From b2bf9e15ebcdbb3cfb7c38f43446bec48b446793 Mon Sep 17 00:00:00 2001
From: David Sidrane <david_s5@nscdg.com>
Date: Fri, 23 Sep 2016 09:09:40 -1000
Subject: [PATCH] Use union of datatypes supported by dataman to reduce wasted
 space

---
 src/modules/dataman/dataman.c |  9 +++++----
 src/modules/dataman/dataman.h | 15 +++++++++++++--
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/modules/dataman/dataman.c b/src/modules/dataman/dataman.c
index 62978e0f7c..6af444d880 100644
--- a/src/modules/dataman/dataman.c
+++ b/src/modules/dataman/dataman.c
@@ -47,6 +47,7 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <systemlib/systemlib.h>
 #include <systemlib/err.h>
@@ -388,7 +389,7 @@ static ssize_t _ram_write(dm_item_t item, unsigned char index, dm_persitence_t p
 
 	/* Make sure caller has not given us more data than we can handle */
 	if (count > DM_MAX_DATA_SIZE) {
-		return -1;
+		return -E2BIG;
 	}
 
 	uint8_t *buffer = &g_task_data[offset];
@@ -429,7 +430,7 @@ _file_write(dm_item_t item, unsigned char index, dm_persitence_t persistence, co
 
 	/* Make sure caller has not given us more data than we can handle */
 	if (count > DM_MAX_DATA_SIZE) {
-		return -1;
+		return -E2BIG;
 	}
 
 	/* Write out the data, prefixed with length and persistence level */
@@ -474,7 +475,7 @@ static ssize_t _ram_read(dm_item_t item, unsigned char index, void *buf, size_t
 
 	/* Make sure the caller hasn't asked for more data than we can handle */
 	if (count > DM_MAX_DATA_SIZE) {
-		return -1;
+		return -E2BIG;
 	}
 
 	/* Read the prefix and data */
@@ -517,7 +518,7 @@ _file_read(dm_item_t item, unsigned char index, void *buf, size_t count)
 
 	/* Make sure the caller hasn't asked for more data than we can handle */
 	if (count > DM_MAX_DATA_SIZE) {
-		return -1;
+		return -E2BIG;
 	}
 
 	/* Read the prefix and data */
diff --git a/src/modules/dataman/dataman.h b/src/modules/dataman/dataman.h
index 34d48f8979..337cdddef1 100644
--- a/src/modules/dataman/dataman.h
+++ b/src/modules/dataman/dataman.h
@@ -42,6 +42,7 @@
 #include <navigator/navigation.h>
 #include <uORB/topics/mission.h>
 #include <uORB/topics/fence.h>
+#include <uORB/topics/fence_vertex.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -102,8 +103,18 @@ typedef enum {
 	DM_INIT_REASON_VOLATILE			/* Data does not survive reset */
 } dm_reset_reason;
 
-/** Maximum size in bytes of a single item instance */
-#define DM_MAX_DATA_SIZE 126
+/** Maximum size in bytes of a single item instance is
+ * defined by adding the structure type to the union below
+ */
+
+typedef union dataman_max_size_t {
+	struct mission_item_s    mission_item;
+	struct mission_s	      mission;
+	struct fence_vertex_s    vertex;
+} dataman_max_size_t;
+
+
+#define DM_MAX_DATA_SIZE sizeof(dataman_max_size_t)
 
 /** Retrieve from the data manager store */
 __EXPORT ssize_t