Adding a very first start section to get people going after flashing.
I tried to condense it to a minimum to avoid as much as possible
redundancy and bloating.
Both read and write operations support variants where either a) a single
call is made to the undelying stream implementation and returned buffer
length may be less than requested, or b) calls are repeated until requested
amount of data is collected, shorter amount is returned only in case of
EOF or error.
These operations are available from the level of C support functions to be
used by other C modules to implementations of Python methods to be used in
user-facing objects.
The rationale of these changes is to allow to write concise and robust
code to work with *blocking* streams of types prone to short reads, like
serial interfaces and sockets. Particular object types may select "exact"
vs "once" types of methods depending on their needs. E.g., for sockets,
revc() and send() methods continue to be "once", while read() and write()
thus converted to "exactly" versions.
These changes don't affect non-blocking handling, e.g. trying "exact"
method on the non-blocking socket will return as much data as available
without blocking. No data available is continued to be signaled as None
return value to read() and write().
From the point of view of CPython compatibility, this model is a cross
between its io.RawIOBase and io.BufferedIOBase abstract classes. For
blocking streams, it works as io.BufferedIOBase model (guaranteeing
lack of short reads/writes), while for non-blocking - as io.RawIOBase,
returning None in case of lack of data (instead of raising expensive
exception, as required by io.BufferedIOBase). Such a cross-behavior
should be optimal for MicroPython needs.
To use frozen bytecode make a subdirectory under the unix/ directory
(eg frozen/), put .py files there, then run:
make FROZEN_MPY_DIR=frozen
Be sure to build from scratch. The .py files will then be available for
importing.
When an mpy file is frozen it must know the values of certain
configuration variables. This patch provides an explicit check in the
generated C file that the configuration variables are what they are
supposed to be.
That one was missing in the module, even if it was available in the
vfs object. The change consist of adding the name and preparing the
call to the underlying vfs module, similar to what was already
implemented e.g. for remove.
Rename is useful by itself, or for instance for a safe file replace,
consisting of the sequence:
write to a temp file
delete the original file
rename the temp file to the original file's name
Calling it from lwIP accept callback will lead incorrect functioning
and/or packet leaks if Python callback has any networking calls, due
to lwIP non-reentrancy. So, instead schedule "poll" callback to do
that, which will be called by lwIP when it does not perform networking
activities. "Poll" callback is called infrequently though (docs say
every 0.5s by default), so for better performance, lwIP needs to be
patched to call poll callback soon after accept callback, but when
current packet is already processed.
For example, the following code now works with a file on the SD card:
f = open('test', 'rb') # test must be 1024 bytes or more in size
f.seek(511)
f.read(513)
Also works for writing.
Fixes issue #1863.
Address printed was truncated anyway and in general confusing to outsider.
A line which dumps it is still left in the source, commented, for peculiar
cases when it may be needed (e.g. when running under debugger).
Torwag
Paul Sokolovsky
Damien George
Robert HH
Radomir Dopieralski