git ssb

1
const ReferanceMap = require('reference-map')
2
const AbstractContainer = require('primea-abstract-container')
3
const ContainerTable = require('primea-container-table')
4
5
module.exports = class WasmContainer extends AbstractContainer {
6
  /**
7
   * The wasm container runs wasm code and provides a basic API for wasm
8
   * interfaces for interacting with the kernel
9
   * @param {object} kernel - the kernel instance
10
   * @param {object} interfaces - a map of interfaces to expose to the wasm binary
11
   */
12
  constructor (kernel, interfaces) {
13
    super()
14
    this.kernel = kernel
15
    this.imports = interfaces
16
    this.referanceMap = new ReferanceMap()
17
  }
18
19
  async onCreation (message) {
20
    let code = this.kernel.code
21
    if (!WebAssembly.validate(code)) {
22
      throw new Error('invalid wasm binary')
23
    } else {
24
      for (const name in this.imports) {
25
        const interf = this.imports[name]
26
        if (interf.initialize) {
27
          code = await interf.initialize(code)
28
        }
29
      }
30
      this.kernel.state.code = code
31
    }
32
    return this._run(message, 'onCreation')
33
  }
34
35
  /**
36
   * Runs the wasm VM given a message
37
   * @param {object} message
38
   * @returns {Promise} a promise that resolves once the compuation is finished
39
   */
40
  onMessage (message) {
41
    return this._run(message, 'onMessage')
42
  }
43
44
  async _run (message, method) {
45
    // Builds a import map with an array of given interfaces
46
    const importMap = {}
47
    for (const name in this.imports) {
48
      importMap[name] = {}
49
      const Import = this.imports[name]
50
      const newInterface = new Import(this)
51
      const props = Object.getOwnPropertyNames(Import.prototype)
52
53
      // bind the methods to the correct 'this'
54
      for (const prop of props) {
55
        if (prop !== 'constructor') {
56
          importMap[name][prop] = newInterface[prop].bind(newInterface)
57
        }
58
      }
59
    }
60
61
    const result = await WebAssembly.instantiate(this.kernel.code, importMap)
62
    this.instance = result.instance
63
64
    // add the message and ports to the refereance map
65
    const messageRef = this.referanceMap.add(message)
66
67
    // runs the wasm code
68
    this.instance.exports[method](messageRef)
69
    return this.onDone()
70
  }
71
72
  /**
73
   * returns a promise that resolves when the wasm instance is done running
74
   * @returns {Promise}
75
   */
76
  async onDone () {
77
    let prevOps
78
    while (prevOps !== this._opsQueue) {
79
      prevOps = this._opsQueue
80
      await prevOps
81
    }
82
    this.referanceMap.clear()
83
  }
84
85
  /**
86
   * Pushed an async operation to the a promise queue that
87
   * @returns {Promise} the returned promise resolves in the order the intail
88
   * operation was pushed to the queue
89
   */
90
  pushOpsQueue (promise) {
91
    this._opsQueue = Promise.all([this._opsQueue, promise])
92
    return this._opsQueue
93
  }
94
95
  /**
96
   * executes a callback given an index in the exported callback container
97
   * @param {integer} cb
98
   * @param {*} val - a value to return to the callback function
99
   */
100
  execute (cb, val) {
101
    this.instance.exports.callbacks.get(cb)(val)
102
  }
103
104
  /**
105
   * returns a section of memory from the wasm instance
106
   * @param {integer} offset
107
   * @param {integer} length
108
   * @returns {Uint8Array}
109
   */
110
  getMemory (offset, length) {
111
    return new Uint8Array(this.instance.exports.memory.buffer, offset, length)
112
  }
113
114
  setMemory (offset, val) {
115
    const mem = this.getMemory(offset, val.length)
116
    mem.set(val)
117
  }
118
119
  static get typeId () {
120
    return ContainerTable.WebAssembly
121
  }
122
}
123