git ssb

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const EventEmitter = require('events')
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const Port = require('./port.js')
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const common = require('./common.js')
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module.exports = class PortManager extends EventEmitter {
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  constructor (state, destParentPort, KernelContructor) {
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    super()
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    this.state = state
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    this.sentMessage = []
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    this.Kernel = KernelContructor
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    // set up the parent port
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    const parentPort = new Port()
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    parentPort.on('message', message => {
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      this.emit('message', message)
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    })
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    // create the cache
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    this.cache = new Map()
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    this.cache.set(common.PARENT, parentPort)
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  }
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  async get (name) {
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    let port = this.cache.get(name)
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    if (!port) {
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      port = new Port()
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      port.on('message', message => {
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        this.emit('message', message)
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      })
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      // create destination kernel
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      const state = await this.state.get(name)
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      const destKernel = new this.Kernel({
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        state: state,
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        parent: port
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      })
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      // shutdown the kernel when it is done doing it work
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      destKernel.on('idle', () => {
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        destKernel.shutdown()
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        this.cache.delete(name)
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      })
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      // find and connect the destination port
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      const destPort = await destKernel.ports.get(common.PARENT)
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      port.connect(destPort)
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      this.cache.set(name, port)
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    }
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    return port
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  }
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  // dequeues the first message that is waiting on a port
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  async dequeue () {
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    // clear the outbox
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    this.sentMessage = []
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    for (let port in this.cache) {
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      const message = port.dequeue()
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      if (message) {
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        return message
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      }
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    }
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  }
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  close () {
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    for (let port in this.cache) {
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      port.emit('close')
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    }
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    this.cache.clear()
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  }
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}
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