[ovs-dev] [risc 1/3] Add types and accessors for working with half-aligned 64-bit values.

[Ben Pfaff]

Both OpenFlow and Netlink contain 64-bit fields that are only guaranteed
to be aligned on 32-bit boundaries.  This commit introduces types for
representing these fields and functions for working with them.  Followup
commits will make the OpenFlow and Netlink code use these types and
functions.
---
 include/openvswitch/types.h |   25 ++++++++++++++++++++++++-
 lib/unaligned.h             |   41 ++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/include/openvswitch/types.h b/include/openvswitch/types.h
index fbd2997..9ddb857 100644
--- a/include/openvswitch/types.h
+++ b/include/openvswitch/types.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010 Nicira Networks.
+ * Copyright (c) 2010, 2011 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,8 @@
 #ifndef OPENVSWITCH_TYPES_H
 #define OPENVSWITCH_TYPES_H 1
 
+#include <arpa/inet.h>
+#include <sys/types.h>
 #include <stdint.h>
 
 #ifdef __CHECKER__
@@ -35,5 +37,26 @@
 typedef uint16_t OVS_BITWISE ovs_be16;
 typedef uint32_t OVS_BITWISE ovs_be32;
 typedef uint64_t OVS_BITWISE ovs_be64;
+
+/* Netlink and OpenFlow both contain 64-bit values that are only guaranteed to
+ * be aligned on 32-bit boundaries.  These types help.
+ *
+ * lib/unaligned.h has helper functions for accessing these. */
+
+/* A 64-bit value, in host byte order, that is only aligned on a 32-bit
+ * boundary.  */
+typedef struct {
+#ifdef WORDS_BIGENDIAN
+	uint32_t hi, lo;
+#else
+	uint32_t lo, hi;
+#endif
+} ovs_32aligned_u64;
+
+/* A 64-bit value, in network byte order, that is only aligned on a 32-bit
+ * boundary. */
+typedef struct {
+	ovs_be32 hi, lo;
+} ovs_32aligned_be64;
 
 #endif /* openvswitch/types.h */
diff --git a/lib/unaligned.h b/lib/unaligned.h
index ef08f4e..6fb131a 100644
--- a/lib/unaligned.h
+++ b/lib/unaligned.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010 Nicira Networks.
+ * Copyright (c) 2010, 2011 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -140,5 +140,44 @@ static inline void put_unaligned_u64(uint64_t *p_, uint64_t x_)
 #define put_unaligned_be32 put_unaligned_u32
 #define put_unaligned_be64 put_unaligned_u64
 #endif
+
+/* Returns the value in 'x'. */
+static inline uint64_t
+get_32aligned_u64(const ovs_32aligned_u64 *x)
+{
+	return ((uint64_t) x->hi << 32) | x->lo;
+}
+
+/* Stores 'value' in 'x'. */
+static inline void
+put_32aligned_u64(ovs_32aligned_u64 *x, uint64_t value)
+{
+	x->hi = value >> 32;
+	x->lo = value;
+}
+
+/* Returns the value of 'x'. */
+static inline ovs_be64
+get_32aligned_be64(const ovs_32aligned_be64 *x)
+{
+#ifdef WORDS_BIGENDIAN
+	return ((ovs_be64) x->hi << 32) | x->lo;
+#else
+	return ((ovs_be64) x->lo << 32) | x->hi;
+#endif
+}
+
+/* Stores host byte order 'value' into 'x'. */
+static inline void
+put_32aligned_be64(ovs_32aligned_be64 *x, ovs_be64 value)
+{
+#if WORDS_BIGENDIAN
+	x->hi = value >> 32;
+	x->lo = value;
+#else
+    x->hi = value;
+    x->lo = value >> 32;
+#endif
+}
 
 #endif /* unaligned.h */
-- 
1.7.1