From 4334114a74fe7155f735407ce62867e8039a4a9e Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Fri, 15 Sep 2017 22:44:51 +0200
Subject: [PATCH] mapshape, maptree: determine endianess at compile time

Removing the unnecessary runtime checks and the byte swapping code
reduces the library size by 5 kB.
---
 mapshape.c | 32 +++++++++++---------------------
 maptree.c  | 23 ++++++++++++-----------
 2 files changed, 23 insertions(+), 32 deletions(-)

diff --git a/mapshape.c b/mapshape.c
index a24f7b0885..19f7b0508d 100644
--- a/mapshape.c
+++ b/mapshape.c
@@ -52,7 +52,17 @@
 
 #define ByteCopy( a, b, c )     memcpy( b, a, c )
 
-static int      bBigEndian;
+#ifdef __BYTE_ORDER__
+/* GCC/clang predefined macro */
+#define bBigEndian (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+#elif defined(_MSC_VER)
+/* MSVC doesn't support the C99 trick below, but all Microsoft
+   platforms are little-endian */
+#define bBigEndian false
+#else
+/* generic check */
+#define bBigEndian (((union{int in;char out;}){1}).out)
+#endif
 
 /* SHX reading */
 static int msSHXLoadAll( SHPHandle psSHP );
@@ -215,16 +225,6 @@ SHPHandle msSHPOpen( const char * pszLayer, const char * pszAccess )
   else
     pszAccess = "rb";
 
-  /* -------------------------------------------------------------------- */
-  /*  Establish the byte order on this machine.         */
-  /* -------------------------------------------------------------------- */
-  i = 1;
-  /* cppcheck-suppress knownConditionTrueFalse */
-  if( *((uchar *) &i) == 1 )
-    bBigEndian = MS_FALSE;
-  else
-    bBigEndian = MS_TRUE;
-
   /* -------------------------------------------------------------------- */
   /*  Initialize the info structure.              */
   /* -------------------------------------------------------------------- */
@@ -464,16 +464,6 @@ SHPHandle msSHPCreate( const char * pszLayer, int nShapeType )
   ms_int32 i32;
   double dValue;
 
-  /* -------------------------------------------------------------------- */
-  /*      Establish the byte order on this system.                        */
-  /* -------------------------------------------------------------------- */
-  i = 1;
-  /* cppcheck-suppress knownConditionTrueFalse */
-  if( *((uchar *) &i) == 1 )
-    bBigEndian = MS_FALSE;
-  else
-    bBigEndian = MS_TRUE;
-
   /* -------------------------------------------------------------------- */
   /*  Compute the base (layer) name.  If there is any extension       */
   /*  on the passed in filename we will strip it off.         */
diff --git a/maptree.c b/maptree.c
index 7149fe8bbd..4dd4be2001 100644
--- a/maptree.c
+++ b/maptree.c
@@ -33,6 +33,18 @@
 
 #include <limits.h>
 
+#ifdef __BYTE_ORDER__
+/* GCC/clang predefined macro */
+#define bBigEndian (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+#elif defined(_MSC_VER)
+/* MSVC doesn't support the C99 trick below, but all Microsoft
+   platforms are little-endian */
+#define bBigEndian false
+#else
+/* generic check */
+#define bBigEndian (((union{int in;char out;}){1}).out)
+#endif
+
 /* -------------------------------------------------------------------- */
 /*      If the following is 0.5, nodes will be split in half.  If it    */
 /*      is 0.6 then each subnode will contain 60% of the parent         */
@@ -89,17 +101,6 @@ SHPTreeHandle msSHPDiskTreeOpen(const char * pszTree, int debug)
 
   char    pabyBuf[16];
   int     i;
-  char    bBigEndian;
-
-  /* -------------------------------------------------------------------- */
-  /*  Establish the byte order on this machine.         */
-  /* -------------------------------------------------------------------- */
-  i = 1;
-  /* cppcheck-suppress knownConditionTrueFalse */
-  if( *((uchar *) &i) == 1 )
-    bBigEndian = MS_FALSE;
-  else
-    bBigEndian = MS_TRUE;
 
   /* -------------------------------------------------------------------- */
   /*  Initialize the info structure.              */