Update libwebp to 0.4.0

third_party/libwebp/utils/bit_reader.h

Index: third_party/libwebp/utils/bit_reader.h
diff --git a/third_party/libwebp/utils/bit_reader.h b/third_party/libwebp/utils/bit_reader.h
index 588222b3be7925186bf651f8478f3916ae631e07..98df98a7678648c1347ba8fad564bb8fa33b2924 100644
--- a/third_party/libwebp/utils/bit_reader.h
+++ b/third_party/libwebp/utils/bit_reader.h
@@ -19,10 +19,9 @@
 #ifdef _MSC_VER
 #include <stdlib.h>  // _byteswap_ulong
 #endif
-#include <string.h>  // For memcpy
 #include "../webp/types.h"
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 extern "C" {
 #endif
 
@@ -55,7 +54,7 @@ extern "C" {
 // And just after calling VP8LoadNewBytes():
 //  [........vvvvvvvvBBBBBBBBBBBBBBBB]LSB || [........vvvvvvvvBBBBBBBBBBBBBBBB]
 //
-// -> we're back to height active 'value_' bits (marked 'v') and BITS cached
+// -> we're back to eight active 'value_' bits (marked 'v') and BITS cached
 // bits (marked 'B')
 //
 // The right-justify strategy tends to use less shifts and is often faster.
@@ -155,7 +154,7 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
   if (br->buf_ + sizeof(lbit_t) <= br->buf_end_) {
     // convert memory type to register type (with some zero'ing!)
     bit_t bits;
-    lbit_t in_bits = *(lbit_t*)br->buf_;
+    const lbit_t in_bits = *(const lbit_t*)br->buf_;
     br->buf_ += (BITS) >> 3;
 #if !defined(__BIG_ENDIAN__)
 #if (BITS > 32)
@@ -179,8 +178,11 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
     bits >>= 64 - BITS;
 #elif (BITS >= 24)
 #if defined(__i386__) || defined(__x86_64__)
-    __asm__ volatile("bswap %k0" : "=r"(in_bits) : "0"(in_bits));
-    bits = (bit_t)in_bits;   // 24b/32b -> 32b/64b zero-extension
+    {
+      lbit_t swapped_in_bits;
+      __asm__ volatile("bswap %k0" : "=r"(swapped_in_bits) : "0"(in_bits));
+      bits = (bit_t)swapped_in_bits;   // 24b/32b -> 32b/64b zero-extension
+    }
 #elif defined(_MSC_VER)
     bits = (bit_t)_byteswap_ulong(in_bits);
 #else
@@ -254,6 +256,7 @@ static WEBP_INLINE void VP8Shift(VP8BitReader* const br) {
   br->bits_ -= shift;
 #endif
 }
+
 static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) {
 #ifndef USE_RIGHT_JUSTIFY
   // It's important to avoid generating a 64bit x 64bit multiply here.
@@ -282,7 +285,6 @@ static WEBP_INLINE int VP8GetSigned(VP8BitReader* const br, int v) {
   return bit ? -v : v;
 }
 
-
 // -----------------------------------------------------------------------------
 // Bitreader for lossless format
 
@@ -316,15 +318,16 @@ static WEBP_INLINE uint32_t VP8LPrefetchBits(VP8LBitReader* const br) {
   return (uint32_t)(br->val_ >> br->bit_pos_);
 }
 
-// Discard 'num_bits' bits from the cache.
-static WEBP_INLINE void VP8LDiscardBits(VP8LBitReader* const br, int num_bits) {
-  br->bit_pos_ += num_bits;
+// For jumping over a number of bits in the bit stream when accessed with
+// VP8LPrefetchBits and VP8LFillBitWindow.
+static WEBP_INLINE void VP8LSetBitPos(VP8LBitReader* const br, int val) {
+  br->bit_pos_ = val;
 }
 
-// Advances the Read buffer by 4 bytes to make room for reading next 32 bits.
+// Advances the read buffer by 4 bytes to make room for reading next 32 bits.
 void VP8LFillBitWindow(VP8LBitReader* const br);
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 }    // extern "C"
 #endif