亚马逊Alexa上的视频教程_JavaScript_下载.zip

# buffer [![travis][travis-image]][travis-url] [![npm][npm-image]][npm-url] [![downloads][downloads-image]][npm-url] #### The buffer module from [node.js](https://nodejs.org/), for the browser. [![saucelabs][saucelabs-image]][saucelabs-url] [travis-image]: https://img.shields.io/travis/feross/buffer/master.svg [travis-url]: https://travis-ci.org/feross/buffer [npm-image]: https://img.shields.io/npm/v/buffer.svg [npm-url]: https://npmjs.org/package/buffer [downloads-image]: https://img.shields.io/npm/dm/buffer.svg [saucelabs-image]: https://saucelabs.com/browser-matrix/buffer.svg [saucelabs-url]: https://saucelabs.com/u/buffer With [browserify](http://browserify.org), simply `require('buffer')` or use the `Buffer` global and you will get this module. The goal is to provide an API that is 100% identical to [node's Buffer API](https://nodejs.org/api/buffer.html). Read the [official docs](https://nodejs.org/api/buffer.html) for the full list of properties, instance methods, and class methods that are supported. ## features - Manipulate binary data like a boss, in all browsers -- even IE6! - Super fast. Backed by Typed Arrays (`Uint8Array`/`ArrayBuffer`, not `Object`) - Extremely small bundle size (**5.04KB minified + gzipped**, 35.5KB with comments) - Excellent browser support (IE 6+, Chrome 4+, Firefox 3+, Safari 5.1+, Opera 11+, iOS, etc.) - Preserves Node API exactly, with one minor difference (see below) - Square-bracket `buf[4]` notation works, even in old browsers like IE6! - Does not modify any browser prototypes or put anything on `window` - Comprehensive test suite (including all buffer tests from node.js core) ## install To use this module directly (without browserify), install it: ```bash npm install buffer ``` This module was previously called **native-buffer-browserify**, but please use **buffer** from now on. A standalone bundle is available [here](https://wzrd.in/standalone/buffer), for non-browserify users. ## usage The module's API is identical to node's `Buffer` API. Read the [official docs](https://nodejs.org/api/buffer.html) for the full list of properties, instance methods, and class methods that are supported. As mentioned above, `require('buffer')` or use the `Buffer` global with [browserify](http://browserify.org) and this module will automatically be included in your bundle. Almost any npm module will work in the browser, even if it assumes that the node `Buffer` API will be available. To depend on this module explicitly (without browserify), require it like this: ```js var Buffer = require('buffer/').Buffer // note: the trailing slash is important! ``` To require this module explicitly, use `require('buffer/')` which tells the node.js module lookup algorithm (also used by browserify) to use the **npm module** named `buffer` instead of the **node.js core** module named `buffer`! ## how does it work? The Buffer constructor returns instances of `Uint8Array` that have their prototype changed to `Buffer.prototype`. Furthermore, `Buffer` is a subclass of `Uint8Array`, so the returned instances will have all the node `Buffer` methods and the `Uint8Array` methods. Square bracket notation works as expected -- it returns a single octet. The `Uint8Array` prototype remains unmodified. ## one minor difference #### In old browsers, `buf.slice()` does not modify parent buffer's memory If you only support modern browsers (specifically, those with typed array support), then this issue does not affect you. If you support super old browsers, then read on. In node, the `slice()` method returns a new `Buffer` that shares underlying memory with the original Buffer. When you modify one buffer, you modify the other. [Read more.](https://nodejs.org/api/buffer.html#buffer_buf_slice_start_end) In browsers with typed array support, this `Buffer` implementation supports this behavior. In browsers without typed arrays, an alternate buffer implementation is used that