avutil/common, macros: Move several macros from common.h to macros.h

common.h currently contains several things: Math macros, UTF-8 macros,
other fundamental macros; furthermore it also contains miscellaneous
math functions and it (directly and indirectly) includes lots of other
headers.

This commit moves the "other fundamental macros" to macros.h which is
a more fitting place.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavutil/macros.h

@@ -25,6 +25,36 @@
 #ifndef AVUTIL_MACROS_H
 #define AVUTIL_MACROS_H
 
+#include "libavutil/avconfig.h"
+
+#if AV_HAVE_BIGENDIAN
+#   define AV_NE(be, le) (be)
+#else
+#   define AV_NE(be, le) (le)
+#endif
+
+/**
+ * Comparator.
+ * For two numerical expressions x and y, gives 1 if x > y, -1 if x < y, and 0
+ * if x == y. This is useful for instance in a qsort comparator callback.
+ * Furthermore, compilers are able to optimize this to branchless code, and
+ * there is no risk of overflow with signed types.
+ * As with many macros, this evaluates its argument multiple times, it thus
+ * must not have a side-effect.
+ */
+#define FFDIFFSIGN(x,y) (((x)>(y)) - ((x)<(y)))
+
+#define FFMAX(a,b) ((a) > (b) ? (a) : (b))
+#define FFMAX3(a,b,c) FFMAX(FFMAX(a,b),c)
+#define FFMIN(a,b) ((a) > (b) ? (b) : (a))
+#define FFMIN3(a,b,c) FFMIN(FFMIN(a,b),c)
+
+#define FFSWAP(type,a,b) do{type SWAP_tmp= b; b= a; a= SWAP_tmp;}while(0)
+#define FF_ARRAY_ELEMS(a) (sizeof(a) / sizeof((a)[0]))
+
+#define MKTAG(a,b,c,d)   ((a) | ((b) << 8) | ((c) << 16) | ((unsigned)(d) << 24))
+#define MKBETAG(a,b,c,d) ((d) | ((c) << 8) | ((b) << 16) | ((unsigned)(a) << 24))
+
 /**
  * @addtogroup preproc_misc Preprocessor String Macros
  *