Added withReadStream option to load a file in chunks (useful for large files which don't fit in RAM)

[redsolver]

Should work with Flutter Web and IO. Also see #465
Can for example be used with a multipart file upload.

[miguelpruivo]

Thank you, this may come in handy for some. I left you some review comments.

[miguelpruivo]

Thank you.

[miguelpruivo]

@redsolver mind to provide an example on how do you create a File instance by using this approach? Thank you!

[redsolver]

@miguelpruivo

The withReadStream option is not meant to be used to create a File instance. Instead it directly returns a Stream<List<int>>, similar to the openRead() method used by a File instance: https://api.dart.dev/stable/2.13.4/dart-io/File/openRead.html

The added benefit of withReadStream is that it works on both dart:io and dart:html with the same API.

[miguelpruivo]

@redsolver that's correct. What would be a good use case for it other than just uploading multipart file?

[redsolver]

@miguelpruivo Uploading large files, encrypting or decrypting large files or just processing large files like importing a database, text file or JSON.

[miguelpruivo]

@redsolver did you manage to find a way to map it to a File instance?

[redsolver]

@miguelpruivo I don't know why someone would want to do that?

[miguelpruivo]

@redsolver because I had someone asking me an example for that and couldn't find a way to. 😄 Maybe you want to help me out over here.