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author | Torne (Richard Coles) <torne@google.com> | 2014-02-21 12:16:55 +0000 |
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committer | Torne (Richard Coles) <torne@google.com> | 2014-02-21 12:16:55 +0000 |
commit | 5d1f7b1de12d16ceb2c938c56701a3e8bfa558f7 (patch) | |
tree | 5d4ae202b870bd86673f596f0d424bc4b3e55ebe /native_client_sdk/doc_generated/overview.html | |
parent | e862bac9c33104a29d98631d62668ae7b6676510 (diff) | |
download | chromium_org-5d1f7b1de12d16ceb2c938c56701a3e8bfa558f7.tar.gz |
Merge from Chromium at DEPS revision 251904
This commit was generated by merge_to_master.py.
Change-Id: I1f9543259d7d2a57d81aa41a1b84f85837439d21
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diff --git a/native_client_sdk/doc_generated/overview.html b/native_client_sdk/doc_generated/overview.html new file mode 100644 index 0000000000..4687419138 --- /dev/null +++ b/native_client_sdk/doc_generated/overview.html @@ -0,0 +1,240 @@ +{{+bindTo:partials.standard_nacl_article}} + +<section id="technical-overview"> +<span id="overview"></span><h1 id="technical-overview"><span id="overview"></span>Technical Overview</h1> +<div class="contents local" id="contents" style="display: none"> +<ul class="small-gap"> +<li><a class="reference internal" href="#introduction" id="id2">Introduction</a></li> +<li><a class="reference internal" href="#why-use-native-client" id="id3">Why use Native Client?</a></li> +<li><a class="reference internal" href="#common-use-cases" id="id4">Common use cases</a></li> +<li><p class="first"><a class="reference internal" href="#how-native-client-works" id="id5">How Native Client works</a></p> +<ul class="small-gap"> +<li><a class="reference internal" href="#security" id="id6">Security</a></li> +<li><a class="reference internal" href="#portability" id="id7">Portability</a></li> +<li><a class="reference internal" href="#toolchains" id="id8">Toolchains</a></li> +</ul> +</li> +<li><p class="first"><a class="reference internal" href="#native-client-in-a-web-application" id="id9">Native Client in a web application</a></p> +<ul class="small-gap"> +<li><a class="reference internal" href="#pepper-plugin-api" id="id10">Pepper Plugin API</a></li> +</ul> +</li> +<li><a class="reference internal" href="#versioning" id="id11">Versioning</a></li> +<li><a class="reference internal" href="#where-to-start" id="id12">Where to start</a></li> +</ul> + +</div><section id="introduction"> +<h2 id="introduction">Introduction</h2> +<p><strong>Native Client</strong> (NaCl) is an open-source technology for running native +compiled code in the browser, with the goal of maintaining the portability +and safety that users expect from web applications. Native Client expands web +programming beyond JavaScript, enabling developers to enhance their web +applications using their preferred language. This document describes some of +the key benefits and common use cases of Native Client.</p> +<p>Google has implemented the open-source <a class="reference external" href="http://www.chromium.org/nativeclient">Native Client project</a> in the Chrome browser on Windows, Mac, +Linux, and Chrome OS. The <a class="reference internal" href="/native-client/sdk/download.html"><em>Native Client Software Development Kit (SDK)</em></a>, itself an open-source project, lets developers create web +applications that use NaCl and run in Chrome across multiple platforms.</p> +<p>A web application that uses Native Client generally consists of a combination of +JavaScript, HTML, CSS, and a NaCl module that is written in a language supported +by the SDK. The NaCl SDK currently supports C and C++; as compilers for +additional languages are developed, the SDK will be updated to support those +languages as well.</p> +<img alt="/native-client/images/web-app-with-nacl.png" src="/native-client/images/web-app-with-nacl.png" /> +</section><section id="why-use-native-client"> +<h2 id="why-use-native-client">Why use Native Client?</h2> +<p>Native Client open-source technology is designed to run compiled code +securely inside a browser at near-native speeds. Native Client puts web +applications on the same playing field as traditional (locally-run) +software—it provides the means to fully harness the client’s computational +resources for applications such as 3D games, multimedia editors, CAD modeling, +client-side data analytics, and interactive simulations. +Native Client also aims to give C and C++ (and eventually other languages) the +same level of portability and safety that JavaScript provides on the web today.