78 lines
1.7 KiB
TypeScript
78 lines
1.7 KiB
TypeScript
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/*---------------------------------------------------------------------------------------------
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* Copyright (c) Microsoft Corporation. All rights reserved.
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* Licensed under the MIT License. See License.txt in the project root for license information.
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*--------------------------------------------------------------------------------------------*/
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import * as jschardet from 'jschardet';
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function detectEncodingByBOM(buffer: Buffer): string | null {
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if (!buffer || buffer.length < 2) {
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return null;
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}
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const b0 = buffer.readUInt8(0);
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const b1 = buffer.readUInt8(1);
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// UTF-16 BE
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if (b0 === 0xFE && b1 === 0xFF) {
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return 'utf16be';
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}
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// UTF-16 LE
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if (b0 === 0xFF && b1 === 0xFE) {
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return 'utf16le';
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}
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if (buffer.length < 3) {
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return null;
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}
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const b2 = buffer.readUInt8(2);
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// UTF-8
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if (b0 === 0xEF && b1 === 0xBB && b2 === 0xBF) {
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return 'utf8';
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}
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return null;
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}
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const IGNORE_ENCODINGS = [
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'ascii',
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'utf-8',
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'utf-16',
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'utf-32'
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];
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const JSCHARDET_TO_ICONV_ENCODINGS: { [name: string]: string } = {
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'ibm866': 'cp866',
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'big5': 'cp950'
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};
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export function detectEncoding(buffer: Buffer): string | null {
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let result = detectEncodingByBOM(buffer);
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if (result) {
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return result;
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}
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const detected = jschardet.detect(buffer);
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if (!detected || !detected.encoding) {
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return null;
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}
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const encoding = detected.encoding;
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// Ignore encodings that cannot guess correctly
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// (http://chardet.readthedocs.io/en/latest/supported-encodings.html)
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if (0 <= IGNORE_ENCODINGS.indexOf(encoding.toLowerCase())) {
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return null;
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}
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const normalizedEncodingName = encoding.replace(/[^a-zA-Z0-9]/g, '').toLowerCase();
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const mapped = JSCHARDET_TO_ICONV_ENCODINGS[normalizedEncodingName];
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return mapped || normalizedEncodingName;
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}
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