73 lines
1.4 KiB
JavaScript
73 lines
1.4 KiB
JavaScript
/*!
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* framer.js - packet framer for bcoin
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* Copyright (c) 2014-2015, Fedor Indutny (MIT License)
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* Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
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* https://github.com/bcoin-org/bcoin
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*/
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'use strict';
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var assert = require('assert');
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var Network = require('../protocol/network');
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var crypto = require('../crypto/crypto');
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/**
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* Protocol packet framer
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* @alias module:net.Framer
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* @constructor
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* @param {Network} network
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*/
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function Framer(network) {
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if (!(this instanceof Framer))
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return new Framer(network);
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this.network = Network.get(network);
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}
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/**
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* Frame a payload with a header.
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* @param {String} cmd - Packet type.
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* @param {Buffer} payload
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* @returns {Buffer} Payload with header prepended.
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*/
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Framer.prototype.packet = function packet(cmd, payload, checksum) {
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var i, packet;
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assert(payload, 'No payload.');
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assert(cmd.length < 12);
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assert(payload.length <= 0xffffffff);
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packet = Buffer.allocUnsafe(24 + payload.length);
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// Magic value
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packet.writeUInt32LE(this.network.magic, 0, true);
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// Command
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packet.write(cmd, 4, 'ascii');
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for (i = 4 + cmd.length; i < 16; i++)
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packet[i] = 0;
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// Payload length
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packet.writeUInt32LE(payload.length, 16, true);
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if (!checksum)
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checksum = crypto.hash256(payload);
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// Checksum
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checksum.copy(packet, 20, 0, 4);
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payload.copy(packet, 24);
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return packet;
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};
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/*
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* Expose
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*/
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module.exports = Framer;
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