</p> +<p>Here are a few of the key benefits that Native Client offers:</p> +<ul class="small-gap"> +<li><strong>Graphics, audio, and much more:</strong> Run native code modules that render 2D +and 3D graphics, play audio, respond to mouse and keyboard events, run on +multiple threads, and access memory directly—all without requiring +the user to install a plugin.</li> +<li><strong>Portability:</strong> Write your applications once and you’ll be able to run them +across operating systems (Windows, Linux, Mac, and Chrome OS) and CPU +architectures (x86 and ARM).</li> +<li><strong>Easy migration path to the web:</strong> Many developers and companies have years +of work invested in existing desktop applications. Native Client makes the +transition from the desktop to a web application significantly easier because +it supports C and C++.</li> +<li><strong>Security:</strong> Native Client uses a double sandbox model designed to protect +the user’s system from malicious or buggy applications. This model offers the +safety of traditional web applications without sacrificing performance and +without requiring users to install a plugin.</li> +<li><strong>Performance:</strong> Native Client allows web applications to run at speeds +comparable to desktop applications (within 5-15% of native speed). +Native Client also allows applications to harness all available CPU cores via +a threading API; this enables demanding applications such as console-quality +games to run inside the browser.</li> +</ul> +</section><section id="common-use-cases"> +<h2 id="common-use-cases">Common use cases</h2> +<p>Typical use cases for Native Client include the following:</p> +<ul class="small-gap"> +<li><strong>Existing software components:</strong> With support for C and C++, Native +Client enables you to reuse existing software modules in +web applications—you don’t need to rewrite and debug code +that’s already proven to work well.</li> +<li><strong>Legacy desktop applications:</strong> Native Client provides a smooth migration +path from desktop applications to the web. You can port and recompile existing +code for the computation engine of your application directly to Native Client, +and need repurpose only the user interface and event handling portions to the +new browser platform. Native Client allows you to embed existing functionality +directly into the browser. At the same time, your application can take +advantage of things the browser does well: handling user interaction and +processing events, based on the latest developments in HTML5.</li> +<li><strong>Heavy computation in enterprise applications:</strong> Native Client can handle the +number crunching required by large-scale enterprise applications. To ensure +protection of user data, Native Client enables you to build complex +cryptographic algorithms directly into the browser so that unencrypted data +never goes out over the network.</li> +<li><strong>Multimedia applications:</strong> Codecs for processing sounds, images, and movies +can be added to the browser in a Native Client module.</li> +<li><strong>Games:</strong> Native Client lets web applications run at close to native +speed, reuse existing multithreaded/multicore C/C++ code bases, and +access low-latency audio, networking APIs, and OpenGL ES with programmable +shaders. Native Client is a natural fit for running a physics engine or +artificial intelligence module that powers a sophisticated web game. +Native Client also enables applications to run unchanged across +many platforms.</li> +<li><strong>Any application that requires acceleration</strong>: Native Client fits seamlessly +into web applications—it’s up to you to decide to what extent to use it. +Use of Native Client covers the full spectrum from complete applications to +small optimized routines that accelerate vital parts of web apps.</li> +</ul> +</section><section id="how-native-client-works"> +<span id="link-how-nacl-works"></span><h2 id="how-native-client-works"><span id="link-how-nacl-works"></span>How Native Client works</h2> +<p>Native Client is an umbrella name for a set of interrelated software components +that work together to provide a way to develop C/C++ applications and run them +securely on the web.