git ssb

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const Graph = require('ipld-graph-builder')
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const multibase = require('multibase')
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const Kernel = require('./kernel.js')
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module.exports = class Hypervisor {
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  constructor (opts) {
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    this._opts = {
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      VMs: {}
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    }
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    this.graph = new Graph(opts.dag)
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    delete opts.dag
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    this._vmInstances = new Map()
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    Object.assign(this._opts, opts)
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  }
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  async getInstance (port) {
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    let id = await this.generateID(port)
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    let kernel = this._vmInstances.get(id)
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    if (!kernel) {
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      // load the container from the state
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      await this.graph.tree(port, 2)
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      // create a new kernel instance
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      const VM = this._opts.VMs[port.type]
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      kernel = new Kernel({
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        parentPort: port,
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        hypervisor: this,
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        VM: VM
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      })
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      await kernel.start()
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      kernel.on('idle', () => {
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        this._vmInstances.delete(id)
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      })
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      this._vmInstances.set(id, kernel)
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    }
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    return kernel
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  }
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  async send (port, message) {
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    const vm = await this.getInstance(port)
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    const id = await this.generateID(port)
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    message._fromPort = id
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    vm.queue(message)
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  }
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  // given a port, wait untill its source contract has reached the threshold
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  // tick count
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  async wait (port, threshold) {
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    let kernel = await this.getInstance(port)
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    return kernel.wait(threshold)
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  }
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  createPort (type, id = {nonce: [0], parent: null}) {
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    const VM = this._opts.VMs[type]
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    return {
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      'messages': [],
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      'id': {
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        '/': id
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      },
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      'type': type,
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      'link': {
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        '/': VM.createState()
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      }
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    }
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  }
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  async createStateRoot (port, ticks) {
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    await this.wait(port, ticks)
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    return this.graph.flush(port)
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  }
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  async generateID (port) {
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    let id = await this.graph.flush(port.id)
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    id = id['/']
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    if (Buffer.isBuffer(id)) {
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      id = multibase.encode('base58btc', id).toString()
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    }
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    return id
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  }
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  addVM (type, vm) {
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    this._opts.VMs[type] = vm
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  }
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}
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