libwebp: update to 0.4.2-rc2

third_party/libwebp/utils/bit_reader.h

 // Copyright 2010 Google Inc. All Rights Reserved.
 //
 // Use of this source code is governed by a BSD-style license
 // that can be found in the COPYING file in the root of the source
 // tree. An additional intellectual property rights grant can be found
 // in the file PATENTS. All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 // -----------------------------------------------------------------------------
 //
 // Boolean decoder
@@ skipping 89 matching lines @@
 // and should be included by the .c files that actually need them.
 // This is to avoid recompiling the whole library whenever this file is touched,
 // and also allowing platform-specific ad-hoc hacks.
 
 // -----------------------------------------------------------------------------
 // Bitreader for lossless format
 
 // maximum number of bits (inclusive) the bit-reader can handle:
 #define VP8L_MAX_NUM_BIT_READ 24
 
+#define VP8L_LBITS 64  // Number of bits prefetched.
+#define VP8L_WBITS 32  // Minimum number of bytes ready after VP8LFillBitWindow.
+
 typedef uint64_t vp8l_val_t;  // right now, this bit-reader can only use 64bit.
 
 typedef struct {
   vp8l_val_t     val_;        // pre-fetched bits
   const uint8_t* buf_;        // input byte buffer
   size_t         len_;        // buffer length
   size_t         pos_;        // byte position in buf_
   int            bit_pos_;    // current bit-reading position in val_
   int            eos_;        // bitstream is finished
   int            error_;      // an error occurred (buffer overflow attempt...)
@@ skipping 11 matching lines @@
 // Flags an error in case end_of_stream or n_bits is more than the allowed limit
 // of VP8L_MAX_NUM_BIT_READ (inclusive).
 // Flags eos_ if this read attempt is going to cross the read buffer.
 uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits);
 
 // Return the prefetched bits, so they can be looked up.
 static WEBP_INLINE uint32_t VP8LPrefetchBits(VP8LBitReader* const br) {
   return (uint32_t)(br->val_ >> br->bit_pos_);
 }
 
+// Returns true if there was an attempt at reading bit past the end of
+// the buffer. Doesn't set br->eos_ flag.
+static WEBP_INLINE int VP8LIsEndOfStream(const VP8LBitReader* const br) {
+  assert(br->pos_ <= br->len_);
+  return (br->pos_ == br->len_) && (br->bit_pos_ > VP8L_LBITS);
+}
+
 // 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;
+  br->eos_ = VP8LIsEndOfStream(br);
 }
 
 // Advances the read buffer by 4 bytes to make room for reading next 32 bits.
-void VP8LFillBitWindow(VP8LBitReader* const br);
+// Speed critical, but infrequent part of the code can be non-inligned.
+extern void VP8LDoFillBitWindow(VP8LBitReader* const br);
+static WEBP_INLINE void VP8LFillBitWindow(VP8LBitReader* const br) {
+  if (br->bit_pos_ >= VP8L_WBITS) VP8LDoFillBitWindow(br);
+}
 
 #ifdef __cplusplus
 }    // extern "C"
 #endif
 
 #endif  /* WEBP_UTILS_BIT_READER_H_ */