is based on `Object` which has no mechanism to point separate `Buffer`s to the same underlying slab of memory. You can see which browser versions lack typed array support [here](https://github.com/feross/buffer/blob/master/index.js#L22-L48). ## tracking the latest node api This module tracks the Buffer API in the latest (unstable) version of node.js. The Buffer API is considered **stable** in the [node stability index](https://nodejs.org/docs/latest/api/documentation.html#documentation_stability_index), so it is unlikely that there will ever be breaking changes. Nonetheless, when/if the Buffer API changes in node, this module's API will change accordingly. ## related packages - [`buffer-equals`](https://www.npmjs.com/package/buffer-equals) - Node.js 0.12 buffer.equals() ponyfill - [`buffer-reverse`](https://www.npmjs.com/package/buffer-reverse) - A lite module for reverse-operations on buffers - [`buffer-xor`](https://www.npmjs.com/package/buffer-xor) - A simple module for bitwise-xor on buffers - [`is-buffer`](https://www.npmjs.com/package/is-buffer) - Determine if an object is a Buffer without including the whole `Buffer` package - [`typedarray-to-buffer`](https://www.npmjs.com/package/typedarray-to-buffer) - Convert a typed array to a Buffer without a copy ## performance See perf tests in `/perf`. `BrowserBuffer` is the browser `buffer` module (this repo). `Uint8Array` is included as a sanity check (since `BrowserBuffer` uses `Uint8Array` under the hood, `Uint8Array` will always be at least a bit faster). Finally, `NodeBuffer` is the node.js buffer module, which is included to compare against. NOTE: Performance has improved since these benchmarks were taken. PR welcoem to update the README. ### Chrome 38 | Method | Operations | Accuracy | Sampled | Fastest | |:-------|:-----------|:---------|:--------|:-------:| | BrowserBuffer#bracket-notation | 11,457,464 ops/sec | ±0.86% | 66 | ✓ | | Uint8Array#bracket-notation | 10,824,332 ops/sec | ±0.74% | 65 | | | | | | | | BrowserBuffer#concat | 450,532 ops/sec | ±0.76% | 68 | | | Uint8Array#concat | 1,368,911 ops/sec | ±1.50% | 62 | ✓ | | | | | | | BrowserBuffer#copy(16000) | 903,001 ops/sec | ±0.96% | 67 | | | Uint8Array#copy(16000) | 1,422,441 ops/sec | ±1.04% | 66 | ✓ | | | | | | | BrowserBuffer#copy(16) | 11,431,358 ops/sec | ±0.46% | 69 | | | Uint8Array#copy(16) | 13,944,163 ops/sec | ±1.12% | 68 | ✓ | | | | | | | BrowserBuffer#new(16000) | 106,329 ops/sec | ±6.70% | 44 | | | Uint8Array#new(16000) | 131,001 ops/sec | ±2.85% | 31 | ✓ | | | | | | | BrowserBuffer#new(16) | 1,554,491 ops/sec | ±1.60% | 65 | | | Uint8Array#new(16) | 6,623,930 ops/sec | ±1.66% | 65 | ✓ | | | | | | | BrowserBuffer#readDoubleBE | 112,830 ops/sec | ±0.51% | 69 | ✓ | | DataView#getFloat64 | 93,500 ops/sec | ±0.57% | 68 | | | | | | | | BrowserBuffer#readFloatBE | 146,678 ops/sec | ±0.95% | 68 | ✓ | | DataView#getFloat32 | 99,311 ops/sec | ±0.41% | 67 | | | | | | | | BrowserBuffer#readUInt32LE | 843,214 ops/sec | ±0.70% | 69 | ✓ | | DataView#getUint32 | 103,024 ops/sec | ±0.64% | 67 | | | | | | | | BrowserBuffer#slice | 1,013,941 ops/sec | ±0.75% | 67 | | | Uint8Array#subarray | 1,903,928 ops/sec | ±0.53% | 67 | ✓ | | | | | | | BrowserBuffer#writeFloatBE | 61,387 ops/sec | ±0.90% | 67 | | | DataView#setFloat32 | 141,249 ops/sec | ±0.40% | 66 | ✓ | ### Firefox 33 | Method | Operations | Accuracy | Sampled | Fastest | |:-------|:-----------|:---------|:--------|:-------:| | BrowserBuffer#bracket-notation | 20,800,421 ops/sec | ±1.84% | 60 | | | Uint8Array#bracket-notation | 20,826,235 ops/sec | ±2.02% | 61 | ✓ | | | | | | | BrowserBuffer#concat | 153,076 ops/sec | ±2.32% | 61 | | | Uint8Array#concat | 1,255,674 ops/sec | ±8.65% | 52 | ✓ | | | | | | | BrowserBuffer#copy(16000) | 1,105,312 ops/sec | ±1.16% | 63 | | | Uint8Array#copy(16000) | 1,615,911 ops/sec | ±0.55% | 66 | ✓ | | | | | | | BrowserBuffer#copy(16) | 16,357,599 ops/sec | ±0.73% | 68 | | | Uint8Array#copy(16) | 3