Use the upstream version of libwebp, v0.4.3.

third_party/libwebp/utils/bit_reader.c

+// 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 non-inlined methods
+//
+// Author: Skal (pascal.massimino@gmail.com)
+
+#ifdef HAVE_CONFIG_H
+#include "../webp/config.h"
+#endif
+
+#include "./bit_reader_inl.h"
+
+//------------------------------------------------------------------------------
+// VP8BitReader
+
+void VP8InitBitReader(VP8BitReader* const br,
+                      const uint8_t* const start, const uint8_t* const end) {
+  assert(br != NULL);
+  assert(start != NULL);
+  assert(start <= end);
+  br->range_   = 255 - 1;
+  br->buf_     = start;
+  br->buf_end_ = end;
+  br->value_   = 0;
+  br->bits_    = -8;   // to load the very first 8bits
+  br->eof_     = 0;
+  VP8LoadNewBytes(br);
+}
+
+void VP8RemapBitReader(VP8BitReader* const br, ptrdiff_t offset) {
+  if (br->buf_ != NULL) {
+    br->buf_ += offset;
+    br->buf_end_ += offset;
+  }
+}
+
+const uint8_t kVP8Log2Range[128] = {
+     7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
+  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  0
+};
+
+// range = ((range - 1) << kVP8Log2Range[range]) + 1
+const range_t kVP8NewRange[128] = {
+  127, 127, 191, 127, 159, 191, 223, 127,
+  143, 159, 175, 191, 207, 223, 239, 127,
+  135, 143, 151, 159, 167, 175, 183, 191,
+  199, 207, 215, 223, 231, 239, 247, 127,
+  131, 135, 139, 143, 147, 151, 155, 159,
+  163, 167, 171, 175, 179, 183, 187, 191,
+  195, 199, 203, 207, 211, 215, 219, 223,
+  227, 231, 235, 239, 243, 247, 251, 127,
+  129, 131, 133, 135, 137, 139, 141, 143,
+  145, 147, 149, 151, 153, 155, 157, 159,
+  161, 163, 165, 167, 169, 171, 173, 175,
+  177, 179, 181, 183, 185, 187, 189, 191,
+  193, 195, 197, 199, 201, 203, 205, 207,
+  209, 211, 213, 215, 217, 219, 221, 223,
+  225, 227, 229, 231, 233, 235, 237, 239,
+  241, 243, 245, 247, 249, 251, 253, 127
+};
+
+void VP8LoadFinalBytes(VP8BitReader* const br) {
+  assert(br != NULL && br->buf_ != NULL);
+  // Only read 8bits at a time
+  if (br->buf_ < br->buf_end_) {
+    br->bits_ += 8;
+    br->value_ = (bit_t)(*br->buf_++) | (br->value_ << 8);
+  } else if (!br->eof_) {
+    br->value_ <<= 8;
+    br->bits_ += 8;
+    br->eof_ = 1;
+  }
+}
+
+//------------------------------------------------------------------------------
+// Higher-level calls
+
+uint32_t VP8GetValue(VP8BitReader* const br, int bits) {
+  uint32_t v = 0;
+  while (bits-- > 0) {
+    v |= VP8GetBit(br, 0x80) << bits;
+  }
+  return v;
+}
+
+int32_t VP8GetSignedValue(VP8BitReader* const br, int bits) {
+  const int value = VP8GetValue(br, bits);
+  return VP8Get(br) ? -value : value;
+}
+
+//------------------------------------------------------------------------------
+// VP8LBitReader
+
+#define VP8L_LOG8_WBITS 4  // Number of bytes needed to store VP8L_WBITS bits.
