Add alignment header

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/ust/align.h b/include/ust/align.h
new file mode 100644 (file)
index 0000000..cd713cc
--- /dev/null
+++ b/include/ust/align.h
@@ -0,0 +1,51 @@
+#ifndef _UST_ALIGN_H
+#define _UST_ALIGN_H
+
+/*
+ * ust/align.h
+ *
+ * (C) Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include <ust/bug.h>
+
+/*
+ * Align pointer on natural object alignment.
+ */
+#define object_align(obj)      PTR_ALIGN(obj, __alignof__(*(obj)))
+#define object_align_floor(obj)        PTR_ALIGN_FLOOR(obj, __alignof__(*(obj)))
+
+/**
+ * offset_align - Calculate the offset needed to align an object on its natural
+ *                alignment towards higher addresses.
+ * @align_drift:  object offset from an "alignment"-aligned address.
+ * @alignment:    natural object alignment. Must be non-zero, power of 2.
+ *
+ * Returns the offset that must be added to align towards higher
+ * addresses.
+ */
+#define offset_align(align_drift, alignment)                                  \
+       ({                                                                     \
+               BUILD_RUNTIME_BUG_ON((alignment) == 0                          \
+                                  || ((alignment) & ((alignment) - 1)));      \
+               (((alignment) - (align_drift)) & ((alignment) - 1));           \
+       })
+
+/**
+ * offset_align_floor - Calculate the offset needed to align an object
+ *                      on its natural alignment towards lower addresses.
+ * @align_drift:  object offset from an "alignment"-aligned address.
+ * @alignment:    natural object alignment. Must be non-zero, power of 2.
+ *
+ * Returns the offset that must be substracted to align towards lower addresses.
+ */
+#define offset_align_floor(align_drift, alignment)                            \
+       ({                                                                     \
+               BUILD_RUNTIME_BUG_ON((alignment) == 0                          \
+                                  || ((alignment) & ((alignment) - 1)));      \
+               (((align_drift) - (alignment)) & ((alignment) - 1);            \
+       })
+
+#endif /* _UST_ALIGN_H */