Implement MacOS (#4)

Author: PhotonQuantum

.github/workflows/build.yaml

@@ -36,8 +36,8 @@ jobs:
           #  triple: x86_64-pc-windows-gnu
           - name: Linux
             triple: x86_64-unknown-linux-gnu
-          # - name: macOS
-          #   triple: x86_64-apple-darwin
+          - name: macOS
+            triple: x86_64-apple-darwin
           - name: FreeBSD
             triple: x86_64-unknown-freebsd
 

Cargo.toml

@@ -14,5 +14,5 @@ targets = ["x86_64-unknown-linux-gnu"]
 
 [dependencies]
 
-[target.'cfg(target_os = "freebsd")'.dependencies]
+[target.'cfg(any(target_os = "macos", target_os = "freebsd"))'.dependencies]
 libc = "0.2.107"

src/lib.rs

@@ -4,6 +4,7 @@ use std::num::NonZeroUsize;
 
 #[cfg_attr(target_os = "linux", path = "linux.rs")]
 #[cfg_attr(target_os = "freebsd", path = "freebsd.rs")]
+#[cfg_attr(target_os = "macos", path = "macos.rs")]
 mod imp;
 
 /// Obtain the number of threads currently part of the active process. Returns `None` if the number

src/macos.rs

@@ -0,0 +1,33 @@
+extern crate libc;
+
+use std::mem;
+use std::num::NonZeroUsize;
+
+const PROC_TASKINFO_SIZE: usize = mem::size_of::<libc::proc_taskinfo>();
+
+pub(crate) fn num_threads() -> Option<NonZeroUsize> {
+    let buffer = unsafe { libc::malloc(PROC_TASKINFO_SIZE) };
+    if buffer.is_null() {
+        return None;
+    }
+
+    let result = unsafe {
+        libc::proc_pidinfo(
+            libc::getpid(),
+            libc::PROC_PIDTASKINFO,
+            0,
+            buffer,
+            PROC_TASKINFO_SIZE as libc::c_int,
+        )
+    };
+    if result != PROC_TASKINFO_SIZE as libc::c_int {
+        return None;
+    }
+
+    let pti = buffer as *mut libc::proc_taskinfo;
+    // Safety: `malloc`ed memory is aligned for repr(C) structs, so dereference is safe.
+    let num_threads = NonZeroUsize::new(unsafe { pti.as_ref() }?.pti_threadnum as usize);
+
+    unsafe { libc::free(pti as *mut libc::c_void) };
+    num_threads
+}