An operation often has two pieces of underlying information:
* the data returned as a result from that operation
* an error that occurred while retrieving that data
Merely returning the data is not good enough. Result<> allows exposing
both the data, and the underlying error, and forces (via clang's
consumable attribute) you to check for the error before you try to
access the data.
Put simply, Error<> is a way of forcing error handling onto an API user.
Given a function like:
bool might_work();
The following code might have been written previously:
might_work(); // but what if it didn't?
The easy way to work around this is of course to [[nodiscard]] might_work.
But this doesn't work for more complex cases like, for instance, a
hypothetical read() function which might return one of _many_ errors
(typically signalled with an int, let's say).
int might_read();
In such a case, the result is often _read_, but not properly handled. Like:
return buffer.substr(0, might_read()); // but what if might_read returned an error?
This is where Error<> comes in:
typedef Error<int, 0> ReadError;
ReadError might_read();
auto res = might_read();
if (might_read.failed()) {
switch (res.value()) {
case EBADF:
...
}
}
Error<> uses clang's consumable attributes to force failed() to be
checked on an Error instance. If it's not checked, then you get smacked.
The goal here is to generate most of this code from IPC protocol
descriptions, but for now I've spelled them all out to get started.
Each message gets a wrapper class in the ASAPI_Client or ASAPI_Server
namespace. They are convertible to and from the old message structs.
The real hotness happens when you want to make a synchronous request
to the other side:
auto response = send_sync<ASAPI_Client::GetMainMixVolume>();
Each request class knows his corresponding response class, so in the
above example, "response" will be an ASAPI_Server::DidGetMainMixVolume
object, and we can get the volume like so:
int volume = response.volume();
For posting messages that don't expect a response, you can still use
post_message() since the message classes are convertible:
post_message(ASAPI_Server::DidGetMainMixVolume(volume));
It's not perfect yet, but I already really like it. :^)
Both on_square_clicked and flood_mark were very similar so I've
introduced the on_square_clicked_impl function which is now
called by on_square_clicked and flood_fill.
Give the mixer a main volume value (percent) that we scale all the
outgoing samples by (before clipping.)
Also add a simple "avol" program for querying and setting the volume:
- "avol" prints the current volume.
- "avol 200" sets the main mix volume to 200%
We had some kernel-specific gizmos in AK that should really just be in the
Kernel subdirectory instead. The only thing remaining after moving those
was mmx_memcpy() which I moved to the ARCH(i386)-specific section of
LibC/string.cpp.
Processes can now have an icon assigned, which is essentially a 16x16 RGBA32
bitmap exposed as a shared buffer ID.
You set the icon ID by calling set_process_icon(int) and the icon ID will be
exposed through /proc/all.
To make this work, I added a mechanism for making shared buffers globally
accessible. For safety reasons, each app seals the icon buffer before making
it global.
Right now the first call to GWindow::set_icon() is what determines the
process icon. We'll probably change this in the future. :^)
Show some information about the file we're playing, and display how many
samples we've played out of how many total.
This might be a bit buggy as I haven't tested it with many different files,
but it's a start. :^)
This is a total hack, because I haven't really looked into why these are
happening. Somehow we're producing one extra sample and it's glitching
up the sound stream ever so slightly.
Each client connection now sets up an ASBufferQueue, which is basically a
queue of ABuffers. This allows us to immediately start streaming the next
pending buffer whenever our current buffer runs out of samples.
This makes the majority of the skippiness go away for me. :^)
Also get rid of the old PlayBuffer API, since we don't need it anymore.
This adds a bounds check to the loop that writes to the buffer
'recognized_symbols'. This prevents buffer overflows in the
case when a programs backtrace is particularly large.
Fixes#371.
The previous implementation of the PIIX3/4 PATA/IDE channel driver only
supported a single drive, as the object model was wrong (the channel
inherits the IRQ, not the disk drive itself). This fixes it by 'attaching'
two `PATADiskDevices` to a `PATAChannel`, which makes more sense.
The reading/writing code is presented as is, which violates the spec
outlined by Seagate in the linked datasheet. That spec is rather old,
so it might not be 100% up to date, though may cause issues on real
hardware, so until we can actually test it, this will suffice.
Now that we can set icons directly "by bitmap", there's no need for passing
around the icon paths anymore, so get rid of all the IPC and API related
to that. :^)
Now that we support more than 2 clients per shared buffer, we can use them
for window icons. I didn't do that previously since it would have made the
Taskbar process unable to access the icons.
This opens up some nice possibilities for programmatically generated icons.
Thanks to Dan for pointing this out on IRC:
<danboid> I see TextEditor still numbers its lines from 0. You're too much of a programmer sometimes kling! :)
< kling> that might be the most extreme form of "programmer design" I've seen in serenity
We were limiting ourselves to only play WAV files smaller than 42 MB
for no particular reason. This patch increases the limit to 1 GB.
Perhaps there should not be any limit at all, but 1GB seems like a
reasonable sanity check at the moment. :^)
This allows us to carry the same buffer all the way from the WAV loader
to the AudioServer mixer.
This alleviates some of the stutter, but there's still a noticeable
skip when switching buffers. We're gonna need to do better. :^)
I had to solve a bunch of things simultaneously to make this work.
Refactor AWavLoader to be a streaming loader rather than a one-shot one.
The constructor parses the header, and if everything looks good, you can
repeatedly ask the AWavLoader for sample buffers until it runs out.
Also send a message from AudioServer when a buffer has finished playing.
That allows us to implement a blocking variant of play().
Use all of this in aplay to play WAV files chunk-at-a-time.
This is definitely not perfect and it's a little glitchy and skippy,
but I think it's a step in the right direction.
