Add Coreaudio ID to Portaudio device index mapping

[douglasheld2]

It is sometimes useful to be able to correlate a coreaudio device to a Portaudio device, especially when multiple coreaudio devices have the same name and need to be differentiated by their ID numbers.

After compiling in this extra function, the IDs can be correlated with the following function in python:

from cffi import FFI

_pa_extra_ffi = FFI()
_pa_extra_ffi.cdef("""
    int PaMacCore_GetDeviceIndexForAudioDeviceID(unsigned int id);
""")

_pa_extra_lib = _pa_extra_ffi.dlopen(
    "/Users/doug/Library/Python/3.12/lib/python/site-packages/_sounddevice_data/portaudio-binaries/libportaudio.dylib"
)


def get_portaudio_index_from_coreaudio_id(target_core_id):
    """
    Convert a macOS CoreAudio AudioDeviceID into a PortAudio/sounddevice index.
    """
    index = _pa_extra_lib.PaMacCore_GetDeviceIndexForAudioDeviceID(target_core_id)

    if index < 0:
        return None

    return index

I have also removed two unused variables i in unrelated parts of the file.

[RossBencina]

I have also removed two unused variables i in unrelated parts of the file.

We welcome this kind of cleanup in separate PRs, but please keep each PRs focused to a single purpose. [I've removed the unrelated changes myself, hope you don't mind.]

[RossBencina]

Phil and I have reviewed this PR and have decided to reject the approach taken here. We would accept a new PR for the inverse function:

AudioDeviceId PaMacCore_DeviceIndexToAudioDeviceID(PaDeviceIndex index)

This would return kAudioDeviceUnknown for any lookup failures. Note that the implementation can use PaUtil_DeviceIndexToHostApiDeviceIndex to get the index into the devIds array but be sure to check for errors.

We would prefer this approach because:

• The implementation would be simpler
• It facilitates lookup both ways (client code can implement the search that your PR implements)
• It is consistent with other PortAudio host API extension functions

[philburk]

CI is failing with whitespace errors:
error: src/hostapi/coreaudio/pa_mac_core.c(2900) contains tab
error: src/hostapi/coreaudio/pa_mac_core.c(2901) contains tab
error: src/hostapi/coreaudio/pa_mac_core.c(2900) trailing whitespace:
b' '