FPG-Alan / file-downloader

File Downloader

Implement a browsers-compatible file system as a basis for download(and upload, perhaps) large files on the front end.

On Chrome, adopt the Filesystem API, the maximum size depends on the client's hard drive size.

On other browsers, use blob saved in RAM, has a 2GB size limit under 64-bit addressing or 1GB size limit under 32-bit addressing.

If the file size exceeds the limit mentioned above, we recommend that users download the file using the desktop application(temporarily a command line program).

Theory

1. (External) call addFile/addFiles, create File instaces.
2. Determine the IO method based on the current browser environment.
3. Each File instance initialize self, calculate and split chunks{start, end}.
4. Traversing all file instaces' chunks, fetch data of each chunk.
5. File instance receive data of chunk, enter write state.