+
+#if !defined(WEBP_FORCE_ALIGNED) && \
+    (defined(__arm__) || defined(_M_ARM) || defined(__aarch64__) || \
+     defined(__i386__) || defined(_M_IX86) || \
+     defined(__x86_64__) || defined(_M_X64))
+#define VP8L_USE_UNALIGNED_LOAD
+#endif
+
+static const uint32_t kBitMask[VP8L_MAX_NUM_BIT_READ + 1] = {
+  0,
+  0x000001, 0x000003, 0x000007, 0x00000f,
+  0x00001f, 0x00003f, 0x00007f, 0x0000ff,
+  0x0001ff, 0x0003ff, 0x0007ff, 0x000fff,
+  0x001fff, 0x003fff, 0x007fff, 0x00ffff,
+  0x01ffff, 0x03ffff, 0x07ffff, 0x0fffff,
+  0x1fffff, 0x3fffff, 0x7fffff, 0xffffff
+};
+
+void VP8LInitBitReader(VP8LBitReader* const br, const uint8_t* const start,
+                       size_t length) {
+  size_t i;
+  vp8l_val_t value = 0;
+  assert(br != NULL);
+  assert(start != NULL);
+  assert(length < 0xfffffff8u);   // can't happen with a RIFF chunk.
+
+  br->len_ = length;
+  br->val_ = 0;
+  br->bit_pos_ = 0;
+  br->eos_ = 0;
+  br->error_ = 0;
+
+  if (length > sizeof(br->val_)) {
+    length = sizeof(br->val_);
+  }
+  for (i = 0; i < length; ++i) {
+    value |= (vp8l_val_t)start[i] << (8 * i);
+  }
+  br->val_ = value;
+  br->pos_ = length;
+  br->buf_ = start;
+}
+
+void VP8LBitReaderSetBuffer(VP8LBitReader* const br,
+                            const uint8_t* const buf, size_t len) {
+  assert(br != NULL);
+  assert(buf != NULL);
+  assert(len < 0xfffffff8u);   // can't happen with a RIFF chunk.
+  br->buf_ = buf;
+  br->len_ = len;
+  // pos_ > len_ should be considered a param error.
+  br->error_ = (br->pos_ > br->len_);
+  br->eos_ = br->error_ || VP8LIsEndOfStream(br);
+}
+
+// If not at EOS, reload up to VP8L_LBITS byte-by-byte
+static void ShiftBytes(VP8LBitReader* const br) {
+  while (br->bit_pos_ >= 8 && br->pos_ < br->len_) {
+    br->val_ >>= 8;
+    br->val_ |= ((vp8l_val_t)br->buf_[br->pos_]) << (VP8L_LBITS - 8);
+    ++br->pos_;
+    br->bit_pos_ -= 8;
+  }
+  br->eos_ = VP8LIsEndOfStream(br);
+}
+
+void VP8LDoFillBitWindow(VP8LBitReader* const br) {
+  assert(br->bit_pos_ >= VP8L_WBITS);
+  // TODO(jzern): given the fixed read size it may be possible to force
+  //              alignment in this block.
+#if defined(VP8L_USE_UNALIGNED_LOAD)
+  if (br->pos_ + sizeof(br->val_) < br->len_) {
+    br->val_ >>= VP8L_WBITS;
+    br->bit_pos_ -= VP8L_WBITS;
+    // The expression below needs a little-endian arch to work correctly.
+    // This gives a large speedup for decoding speed.
+    br->val_ |= (vp8l_val_t)*(const uint32_t*)(br->buf_ + br->pos_) <<
+                (VP8L_LBITS - VP8L_WBITS);
+    br->pos_ += VP8L_LOG8_WBITS;
+    return;
+  }
+#endif
+  ShiftBytes(br);       // Slow path.
+}
+
+uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits) {
+  assert(n_bits >= 0);
+  // Flag an error if end_of_stream or n_bits is more than allowed limit.
+  if (!br->eos_ && n_bits <= VP8L_MAX_NUM_BIT_READ) {
+    const uint32_t val =
+        (uint32_t)(br->val_ >> br->bit_pos_) & kBitMask[n_bits];
+    const int new_bits = br->bit_pos_ + n_bits;
+    br->bit_pos_ = new_bits;
+    ShiftBytes(br);
+    return val;
+  } else {
+    br->error_ = 1;
+    return 0;
+  }
+}
+
+//------------------------------------------------------------------------------