The mbed_sdk_init can be called either during cold boot or during
application boot after bootloader has been executed.
In case the bootloader has already enabled the cache,
is is needed to not enable it again.
Index the FileHandle array from 0 - now if filehandle[0..2] is
NULL, it uses the built-in serial for stdin/stdout/stderr,
else it will use a FileHandle.
No mechanism to actually put a FileHandle in that position yet.
Fill in a gap by providing the POSIX file functions corresponding
to the FileHandle API, so FileHandles can be used from C without
going through the C library stdio layer.
This aligns with the fact we already provide POSIX directory
functions.
Fix EOF handling for ARM C Library _sys_read.
Given the 64-bit timebase, add wait_until to Semaphore.
Naming is based on Thread::wait_until.
pthreads uses "timedwait", but that's not a good fit against our
existing wait() - pthreads only has an absolute-time wait, not relative.
Given the 64-bit timebase, add trylock_until to Mutex.
Naming is based on a combination of Mutex::trylock, Thread::wait_until,
and C++11 timed_mutex::try_lock_until.
pthreads and C11 use "timedlock", but that's not a good fit against our
existing trylock() and lock(timeout) - they have only absolute-time
waits, not relative.
To increase the similarity to C++11, add trylock_for - same parameters
as lock, but with the bool return value of trylock and trylock_until.
Add an assertion when convering status codes to booleans to check that
there are no non-timeout errors.
Given the 64-bit timebase, add wait_until to ConditionVariable.
Move the timeout example to wait_until(), and give wait_for() an
alternative example, as it's no longer the best option for a
timeout.
Tidy up - remove the redundant RESUME_SIGNAL definition.
Give C++ access to the RTOS's absolute timebase, reducing the need to
run private Timers and similar. Allows wait_until functionality, and
makes it easier to avoid time drift.
Place it in a new header and namespace in case we want more kernel
functions in future.
Try to cover over the breaking API change potentially upcoming in
CMSIS-RTOS 2.1.1, when it reduces the tick count from 64-bit to 32-bit.
(See https://github.com/ARM-software/CMSIS_5/issues/277)
Explicitly state that ticks are milliseconds in mbed OS, despite CMSIS
RTOS 2 permitting different tick rates.
See also https://github.com/ARMmbed/mbed-os/pull/3648 (wait_until
for condition variables) and
https://github.com/ARMmbed/mbed-os/issues/5378 (EventQueue should
use RTOS tick count).