sys/progress_bar: add module for managing a progress bar in stdout

[aabadie]

Contribution description

This PR add a module for managing a progress on the stdout of RIOT.
The feature makes use of ASCII escape codes to fully redraw the progress bar when the update function is called.

Note that the progress bar doesn't work well with pyterm as a redraw of the progress bar doesn't contain the \n character. It's possible to hack around this but the result is not nice.

The goal of the progress bar is to display the download status of a firmware during an update (PR will come soon)

Testing procedure

make BOARD=<board of your choice> -C tests/progress_bar flash test

Issues/PRs references

None

[kaspar030]

Nice one.

I'm not happy with the forced 68b per progress bar. See my suggestion on removing that for the simple use case.

[kaspar030]

If you change this to use 0-255 instead of 0-100, the two multiplications turn into shifts. Also, the assert on top of this function becomes obsolete. Similar at the call site.

Not sure that justifies not using percentages.

[kaspar030]

this check is redundant, printf will printf will not print if the string is empty.

[aabadie]

I removed it here but kept the check on the prefix as otherwise some garbage is printed if nothing is set in the buffer.

[kaspar030]

How is that possible? Is the structure allocated on the stack and not emptied?
Shouldn't printf("%s", { \0, ... }) print nothing?

[aabadie]

Declaring the progress bar static works but not on the stack indeed.

[kaspar030]

That might be because defined statically, it'll be zeroed. On the stack it has random contents unless cleared.

[aabadie]

That might be because defined statically, it'll be zeroed. On the stack it has random contents unless cleared.

Makes sense. Maybe there should be a note about this in the documentation. Another possibility is to introduce a progress_bar_init function to ensure buffers are correctly cleared before using a progress bar allocated on the stack.

[aabadie]

Thanks for your review @kaspar030!
I'll address your comments ASAP.

[aabadie]

I pushed a couple of commits that makes the progress bar usable even with pyterm. It's a bit hacky (use ascii escape codes to save and restore the cursor position) but it works. Is it worth though ?

[fjmolinas]

@kaspar030 seems like your comments have been addressed, except for some style comments, are you ok with the changes?

[kaspar030]

ACK. Tested on native and arduino-mega2560.

Personally I don't agree with in-memory buffers within progress_bar_t, and the need to handle multiple progress bars within the library. But with the change to an independent progress_bar_print(), that's now optional, so it won't hurt.