Make endianess detection more robust

This moves the byte order detection into the internal plot header and
makes teh detection much more robust searching for more macros in
common use. This should fix compilation on big endian openBSD systems

Thanks to Anthony J. Bentley for a patch used as inspiration for this change

3 files changed, 113 insertions, 40 deletions

diff --git a/src/plot/24bpp.c b/src/plot/24bpp.c
index 011765a..651abe1 100644
--- a/src/plot/24bpp.c
+++ b/src/plot/24bpp.c
@@ -9,13 +9,6 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
-#ifndef _WIN32
-#include <endian.h>
-#else
-#define __BYTE_ORDER __BYTE_ORDER__
-#define __BIG_ENDIAN __ORDER_BIG_ENDIAN__
-#endif
-
 #include "libnsfb.h"
 #include "libnsfb_plot.h"
 #include "libnsfb_plot_util.h"
@@ -23,24 +16,43 @@
 #include "nsfb.h"
 #include "plot.h"
 
-static inline uint8_t *
-get_xy_loc(nsfb_t *nsfb, int x, int y)
+/**
+ * Get the address of a logical location on the framebuffer
+ */
+static inline uint8_t *get_xy_loc(nsfb_t *nsfb, int x, int y)
 {
         return (uint8_t *)(nsfb->ptr + (y * nsfb->linelen) + (x * 3));
 }
 
-#if __BYTE_ORDER == __BIG_ENDIAN
-static inline nsfb_colour_t pixel_to_colour(uint8_t pixel)
+#ifdef NSFB_BE_BYTE_ORDER
+
+/**
+ * convert a 24bpp big endian pixel value to netsurf colour
+ */
+static inline nsfb_colour_t pixel_to_colour(uint32_t pixel)
 {
         return (pixel >> 8) & ~0xFF000000U;
 }
 
-/* convert a colour value to a 32bpp pixel value ready for screen output */
+/**
+ * convert a colour value to a big endian 24bpp pixel value
+ *
+ * The resulting value is ready for screen output
+ */
 static inline uint32_t colour_to_pixel(nsfb_colour_t c)
 {
         return (c << 8);
 }
-#else /* __BYTE_ORDER == __BIG_ENDIAN */
+
+#else
+
+/**
+ * convert a 24bpp little endian pixel value to netsurf colour
+ *
+ * \param nsfb The framebuffer
+ * \param pixel The pixel values
+ * \return The netsurf colour value.
+ */
 static inline nsfb_colour_t pixel_to_colour(uint32_t pixel)
 {
         return ((pixel & 0xFF) << 16) |
@@ -48,11 +60,17 @@ static inline nsfb_colour_t pixel_to_colour(uint32_t pixel)
                 ((pixel & 0xFF0000) >> 16);
 }
 
-/* convert a colour value to a 32bpp pixel value ready for screen output */
+/**
+ * convert a colour value to a little endian 24bpp pixel value
+ *
+ * \param c The netsurf colour
+ * \return A pixel value ready for screen output.
+ */
 static inline uint32_t colour_to_pixel(nsfb_colour_t c)
 {
         return ((c & 0xff0000) >> 16) | (c & 0xff00) | ((c & 0xff) << 16);
 }
+
 #endif
 
 #define SIGN(x)  ((x<0) ?  -1  :  ((x>0) ? 1 : 0))
diff --git a/src/plot/32bpp-xbgr8888.c b/src/plot/32bpp-xbgr8888.c
index a0ed066..2492054 100644
--- a/src/plot/32bpp-xbgr8888.c
+++ b/src/plot/32bpp-xbgr8888.c
@@ -10,13 +10,6 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
-#ifndef _WIN32
-#include <endian.h>
-#else
-#define __BYTE_ORDER __BYTE_ORDER__
-#define __BIG_ENDIAN __ORDER_BIG_ENDIAN__
-#endif
-
 #include "libnsfb.h"
 #include "libnsfb_plot.h"
 #include "libnsfb_plot_util.h"
@@ -24,37 +17,71 @@
 #include "nsfb.h"
 #include "plot.h"
 
+#define UNUSED __attribute__((unused))
 
-#define UNUSED __attribute__((unused)) 
 
+/**
+ * Get the address of a logical location on the framebuffer
+ */
 static inline uint32_t *get_xy_loc(nsfb_t *nsfb, int x, int y)
 {
         return (void *)(nsfb->ptr + (y * nsfb->linelen) + (x << 2));
 }
 
-#if __BYTE_ORDER == __BIG_ENDIAN
+#ifdef NSFB_BE_BYTE_ORDER
+
+/**
+ * convert a 32bpp big endian pixel value to netsurf colour
+ *
+ * \param nsfb The framebuffer
+ * \param pixel The pixel value
+ * \return The netsurf colour value.
+ */
 static inline nsfb_colour_t pixel_to_colour(UNUSED nsfb_t *nsfb, uint32_t pixel)
 {
-	/* TODO: FIX */
+        /** \todo fix this conversion as it is probably wrong */
         return (pixel >> 8) & ~0xFF000000U;
 }
 
