Fix track description traversal

src/audio.rs

@@ -5,7 +5,7 @@
 use vlc_sys as sys;
 use crate::MediaPlayer;
 use crate::TrackDescription;
-use crate::tools::from_cstr;
+use crate::tools::track_descriptions_from_raw;
 
 pub trait MediaPlayerAudioEx {
     fn get_mute(&self) -> Option<bool>;
@@ -44,16 +44,9 @@ impl MediaPlayerAudioEx for MediaPlayer {
         unsafe{
             let p0 = sys::libvlc_audio_get_track_description(self.ptr);
             if p0.is_null() { return None; }
-            let mut td = Vec::new();
-            let mut p = p0;
-
-            while !(*p).p_next.is_null() {
-                td.push(TrackDescription{ id: (*p).i_id, name: from_cstr((*p).psz_name) });
-                p = (*p).p_next;
-            }
+            let td = track_descriptions_from_raw(p0);
             sys::libvlc_track_description_list_release(p0);
             Some(td)
         }
     }
-
 }

src/tools.rs

@@ -2,10 +2,12 @@
 // This file is part of vlc-rs.
 // Licensed under the MIT license, see the LICENSE file.
 
-use std::ffi::{CString, CStr, NulError};
-use std::path::Path;
-use std::borrow::Cow;
+use crate::TrackDescription;
 use libc::c_char;
+use std::borrow::Cow;
+use std::ffi::{CStr, CString, NulError};
+use std::path::Path;
+use vlc_sys as sys;
 
 // Convert String to CString.
 // Panic if the string includes null bytes.
@@ -41,3 +43,86 @@ pub fn path_to_cstr(path: &Path) -> Result<CString, NulError> {
 
     Ok(path)
 }
+
+/// Convert a libVLC track-description linked list into owned Rust values.
+///
+/// The caller retains ownership of the list and must release it using
+/// `libvlc_track_description_list_release` when appropriate.
+pub unsafe fn track_descriptions_from_raw(
+    mut track: *mut sys::libvlc_track_description_t,
+) -> Vec<TrackDescription> {
+    let mut descriptions = Vec::new();
+
+    while !track.is_null() {
+        descriptions.push(TrackDescription {
+            id: (*track).i_id,
+            name: from_cstr((*track).psz_name),
+        });
+        track = (*track).p_next;
+    }
+
+    descriptions
+}
+
+#[cfg(test)]
+mod tests {
+    use super::track_descriptions_from_raw;
+    use std::ffi::CString;
+    use std::ptr;
+    use vlc_sys::libvlc_track_description_t;
+
+    fn track(
+        id: i32,
+        name: &CString,
+        next: *mut libvlc_track_description_t,
+    ) -> libvlc_track_description_t {
+        libvlc_track_description_t {
+            i_id: id,
+            psz_name: name.as_ptr() as *mut _,
+            p_next: next,
+        }
+    }
+
+    #[test]
+    fn track_descriptions_from_raw_handles_a_null_list() {
+        let descriptions = unsafe { track_descriptions_from_raw(ptr::null_mut()) };
+
+        assert!(descriptions.is_empty());
+    }
+
+    #[test]
+    fn track_descriptions_from_raw_includes_a_singleton() {
+        let name = CString::new("English").unwrap();
+        let mut node = track(1, &name, ptr::null_mut());
+
+        let descriptions = unsafe { track_descriptions_from_raw(&mut node) };
+
+        assert_eq!(descriptions.len(), 1);
+        assert_eq!(descriptions[0].id, 1);
+        assert_eq!(descriptions[0].name.as_deref(), Some("English"));
+    }
+
+    #[test]
+    fn track_descriptions_from_raw_includes_the_final_node() {
+        let first_name = CString::new("English").unwrap();
+        let second_name = CString::new("French").unwrap();
+        let mut second = track(2, &second_name, ptr::null_mut());
+        let mut first = track(1, &first_name, &mut second);
+
+        let descriptions = unsafe { track_descriptions_from_raw(&mut first) };
+
+        assert_eq!(
+            descriptions,
+            vec![
+                crate::TrackDescription {
+                    id: 1,
+                    name: Some("English".to_owned()),
+                },
+                crate::TrackDescription {
+                    id: 2,
+                    name: Some("French".to_owned()),
+                },
+            ]
+        );
+    }
+}

src/video.rs

@@ -6,7 +6,7 @@ use vlc_sys as sys;
 use crate::MediaPlayer;
 use crate::TrackDescription;
 use crate::enums::VideoAdjustOption;
-use crate::tools::{to_cstr, from_cstr};
+use crate::tools::{to_cstr, from_cstr, track_descriptions_from_raw};
 use libc::c_void;
 
 pub trait MediaPlayerVideoEx {
@@ -98,13 +98,7 @@ impl MediaPlayerVideoEx for MediaPlayer {
         unsafe{
             let p0 = sys::libvlc_video_get_track_description(self.ptr);
             if p0.is_null() { return None; }
-            let mut td = Vec::new();
-            let mut p = p0;
-
-            while !(*p).p_next.is_null() {
-                td.push(TrackDescription{ id: (*p).i_id, name: from_cstr((*p).psz_name) });
-                p = (*p).p_next;
-            }
+            let td = track_descriptions_from_raw(p0);
             sys::libvlc_track_description_list_release(p0);
             Some(td)
         }