From 0c836ebc47cab2f37274ae03ab2be6c7b2fd0456 Mon Sep 17 00:00:00 2001
From: Dirk Hohndel <dirk@hohndel.org>
Date: Tue, 6 May 2014 14:08:17 -0700
Subject: Simplify string comparison

This is based on Linus' idea on the mailing list.
Treat NULL strings and empty strings as identical.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
---
 dive.h            |  6 ++++++
 equipment.c       | 10 +---------
 qt-ui/maintab.cpp | 11 +++++------
 3 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/dive.h b/dive.h
index 5215c4997..13606f39e 100644
--- a/dive.h
+++ b/dive.h
@@ -7,6 +7,7 @@
 #include <math.h>
 #include <zip.h>
 #include <sqlite3.h>
+#include <string.h>
 
 /* Windows has no MIN/MAX macros - so let's just roll our own */
 #define MIN(x, y) ({                \
@@ -23,6 +24,11 @@
 
 #define IS_FP_SAME(_a, _b) (fabs((_a) - (_b)) < 0.000001 * MAX(fabs(_a), fabs(_b)))
 
+static inline int same_string(const char *a, const char *b)
+{
+	return !strcmp(a ? : "", b ? : "");
+}
+
 #include <libxml/tree.h>
 #include <libxslt/transform.h>
 
diff --git a/equipment.c b/equipment.c
index e63a876d0..548f15b5e 100644
--- a/equipment.c
+++ b/equipment.c
@@ -71,14 +71,6 @@ bool cylinder_none(void *_data)
 	return cylinder_nodata(cyl) && cylinder_nosamples(cyl);
 }
 
-/* descriptions are equal if they are both NULL or both non-NULL
-   and the same text */
-static bool description_equal(const char *desc1, const char *desc2)
-{
-	return ((!desc1 && !desc2) ||
-		(desc1 && desc2 && strcmp(desc1, desc2) == 0));
-}
-
 bool weightsystem_none(void *_data)
 {
 	weightsystem_t *ws = _data;
@@ -98,7 +90,7 @@ bool no_weightsystems(weightsystem_t *ws)
 static bool one_weightsystem_equal(weightsystem_t *ws1, weightsystem_t *ws2)
 {
 	return ws1->weight.grams == ws2->weight.grams &&
-	       description_equal(ws1->description, ws2->description);
+	       same_string(ws1->description, ws2->description);
 }
 
 bool weightsystems_equal(weightsystem_t *ws1, weightsystem_t *ws2)
diff --git a/qt-ui/maintab.cpp b/qt-ui/maintab.cpp
index ec4065d85..5bcc07cf9 100644
--- a/qt-ui/maintab.cpp
+++ b/qt-ui/maintab.cpp
@@ -856,12 +856,11 @@ void MainTab::rejectChanges()
 
 // this macro is rather fragile and is intended to be used as WHAT inside
 // an invocation of EDIT_SELECTED_DIVES(WHAT)
-#define EDIT_TEXT(what, text)                                                                        \
-	if ((!mydive->what && !current_dive->what) ||                                                \
-	    (mydive->what && current_dive->what && strcmp(mydive->what, current_dive->what) == 0)) { \
-		QByteArray textByteArray = text.toUtf8();                                            \
-		free(mydive->what);                                                                  \
-		mydive->what = strdup(textByteArray.data());                                         \
+#define EDIT_TEXT(what, text)                                \
+	if (same_string(mydive->what, current_dive->what)) { \
+		QByteArray textByteArray = text.toUtf8();    \
+		free(mydive->what);                          \
+		mydive->what = strdup(textByteArray.data()); \
 	}
 
 #define EDIT_VALUE(what, value)                      \
-- 
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