what WebAssembly and its predecessors were originally conceived to address.
However, WebAssembly isn’t just for browsers. In 2019, [Mozilla announced a project called WASI][5] (WebAssembly System Interface) to standardize how WebAssembly code interacts with operating systems outside of a browser context. With the combination of browser support for WebAssembly and WASI, compiled binaries will be able to run both within and without browsers, across different devices and operating systems, at near-native speeds.
WebAssembly’s low overhead immediately makes it practical for use beyond browsers, but that’s arguably table stakes; there are obviously other ways to run applications that don’t introduce performance bottlenecks. Why use WebAssembly, specifically?
One important reason is its portability. Widely used compiled languages like C++ and Rust are probably the ones most associated with WebAssembly today. However, [a wide range of other languages][6] compile to or have their virtual machines in WebAssembly. Furthermore, while WebAssembly [assumes certain prerequisites][7] for its execution environments, it is designed to execute efficiently on a variety of operating systems and instruction set architectures. WebAssembly code can, therefore, be written using a wide range of languages and run on a wide range of operating systems and processor types.
Another WebAssembly advantage stems from the fact that code runs within a virtual machine. As a result, each WebAssembly module executes within a sandboxed environment, separated from the host runtime using fault isolation techniques. This implies, among other things, that applications execute in isolation from the rest of their host environment and can’t escape the sandbox without going through appropriate APIs.
### WebAssembly in action
What does all this mean in practice?
One example of WebAssembly in action is [Enarx][8].
Enarx is a project that provides hardware independence for securing applications using Trusted Execution Environments (TEE). Enarx lets you securely deliver an application compiled into WebAssembly all the way into a cloud provider and execute it remotely. As Red Hat security engineer [Nathaniel McCallum puts it][9], "The way that we do this is, we take your application as inputs, and we perform an attestation process with the remote hardware. We validate that the remote hardware is, in fact, the hardware that it claims to be, using cryptographic techniques. The end result of that is not only an increased level of trust in the hardware that we’re speaking to; it’s also a session key, which we can then use to deliver encrypted code and data into this environment that we have just asked for cryptographic attestation on."
Another example is OPA, the Open Policy Agent, which [announced][10] in November 2019 that you could [compile][11] their policy definition language, Rego, into WebAssembly. Rego lets you write logic to search and combine JSON/YAML data from different sources to ask questions like, "Is this API allowed?"
OPA has been used to policy-enable software including, but not limited to, Kubernetes. Simplifying policy using tools like OPA [is considered an important step][12] for properly securing Kubernetes deployments across a variety of different environments. WebAssembly’s portability and built-in security features are a good match for these tools.