</p> +<p>At a high level, Native Client consists of:</p> +<ul class="small-gap"> +<li><strong>Toolchains</strong>: collections of development tools (compilers, linkers, etc.) +that transform C/C++ code to Native Client modules.</li> +<li><strong>Runtime components</strong>: components embedded in the browser or other +host platforms that allow execution of Native Client modules +securely and efficiently.</li> +</ul> +<p>The following diagram shows how these components interact:</p> +<img alt="/native-client/images/nacl-pnacl-component-diagram.png" src="/native-client/images/nacl-pnacl-component-diagram.png" /> +<p>The left side of the diagram shows how to use Portable Native Client +(PNaCl, pronounced “pinnacle”). Developers use the PNaCl toolchain +to produce a single, portable (<strong>pexe</strong>) module. At runtime, a translator +built into the browser translates the pexe into native code for the +relevant client architecture.</p> +<p>The right side of the diagram shows how to use traditional (non-portable) +Native Client. Developers use a nacl-gcc based toolchain to produce multiple +architecture-dependent (<strong>nexe</strong>) modules, which are packaged into an +application. At runtime, the browser decides which nexe to load based +on the architecture of the client machine.</p> +<section id="security"> +<h3 id="security">Security</h3> +<p>Since Native Client permits the execution of native code on client machines, +special security measures have to be implemented:</p> +<ul class="small-gap"> +<li>The NaCl sandbox ensures that code accesses system resources only through +safe, whitelisted APIs, and operates within its limits without attempting to +interfere with other code running either within the browser or outside it.</li> +<li>The NaCl validator statically analyzes code prior to running it +to make sure it only uses code and data patterns that are permitted and safe.</li> +</ul> +<p>The above security measures are in addition to the existing sandbox in the +Chrome browser—the Native Client module always executes in a process with +restricted permissions. The only interaction between this process and the +outside world is through sanctioned browser interfaces. Because of the +combination of the NaCl sandbox and the Chrome sandbox, we say that +Native Client employs a double sandbox design.</p> +</section><section id="portability"> +<h3 id="portability">Portability</h3> +<p>Portable Native Client (PNaCl, prounounced “pinnacle”) employs state-of-the-art +compiler technology to compile C/C++ source code to a portable bitcode +executable (<strong>pexe</strong>). PNaCl bitcode is an OS- and architecture-independent +format that can be freely distributed on the web and <a class="reference internal" href="#link-nacl-in-web-apps"><em>embedded in web +applications</em></a>.</p> +<p>The PNaCl translator is a component embedded in the Chrome browser; its task is +to run pexe modules. Internally, the translator compiles a pexe to a nexe +(a native executable for the client platform’s architecture), and then executes +the nexe within the Native Client sandbox as described above. It also uses +intelligent caching to avoid re-compiling the pexe if it was previously compiled +on the client’s browser.</p> +<p>Native Client also supports the execution of nexe modules directly in the +browser. However, since nexes contain architecture-specific machine code, +they are not allowed to be distributed on the open web—they can only be +used as part of applications and extensions that are installed from the +Chrome Web Store.</p> +<p>For more details on the difference between NaCl and PNaCl, see +<a class="reference internal" href="/native-client/nacl-and-pnacl.html"><em>NaCl and PNaCl</em></a>.</p> +</section><section id="toolchains"> +<span id="id1"></span><h3 id="toolchains"><span id="id1"></span>Toolchains</h3> +<p>A toolchain is a set of tools used to create an application from a set of +source files. In the case of Native Client, a toolchain consists of a compiler, +linker, assembler and other tools that are used to convert an +application written in C/C++ into a module that is loadable by the browser.