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var duplexify = require('duplexify')
var lpstream = require('length-prefixed-stream')
var ids = require('numeric-id-map')
var util = require('util')
function RPC () {
duplexify.call(this) // subclass yolo
this._encode = lpstream.encode()
this._decode = lpstream.decode()
this._pending = ids()
this.setReadable(this._encode) // read from the encoder
this.setWritable(this._decode) // write to the decoder
var self = this
this._decode.on('data', function (data) {
data = JSON.parse(data)
if (data.type === 'request') {
self.emit('request', data.data, function (err, res) {
if (err) self._encode.write(JSON.stringify({id: data.id, type: 'error', error: err.message}))
else self._encode.write(JSON.stringify({id: data.id, type: 'response', data: res}))
})
}
if (data.type === 'error') {
var req = self._pending.remove(data.id)
if (req.callback) req.callback(new Error(req.error))
}
if (data.type === 'response') {
var req = self._pending.remove(data.id)
if (req.callback) req.callback(null, data.data)
}
})
}
util.inherits(RPC, duplexify)
RPC.prototype.request = function (msg, cb) {
var req = {type: 'request', data: msg}
req.id = this._pending.add(req)
this._encode.write(JSON.stringify(req))
req.callback = cb || function () {} // hack to not stringify callback
}
// usage
var net = require('net')
net.createServer(function (stream) {
var rpc = new RPC()
rpc.on('request', function (req, cb) {
cb(null, {echo: req})
})
stream.pipe(rpc).pipe(stream)
}).listen(10000, function() {
var rpc = new RPC()
var stream = net.connect(10000)
rpc.request({hello: 'world'}, console.log) // prints {echo: {hello: 'world'}}
stream.pipe(rpc).pipe(stream)
})
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