Upon start-up, _boot module is executed from frozen files to do early
initialization, e.g. create and mount the flash filesystem. Then
"boot.py" is executed if it exists in the filesystem. Finally, "main.py"
is executed if exists to allow start-on-boot user applications.
This allows a user to make a custom boot file or startup application
without recompiling the firmware, while letting to do early initialization
in Python code.
Based on RFC https://github.com/micropython/micropython/issues/1955.
Will call underlying C virtual methods of stream interface. This isn't
intended to be added to every stream object (it's not in CPython), but
is convenient way to expose extra operation on Python side without
adding bunch of Python-level methods.
This is strange asymmetry which is sometimes needed, e.g. for WebREPL: we
want to process only available input and no more; but for output, we want
to get rid of all of it, because there's no other place to buffer/store
it. This asymmetry is akin to CPython's asyncio asymmetry, where reads are
asynchronous, but writes are synchronous (asyncio doesn't expect them to
block, instead expects there to be (unlimited) buffering for any sync write
to completely immediately).
Damien George
Paul Sokolovsky
pohmelie
Tom Sparks
Martin Fischer