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48 lines
1.3 KiB
JavaScript

"use strict";
const iconvLite = require("iconv-lite");
const supportedNames = require("./supported-names.json");
const labelsToNames = require("./labels-to-names.json");
const supportedNamesSet = new Set(supportedNames);
// https://encoding.spec.whatwg.org/#concept-encoding-get
exports.labelToName = label => {
label = String(label).trim().toLowerCase();
return labelsToNames[label] || null;
};
// https://encoding.spec.whatwg.org/#decode
exports.decode = (buffer, fallbackEncodingName) => {
let encoding = fallbackEncodingName;
if (!exports.isSupported(encoding)) {
throw new RangeError(`"${encoding}" is not a supported encoding name`);
}
const bomEncoding = exports.getBOMEncoding(buffer);
if (bomEncoding !== null) {
encoding = bomEncoding;
}
// iconv-lite will strip BOMs for us, so no need to do the stuff the spec does
return iconvLite.decode(buffer, encoding);
};
// https://github.com/whatwg/html/issues/1910#issuecomment-254017369
exports.getBOMEncoding = buffer => {
if (buffer[0] === 0xFE && buffer[1] === 0xFF) {
return "UTF-16BE";
} else if (buffer[0] === 0xFF && buffer[1] === 0xFE) {
return "UTF-16LE";
} else if (buffer[0] === 0xEF && buffer[1] === 0xBB && buffer[2] === 0xBF) {
return "UTF-8";
}
return null;
};
exports.isSupported = name => {
return supportedNamesSet.has(String(name));
};