1 files changed, 123 insertions, 0 deletions
diff --git a/ext/fiddle/pinned.c b/ext/fiddle/pinned.c
new file mode 100644
index 0000000000..019a3020e2
--- /dev/null
+++ b/ext/fiddle/pinned.c
@@ -0,0 +1,123 @@
+#include <fiddle.h>
+
+VALUE rb_cPinned;
+VALUE rb_eFiddleClearedReferenceError;
+
+struct pinned_data {
+    VALUE ptr;
+};
+
+static void
+pinned_mark(void *ptr)
+{
+    struct pinned_data *data = (struct pinned_data*)ptr;
+    /* Ensure reference is pinned */
+    if (data->ptr) {
+        rb_gc_mark(data->ptr);
+    }
+}
+
+static size_t
+pinned_memsize(const void *ptr)
+{
+    return sizeof(struct pinned_data);
+}
+
+static const rb_data_type_t pinned_data_type = {
+    "fiddle/pinned",
+    {pinned_mark, xfree, pinned_memsize, },
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
+};
+
+static VALUE
+allocate(VALUE klass)
+{
+    struct pinned_data *data;
+    VALUE obj = TypedData_Make_Struct(klass, struct pinned_data, &pinned_data_type, data);
+    data->ptr = 0;
+    return obj;
+}
+
+/*
+ * call-seq:
+ *    Fiddle::Pinned.new(object)      => pinned_object
+ *
+ * Create a new pinned object reference.  The Fiddle::Pinned instance will
+ * prevent the GC from moving +object+.
+ */
+static VALUE
+initialize(VALUE self, VALUE ref)
+{
+    struct pinned_data *data;
+    TypedData_Get_Struct(self, struct pinned_data, &pinned_data_type, data);
+    RB_OBJ_WRITE(self, &data->ptr, ref);
+    return self;
+}
+
+/*
+ * call-seq: ref
+ *
+ * Return the object that this pinned instance references.
+ */
+static VALUE
+ref(VALUE self)
+{
+    struct pinned_data *data;
+    TypedData_Get_Struct(self, struct pinned_data, &pinned_data_type, data);
+    if (data->ptr) {
+      return data->ptr;
+    } else {
+      rb_raise(rb_eFiddleClearedReferenceError, "`ref` called on a cleared object");
+    }
+}
+
+/*
+ * call-seq: clear
+ *
+ * Clear the reference to the object this is pinning.
+ */
+static VALUE
+clear(VALUE self)
+{
+    struct pinned_data *data;
+    TypedData_Get_Struct(self, struct pinned_data, &pinned_data_type, data);
+    data->ptr = 0;
+    return self;
+}
+
+/*
+ * call-seq: cleared?
+ *
+ * Returns true if the reference has been cleared, otherwise returns false.
+ */
+static VALUE
+cleared_p(VALUE self)
+{
+    struct pinned_data *data;
+    TypedData_Get_Struct(self, struct pinned_data, &pinned_data_type, data);
+    if (data->ptr) {
+        return Qfalse;
+    } else {
+        return Qtrue;
+    }
+}
+
+extern VALUE rb_eFiddleError;
+
+void
+Init_fiddle_pinned(void)
+{
+    rb_cPinned = rb_define_class_under(mFiddle, "Pinned", rb_cObject);
+    rb_define_alloc_func(rb_cPinned, allocate);
+    rb_define_method(rb_cPinned, "initialize", initialize, 1);
+    rb_define_method(rb_cPinned, "ref", ref, 0);
+    rb_define_method(rb_cPinned, "clear", clear, 0);
+    rb_define_method(rb_cPinned, "cleared?", cleared_p, 0);
+
+    /*
+     * Document-class: Fiddle::ClearedReferenceError
+     *
+     * Cleared reference exception
+     */
+    rb_eFiddleClearedReferenceError = rb_define_class_under(mFiddle, "ClearedReferenceError", rb_eFiddleError);
+}