Allow XmpMeta::array_item to accept XmpMeta::LAST_ITEM (#127)

src/ffi.rs

@@ -392,7 +392,7 @@ extern "C" {
         out_error: *mut CXmpError,
         schema_ns: *const c_char,
         prop_name: *const c_char,
-        index: u32,
+        index: i32,
         out_options: *mut u32,
     ) -> *const c_char;
 

src/tests/xmp_meta.rs

@@ -1664,6 +1664,19 @@ mod array_item {
         );
     }
 
+    #[test]
+    fn last_item() {
+        let m = XmpMeta::from_str(ARRAY_EXAMPLE).unwrap();
+
+        assert_eq!(
+            m.array_item(xmp_ns::DC, "subject", XmpMeta::LAST_ITEM),
+            Some(XmpValue {
+                value: "test".to_owned(),
+                options: 0
+            })
+        );
+    }
+
     #[test]
     fn item_options() {
         let mut m = XmpMeta::from_str(ARRAY_EXAMPLE).unwrap();

src/xmp_meta.rs

@@ -820,14 +820,14 @@ impl XmpMeta {
     ///
     /// * `namespace` and `array_name`: See [Accessing
     ///   properties](#accessing-properties).
-    /// * `item_index`: Index into the array.
-    ///  **IMPORTANT:** Indices in XMP are 1-based, unlike Rust where
-    /// indices are typically 0-based.
+    /// * `item_index`: Index into the array. **IMPORTANT:** Indices in XMP are
+    ///   1-based, unlike Rust where indices are typically 0-based.  Use
+    ///   [`XmpMeta::LAST_ITEM`] to specify the last existing array item.
     pub fn array_item(
         &self,
         namespace: &str,
         array_name: &str,
-        item_index: u32,
+        item_index: i32,
     ) -> Option<XmpValue<String>> {
         if let Some(m) = self.m {
             let c_ns = CString::new(namespace).unwrap_or_default();
@@ -1506,7 +1506,7 @@ pub struct ArrayProperty<'a> {
     meta: &'a XmpMeta,
     ns: CString,
     name: CString,
-    index: u32,
+    index: i32,
 }
 
 impl<'a> Iterator for ArrayProperty<'a> {