This commit adds a C99 stdio value formatter capability where
generated text is emitted through a callback. This allows generation
of arbitrarily long output without a buffer, functionality that is
core to printk, logging, and other system and application needs.
The formatter supports most C99 specifications, excluding:
* %Lf long double conversion
* wide character output
Kconfig options allow disabling features like floating-point
conversion if they are not necessary. By default most conversions are
enabled.
The original z_vprintk() implementation is adapted to meet the
interface requirements of cbvprintf, and made available as an opt-in
feature for space-constrained applications that do not need full
formatting support.
Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
