opportunitylivetv / text-encode-transform-prollyfill

Prollyfill for using TextEncoder and TextDecoder as transform streams

Text Encode Transformations

Overview

This is a prollyfill enabling TextEncoder and TextDecoder to be used as Stream transforms. It is based on the draft changes to the Encoding Standard here:

http://htmlpreview.github.io/?https://github.com/ricea/encoding-streams/blob/master/patch.html

However, it may be out-of-sync with that document.

This is intended for experimentation and development of the standard.

Requirements

You need existing working TextEncoder and TextDecoder implementations in your user agent, either natively or via polyfill. This prollyfill wraps the implementation you already have.

You need working ReadableStream, WritableStream and TransformStream implementations in your user agent, either natively or via polyfill.

How to use

Include the prollyfill in the page:

<script src="text-encode-transform.js">

It can also be used in a Worker environment:

importScripts('text-encode-transform.js');

Then you can use it in a pipe like this:

byteSource
  .pipeThrough(new TextDecoder())
  .pipeTo(textDestination);

Any arguments that the TextDecoder constructor normally accepts will also work when used as a stream transform.

TextEncoder works the same way:

textSource
  .pipeThrough(new TextEncoder())
  .pipeTo(byteDestination);

Tests

Tests in web-platform-test format are included in the tests/ directory. The tests use infrastructure from the https://github.com/w3c/web-platform-tests repository. You will need to run the tests under the web-platform-tests HTTP server.

The tests expect the TransformStream polyfill to be installed in a parallel directory to this one named transform-stream-polyfill. You can get the polyfill from https://github.com/whatwg/streams/blob/transform-stream-polyfill/reference-implementation/contrib/transform-stream-polyfill.js

The tests import the polyfills from tests/resources. By default symbolic links are used; if they don't work in your environment they can just be copied there. If your browser supports TransformStream natively then replacing tests/releases/transform-stream.js with an empty file should work.

See also

• Encoding Living Standard
• Streams Living Standard

Disclaimer

This is not an official Google product.