git ssb

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const Graph = require('ipld-graph-builder')
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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, parentPort) {
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    let kernel = this._vmInstances.get(port)
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    if (!kernel) {
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      kernel = await this.createInstance(port.type, port.link, port, parentPort)
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      kernel.on('idle', () => {
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        this._vmInstances.delete(port)
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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 = this._vmInstances.get(port)
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    if (kernel) {
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      return kernel.wait(threshold, fromPort)
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    } else {
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      return threshold
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    }
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  }
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  async createInstance (type, state, entryPort = null, parentPort) {
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    const VM = this._VMs[type]
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    if (!state) {
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      state = {
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        '/': VM.createState()
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      }
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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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    // save the newly created instance
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    this._vmInstances.set(entryPort, kernel)
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    await kernel.start()
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    return kernel
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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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  registerContainer (type, vm) {
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    this._VMs[type] = vm
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  }
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}
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