// Copyright (c) 2013, Benjamin J. Kelly ("Author")

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

// 1. Redistributions of source code must retain the above copyright notice, this

// list of conditions and the following disclaimer.

// 2. Redistributions in binary form must reproduce the above copyright notice,

// this list of conditions and the following disclaimer in the documentation

// and/or other materials provided with the distribution.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR

// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

/**

* @author https://github.com/wanderview

*/

import MAC from './mac'

const TYPE_TO_STRING = {

0x0800: 'ip',

0x0806: 'arp'

}

const TYPE_FROM_STRING = {

ip: 0x0800,

arp: 0x0806

}

export default class Ethernet {

constructor(option){

if (option instanceof Buffer)

return Ethernet.fromBuffer(option)

option = option || {}

this.src = option.src || MAC.empty

this.dst = option.dst || MAC.full

if (option.type) {

this.type = option.type

this.typeCode = TYPE_FROM_STRING[this.type]

} else if (option.typeCode) {

this.typeCode = option.typeCode

this.type = TYPE_TO_STRING[this.typeCode]

} else {

this.type = 'ip'

this.typeCode = TYPE_FROM_STRING[this.type]

}

if (typeof this.typeCode !== 'number')

throw(new Error('Unsupported type [' + this.type + ']'))

this.length = option.length || 14

if (this.length !== 14) {

throw new Error(

'Unsupported ethernet frame length [' + this.length +

']; must be 14 as only most common cases are implemented.')

}

return this

}

fromBuffer(buffer, offset) {

offset = ~~offset

let length = 0

let dst = MAC.toString(buffer, offset + length)

length += MAC.length

let src = MAC.toString(buffer, offset + length)

length += MAC.length

let typeCode = buffer.readUInt16BE(offset + length)

length += 2

let type = TYPE_TO_STRING[typeCode]

if (!type)

throw(new Error('Unsupported type code [' + typeCode + ']'))

return new Ethernet({

dst,

src,

type,

typeCode,

length

})

}

toBuffer(buffer, offset) {

offset = ~~offset

buffer = (buffer instanceof Buffer) ?

buffer : Buffer.alloc(offset + this.length)

MAC.toBuffer(this.dst, buffer, offset)

offset += MAC.length

MAC.toBuffer(this.src, buffer, offset)

offset += MAC.length

buffer.writeUInt16BE(this.typeCode, offset)

offset += 2

return buffer

}

}