41 lines
1.2 KiB
JavaScript
41 lines
1.2 KiB
JavaScript
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*/
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'use strict';
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/* global Buffer: true */
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const crypto = require('crypto');
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const isUTF8 = encoding => /^utf-?8$/i.test(encoding);
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const constantFor = encoding =>
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/^ascii$/i.test(encoding) ? 1 :
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isUTF8(encoding) ? 2 :
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/^(?:utf-?16(?:le)?|ucs-?2)$/.test(encoding) ? 3 : 0;
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module.exports = function(code, encoding) {
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const hash = crypto.createHash('sha1');
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hash.update(code, encoding);
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const digest = hash.digest('binary');
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const signature = Buffer(digest.length + 1);
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signature.write(digest, 'binary');
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signature.writeUInt8(
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constantFor(tryAsciiPromotion(code, encoding)),
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signature.length - 1);
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return signature;
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};
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function tryAsciiPromotion(string, encoding) {
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if (!isUTF8(encoding)) { return encoding; }
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for (let i = 0, n = string.length; i < n; i++) {
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if (string.charCodeAt(i) > 0x7f) { return encoding; }
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}
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return 'ascii';
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}
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