Update libwebp to 0.4.0

third_party/libwebp/enc/backward_references.h

Index: third_party/libwebp/enc/backward_references.h
diff --git a/third_party/libwebp/enc/backward_references.h b/third_party/libwebp/enc/backward_references.h
index b0d18135f78b6acfed9a29947e7478ba2ca7de67..e1c75f04f9dc3e045252214ed0be163efee68e1a 100644
--- a/third_party/libwebp/enc/backward_references.h
+++ b/third_party/libwebp/enc/backward_references.h
@@ -18,7 +18,7 @@
 #include "../webp/types.h"
 #include "../webp/format_constants.h"
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 extern "C" {
 #endif
 
@@ -31,73 +31,6 @@ extern "C" {
     (NUM_LITERAL_CODES + NUM_LENGTH_CODES + (1 << MAX_COLOR_CACHE_BITS))
 
 // -----------------------------------------------------------------------------
-// PrefixEncode()
-
-// use GNU builtins where available.
-#if defined(__GNUC__) && \
-    ((__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || __GNUC__ >= 4)
-static WEBP_INLINE int BitsLog2Floor(uint32_t n) {
-  assert(n != 0);
-  return 31 ^ __builtin_clz(n);
-}
-#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_IX86))
-#include <intrin.h>
-#pragma intrinsic(_BitScanReverse)
-
-static WEBP_INLINE int BitsLog2Floor(uint32_t n) {
-  unsigned long first_set_bit;
-  assert(n != 0);
-  _BitScanReverse(&first_set_bit, n);
-  return first_set_bit;
-}
-#else
-// Returns (int)floor(log2(n)). n must be > 0.
-static WEBP_INLINE int BitsLog2Floor(uint32_t n) {
-  int log = 0;
-  uint32_t value = n;
-  int i;
-
-  assert(n != 0);
-  for (i = 4; i >= 0; --i) {
-    const int shift = (1 << i);
-    const uint32_t x = value >> shift;
-    if (x != 0) {
-      value = x;
-      log += shift;
-    }
-  }
-  return log;
-}
-#endif
-
-static WEBP_INLINE int VP8LBitsLog2Ceiling(uint32_t n) {
-  const int log_floor = BitsLog2Floor(n);
-  if (n == (n & ~(n - 1)))  // zero or a power of two.
-    return log_floor;
-  else
-    return log_floor + 1;
-}
-
-// Splitting of distance and length codes into prefixes and
-// extra bits. The prefixes are encoded with an entropy code
-// while the extra bits are stored just as normal bits.
-static WEBP_INLINE void PrefixEncode(int distance, int* const code,
-                                     int* const extra_bits_count,
-                                     int* const extra_bits_value) {
-  if (distance > 2) {  // Collect the two most significant bits.
-    const int highest_bit = BitsLog2Floor(--distance);
-    const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
-    *extra_bits_count = highest_bit - 1;
-    *extra_bits_value = distance & ((1 << *extra_bits_count) - 1);
-    *code = 2 * highest_bit + second_highest_bit;
-  } else {
-    *extra_bits_count = 0;
-    *extra_bits_value = 0;
-    *code = (distance == 2) ? 1 : 0;
-  }
-}
-
-// -----------------------------------------------------------------------------
 // PixOrCopy
 
 enum Mode {
@@ -212,7 +145,7 @@ int VP8LCalculateEstimateForCacheSize(const uint32_t* const argb,
                                       int xsize, int ysize,
                                       int* const best_cache_bits);
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 }
 #endif