-/* convert a colour value to a 32bpp pixel value ready for screen output */
+/**
+ * convert a colour value to a big endian 32bpp pixel value
+ *
+ * \param nsfb The framebuffer
+ * \param c The framebuffer colour
+ * \return A pixel value ready for screen output.
+ */
 static inline uint32_t colour_to_pixel(UNUSED nsfb_t *nsfb, nsfb_colour_t c)
 {
-	return ((c & 0xFF) << 24) | ((c & 0xFF00) << 8) | ((c & 0xFF0000) >> 8);
+        return ((c & 0xFF) << 24) | ((c & 0xFF00) << 8) | ((c & 0xFF0000) >> 8);
 }
-#else /* __BYTE_ORDER == __BIG_ENDIAN */
+
+#else
+
+/**
+ * convert a 32bpp little endian pixel value to netsurf colour
+ *
+ * \param nsfb The framebuffer
+ * \param pixel The pixel value
+ * \return The netsurf colour value.
+ */
 static inline nsfb_colour_t pixel_to_colour(UNUSED nsfb_t *nsfb, uint32_t pixel)
 {
         return pixel | 0xFF000000U;
 }
 
-/* convert a colour value to a 32bpp pixel value ready for screen output */
+
+/**
+ * convert a colour value to a little endian 32bpp pixel value
+ *
+ * \param nsfb The framebuffer
+ * \param c The netsurf colour
+ * \return A pixel value ready for screen output.
+ */
 static inline uint32_t colour_to_pixel(UNUSED nsfb_t *nsfb, nsfb_colour_t c)
 {
         return c;
 }
+
 #endif
 
 #define PLOT_TYPE uint32_t
diff --git a/src/plot/32bpp-xrgb8888.c b/src/plot/32bpp-xrgb8888.c
index 476f6b2..6f77f44 100644
--- a/src/plot/32bpp-xrgb8888.c
+++ b/src/plot/32bpp-xrgb8888.c
@@ -10,13 +10,6 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
-#ifndef _WIN32
-#include <endian.h>
-#else
-#define __BYTE_ORDER __BYTE_ORDER__
-#define __BIG_ENDIAN __ORDER_BIG_ENDIAN__
-#endif
-
 #include "libnsfb.h"
 #include "libnsfb_plot.h"
 #include "libnsfb_plot_util.h"
@@ -24,26 +17,53 @@
 #include "nsfb.h"
 #include "plot.h"
 
+#define UNUSED __attribute__((unused))
 
-#define UNUSED __attribute__((unused)) 
 
+/**
+ * Get the address of a logical location on the framebuffer
+ */
 static inline uint32_t *get_xy_loc(nsfb_t *nsfb, int x, int y)
 {
         return (void *)(nsfb->ptr + (y * nsfb->linelen) + (x << 2));
 }
 
-#if __BYTE_ORDER == __BIG_ENDIAN
+
+#ifdef NSFB_BE_BYTE_ORDER
+
+/**
+ * convert a 32bpp big endian pixel value to netsurf colour
+ *
+ * \param nsfb The framebuffer
+ * \param pixel The pixel value
+ * \return The netsurf colour value.
+ */
 static inline nsfb_colour_t pixel_to_colour(UNUSED nsfb_t *nsfb, uint32_t pixel)
 {
         return (pixel >> 8) & ~0xFF000000U;
 }
 
-/* convert a colour value to a 32bpp pixel value ready for screen output */
+/**
+ * convert a colour value to a big endian 32bpp pixel value
+ *
+ * \param nsfb The framebuffer
+ * \param c The framebuffer colour
+ * \return A pixel value ready for screen output.
+ */
 static inline uint32_t colour_to_pixel(UNUSED nsfb_t *nsfb, nsfb_colour_t c)
 {
         return (c << 8);
 }
-#else /* __BYTE_ORDER == __BIG_ENDIAN */
+
+#else
+
+/**
+ * convert a 32bpp little endian pixel value to netsurf colour
+ *
+ * \param nsfb The framebuffer
+ * \param pixel The pixel value
+ * \return The netsurf colour value.
+ */
 static inline nsfb_colour_t pixel_to_colour(UNUSED nsfb_t *nsfb, uint32_t pixel)
 {
         return ((pixel & 0xFF) << 16) |
@@ -51,11 +71,19 @@ static inline nsfb_colour_t pixel_to_colour(UNUSED nsfb_t *nsfb, uint32_t pixel)
                 ((pixel & 0xFF0000) >> 16);
 }
 
-/* convert a colour value to a 32bpp pixel value ready for screen output */
+
+/**
+ * convert a colour value to a little endian 32bpp pixel value
+ *
+ * \param nsfb The framebuffer
+ * \param c The netsurf colour
+ * \return A pixel value ready for screen output.
+ */
 static inline uint32_t colour_to_pixel(UNUSED nsfb_t *nsfb, nsfb_colour_t c)
 {
         return ((c & 0xff0000) >> 16) | (c & 0xff00) | ((c & 0xff) << 16);
 }
+
 #endif
 
 #define PLOT_TYPE uint32_t