313 lines
8.5 KiB
JavaScript
313 lines
8.5 KiB
JavaScript
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'use strict';
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var stream = require('stream');
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var util = require('util');
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var Transform = stream.Transform;
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// expose to the world
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module.exports = {
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encode: encode,
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decode: decode,
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wrap: wrap,
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Encoder: Encoder,
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Decoder: Decoder
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};
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/**
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* Encodes a Buffer into a Quoted-Printable encoded string
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*
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* @param {Buffer} buffer Buffer to convert
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* @returns {String} Quoted-Printable encoded string
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*/
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function encode(buffer) {
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if (typeof buffer === 'string') {
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buffer = new Buffer(buffer, 'utf-8');
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}
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// usable characters that do not need encoding
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var ranges = [
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// https://tools.ietf.org/html/rfc2045#section-6.7
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[0x09], // <TAB>
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[0x0A], // <LF>
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[0x0D], // <CR>
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[0x20, 0x3C], // <SP>!"#$%&'()*+,-./0123456789:;
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[0x3E, 0x7E] // >?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}
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];
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var result = '';
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var ord;
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for (var i = 0, len = buffer.length; i < len; i++) {
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ord = buffer[i];
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// if the char is in allowed range, then keep as is, unless it is a ws in the end of a line
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if (checkRanges(ord, ranges) && !((ord === 0x20 || ord === 0x09) && (i === len - 1 || buffer[i + 1] === 0x0a || buffer[i + 1] === 0x0d))) {
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result += String.fromCharCode(ord);
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continue;
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}
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result += '=' + (ord < 0x10 ? '0' : '') + ord.toString(16).toUpperCase();
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}
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return result;
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}
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/**
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* Decodes a Quoted-Printable encoded string to a Buffer object
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*
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* @param {String} str Quoted-Printable encoded string
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* @returns {Buffer} Decoded value
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*/
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function decode(str) {
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str = (str || '').toString().
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// remove invalid whitespace from the end of lines
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replace(/[\t ]+$/gm, '').
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// remove soft line breaks
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replace(/\=(?:\r?\n|$)/g, '');
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var encodedBytesCount = (str.match(/\=[\da-fA-F]{2}/g) || []).length,
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bufferLength = str.length - encodedBytesCount * 2,
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chr, hex,
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buffer = new Buffer(bufferLength),
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bufferPos = 0;
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for (var i = 0, len = str.length; i < len; i++) {
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chr = str.charAt(i);
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if (chr === '=' && (hex = str.substr(i + 1, 2)) && /[\da-fA-F]{2}/.test(hex)) {
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buffer[bufferPos++] = parseInt(hex, 16);
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i += 2;
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continue;
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}
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buffer[bufferPos++] = chr.charCodeAt(0);
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}
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return buffer;
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}
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/**
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* Adds soft line breaks to a Quoted-Printable string
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*
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* @param {String} str Quoted-Printable encoded string that might need line wrapping
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* @param {Number} [lineLength=76] Maximum allowed length for a line
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* @returns {String} Soft-wrapped Quoted-Printable encoded string
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*/
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function wrap(str, lineLength) {
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str = (str || '').toString();
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lineLength = lineLength || 76;
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if (str.length <= lineLength) {
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return str;
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}
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var pos = 0,
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len = str.length,
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match, code, line,
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lineMargin = Math.floor(lineLength / 3),
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result = '';
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// insert soft linebreaks where needed
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while (pos < len) {
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line = str.substr(pos, lineLength);
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if ((match = line.match(/\r\n/))) {
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line = line.substr(0, match.index + match[0].length);
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result += line;
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pos += line.length;
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continue;
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}
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if (line.substr(-1) === '\n') {
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// nothing to change here
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result += line;
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pos += line.length;
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continue;
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} else if ((match = line.substr(-lineMargin).match(/\n.*?$/))) {
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// truncate to nearest line break
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line = line.substr(0, line.length - (match[0].length - 1));
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result += line;
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pos += line.length;
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continue;
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} else if (line.length > lineLength - lineMargin && (match = line.substr(-lineMargin).match(/[ \t\.,!\?][^ \t\.,!\?]*$/))) {
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// truncate to nearest space
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line = line.substr(0, line.length - (match[0].length - 1));
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} else {
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if (line.match(/\=[\da-f]{0,2}$/i)) {
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// push incomplete encoding sequences to the next line
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if ((match = line.match(/\=[\da-f]{0,1}$/i))) {
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line = line.substr(0, line.length - match[0].length);
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}
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// ensure that utf-8 sequences are not split
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while (line.length > 3 && line.length < len - pos && !line.match(/^(?:=[\da-f]{2}){1,4}$/i) && (match = line.match(/\=[\da-f]{2}$/ig))) {
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code = parseInt(match[0].substr(1, 2), 16);
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if (code < 128) {
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break;
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}
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line = line.substr(0, line.length - 3);
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if (code >= 0xC0) {
