mirror of https://github.com/actions/setup-python
51 lines
2.8 KiB
Markdown
51 lines
2.8 KiB
Markdown
# Decode According to the WHATWG Encoding Standard
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This package provides a thin layer on top of [iconv-lite](https://github.com/ashtuchkin/iconv-lite) which makes it expose some of the same primitives as the [Encoding Standard](https://encoding.spec.whatwg.org/).
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```js
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const whatwgEncoding = require("whatwg-encoding");
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console.assert(whatwgEncoding.labelToName("latin1") === "windows-1252");
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console.assert(whatwgEncoding.labelToName(" CYRILLic ") === "ISO-8859-5");
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console.assert(whatwgEncoding.isSupported("IBM866") === true);
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// Not supported by the Encoding Standard
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console.assert(whatwgEncoding.isSupported("UTF-32") === false);
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// In the Encoding Standard, but this package can't decode it
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console.assert(whatwgEncoding.isSupported("x-mac-cyrillic") === false);
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console.assert(whatwgEncoding.getBOMEncoding(new Buffer([0xFE, 0xFF])) === "UTF-16BE");
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console.assert(whatwgEncoding.getBOMEncoding(new Buffer([0x48, 0x69])) === null);
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console.assert(whatwgEncoding.decode(new Buffer([0x48, 0x69]), "UTF-8") === "Hi");
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```
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## API
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- `decode(buffer, fallbackEncodingName)`: performs the [decode](https://encoding.spec.whatwg.org/#decode) algorithm (in which any BOM will override the passed fallback encoding), and returns the resulting string
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- `labelToName(label)`: performs the [get an encoding](https://encoding.spec.whatwg.org/#concept-encoding-get) algorithm and returns the resulting encoding's name, or `null` for failure
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- `isSupported(name)`: returns whether the encoding is one of [the encodings](https://encoding.spec.whatwg.org/#names-and-labels) of the Encoding Standard, _and_ is an encoding that this package can decode (via iconv-lite)
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- `getBOMEncoding(buffer)`: sniffs the first 2–3 bytes of the supplied `Buffer`, returning one of the encoding names `"UTF-8"`, `"UTF-16LE"`, or `"UTF-16BE"` if the appropriate BOM is present, or `null` if no BOM is present
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## Unsupported encodings
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Since we rely on iconv-lite, we are limited to support only the encodings that they support. Currently we are missing support for:
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- ISO-2022-JP
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- ISO-8859-8-I
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- replacement
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- x-mac-cyrillic
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- x-user-defined
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Passing these encoding names will return `false` when calling `isSupported`, and passing any of the possible labels for these encodings to `labelToName` will return `null`.
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## Credits
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This package was originally based on the excellent work of [@nicolashenry](https://github.com/nicolashenry), [in jsdom](https://github.com/tmpvar/jsdom/blob/7ce11776ce161e8d5921a7a183585327400f786b/lib/jsdom/living/helpers/encoding.js). It has since been pulled out into this separate package.
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## Alternatives
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If you are looking for a JavaScript implementation of the Encoding Standard's `TextEncoder` and `TextDecoder` APIs, you'll want [@inexorabletash](https://github.com/inexorabletash)'s [text-encoding](https://github.com/inexorabletash/text-encoding) package.
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