napi-rs/wasm-runtime/fs-proxy.cjs

// @ts-check

/**
 * @param {unknown} value
 */
const getType = (value) => {
  if (value === undefined) return 0
  if (value === null) return 1
  const t = typeof value
  if (t === 'boolean') return 2
  if (t === 'number') return 3
  if (t === 'string') return 4
  if (t === 'object') return 6
  if (t === 'bigint') return 9
  return -1
}

/**
 * @param {import('memfs').IFs} memfs
 * @param {any} value
 * @param {ReturnType<typeof getType>} type
 * @returns {Uint8Array}
 */
const encodeValue = (memfs, value, type) => {
  switch (type) {
    case 0:
    case 1:
      return new Uint8Array(0)
    case 2: {
      const view = new Int32Array(1)
      view[0] = value ? 1 : 0
      return new Uint8Array(view.buffer)
    }
    case 3: {
      const view = new Float64Array(1)
      view[0] = value
      return new Uint8Array(view.buffer)
    }
    case 4: {
      const view = new TextEncoder().encode(value)
      return view
    }
    case 6: {
      const [entry] = Object.entries(memfs).filter(([_, v]) => v === value.constructor)[0] ?? []
      if (entry) {
        Object.defineProperty(value, '__constructor__', {
          configurable: true,
          writable: true,
          enumerable: true,
          value: entry
        })
      }

      const json = JSON.stringify(value, (_, value) => {
        if (typeof value === 'bigint') {
          return `BigInt(${String(value)})`
        }
        return value
      })
      const view = new TextEncoder().encode(json)
      return view
    }
    case 9: {
      const view = new BigInt64Array(1)
      view[0] = value
      return new Uint8Array(view.buffer)
    }
    case -1:
    default:
      throw new Error('unsupported data')
  }
}

/**
 * @param {import('memfs').IFs} fs
 * @returns {(e: { data: { __fs__: { sab: Int32Array, type: keyof import('memfs').IFs, payload: any[] } } }) => void}
 */
module.exports.createOnMessage = (fs) => function onMessage(e) {
  if (e.data.__fs__) {
    /**
     * 0..4                    status(int32_t):        21(waiting) 0(success) 1(error)
     * 5..8                    type(napi_valuetype):   0(undefined) 1(null) 2(boolean) 3(number) 4(string) 6(jsonstring) 9(bigint) -1(unsupported)
     * 9..16                   payload_size(uint32_t)  <= 1024
     * 16..16 + payload_size   payload_content
     */
    const { sab, type, payload } = e.data.__fs__
    const fn = fs[type]
    const args = payload ? payload.map((value) => {
      if (value instanceof Uint8Array) {
        // buffer polyfill bug
        // @ts-expect-error
        value._isBuffer = true
      }
      return value
    }) : payload
    try {
      const ret = fn.apply(fs, args)
      const t = getType(ret)
      const v = encodeValue(fs, ret, t)
      Atomics.store(sab, 0, 0)
      Atomics.store(sab, 1, t)
      Atomics.store(sab, 2, v.length)
      new Uint8Array(sab.buffer).set(v, 16)

    } catch (/** @type {any} */ err) {
      Atomics.store(sab, 0, 1)
      Atomics.store(sab, 1, 6)
      const payloadContent = new TextEncoder().encode(JSON.stringify({
        ...err,
        message: err.message,
        stack: err.stack
      }))
      Atomics.store(sab, 2, payloadContent.length)
      new Uint8Array(sab.buffer).set(payloadContent, 16)
    } finally {
      Atomics.notify(sab, 0)
    }
  }
}

/**
 * @param {import('memfs').IFs} memfs
 */
module.exports.createFsProxy = (memfs) => new Proxy({}, {
  get (_target, p, _receiver) {
    /**
     * @param {any[]} args
     */
    return function (...args) {
      const sab = new SharedArrayBuffer(16 + 1024)
      const i32arr = new Int32Array(sab)
      Atomics.store(i32arr, 0, 21)

      // @ts-expect-error
      postMessage({
        __fs__: {
          sab: i32arr,
          type: p,
          payload: args
        }
      })

      Atomics.wait(i32arr, 0, 21)

      const status = Atomics.load(i32arr, 0)
      const type = Atomics.load(i32arr, 1)
      const size = Atomics.load(i32arr, 2)
      const content = new Uint8Array(sab, 16, size)
      if (status === 1) {
        const errobj = JSON.parse(new TextDecoder().decode(content.slice()))
        const err = new Error(errobj.message)
        Object.defineProperty(err, 'stack', {
          configurable: true,
          enumerable: false,
          writable: true,
          value: errobj.stack
        })
        for (const [k, v] of Object.entries(errobj)) {
          if (k === 'message' || k === 'stack') continue
          // @ts-expect-error
          err[k] = v
        }
        throw err
      }
      if (type === 0) return undefined
      if (type === 1) return null
      if (type === 2) return Boolean(content[0])
      if (type === 3) return new Float64Array(sab, 16, 1)[0]
      if (type === 4) return new TextDecoder().decode(content.slice())
      if (type === 6) {
        const obj = JSON.parse(new TextDecoder().decode(content.slice()), (_key, value) => {
          if (typeof value === 'string') {
            const matched = value.match(/^BigInt\((-?\d+)\)$/)
            if (matched && matched[1]) {
              return BigInt(matched[1])
            }
          }
          return value
        })
        if (obj.__constructor__) {
          const ctor = obj.__constructor__
          delete obj.__constructor__
          // @ts-expect-error
          Object.setPrototypeOf(obj, memfs[ctor].prototype)
        }
        return obj
      }
      if (type === 9) return new BigInt64Array(sab, 16, 1)[0]
      throw new Error('unsupported data')
    }
  }
})