feat(arrow-array): add GenericByteViewArray::total_bytes_len

arrow-array/src/array/byte_view_array.rs

@@ -670,6 +670,37 @@ impl<T: ByteViewType + ?Sized> GenericByteViewArray<T> {
         }
     }
 
+    /// Returns the total number of bytes of all non-null values in this array.
+    ///
+    /// Unlike [`Self::total_buffer_bytes_used`], this method includes inlined strings
+    /// (those with length ≤ [`MAX_INLINE_VIEW_LEN`]), making it suitable as a
+    /// capacity hint when pre-allocating output buffers.
+    ///
+    /// Null values are excluded from the sum.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # use arrow_array::StringViewArray;
+    /// let array = StringViewArray::from_iter(vec![
+    ///     Some("hello"),   // 5 bytes, inlined
+    ///     None,            // excluded
+    ///     Some("large payload over 12 bytes"),  // 27 bytes, non-inlined
+    /// ]);
+    /// assert_eq!(array.total_bytes_len(), 5 + 27);
+    /// ```
+    pub fn total_bytes_len(&self) -> usize {
+        match self.nulls() {
+            None => self.views().iter().map(|v| (*v as u32) as usize).sum(),
+            Some(nulls) => self
+                .views()
+                .iter()
+                .zip(nulls.iter())
+                .map(|(v, is_valid)| if is_valid { (*v as u32) as usize } else { 0 })
+                .sum(),
+        }
+    }
+
     /// Returns the total number of bytes used by all non inlined views in all
     /// buffers.
     ///
@@ -1809,4 +1840,41 @@ mod tests {
         assert!(from_utf8(array.value(2)).is_ok());
         array
     }
+
+    #[test]
+    fn test_total_bytes_len() {
+        // inlined: "hello"=5, "world"=5, "lulu"=4 → 14
+        // non-inlined: "large payload over 12 bytes"=27
+        // null: should not count
+        let mut builder = StringViewBuilder::new();
+        builder.append_value("hello");
+        builder.append_value("world");
+        builder.append_value("lulu");
+        builder.append_null();
+        builder.append_value("large payload over 12 bytes");
+        let array = builder.finish();
+        assert_eq!(array.total_bytes_len(), 5 + 5 + 4 + 27);
+    }
+
+    #[test]
+    fn test_total_bytes_len_empty() {
+        let array = StringViewArray::from_iter::<Vec<Option<&str>>>(vec![]);
+        assert_eq!(array.total_bytes_len(), 0);
+    }
+
+    #[test]
+    fn test_total_bytes_len_all_nulls() {
+        let array = StringViewArray::new_null(5);
+        assert_eq!(array.total_bytes_len(), 0);
+    }
+
+    #[test]
+    fn test_total_bytes_len_binary_view() {
+        let array = BinaryViewArray::from_iter(vec![
+            Some(b"hi".as_ref()),
+            None,
+            Some(b"large payload over 12 bytes".as_ref()),
+        ]);
+        assert_eq!(array.total_bytes_len(), 2 + 27);
+    }
 }