Add a function to get os version

Author: ChunMinChang

Cargo.toml

@@ -19,3 +19,4 @@ mach = "0.3"
 audio-mixer = "0.1"
 ringbuf = "0.2.6"
 triple_buffer = "5.0.5"
+plist = "1"

src/backend/utils.rs

@@ -56,6 +56,21 @@ pub fn finally<F: FnOnce()>(f: F) -> Finalizer<F> {
     Finalizer(Some(f))
 }
 
+pub fn os_version() -> Result<String, cubeb_backend::Error> {
+    if let Some(s) = plist::Value::from_file("/System/Library/CoreServices/SystemVersion.plist")
+        .map_err(|e| {
+            cubeb_log!("Could not read SystemVersion.plist. Error: {}", e);
+            cubeb_backend::Error::error()
+        })?
+        .as_dictionary()
+        .and_then(|dict| dict.get("ProductVersion"))
+        .and_then(|version| version.as_string())
+    {
+        return Ok(s.to_string());
+    }
+    Err(cubeb_backend::Error::error())
+}
+
 #[test]
 fn test_forget_vec_and_retake_it() {
     let expected: Vec<u32> = (10..20).collect();
@@ -105,3 +120,8 @@ fn test_finally() {
     }
     assert_eq!(x, 100);
 }
+
+#[test]
+fn test_os_version() {
+    assert!(!os_version().unwrap().is_empty());
+}