git ssb

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const Vertex = require('merkle-trie')
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const imports = require('./EVMinterface.js')
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const codeHandler = require('./codeHandler.js')
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const MessageQueue = require('./messageQueue')
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const PARENT_SYMBOL = Symbol('parent')
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const ROOT_SYMBOL = Symbol('root')
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module.exports = class Kernel {
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  constructor (opts = {}) {
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    const state = this.state = opts.state || new Vertex()
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    state.value = opts.code || state.value
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    this.imports = opts.imports || [imports]
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    // RENAME agent
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    this._vm = (opts.codeHandler || codeHandler).init(state.value)
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    this._messageQueue = new MessageQueue(this)
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    this._instanceCache = new Map()
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    if (opts.parent) {
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      this._instanceCache.set(opts.parent)
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    }
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  }
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  static get PARENT () {
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    return PARENT_SYMBOL
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  }
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  static get ROOT () {
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    return ROOT_SYMBOL
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  }
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  get PARENT () {
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    return PARENT_SYMBOL
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  }
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  get ROOT () {
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    return ROOT_SYMBOL
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  }
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  /**
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   * run the kernels code with a given enviroment
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   * The Kernel Stores all of its state in the Environment. The Interface is used
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   * to by the VM to retrive infromation from the Environment.
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   */
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  async run (message, imports = this.imports) {
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    const state = this.state.copy()
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    const result = await this._vm.run(message, this, imports)
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    if (!result.execption) {
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      // update the state
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      this.state.set([], state)
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    }
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    return result
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  }
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  async recieve (message) {
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    if (message.isCyclic(this)) {
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      const result = await this.run(message)
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      message.finished()
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      return result
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    } else {
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      return this._messageQueue.add(message)
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    }
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  }
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  async send (port, message) {
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    message.sending(this, this._messageQueue.currentMessage)
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    // replace root with parent path to root
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    if (port === ROOT_SYMBOL) {
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      port = PARENT_SYMBOL
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      message.to = new Array(this.state.path.length - 1).fill(PARENT_SYMBOL).concat(message.to)
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    }
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    if (port === PARENT_SYMBOL) {
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      message.from.push(this.state.name)
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    } else {
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      message.from.push(this.PARENT)
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    }
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    const dest = await this.getPort(port)
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    return dest.recieve(message)
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  }
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  async getPort (port) {
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    if (this._instanceCache.has(port)) {
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      return this._instanceCache.get(port)
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    } else {
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      const destState = await (
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        port === this.PARENT
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        ? this.state.getParent()
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        : this.state.get([port]))
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      const kernel = new Kernel({
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        state: destState
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      })
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      this._instanceCache.set(port, kernel)
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      return kernel
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    }
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  }
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}
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