Our last example is [Unity][13]. Remember, we mentioned at the beginning of the article that WebAssembly is used for gaming? Well, Unity, the cross-platform game engine, was an early adopter of WebAssembly, providing the first demo of Wasm running in browsers, and, since August 2018, [has used WebAssembly][14] as the output target for the Unity WebGL build target.
These are just a few of the ways WebAssembly has already begun to make an impact. Find out more and keep up to date with all things Wasm at <https://webassembly.org/>
--------------------------------------------------------------------------------
via: https://opensource.com/article/20/1/webassembly
作者：[Mike Bursell][a]
选题：[lujun9972][b]
译者：[laingke](https://github.com/laingke)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]: https://opensource.com/users/mikecamel
[b]: https://github.com/lujun9972
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/browser_web_internet_website.png?itok=g5B_Bw62 (Digital creative of a browser on the internet)
[2]: https://opensource.com/article/19/8/webassembly-speed-code-reuse
[3]: https://www.cnet.com/news/the-secret-alliance-that-could-give-the-web-a-massive-speed-boost/
[4]: https://www.w3.org/blog/news/archives/8123
[5]: https://hacks.mozilla.org/2019/03/standardizing-wasi-a-webassembly-system-interface/
[6]: https://github.com/appcypher/awesome-wasm-langs
[7]: https://webassembly.org/docs/portability/
[8]: https://enarx.io
[9]: https://enterprisersproject.com/article/2019/9/application-security-4-facts-confidential-computing-consortium
[10]: https://blog.openpolicyagent.org/tagged/webassembly
[11]: https://github.com/open-policy-agent/opa/tree/master/wasm
[12]: https://enterprisersproject.com/article/2019/11/kubernetes-reality-check-3-takeaways-kubecon
[13]: https://opensource.com/article/20/1/www.unity.com
[14]: https://blogs.unity3d.com/2018/08/15/webassembly-is-here/

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[#]: collector: (lujun9972)
[#]: translator: (laingke)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
[#]: subject: (Why everyone is talking about WebAssembly)
[#]: via: (https://opensource.com/article/20/1/webassembly)
[#]: author: (Mike Bursell https://opensource.com/users/mikecamel)
为什么每个人都在谈论 WebAssembly
======
了解有关在 Web 浏览器中运行任何代码的最新方法的更多信息。
![Digital creative of a browser on the internet][1]
如果你还没有听说过 [WebAssembly][2]，那么你很快就会知道。这是业界保存最完好的秘密之一，但无处不在。所有主流的浏览器都支持它，并且它也将在服务器端使用。它很快。它被用于游戏。这是一个开放的万维网联盟（W3C），主要的国际网络标准组织。它与平台无关，可以在 Linux，Mac 和 Windows 上运行。
你可能会说：“哇，这听起来像是我应该学习编程的东西！” 你可能是对的，但你也可能是错的。你不需要用 WebAssembly 编码。让我们花一些时间来学习通常被缩写为“Wasm”的技术。
### 它从哪里来？
大约十年前，人们越来越认识到，广泛使用的 JavaScript 不够快速，无法满足许多目的。JavaScript 无疑是成功和方便的。它可以在任何浏览器中运行，并启用了今天我们认为理所当然的动态网页类型。但这是一种高级语言，在设计时并没有考虑到计算密集型工作负载。
然而，尽管负责主流 web 浏览器的工程师们对性能问题的看法大体一致，但他们对如何解决这个问题却意见不一。两个阵营出现。谷歌开始了它的<ruby>原生客户端<rt>Native Client</rt></ruby>项目，后来又推出了<ruby>可移植原生客户端<rt>Portable Native Client</rt></ruby>变体，着重于允许用 C/C++ 编写的游戏和其它软件在 Chrome 的一个安全隔间中运行。与此同时，Mozilla 赢得了微软对 asm.js 的支持。该方法更新了浏览器，因此它可以非常快速地运行底层的 JavaScript 指令子集（另一个项目使 C/C++ 代码可以转换为这些指令）。
在这两个阵营都没有得到广泛采用的情况下，各方在 2015 年同意围绕一种称为 WebAssembly 的新标准，以 asm.js 所采用的基本方法为基础，共同努力。[如 CNET 的 Stephen Shankland 当时所写][3]，“在当今的 Web 上，浏览器的 JavaScript 将这些指令转换为机器代码。但是，通过 WebAssembly，程序员可以在此过程的早期阶段完成很多工作，从而生成介于两种状态之间的程序。这使浏览器摆脱了创建机器代码的繁琐工作，但也实现了 Web 的承诺——该软件将在具有浏览器的任何设备上运行，而无需考虑基础硬件的详细信息。”
