shell bypass 403
/**
* @module create-prefix-transform-stream
* @author Toru Nagashima
* @copyright 2016 Toru Nagashima. All rights reserved.
* See LICENSE file in root directory for full license.
*/
"use strict"
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const stream = require("stream")
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const ALL_BR = /\n/g
/**
* The transform stream to insert a specific prefix.
*
* Several streams can exist for the same output stream.
* This stream will insert the prefix if the last output came from other instance.
* To do that, this stream is using a shared state object.
*
* @private
*/
class PrefixTransform extends stream.Transform {
/**
* @param {string} prefix - A prefix text to be inserted.
* @param {object} state - A state object.
* @param {string} state.lastPrefix - The last prefix which is printed.
* @param {boolean} state.lastIsLinebreak -The flag to check whether the last output is a line break or not.
*/
constructor(prefix, state) {
super()
this.prefix = prefix
this.state = state
}
/**
* Transforms the output chunk.
*
* @param {string|Buffer} chunk - A chunk to be transformed.
* @param {string} _encoding - The encoding of the chunk.
* @param {function} callback - A callback function that is called when done.
* @returns {void}
*/
_transform(chunk, _encoding, callback) {
const prefix = this.prefix
const nPrefix = `\n${prefix}`
const state = this.state
const firstPrefix =
state.lastIsLinebreak ? prefix :
(state.lastPrefix !== prefix) ? "\n" :
/* otherwise */ ""
const prefixed = `${firstPrefix}${chunk}`.replace(ALL_BR, nPrefix)
const index = prefixed.indexOf(prefix, Math.max(0, prefixed.length - prefix.length))
state.lastPrefix = prefix
state.lastIsLinebreak = (index !== -1)
callback(null, (index !== -1) ? prefixed.slice(0, index) : prefixed)
}
}
//------------------------------------------------------------------------------
// Public API
//------------------------------------------------------------------------------
/**
* Create a transform stream to insert the specific prefix.
*
* Several streams can exist for the same output stream.
* This stream will insert the prefix if the last output came from other instance.
* To do that, this stream is using a shared state object.
*
* @param {string} prefix - A prefix text to be inserted.
* @param {object} state - A state object.
* @param {string} state.lastPrefix - The last prefix which is printed.
* @param {boolean} state.lastIsLinebreak -The flag to check whether the last output is a line break or not.
* @returns {stream.Transform} The created transform stream.
*/
module.exports = function createPrefixTransform(prefix, state) {
return new PrefixTransform(prefix, state)
}