git ssb

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