Originally this restriction was placed due to uncertainty around the
thread safety of the ASIO API. While the ASIO API itself makes no
thread-safety guarantees that we are aware of, the `asio-sys` high-level
bindings enforce synchronised access to the API and state transitions
via a mutex.
This is in order to ensure consistent restrictions across platforms in a
manner that ensures thread safety across each of the supported
platforms.
Please see added comments in the diff for details on which platforms
impose these restrictions.
For the most part, behaviour should be largely unchanged, however each
individual stream now has its own `set_timeout` callback loop, rather
than using one for processing all streams at once.
Many TODOs remain within the `emscripten` backend. These were left
untouched for the most part in favour of addressing this in a more
web-focused, future PR.
This existed prior to the introduction of the `Host` API, but was lost
in translation. This re-adds the bounds so that downstream code does not
suddenly break due to a lacking `Hash` implementation in the next
CPAL version.
Now runs the beep and enumerate examples nicely! Time to do a proper
code review of the ASIO stuff and see how to best take advantage of the
new `Host` API.
This is a draft implementation of #294. I'll leave this open for
feedback and potentially better trait naming suggestions or better
solutions in general!
cc @ishitatsuyuki
Re-exports host-specific types so that they are available within the
platform module if necessary (e.g. host::asla::Host as AlsaHost).
Allows for converting platform-specific host types (e.g. AlsaHost) into
the dynamically dispatched type generated for the target platform
(`Host`).
This is an implementation of the API described at #204. Please see that
issue for more details on the motivation.
-----
A **Host** provides access to the available audio devices on the system.
Some platforms have more than one host available, e.g.
wasapi/asio/dsound on windows, alsa/pulse/jack on linux and so on. As a
result, some audio devices are only available on certain hosts, while
others are only available on other hosts. Every platform supported by
CPAL has at least one **DefaultHost** that is guaranteed to be available
(alsa, wasapi and coreaudio). Currently, the default hosts are the only
hosts supported by CPAL, however this will change as of landing #221 (cc
@freesig). These changes should also accommodate support for other hosts
such as jack #250 (cc @derekdreery) and pulseaudio (cc @knappador) #259.
This introduces a suite of traits allowing for both compile time and
runtime dispatch of different hosts and their uniquely associated device
and event loop types.
A new private **host** module has been added containing the individual
host implementations, each in their own submodule gated to the platforms
on which they are available.
A new **platform** module has been added containing platform-specific
items, including a dynamically dispatched host type that allows for
easily switching between hosts at runtime.
The **ALL_HOSTS** slice contains a **HostId** for each host supported on
the current platform. The **available_hosts** function produces a
**HostId** for each host that is currently *available* on the platform.
The **host_from_id** function allows for initialising a host from its
associated ID, failing with a **HostUnavailable** error. The
**default_host** function returns the default host and should never
fail.
Please see the examples for a demonstration of the change in usage. For
the most part, things look the same at the surface level, however the
role of device enumeration and creating the event loop have been moved
from global functions to host methods. The enumerate.rs example has been
updated to enumerate all devices for each host, not just the default.
**TODO**
- [x] Add the new **Host** API
- [x] Update examples for the new API.
- [x] ALSA host
- [ ] WASAPI host
- [ ] CoreAudio host
- [ ] Emscripten host **Follow-up PR**
- [ ] ASIO host #221
cc @ishitatsuyuki more to review for you if you're interested, but it
might be easier after #288 lands and this gets rebased.
