os2: better copy_directory, and add native copy_file and copy_directory variants on MacOS

core/os/os2/file_posix_darwin.odin

@@ -3,6 +3,7 @@ package os2
 
 import "base:runtime"
 
+import "core:sys/darwin"
 import "core:sys/posix"
 
 _posix_absolute_path :: proc(fd: posix.FD, name: string, allocator: runtime.Allocator) -> (path: cstring, err: Error) {
@@ -16,3 +17,30 @@ _posix_absolute_path :: proc(fd: posix.FD, name: string, allocator: runtime.Allo
 
 	return clone_to_cstring(string(cstring(&buf[0])), allocator)
 }
+
+_copy_file_native :: proc(dst_path, src_path: string) -> (err: Error) {
+	temp_allocator := TEMP_ALLOCATOR_GUARD({})
+
+	csrc := clone_to_cstring(src_path, temp_allocator) or_return
+	cdst := clone_to_cstring(dst_path, temp_allocator) or_return
+
+	// Disallow directories, as specified by the generic implementation.
+
+	stat: posix.stat_t
+	if posix.stat(csrc, &stat) != .OK {
+		err = _get_platform_error()
+		return
+	}
+
+	if posix.S_ISDIR(stat.st_mode) {
+		err = .Invalid_File
+		return
+	}
+
+	ret := darwin.copyfile(csrc, cdst, nil, darwin.COPYFILE_ALL)
+	if ret < 0 {
+		err = _get_platform_error()
+	}
+
+	return
+}