Allow for v8.serialize() to write to a target Uint8Array

[mcollina]

Consider this function that writes a given object to a SharedArrayBuffer, using v8.serialize():

function write (buffer, object, byteOffset = 0) {
  const data = serialize(object)

  if (buffer.byteLength < data.byteLength + 4 + byteOffset) {
    if (!buffer.growable) {
      throw new Error('Buffer is not growable')
    }
    /* c8 ignore next 2 */
    buffer.grow(data.byteLength + 4 + byteOffset)
  }
  const view = new DataView(buffer, byteOffset)
  view.setUint32(0, data.byteLength, true)
  new Uint8Array(buffer, byteOffset + 4).set(data)
}

This unfortunately causes a full copy of the object from the output of v8.serialize() into the target SharedArrayBuffer. If we could add a target, something like:

serialize(object, {
  buffer,
  offset,
  growIfNeeded: true
})

We could save a full copy of the buffer in this way.

If growing as needed is not feasible, we could do:

function write (object, buffer, offset) {
  try {
    serialize(object, { buffer, offset })
  } catch (err) {
    if (err.code === 'BUFFER_TOO_SMALL') {
      buffer = buffer.grow(err.neededSize)
      serialize(object, buffer, offset)
    } else {
      throw err
    }
  }
}