From 3ba6bf972bc7f0b90dfafbb61bf31c1663c71117 Mon Sep 17 00:00:00 2001
From: Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
Date: Fri, 18 Jul 2014 16:05:48 +0000
Subject: [PATCH] made message format more portable by adding a endian field

git-svn-id: https://zerberus.eonerc.rwth-aachen.de:8443/svn/s2ss/trunk@167 8ec27952-4edc-4aab-86aa-e87bb2611832
---
 server/include/msg_format.h | 61 +++++++++++++++++++++++++++++--------
 1 file changed, 48 insertions(+), 13 deletions(-)

diff --git a/server/include/msg_format.h b/server/include/msg_format.h
index 37769b5fe..f738a4638 100644
--- a/server/include/msg_format.h
+++ b/server/include/msg_format.h
@@ -10,34 +10,69 @@
 
 #include <stdint.h>
 
+#ifndef BYTE_ORDER
+ #define _BSD_SOURCE    	1
+ #include <endian.h>
+#endif
+
 /** Maximum number of dword values in a message */
-#define MSG_VALUES	16
+#define MSG_VALUES		16
+
 /** The current version number for the message format */
-#define MSG_VERSION	0
+#define MSG_VERSION		0
 
 /** @todo Implement more message types */
-#define MSG_TYPE_DATA	0
-#define MSG_TYPE_START	1
-#define MSG_TYPE_STOP	2
+#define MSG_TYPE_DATA		0 /**< Message contains float values */
+#define MSG_TYPE_START		1 /**< Message marks the beginning of a new simulation case */
+#define MSG_TYPE_STOP		2 /**< Message marks the end of a simulation case */
 
-/** This message format is used by all clients.
+#define MSG_ENDIAN_LITTLE       0 /**< Message values are in little endian format (float too!) */
+#define MSG_ENDIAN_BIG          1 /**< Message values are in bit endian format */
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+ #define MSG_ENDIAN_HOST        MSG_ENDIAN_LITTLE
+#elif BYTE_ORDER == BIG_ENDIAN
+ #define MSG_ENDIAN_HOST        MSG_ENDIAN_BIG
+#endif
+
+/** The total length of a message */
+#define MSG_LEN(values)	(4 * (values + 1))
+
+/** Initialize a message */
+#define MSG_INIT(i)	{ \
+	.version = MSG_VERSION, \
+	.type = MSG_TYPE_DATA, \
+	.endian = MSG_ENDIAN_HOST, \
+	.length = i, \
+	.sequence = 0 \
+}
+
+/** This message format is used by all clients
  *
  * @diafile msg_format.dia
  **/
 struct msg
 {
-	/** The version specifies the format of the remaining message */
-	unsigned version	: 4;
-	/** Data or control message */
-	unsigned type		: 2;
-	/** These bits are reserved for future extensions */
-	unsigned __padding	: 2;
+#if BYTE_ORDER == BIG_ENDIAN
+	unsigned version: 4; /**< Specifies the format of the remaining message (see MGS_VERSION) */
+	unsigned type	: 2; /**< Data or control message (see MSG_TYPE_*) */
+	unsigned endian	: 1; /**< Specifies the byteorder of the message (see MSG_ENDIAN_*) */
+	unsigned 	: 1; /**< Reserved padding bits */
+#else
+	unsigned 	: 1; /**< Reserved padding bits */
+	unsigned endian	: 1; /**< Specifies the byteorder of the message (see MSG_ENDIAN_*) */
+	unsigned type	: 2; /**< Data or control message (see MSG_TYPE_*) */
+	unsigned version: 4; /**< Specifies the format of the remaining message (see MGS_VERSION) */
+#endif
 	/** Number of valid dword values in msg::data[] */
 	uint8_t length;
 	/** The sequence number gets incremented by one for consecutive messages */
 	uint16_t sequence;
 	/** The message payload */
-	float data[MSG_VALUES];
+	union {
+		float f;
+		uint32_t i;
+	} data[MSG_VALUES];
 } __attribute__((packed));
 
 #endif /* _MSG_FORMAT_H_ */