Update modem.js

[ghost]

you have 2 issues this proposes to fix:

1. you read the tar synchronously. so you're blocking the event loop.
2. you create a single consistent buffer for the entire content of the tar, so a tar of 1GB has no chance of passing.

replacing readFileSync with stream solves these issues.

FYI

[apocas]

I will test this fix.

Many versions ago reading the contents asynchronously would create havoc on docker side.
There were also some issues regarding the content-length which I can't remember right now.

I will take a look and if everything runs great will merge it :)

[apocas]

Have you checked this: apocas/dockerode#128 ?

PS: bigger files should/can use stream interface directly, this doesn't invalidate investigation into the possibility to replace *sync functions.

[apocas]

Let's keep these sync calls for now, this way it is possible to use a sync strategy directly or an async strategy using streams as apocas/dockerode#128
keeping everyone happy for now :)