Fix membership test

examples/membership/src/lib.rs

@@ -1,9 +1,13 @@
 #[macro_use]
 extern crate helix;
 
+pub struct RubyArray<'a>(&'a [usize]);
+
 ruby! {
     reopen class Array {
-        def is_superset_of(&self, needle: &[usize]) -> bool {
+        def is_superset_of(&self, needle: RubyArray) -> bool {
+            let needle = needle.0;
+
             if needle.is_empty() { return true }
 
             let haystack = self.as_ref();
@@ -27,13 +31,29 @@ ruby! {
     }
 }
 
-// Delete me:
+use helix::{FromRuby, CheckedValue, CheckResult, ToRust, sys};
 
-use helix::{FromRuby, ToRust};
-
-impl AsRef<[usize]> for Array {
-    fn as_ref(&self) -> &[usize] {
-        let checked = FromRuby::from_ruby(self.helix);
-        checked.unwrap().to_rust()
+impl<'a> FromRuby for RubyArray<'a> {
+    fn from_ruby(value: sys::VALUE) -> CheckResult<RubyArray<'a>> {
+        if unsafe { sys::RB_TYPE_P(value, sys::T_ARRAY) } {
+            Ok(unsafe { CheckedValue::new(value) })
+        } else {
+            type_error!(value, "an Array of unsigned pointer-sized integers")
+        }
+    }
+}
+
+impl<'a> ToRust<RubyArray<'a>> for CheckedValue<RubyArray<'a>> {
+    fn to_rust(self) -> RubyArray<'a> {
+        let size = unsafe { sys::RARRAY_LEN(self.inner) };
+        let ptr = unsafe { sys::RARRAY_PTR(self.inner) };
+        RubyArray(unsafe { std::slice::from_raw_parts(ptr as *const usize, size as usize) })
+    }
+}
+
+impl AsRef<[usize]> for Array {
+    fn as_ref<'a>(&'a self) -> &'a [usize] {
+        let checked = RubyArray::from_ruby(self.helix);
+        checked.unwrap().to_rust().0
     }
 }