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.graph = new Graph(opts.dag)
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    this._vmInstances = new Map()
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    this._VMs = {}
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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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      const parentID = await this.generateID(port.id['/'].parent)
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      const parentKernel = await this._vmInstances.get(parentID)
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      const parentPort = parentKernel.entryPort
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      kernel = await this.createInstanceFromPort(port, parentPort)
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      // don't delete the root contracts
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      if (id) {
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        kernel.on('idle', () => {
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          this._vmInstances.delete(id)
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        })
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      }
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    }
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    return kernel
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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, fromPort) {
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    let kernel = await this.getInstance(port)
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    return kernel.wait(threshold, fromPort)
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  }
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  async createInstance (type, state, entryPort, parentPort) {
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    const VM = this._VMs[type]
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    if (!state) {
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      state = VM.createState()
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    }
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    // create a new kernel instance
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    const kernel = new Kernel({
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      entryPort: entryPort,
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      parentPort: parentPort,
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      hypervisor: this,
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      state: state,
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      VM: VM
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    })
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    const id = await this.generateID(entryPort)
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    this._vmInstances.set(id, kernel)
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    await kernel.start()
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    return kernel
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  }
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  /**
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   * opts.entryPort
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   * opts.parentPort
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   */
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  async createInstanceFromPort (entryPort, parentPort) {
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    const state = entryPort.link['/']
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    return this.createInstance(entryPort.type, state, entryPort, parentPort)
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  }
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  async createStateRoot (container, ticks) {
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    await container.wait(ticks)
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    return this.graph.flush(container.state)
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  }
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  async generateID (port) {
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    if (!port || !port.id) {
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      return null
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    }
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    let id = Object.assign({}, port.id)
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    id = await this.graph.flush(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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  registerContainer (type, vm) {
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    this._VMs[type] = vm
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  }
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}
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