63 lines
1.6 KiB
JavaScript
63 lines
1.6 KiB
JavaScript
'use strict';
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/**
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* Checks if a given buffer contains only correct UTF-8.
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* Ported from https://www.cl.cam.ac.uk/%7Emgk25/ucs/utf8_check.c by
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* Markus Kuhn.
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*
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* @param {Buffer} buf The buffer to check
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* @return {Boolean} `true` if `buf` contains only correct UTF-8, else `false`
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* @public
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*/
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function isValidUTF8(buf) {
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const len = buf.length;
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let i = 0;
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while (i < len) {
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if ((buf[i] & 0x80) === 0x00) { // 0xxxxxxx
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i++;
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} else if ((buf[i] & 0xe0) === 0xc0) { // 110xxxxx 10xxxxxx
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if (
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i + 1 === len ||
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(buf[i + 1] & 0xc0) !== 0x80 ||
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(buf[i] & 0xfe) === 0xc0 // overlong
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) {
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return false;
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}
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i += 2;
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} else if ((buf[i] & 0xf0) === 0xe0) { // 1110xxxx 10xxxxxx 10xxxxxx
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if (
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i + 2 >= len ||
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(buf[i + 1] & 0xc0) !== 0x80 ||
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(buf[i + 2] & 0xc0) !== 0x80 ||
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buf[i] === 0xe0 && (buf[i + 1] & 0xe0) === 0x80 || // overlong
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buf[i] === 0xed && (buf[i + 1] & 0xe0) === 0xa0 // surrogate (U+D800 - U+DFFF)
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) {
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return false;
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}
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i += 3;
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} else if ((buf[i] & 0xf8) === 0xf0) { // 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
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if (
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i + 3 >= len ||
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(buf[i + 1] & 0xc0) !== 0x80 ||
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(buf[i + 2] & 0xc0) !== 0x80 ||
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(buf[i + 3] & 0xc0) !== 0x80 ||
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buf[i] === 0xf0 && (buf[i + 1] & 0xf0) === 0x80 || // overlong
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buf[i] === 0xf4 && buf[i + 1] > 0x8f || buf[i] > 0xf4 // > U+10FFFF
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) {
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return false;
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}
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i += 4;
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} else {
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return false;
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}
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}
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return true;
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}
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module.exports = isValidUTF8;
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