fix(ncnn-rs): compatible with arm 32bit

ncnn-bind/src/lib.rs

@@ -1,7 +1,6 @@
 #![allow(non_upper_case_globals)]
 #![allow(non_camel_case_types)]
 #![allow(non_snake_case)]
-
 // Suppress bindgen test warnings
 #![allow(deref_nullptr)]
 

ncnn-rs/src/mat.rs

@@ -396,8 +396,16 @@ impl Mat {
         unsafe { ncnn_mat_get_elempack(self.ptr) }
     }
 
-    pub fn cstep(&self) -> u64 {
-        unsafe { ncnn_mat_get_cstep(self.ptr) }
+    pub fn cstep(&self) -> usize {
+        #[cfg(target_pointer_width = "32")]
+        {
+            unsafe { ncnn_mat_get_cstep(self.ptr) as u32 as usize }
+        }
+
+        #[cfg(target_pointer_width = "64")]
+        {
+            unsafe { ncnn_mat_get_cstep(self.ptr) as u64 as usize }
+        }
     }
 
     /// Pointer to raw matrix data

ncnn-rs/src/net.rs

@@ -69,8 +69,12 @@
 mod tests {
     use super::*;
 
-    fn is_send<T: Send>() -> bool { true }
-    fn is_sync<T: Sync>() -> bool { true }
+    fn is_send<T: Send>() -> bool {
+        true
+    }
+    fn is_sync<T: Sync>() -> bool {
+        true
+    }
 
     #[test]
     fn load_not_exist_model() {