Volatile will provide protection to sequence re-ordering and guarantee
the variable is fetched from memory, but it won't provide the memory
barrier needed to ensure that no re-ordering (by either the compiler or
the CPU) will happen among other threads of execution
accessing the same variables.
For more info about this effect can be found on articles about
std::memory_order.
When using reserved(), the reserved memory cannot be read before it's
written, therefore we cannot update 'tail' until the caller of
reserved() is done writing.
To solve that, a method called 'commit()' was added so the caller can
inform that is done with the memory usage and is safe to update 'tail'.
The caller also has to inform the length that was actually written.
This solution was developed to work considering the usage context of
this class: 1 reader and 1 writer **only**.
Adds a method called `reserve()`, that will take a ByteBuffer::IoVec
array of at least two elements, and return the number of elements
filled out. 0 will be returned if `len` is over the total space of
the buffer; 1 will be returned if there's enough contiguous bytes in
the buffer; 2 will be returned if there are two non-contiguous blocks
of memory.
This method is suitable to be used with POSIX system calls such as
readv(), and is an optimization to not require temporary memory copies
while reading from a file descriptor.
Also modify the write() method to use reserve(), so that similar checks
are performed only in one place.
Modify ByteBuffer class to have a `peekiovec()` method, that takes in a
`struct IoVec` array (similar to `struct iovec` from POSIX), and a
number of bytes, and returns the number of elements from this array
that have been filled out. It is either 0 (buffer is empty), 1
(there's enough contiguous bytes to read that amount) or 2 (ring buffer
is wrapping around).
This enables using scatter-gather I/O (i.e. writev()), removing calls
to memcpy(). That's one call when no wrap-around is happening, and
two calls if it is.
Also, rewrite `ByteBuffer::peekbytes()` to use `peekiovec()`, so that
some of the checks performed by the former are not replicated in the
latter.
../../libraries/AP_HAL/examples/Printf/Printf.cpp:63:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
if (ret != strlen(float_tests[i].result)) {
^
...
ardupilot/modules/gtest/include/gtest/gtest.h:1448:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
if (expected == actual) {
^
And similar ones.
This is very similar to std::unique_ptr, but doesn't require including
the <memory> header which pulls lots of c++ headers and cause problems
with nuttx headers. It's header-only. It contains an explanation on what
it solves, how to use and unit tests.
Fix warning that reveals a real bug:
In file included from libraries/AP_HAL_Linux/UARTDriver.cpp:25:0:
libraries/AP_HAL_Linux/UARTDriver.cpp: In member function 'virtual bool Linux::UARTDriver::tx_pending()':
libraries/AP_HAL/utility/RingBuffer.h:21:35: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
#define BUF_EMPTY(buf) buf##_head == buf##_tail
^
libraries/AP_HAL_Linux/UARTDriver.cpp:355:13: note: in expansion of macro 'BUF_EMPTY'
return !BUF_EMPTY(_writebuf);
The problem is when there's a ! operator: without the parenthesis we would actually be doing
return !_write_buf_head == _write_buf_tail
which is not what we want.
As commented in 8218140 ("AP_Common: add scanf format macro"), "FORMAT"
was a bad name for this macro since there's also the scanf. Rename to
FMT_PRINTF to follow the scanf name.
Most of AP_Progmem is already gone so we can stop including it in most
of the places. The only places that need it are the ones using
pgm_read_*() APIs.
In some cases the header needed to be added in the .cpp since it was
removed from the .h to reduce scope. In those cases the headers were
also reordered.
prog_char and prog_char_t are now the same as char on supported
platforms. So, just change all places that use them and prefer char
instead.
AVR-specific places were not changed.
Now variables don't have to be declared with PROGMEM anymore, so remove
them. This was automated with:
git grep -l -z PROGMEM | xargs -0 sed -i 's/ PROGMEM / /g'
git grep -l -z PROGMEM | xargs -0 sed -i 's/PROGMEM//g'
The 2 commands were done so we don't leave behind spurious spaces.
AVR-specific places were not changed.
The PSTR is already define as a NOP for all supported platforms. It's
only needed for AVR so here we remove all the uses throughout the
codebase.
This was automated with a simple python script so it also converts
places which spans to multiple lines, removing the matching parentheses.
AVR-specific places were not changed.
This commit changes the way libraries headers are included in source files:
- If the header is in the same directory the source belongs to, so the
notation '#include ""' is used with the path relative to the directory
containing the source.
- If the header is outside the directory containing the source, then we use
the notation '#include <>' with the path relative to libraries folder.
Some of the advantages of such approach:
- Only one search path for libraries headers.
- OSs like Windows may have a better lookup time.
Now that we are using C++11 we can use variadic templates to simplify
the FastDelegate classes. It also simplifies moving away from the
FastDelegate implementation.
This is a Functor implementation that should cover the use cases we have
for FastDelegate. In contrary to the latter, it can be constructed at
compile time so the compiler can safely put it in a read-only section
which covers the cases in which we are not using it.
the function:
virtual size_t AP_HAL::Print::write(const uint8_t *buffer, size_t size);
was hidden in all derived classes by their
virtual size_t write(uint8_t) = 0; implementations.
To solve this, a non-virtual write(const uint8_t *, size_t) that calls a
virtual write_implementation was added.
This isn't necessary atm, because the derived classes don't call
write(const uint8_t *, size_t), BUT this decreases the apm2-quad Program
size by 40 bytes :D and removes warnings.
- Define float versions of math functions to the double versions
on AVR (eg. #define sinf sin).
- These macros appear to be missing in older versions of avr-libs.
- Include AP_Math.h rather than math.h to get these definitions.
- Allows use of hardware floating point on the Cortex-M4.
- Added "f" suffix to floating point literals.
- Call floating point versions of stdlib math functions.
* BetterStream Means AP_HAL depends on AP_Common, for now, in order to have
the AVR specific pgm_char_t defined.
I'll need to factor that out in the future but for now it can stay
Lucas De Marchi
Murilo Belluzzo
Leandro Pereira
Andrew Tridgell
Ricardo de Almeida Gonzaga
Tom Pittenger
Gustavo Jose de Sousa
Staroselskii Georgii
Grant Morphett
Andrew Tridgell
Tobias
James Bielman
Pat Hickey