txr-011 2009-09-25txr-011

1 files changed, 88 insertions, 0 deletions

diff --git a/unwind.c b/unwind.c
new file mode 100644
index 00000000..c573c16d
--- /dev/null
+++ b/unwind.c
@@ -0,0 +1,88 @@
+/* Copyright 2009
+ * Kaz Kylheku <kkylheku@gmail.com>
+ * Vancouver, Canada
+ * All rights reserved.
+ *
+ * BSD License:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in
+ *      the documentation and/or other materials provided with the
+ *      distribution.
+ *   3. The name of the author may not be used to endorse or promote
+ *      products derived from this software without specific prior
+ *      written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <setjmp.h>
+#include <dirent.h>
+#include "lib.h"
+#include "unwind.h"
+
+static uw_frame_t *uw_stack;
+static uw_frame_t *uw_exit_point;
+
+static void uw_unwind_to_exit_point()
+{
+  while (uw_stack && uw_stack != uw_exit_point)
+    uw_stack = uw_stack->uw.up;
+
+  if (!uw_stack)
+    abort();
+
+  uw_exit_point = 0;
+
+  switch (uw_stack->uw.type) {
+  case UW_BLOCK:
+    longjmp(uw_stack->bl.jb, 1);
+    break;
+  }
+
+  abort();
+}
+
+void uw_push_block(uw_frame_t *fr, obj_t *tag)
+{
+  fr->bl.type = UW_BLOCK;
+  fr->bl.tag = tag;
+  fr->bl.result = nil;
+  fr->bl.up = uw_stack;
+  uw_stack = fr;
+}
+
+void uw_pop_frame(uw_frame_t *fr)
+{
+  assert (fr == uw_stack);
+  uw_stack = uw_stack->uw.up;
+}
+
+obj_t *uw_block_return(obj_t *tag, obj_t *result)
+{
+  uw_frame_t *ex;
+
+  for (ex = uw_stack; ex != 0; ex = ex->uw.up) {
+    if (ex->uw.type == UW_BLOCK && ex->bl.tag == tag)
+      break;
+  }
+
+  if (ex == 0)
+    return nil;
+
+  ex->bl.result = result;
+  uw_exit_point = ex;
+  uw_unwind_to_exit_point();
+  abort();
+}