</p> +<p>The Native Client SDK provides two toolchains:</p> +<ul class="small-gap"> +<li>a <strong>PNaCl toolchain</strong> for generating portable NaCl modules (pexe files)</li> +<li>a <strong>gcc-based toolchain (nacl-gcc)</strong> for generating non-portable NaCl modules +(nexe files)</li> +</ul> +<p>The PNaCl toolchain is recommended for most applications. The nacl-gcc +toolchain should only be used for applications that will not be distributed +on the open web.</p> +</section></section><section id="native-client-in-a-web-application"> +<span id="link-nacl-in-web-apps"></span><h2 id="native-client-in-a-web-application"><span id="link-nacl-in-web-apps"></span>Native Client in a web application</h2> +<p id="application-files">A Native Client application consists of a set of files:</p> +<ul class="small-gap"> +<li><strong>HTML</strong>, <strong>CSS</strong>, and <strong>JavaScript</strong> files, as in any modern web +application. The JavaScript code is responsible for communicating with the +NaCl module.</li> +<li>A <strong>pexe</strong> (portable NaCl) file. This module uses the <a class="reference internal" href="#link-pepper"><em>Pepper</em></a> API, which provides the bridge to JavaScript and +browser resources.</li> +<li>A Native Client <strong>manifest</strong> file that specifies the pexe to load, along with +some loading options. This manifest file is embedded into the HTML page +through an <code><embed></code> tag, as shown in the figure below.</li> +</ul> +<img alt="/native-client/images/nacl-in-a-web-app.png" src="/native-client/images/nacl-in-a-web-app.png" /> +<p>For more details, see <a class="reference internal" href="/native-client/devguide/coding/application-structure.html"><em>Application Structure</em></a>.</p> +<section id="pepper-plugin-api"> +<span id="link-pepper"></span><h3 id="pepper-plugin-api"><span id="link-pepper"></span>Pepper Plugin API</h3> +<p>The Pepper Plugin API (PPAPI), called <strong>Pepper</strong> for convenience, is an +open-source, cross-platform C/C++ API for web browser plugins. From the point +of view of Native Client, Pepper allows a C/C++ module to communicate with +the hosting browser and get access to system-level functions in a safe and +portable way. One of the security constraints in Native Client is that modules +cannot make any OS-level calls directly. Pepper provides analogous APIs that +modules can target instead.</p> +<p>You can use the Pepper APIs to gain access to the full array of browser +capabilities, including:</p> +<ul class="small-gap"> +<li><a class="reference internal" href="/native-client/devguide/coding/message-system.html"><em>Talking to the JavaScript code in your application</em></a> from the C++ code in your NaCl module.</li> +<li><a class="reference internal" href="/native-client/devguide/coding/file-io.html"><em>Doing file I/O</em></a>.</li> +<li><a class="reference internal" href="/native-client/devguide/coding/audio.html"><em>Playing audio</em></a>.</li> +<li><a class="reference internal" href="/native-client/devguide/coding/3D-graphics.html"><em>Rendering 3D graphics</em></a>.</li> +</ul> +<p>Pepper includes both a C API and a C++ API. The C++ API is a set of bindings +written on top of the C API. For additional information about Pepper, see +<a class="reference external" href="http://code.google.com/p/ppapi/wiki/Concepts">Pepper Concepts</a>.</p> +</section></section><section id="versioning"> +<h2 id="versioning">Versioning</h2> +<p>Chrome is released on a six week cycle, and developer versions of Chrome are +pushed to the public beta channel three weeks before each release. As with any +software, each release of Chrome may include changes to Native Client and the +Pepper interfaces that may require modification to existing applications. +However, modules compiled for one version of Pepper/Chrome should work with +subsequent versions of Pepper/Chrome. The SDK includes multiple <a class="reference external" href="https://developers.google.com/native-client/version">versions</a> of the Pepper APIs to +help developers make adjustments to API changes and take advantage of new +features.</p> +</section><section id="where-to-start"> +<h2 id="where-to-start">Where to start</h2> +<p>The <a class="reference internal" href="/native-client/quick-start.html"><em>Quick Start</em></a> document provides links to downloads and +documentation that should help you get started with developing and distributing +Native Client applications.</p> +</section></section> + +{{/partials.standard_nacl_article}} |