MacOS support

[mikekosulin]

I tried to compile pbpctrl for MacOS.
To solve dependency issues, I installed the missing packages: brew install dbus protobuf.
Then I ran cargo build --release --target aarch64-apple-darwin, but as expected, no success.

Compile output

$ cargo build --release --target aarch64-apple-darwin
   Compiling bluer v0.15.4
error[E0432]: unresolved imports `libc::Ioctl`, `libc::SOCK_CLOEXEC`, `libc::SOCK_NONBLOCK`
 --> ~/.cargo/registry/src/github.com-1ecc6299db9ec823/bluer-0.15.4/src/sock.rs:3:40
  |
3 | use libc::{c_int, sockaddr, socklen_t, Ioctl, SOCK_CLOEXEC, SOCK_NONBLOCK};
  |                                        ^^^^^  ^^^^^^^^^^^^  ^^^^^^^^^^^^^ no `SOCK_NONBLOCK` in the root
  |                                        |      |
  |                                        |      no `SOCK_CLOEXEC` in the root
  |                                        no `Ioctl` in the root
  |
help: a similar name exists in the module
  |
3 | use libc::{c_int, sockaddr, socklen_t, ioctl, SOCK_CLOEXEC, SOCK_NONBLOCK};
  |                                        ~~~~~
help: a similar name exists in the module
  |
3 | use libc::{c_int, sockaddr, socklen_t, Ioctl, O_CLOEXEC, SOCK_NONBLOCK};
  |                                               ~~~~~~~~~
help: a similar name exists in the module
  |
3 | use libc::{c_int, sockaddr, socklen_t, Ioctl, SOCK_CLOEXEC, O_NONBLOCK};
  |                                                             ~~~~~~~~~~

error[E0432]: unresolved imports `libc::SOCK_CLOEXEC`, `libc::SOCK_NONBLOCK`
 --> ~/.cargo/registry/src/github.com-1ecc6299db9ec823/bluer-0.15.4/src/gatt/mod.rs:5:22
  |
5 | use libc::{AF_LOCAL, SOCK_CLOEXEC, SOCK_NONBLOCK, SOCK_SEQPACKET};
  |                      ^^^^^^^^^^^^  ^^^^^^^^^^^^^ no `SOCK_NONBLOCK` in the root
  |                      |
  |                      no `SOCK_CLOEXEC` in the root
  |
help: a similar name exists in the module
  |
5 | use libc::{AF_LOCAL, O_CLOEXEC, SOCK_NONBLOCK, SOCK_SEQPACKET};
  |                      ~~~~~~~~~
help: a similar name exists in the module
  |
5 | use libc::{AF_LOCAL, SOCK_CLOEXEC, O_NONBLOCK, SOCK_SEQPACKET};
  |                                    ~~~~~~~~~~

error[E0432]: unresolved imports `libc::AF_BLUETOOTH`, `libc::SOL_BLUETOOTH`, `libc::TIOCINQ`
  --> ~/.cargo/registry/src/github.com-1ecc6299db9ec823/bluer-0.15.4/src/rfcomm/mod.rs:16:12
   |
16 |     c_int, AF_BLUETOOTH, EAGAIN, EINPROGRESS, MSG_PEEK, SHUT_RD, SHUT_RDWR, SHUT_WR, SOCK_RAW, SOCK_STREAM,
   |            ^^^^^^^^^^^^ no `AF_BLUETOOTH` in the root
17 |     SOL_BLUETOOTH, SOL_SOCKET, SO_ERROR, SO_RCVBUF, TIOCINQ, TIOCOUTQ,
   |     ^^^^^^^^^^^^^ no `SOL_BLUETOOTH` in the root    ^^^^^^^ no `TIOCINQ` in the root

error[E0425]: cannot find function `accept4` in crate `libc`
   --> ~/.cargo/registry/src/github.com-1ecc6299db9ec823/bluer-0.15.4/src/sock.rs:147:15
    |
147 |         libc::accept4(socket.as_raw_fd(), saddr.as_mut_ptr() as *mut _, &mut length, SOCK_CLOEXEC | SOCK_NONBLOCK)
    |               ^^^^^^^ help: a function with a similar name exists: `accept`
    |
   ::: ~/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.139/src/unix/mod.rs:641:5
    |
641 |     pub fn accept(socket: ::c_int, address: *mut sockaddr, address_len: *mut socklen_t) -> ::c_int;
    |     ---------------------------------------------------------------------------------------------- similarly named function `accept` defined here

Some errors have detailed explanations: E0425, E0432.
For more information about an error, try `rustc --explain E0425`.
error: could not compile `bluer` due to 4 previous errors
warning: build failed, waiting for other jobs to finish...
error: could not compile `bluer` due to 4 previous errors

Is it possible to use something crossplatform for bluetooth bindings?

[qzed]

I currently don't have any plans for supporting other operating systems, but I'd consider PRs.

As you've spotted correctly, the problem is that we depend on the bluer crate for anything bluetooth related, which is a rust-frontend to BlueZ (Linux-only). I had a brief look at rust bluetooth libraries when I started this project, but it doesn't look like there is any (BT-classic) cross-platform crate. The only cross-platform crates I've found are for BLE only (e.g. btleplug), but we need RFCOMM support.