configure.ac: add AC_C_BIGENDIAN

this defines WORDS_BIGENDIAN, replacing uses of
__BIG_ENDIAN__/__BYTE_ORDER__ with it

+ fixes lossless BGRA output with big-endian toolchains
  that do not define __BIG_ENDIAN__ (codesourcery mips gcc)

Change-Id: Ieaccd623292d235343b5e34b7a720fc251c432d7

configure.ac

@@ -15,6 +15,9 @@ AM_PROG_CC_C_O
 dnl === Enable less verbose output when building.
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
+dnl == test endianness
+AC_C_BIGENDIAN
+
 dnl === SET_IF_UNSET(shell_var, value)
 dnl ===   Set the shell variable 'shell_var' to 'value' if it is unset.
 AC_DEFUN([SET_IF_UNSET], [test "${$1+set}" = "set" || $1=$2])

examples/tiffdec.c

@@ -97,7 +97,7 @@ int ReadTIFF(const char* const filename,
       pic->width = width;
       pic->height = height;
       // TIFF data is ABGR
-#ifdef __BIG_ENDIAN__
+#ifdef WORDS_BIGENDIAN
       TIFFSwabArrayOfLong(raster, width * height);
 #endif
       pic->use_argb = 1;

src/dsp/lossless.c

@@ -1360,7 +1360,7 @@ static void CopyOrSwap(const uint32_t* src, int num_pixels, uint8_t* dst,
     while (src < src_end) {
       const uint32_t argb = *src++;
 
-#if !defined(__BIG_ENDIAN__)
+#if !defined(WORDS_BIGENDIAN)
 #if !defined(WEBP_REFERENCE_IMPLEMENTATION)
       *(uint32_t*)dst = BSwap32(argb);
 #else  // WEBP_REFERENCE_IMPLEMENTATION
@@ -1369,7 +1369,7 @@ static void CopyOrSwap(const uint32_t* src, int num_pixels, uint8_t* dst,
       dst[2] = (argb >>  8) & 0xff;
       dst[3] = (argb >>  0) & 0xff;
 #endif
-#else  // __BIG_ENDIAN__
+#else  // WORDS_BIGENDIAN
       dst[0] = (argb >>  0) & 0xff;
       dst[1] = (argb >>  8) & 0xff;
       dst[2] = (argb >> 16) & 0xff;

src/utils/bit_reader_inl.h

@@ -70,7 +70,7 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
     const lbit_t in_bits = *(const lbit_t*)br->buf_;
 #endif
     br->buf_ += BITS >> 3;
-#if !defined(__BIG_ENDIAN__)
+#if !defined(WORDS_BIGENDIAN)
 #if (BITS > 32)
     bits = BSwap64(in_bits);
     bits >>= 64 - BITS;
@@ -83,7 +83,7 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
 #else   // BITS == 8
     bits = (bit_t)in_bits;
 #endif  // BITS > 32
-#else    // BIG_ENDIAN
+#else    // WORDS_BIGENDIAN
     bits = (bit_t)in_bits;
     if (BITS != 8 * sizeof(bit_t)) bits >>= (8 * sizeof(bit_t) - BITS);
 #endif

src/utils/endian_inl.h

@@ -12,12 +12,17 @@
 #ifndef WEBP_UTILS_ENDIAN_INL_H_
 #define WEBP_UTILS_ENDIAN_INL_H_
 
+#ifdef HAVE_CONFIG_H
+#include "../webp/config.h"
+#endif
+
 #include "../webp/types.h"
 
 // some endian fix (e.g.: mips-gcc doesn't define __BIG_ENDIAN__)
-#if !defined(__BIG_ENDIAN__) && defined(__BYTE_ORDER__) && \
-    (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
-#define __BIG_ENDIAN__
+#if !defined(WORDS_BIGENDIAN) && \
+    (defined(__BIG_ENDIAN__) || \
+     (defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)))
+#define WORDS_BIGENDIAN
 #endif
 
 //  endian-specific htoleXX() definition