Add XmpMeta::array_len (#122)

src/ffi.cpp

@@ -744,6 +744,29 @@ extern "C" {
         #endif
     }
 
+	bool CXmpMetaCountArrayItems(CXmpMeta* m,
+                                 CXmpError* outError,
+                                 const char* arrayNS,
+                                 const char* arrayName,
+                                 AdobeXMPCommon::uint32* outValue) {
+        *outValue = 0;
+
+        #ifndef NOOP_FFI
+            try {
+                *outValue = m->m.CountArrayItems(arrayNS, arrayName);
+                return true;
+            }
+            catch (XMP_Error& e) {
+                copyErrorForResult(e, outError);
+            }
+            catch (...) {
+                signalUnknownError(outError);
+            }
+        #endif
+
+        return false;
+    }
+
     const char* CXmpMetaGetStructField(CXmpMeta* m,
                                        CXmpError* outError,
                                        const char* schemaNS,

src/ffi.rs

@@ -336,6 +336,14 @@ extern "C" {
         item_options: u32,
     );
 
+    pub(crate) fn CXmpMetaCountArrayItems(
+        meta: *const CXmpMeta,
+        out_error: *mut CXmpError,
+        array_ns: *const c_char,
+        array_name: *const c_char,
+        count: *mut u32,
+    ) -> bool;
+
     pub(crate) fn CXmpMetaSetStructField(
         meta: *mut CXmpMeta,
         out_error: *mut CXmpError,

src/tests/xmp_meta.rs

@@ -1906,6 +1906,49 @@ mod append_array_item {
     }
 }
 
+mod array_len {
+    use std::str::FromStr;
+
+    use crate::{tests::fixtures::*, XmpMeta};
+
+    #[test]
+    fn happy_path_creator_seq() {
+        let m = XmpMeta::from_str(PURPLE_SQUARE_XMP).unwrap();
+        assert_eq!(
+            m.array_len("http://purl.org/dc/elements/1.1/", "creator"),
+            1
+        );
+    }
+
+    #[test]
+    fn happy_path_creator_bag() {
+        let m = XmpMeta::from_str(PURPLE_SQUARE_XMP).unwrap();
+        assert_eq!(
+            m.array_len("http://purl.org/dc/elements/1.1/", "subject"),
+            6
+        );
+    }
+
+    #[test]
+    fn init_fail() {
+        let m = XmpMeta::new_fail();
+        assert_eq!(
+            m.array_len("http://purl.org/dc/elements/1.1/", "creator"),
+            0
+        );
+    }
+
+    #[test]
+    fn no_such_property() {
+        let m = XmpMeta::from_str(PURPLE_SQUARE_XMP).unwrap();
+
+        assert_eq!(
+            m.array_len("http://purl.org/dc/elements/1.1/", "creatorx"),
+            0
+        );
+    }
+}
+
 mod set_struct_field {
     use std::str::FromStr;
 

src/xmp_meta.rs

@@ -899,6 +899,37 @@ impl XmpMeta {
         }
     }
 
+    /// Reports the number of items currently defined in an array.
+    ///
+    /// ## Arguments
+    ///
+    /// * `array_ns` and `array_name`: See [Accessing
+    ///   properties](#accessing-properties).
+    ///
+    /// If any error occurs (for instance, the array does not exist),
+    /// this function will return 0.
+    pub fn array_len(&self, array_ns: &str, array_name: &str) -> usize {
+        let mut result: u32 = 0;
+
+        if let Some(m) = self.m {
+            let c_array_ns = CString::new(array_ns).unwrap_or_default();
+            let c_array_name = CString::new(array_name.as_bytes()).unwrap_or_default();
+            let mut err = ffi::CXmpError::default();
+
+            unsafe {
+                ffi::CXmpMetaCountArrayItems(
+                    m,
+                    &mut err,
+                    c_array_ns.as_ptr(),
+                    c_array_name.as_ptr(),
+                    &mut result,
+                );
+            }
+        }
+
+        result as usize
+    }
+
     /// Creates or sets the value of a field within a nested structure,
     /// using a string value.
     ///