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break;
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}
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}
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}
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}
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if (pos + line.length < len && line.substr(-1) !== '\n') {
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if (line.length === lineLength && line.match(/\=[\da-f]{2}$/i)) {
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line = line.substr(0, line.length - 3);
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} else if (line.length === lineLength) {
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line = line.substr(0, line.length - 1);
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}
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pos += line.length;
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line += '=\r\n';
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} else {
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pos += line.length;
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}
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result += line;
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}
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return result;
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}
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/**
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* Helper function to check if a number is inside provided ranges
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*
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* @param {Number} nr Number to check for
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* @param {Array} ranges An Array of allowed values
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* @returns {Boolean} True if the value was found inside allowed ranges, false otherwise
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*/
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function checkRanges(nr, ranges) {
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for (var i = ranges.length - 1; i >= 0; i--) {
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if (!ranges[i].length) {
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continue;
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}
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if (ranges[i].length === 1 && nr === ranges[i][0]) {
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return true;
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}
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if (ranges[i].length === 2 && nr >= ranges[i][0] && nr <= ranges[i][1]) {
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return true;
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}
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}
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return false;
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}
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/**
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* Creates a transform stream for encoding data to Quoted-Printable encoding
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*
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* @constructor
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* @param {Object} options Stream options
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* @param {Number} [options.lineLength=76] Maximum lenght for lines, set to false to disable wrapping
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*/
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function Encoder(options) {
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// init Transform
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this.options = options || {};
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if (this.options.lineLength !== false) {
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this.options.lineLength = this.options.lineLength || 76;
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}
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this._curLine = '';
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this.inputBytes = 0;
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this.outputBytes = 0;
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Transform.call(this, this.options);
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}
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util.inherits(Encoder, Transform);
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Encoder.prototype._transform = function(chunk, encoding, done) {
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var qp, _self = this;
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if (encoding !== 'buffer') {
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chunk = new Buffer(chunk, encoding);
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}
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if (!chunk || !chunk.length) {
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return done();
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}
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this.inputBytes += chunk.length;
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if (this.options.lineLength) {
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qp = this._curLine + encode(chunk);
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qp = wrap(qp, this.options.lineLength);
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qp = qp.replace(/(^|\n)([^\n]*)$/, function(match, lineBreak, lastLine) {
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_self._curLine = lastLine;
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return lineBreak;
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});
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if (qp) {
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this.outputBytes += qp.length;
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this.push(qp);
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}
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} else {
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qp = encode(chunk);
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this.outputBytes += qp.length;
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this.push(qp, 'ascii');
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}
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done();
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};
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Encoder.prototype._flush = function(done) {
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if (this._curLine) {
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this.outputBytes += this._curLine.length;
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this.push(this._curLine, 'ascii');
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}
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done();
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};
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/**
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* Creates a transform stream for decoding Quoted-Printable encoded strings
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*
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* @constructor
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* @param {Object} options Stream options
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*/
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function Decoder(options) {
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// init Transform
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this.options = options || {};
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this._curLine = '';
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this.inputBytes = 0;
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this.outputBytes = 0;
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Transform.call(this, this.options);
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}
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util.inherits(Decoder, Transform);
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Decoder.prototype._transform = function(chunk, encoding, done) {
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var qp, buf, _self = this;
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chunk = chunk.toString('ascii');
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if (!chunk || !chunk.length) {
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return done();
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}
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this.inputBytes += chunk.length;
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qp = (this._curLine + chunk);
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this._curLine = '';
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qp = qp.replace(/=[^\n]?$/, function(lastLine) {
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_self._curLine = lastLine;
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return '';
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});
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if (qp) {
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buf = decode(qp);
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this.outputBytes += buf.length;
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this.push(buf);
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}
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done();
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};
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Decoder.prototype._flush = function(done) {
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var qp, buf;
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if (this._curLine) {
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buf = decode(this._curLine);
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this.outputBytes += buf.length;
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this.push(buf);
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}
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done();
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};
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