'use strict'
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/**
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* Converts an attribute value into an escaped string as described in
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* https://www.rfc-editor.org/rfc/rfc4514#section-2.4.
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*
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* This function supports up to 4 byte unicode characters.
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*
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* @param {string} value
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* @returns {string} The escaped string.
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*/
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module.exports = function escapeValue (value) {
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if (typeof value !== 'string') {
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throw Error('value must be a string')
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}
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const toEscape = Buffer.from(value, 'utf8')
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const escaped = []
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// We will handle the reverse solidus ('\') on its own.
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const embeddedReservedChars = [
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0x22, // '"'
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0x2b, // '+'
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0x2c, // ','
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0x3b, // ';'
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0x3c, // '<'
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0x3e // '>'
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]
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for (let i = 0; i < toEscape.byteLength;) {
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const charHex = toEscape[i]
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// Handle leading space or #.
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if (i === 0 && (charHex === 0x20 || charHex === 0x23)) {
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escaped.push(toEscapedHexString(charHex))
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i += 1
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continue
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}
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// Handle trailing space.
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if (i === toEscape.byteLength - 1 && charHex === 0x20) {
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escaped.push(toEscapedHexString(charHex))
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i += 1
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continue
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}
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if (embeddedReservedChars.includes(charHex) === true) {
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escaped.push(toEscapedHexString(charHex))
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i += 1
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continue
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}
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if (charHex >= 0xc0 && charHex <= 0xdf) {
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// Represents the first byte in a 2-byte UTF-8 character.
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escaped.push(toEscapedHexString(charHex))
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escaped.push(toEscapedHexString(toEscape[i + 1]))
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i += 2
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continue
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}
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if (charHex >= 0xe0 && charHex <= 0xef) {
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// Represents the first byte in a 3-byte UTF-8 character.
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escaped.push(toEscapedHexString(charHex))
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escaped.push(toEscapedHexString(toEscape[i + 1]))
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escaped.push(toEscapedHexString(toEscape[i + 2]))
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i += 3
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continue
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}
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if (charHex >= 0xf0 && charHex <= 0xf7) {
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// Represents the first byte in a 4-byte UTF-8 character.
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escaped.push(toEscapedHexString(charHex))
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escaped.push(toEscapedHexString(toEscape[i + 1]))
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escaped.push(toEscapedHexString(toEscape[i + 2]))
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escaped.push(toEscapedHexString(toEscape[i + 3]))
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i += 4
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continue
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}
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if (charHex <= 31) {
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// Represents an ASCII control character.
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escaped.push(toEscapedHexString(charHex))
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i += 1
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continue
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}
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escaped.push(String.fromCharCode(charHex))
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i += 1
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continue
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}
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return escaped.join('')
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}
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/**
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* Given a byte, convert it to an escaped hex string.
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*
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* @example
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* toEscapedHexString(0x20) // '\20'
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*
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* @param {number} char
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* @returns {string}
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*/
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function toEscapedHexString (char) {
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return '\\' + char.toString(16).padStart(2, '0')
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}
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