std.c: adding cpu affinity api for macOs (mainly x86_64)

Author: devnexen

lib/std/c/darwin.zig

@@ -3896,3 +3896,23 @@ pub const MIN = struct {
 
 pub extern "c" fn mincore(addr: *align(std.mem.page_size) const anyopaque, length: usize, vec: [*]u8) c_int;
 pub extern "c" fn os_proc_available_memory() usize;
+
+pub const thread_affinity_policy = extern struct {
+    tag: integer_t,
+};
+
+pub const thread_policy_flavor_t = natural_t;
+pub const thread_policy_t = [*]integer_t;
+pub const thread_affinity_policy_data_t = thread_affinity_policy;
+pub const thread_affinity_policy_t = [*]thread_affinity_policy;
+
+pub const THREAD_AFFINITY = struct {
+    pub const POLICY = 0;
+    pub const POLICY_COUNT = @intCast(mach_msg_type_number_t, @sizeOf(thread_affinity_policy_data_t) / @sizeOf(integer_t));
+};
+
+/// cpu affinity api
+/// albeit it is also available on arm64, it always fails as in this architecture there is no sense of
+/// individual cpus (high performance cpus group and low consumption one), thus the pthread QOS api is more appropriate in this case.
+pub extern "c" fn thread_affinity_get(thread: thread_act_t, flavor: thread_policy_flavor_t, info: thread_policy_t, infocnt: [*]mach_msg_type_number_t, default: *boolean_t) kern_return_t;
+pub extern "c" fn thread_affinity_set(thread: thread_act_t, flavor: thread_policy_flavor_t, info: thread_policy_t, infocnt: mach_msg_type_number_t) kern_return_t;