1 files changed, 70 insertions, 0 deletions
diff --git a/mrbgems/mruby-catch/src/mruby-catch.c b/mrbgems/mruby-catch/src/mruby-catch.c
new file mode 100644
index 000000000..d0a50b821
--- /dev/null
+++ b/mrbgems/mruby-catch/src/mruby-catch.c
@@ -0,0 +1,70 @@
+#include <mruby.h>
+#include <mruby/class.h>
+#include <mruby/variable.h>
+#include <mruby/error.h>
+#include <mruby/proc.h>
+#include <mruby/presym.h>
+
+#define ID_PRESERVED_CATCH MRB_SYM(__preserved_catch_proc)
+
+static const mrb_callinfo *
+find_catcher(mrb_state *mrb, mrb_value tag)
+{
+  mrb_value pval = mrb_obj_iv_get(mrb, (struct RObject *)mrb->kernel_module, ID_PRESERVED_CATCH);
+  mrb_assert(mrb_proc_p(pval));
+  const struct RProc *proc = mrb_proc_ptr(pval);
+
+  const mrb_callinfo *ci = mrb->c->ci;
+  size_t n = ci - mrb->c->cibase;
+  ci--;
+  for (; n > 0; n--, ci--) {
+    const mrb_value *arg1 = ci->stack + 1;
+    if (ci->proc == proc && mrb_obj_eq(mrb, *arg1, tag)) {
+      return ci;
+    }
+  }
+
+  return NULL;
+}
+
+static mrb_value
+mrb_f_throw(mrb_state *mrb, mrb_value self)
+{
+  mrb_value tag, obj;
+  mrb_get_args(mrb, "oo", &tag, &obj);
+
+  const mrb_callinfo *ci = find_catcher(mrb, tag);
+  if (ci) {
+    struct RBreak *b = (struct RBreak *)mrb_obj_alloc(mrb, MRB_TT_BREAK, NULL);
+    mrb_break_value_set(b, obj);
+    mrb_break_proc_set(b, ci[2].proc); /* Back to the closure in `catch` method */
+    mrb_exc_raise(mrb, mrb_obj_value(b));
+  }
+
+  return mrb_nil_value();
+}
+
+static mrb_value
+mrb_s_preserve_catch(mrb_state *mrb, mrb_value self)
+{
+  mrb_method_t m = mrb_method_search(mrb, mrb->kernel_module, MRB_SYM(catch));
+  mrb_assert(!MRB_METHOD_UNDEF_P(m));
+  mrb_assert(!MRB_METHOD_CFUNC_P(m));
+  mrb_obj_iv_set(mrb, (struct RObject *)mrb->kernel_module, ID_PRESERVED_CATCH, mrb_obj_value(MRB_METHOD_PROC(m)));
+
+  mrb_remove_method(mrb, mrb_class(mrb, mrb_obj_value(mrb->kernel_module)), MRB_SYM(__preserve_catch_method));
+
+  return mrb_nil_value();
+}
+
+void
+mrb_mruby_catch_gem_init(mrb_state *mrb)
+{
+  mrb_define_method(mrb, mrb->kernel_module, "__throw", mrb_f_throw, MRB_ARGS_REQ(2));
+  mrb_define_class_method(mrb, mrb->kernel_module, "__preserve_catch_method", mrb_s_preserve_catch, MRB_ARGS_NONE());
+}
+
+void
+mrb_mruby_catch_gem_final(mrb_state *mrb)
+{
+}