X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Flibpspp%2Fbt.h;h=41fc5d44b0a3bc27ee23277ea2fc5abb27764398;hb=28c9cdd6ad22eae547cc5b3b18395ac733a7c8d4;hp=340b8760166c31fec29ea42ae8ecc50c24911806;hpb=43b1296aafe7582e7dbe6c2b6a8b478d7d9b0fcf;p=pspp

diff --git a/src/libpspp/bt.h b/src/libpspp/bt.h
index 340b876016..41fc5d44b0 100644
--- a/src/libpspp/bt.h
+++ b/src/libpspp/bt.h
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009, 2010, 2011 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -23,13 +23,16 @@
    balancing applied to the balanced tree, as its operation is
    fully encapsulated. */
 
+#include <stdbool.h>
 #include <stddef.h>
+#include "libpspp/cast.h"
 
 /* Returns the data structure corresponding to the given NODE,
    assuming that NODE is embedded as the given MEMBER name in
    data type STRUCT. */
-#define bt_data(NODE, STRUCT, MEMBER)                                  \
-        ((STRUCT *) ((char *) (NODE) - offsetof (STRUCT, MEMBER)))
+#define bt_data(NODE, STRUCT, MEMBER)                           \
+        (CHECK_POINTER_HAS_TYPE (NODE, struct bt_node *),       \
+         UP_CAST (NODE, STRUCT, MEMBER))
 
 /* Node in a balanced binary tree. */
 struct bt_node
@@ -78,4 +81,11 @@ static inline size_t bt_count (const struct bt *bt)
   return bt->size;
 }
 
+/* Return true if BT contains no nodes,
+   false if BT contains at least one node. */
+static inline bool bt_is_empty (const struct bt *bt)
+{
+  return bt->size == 0;
+}
+
 #endif /* libpspp/bt.h */