exposing

src/lib.rs

@@ -62,6 +62,14 @@ unsafe impl GlobalAlloc for MiMalloc {
     }
 }
 
+impl MiMalloc {
+    #[allow(dead_code)]
+    #[inline]
+    unsafe fn usable_size(&self, ptr: *const u8) -> usize {
+        mi_usable_size(ptr as *const c_void)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -133,4 +141,17 @@ mod tests {
             alloc.dealloc(ptr, layout);
         }
     }
+
+    #[test]
+    fn it_usable_size() {
+        unsafe {
+            let layout = Layout::from_size_align(8, 8).unwrap();
+            let alloc = MiMalloc;
+
+            let ptr = alloc.alloc(layout);
+            let usable_size = alloc.usable_size(ptr);
+            alloc.dealloc(ptr, layout);
+            assert!(usable_size >= 8);
+        }
+    }
 }