在 2017 年，Mozilla 宣布了它的最小可行的产品，并使其脱离预览版。到该年年底，所有主流的浏览器都采用了它。[2019 年 12 月][4]，WebAssembly 工作组发布了三个 W3C 推荐的 WebAssembly 规范。
WebAssembly 为可执行程序、相应的文本汇编语言以及用于促进此类程序与其主机环境之间的交互的接口定义了一种可移植的二进制代码格式。WebAssembly 代码在低级虚拟机中运行，该虚拟机模仿可以在其上运行的许多微处理器的功能。通过即时（JIT）编译或解释，WebAssembly 引擎可以以近乎原生平台编译代码的速度执行。
### 为什么现在感兴趣？
当然，最近对 WebAssembly 感兴趣的部分原因是最初希望在浏览器中运行更多计算密集型代码。尤其是笔记本电脑用户，越来越多的时间都花在浏览器上（或者，对于 Chromebook 用户来说，基本上是所有时间）。这种趋势已经迫切需要消除在浏览器中运行各种应用程序的障碍。这些障碍之一通常是性能的某些方面，这正是 WebAssembly 及其前身最初旨在解决的问题。
但是，WebAssembly 并不仅仅适用于浏览器。在 2019 年，[Mozilla 宣布了一个名为 WASI][5]（WebAssembly 系统接口）的项目，以标准化 WebAssembly 代码如何与浏览器上下文之外的操作系统进行交互。通过将浏览器对 WebAssembly 和 WASI 的支持结合在一起，编译后的二进制文件将能够以接近本机的速度跨不同的设备和操作系统在浏览器内外运行。
WebAssembly 的低开销立即使它可以在浏览器之外使用，但这无疑是赌注；显然，还有其它不会引入性能瓶颈的运行应用程序的方法。为什么要专门使用 WebAssembly？
一个重要的原因是它的可移植性。如今，像 C++ 和 Rust 这样的广泛使用的编译语言可能是与 WebAssembly 关联最紧密的语言。但是，[各种各样的其他语言][6] 可以在 WebAssembly 中将其虚拟机编译或拥有它们的虚拟机。此外，尽管 WebAssembly 为其执行环境[假定了某些先决条件][7]，但它被设计为在各种操作系统和指令集体系结构上有效执行。因此，WebAssembly 代码可以使用多种语言编写，并可以在多种操作系统和处理器类型上运行。
另一个 WebAssembly 优势源于这样一个事实：代码在虚拟机中运行。因此，每个 WebAssembly 模块都在沙盒环境中执行，并使用故障隔离技术将其与主机运行时分开。这意味着，对于其它部分而言，应用程序独立于其主机环境的其余部分执行，如果不调用适当的 API，就无法摆脱沙箱。
### WebAssembly 在行动
这一切在实践中意味着什么？
WebAssembly 的一个例子是 [Enarx][8]。
Enarx 是一个提供硬件独立性的项目，可使用<ruby>受信任的执行环境<rt>Trusted Execution Environments(TEE)</rt></ruby>保护应用程序的安全。Enarx 使你可以安全地将编译为 WebAssembly 的应用程序始终交付到云提供程序中，并远程执行它。正如 Red Hat 安全工程师 [Nathaniel McCallum 指出的那样][9]：“我们这样做的方式是，我们将你的应用程序作为输入，并使用远程硬件执行认证过程。我们使用加密技术验证了远程硬件实际上是它声称的硬件。最终的结果不仅是我们对硬件的信任度提高了；它也是一个会话密钥，我们可以使用它将加密的代码和数据传递到我们刚刚要求加密验证的环境中。”
另一个例子是 OPA，开放政策代理，它在 2019 年 11 月[发布][10]，你可以[编译][11]他们的政策定义语言，Rego，为 WebAssembly。
Rego 允许你编写逻辑来搜索和组合来自不同来源的 JSON/YAML 数据，以询问诸如“是否允许使用此 API？”之类的问题。
OPA 已被用于支持策略的软件，包括但不限于 Kubernetes。使用 OPA 之类的工具简化策略[被认为是在各种不同环境中正确保护 Kubernetes 部署的重要步骤][12]。WebAssembly 的可移植性和内置的安全功能非常适合这些工具。
我们的最后一个例子是 [Unity][13]。还记得我们在文章开头提到过 WebAssembly 用于游戏吗？好吧，跨平台游戏引擎 Unity 是 WebAssembly 的较早采用者，它提供了在浏览器中运行的 Wasm 的首个演示，并且自 2018 年 8 月以来，[已使用 WebAssembly][14]作为 Unity WebGL 构建目标的输出目标。
这些只是 WebAssembly 已经开始产生影响的几种方式。你可以在 <https://webassembly.org/> 上查找更多信息并了解 Wasm 的所有最新信息。
--------------------------------------------------------------------------------
via: https://opensource.com/article/20/1/webassembly
作者：[Mike Bursell][a]
选题：[lujun9972][b]
译者：[laingke](https://github.com/laingke)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]: https://opensource.com/users/mikecamel
[b]: https://github.com/lujun9972
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/browser_web_internet_website.png?itok=g5B_Bw62 (Digital creative of a browser on the internet)
[2]: https://opensource.com/article/19/8/webassembly-speed-code-reuse
[3]: https://www.cnet.com/news/the-secret-alliance-that-could-give-the-web-a-massive-speed-boost/
[4]: https://www.w3.org/blog/news/archives/8123
[5]: https://hacks.mozilla.org/2019/03/standardizing-wasi-a-webassembly-system-interface/
[6]: https://github.com/appcypher/awesome-wasm-langs
[7]: https://webassembly.org/docs/portability/
[8]: https://enarx.io
[9]: https://enterprisersproject.com/article/2019/9/application-security-4-facts-confidential-computing-consortium
[10]: https://blog.openpolicyagent.org/tagged/webassembly
[11]: https://github.com/open-policy-agent/opa/tree/master/wasm
[12]: https://enterprisersproject.com/article/2019/11/kubernetes-reality-check-3-takeaways-kubecon
[13]: https://opensource.com/article/20/1/www.unity.com
[14]: https://blogs.unity3d.com/2018/08/15/webassembly-is-here/