libwebp: update snapshot to v0.2.0-rc1

third_party/libwebp/utils/bit_reader.c

-// Copyright 2010 Google Inc.
+// Copyright 2010 Google Inc. All Rights Reserved.
 //
 // This code is licensed under the same terms as WebM:
 //  Software License Agreement:  http://www.webmproject.org/license/software/
 //  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
 // -----------------------------------------------------------------------------
 //
 // Boolean decoder
 //
 // Author: Skal (pascal.massimino@gmail.com)
 
 #include "./bit_reader.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
 extern "C" {
 #endif
 
+#define MK(X) (((bit_t)(X) << (BITS)) | (MASK))
+
 //------------------------------------------------------------------------------
 // VP8BitReader
 
 void VP8InitBitReader(VP8BitReader* const br,
                       const uint8_t* const start, const uint8_t* const end) {
-  assert(br);
-  assert(start);
+  assert(br != NULL);
+  assert(start != NULL);
   assert(start <= end);
-  br->range_   = 255 - 1;
+  br->range_   = MK(255 - 1);
   br->buf_     = start;
   br->buf_end_ = end;
   br->value_   = 0;
-  br->missing_ = 8;
+  br->missing_ = 8;   // to load the very first 8bits
   br->eof_     = 0;
 }
 
 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 uint8_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
+// range = (range << kVP8Log2Range[range]) + trailing 1's
+const bit_t kVP8NewRange[128] = {
+  MK(127), MK(127), MK(191), MK(127), MK(159), MK(191), MK(223), MK(127),
+  MK(143), MK(159), MK(175), MK(191), MK(207), MK(223), MK(239), MK(127),
+  MK(135), MK(143), MK(151), MK(159), MK(167), MK(175), MK(183), MK(191),
+  MK(199), MK(207), MK(215), MK(223), MK(231), MK(239), MK(247), MK(127),
+  MK(131), MK(135), MK(139), MK(143), MK(147), MK(151), MK(155), MK(159),
+  MK(163), MK(167), MK(171), MK(175), MK(179), MK(183), MK(187), MK(191),
+  MK(195), MK(199), MK(203), MK(207), MK(211), MK(215), MK(219), MK(223),
+  MK(227), MK(231), MK(235), MK(239), MK(243), MK(247), MK(251), MK(127),
+  MK(129), MK(131), MK(133), MK(135), MK(137), MK(139), MK(141), MK(143),
+  MK(145), MK(147), MK(149), MK(151), MK(153), MK(155), MK(157), MK(159),
+  MK(161), MK(163), MK(165), MK(167), MK(169), MK(171), MK(173), MK(175),
+  MK(177), MK(179), MK(181), MK(183), MK(185), MK(187), MK(189), MK(191),
+  MK(193), MK(195), MK(197), MK(199), MK(201), MK(203), MK(205), MK(207),
+  MK(209), MK(211), MK(213), MK(215), MK(217), MK(219), MK(221), MK(223),
+  MK(225), MK(227), MK(229), MK(231), MK(233), MK(235), MK(237), MK(239),
+  MK(241), MK(243), MK(245), MK(247), MK(249), MK(251), MK(253), MK(127)
 };
 
+#undef MK
+
+void VP8LoadFinalBytes(VP8BitReader* const br) {
+  assert(br != NULL && br->buf_ != NULL);
+  // Only read 8bits at a time
+  if (br->buf_ < br->buf_end_) {
+    br->value_ |= (bit_t)(*br->buf_++) << ((BITS) - 8 + br->missing_);
+    br->missing_ -= 8;
+  } else {
+    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 MAX_NUM_BIT_READ 25
+
+static const uint32_t kBitMask[MAX_NUM_BIT_READ] = {
+  0, 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767,
+  65535, 131071, 262143, 524287, 1048575, 2097151, 4194303, 8388607, 16777215
+};
+
+void VP8LInitBitReader(VP8LBitReader* const br,
+                       const uint8_t* const start,
+                       size_t length) {
+  size_t i;
+  assert(br != NULL);
+  assert(start != NULL);
+  assert(length < 0xfffffff8u);   // can't happen with a RIFF chunk.
+
+  br->buf_ = start;
+  br->len_ = length;
+  br->val_ = 0;
+  br->pos_ = 0;
+  br->bit_pos_ = 0;
+  br->eos_ = 0;
+  br->error_ = 0;
+  for (i = 0; i < sizeof(br->val_) && i < br->len_; ++i) {
+    br->val_ |= ((uint64_t)br->buf_[br->pos_]) << (8 * i);
+    ++br->pos_;
+  }
+}
+
+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->eos_ = (br->pos_ >= len);
+  br->buf_ = buf;
+  br->len_ = len;
+}
+
+static void ShiftBytes(VP8LBitReader* const br) {
+  while (br->bit_pos_ >= 8 && br->pos_ < br->len_) {
+    br->val_ >>= 8;
+    br->val_ |= ((uint64_t)br->buf_[br->pos_]) << 56;
+    ++br->pos_;
+    br->bit_pos_ -= 8;
+  }
+}
+
+void VP8LFillBitWindow(VP8LBitReader* const br) {
+  if (br->bit_pos_ >= 32) {
+#if defined(__x86_64__) || defined(_M_X64)
+    if (br->pos_ + 8 < br->len_) {
+      br->val_ >>= 32;
+      // The expression below needs a little-endian arch to work correctly.
+      // This gives a large speedup for decoding speed.
+      br->val_ |= *(const uint64_t *)(br->buf_ + br->pos_) << 32;
+      br->pos_ += 4;
+      br->bit_pos_ -= 32;
+    } else {
+      // Slow path.
+      ShiftBytes(br);
+    }
+#else
+    // Always the slow path.
+    ShiftBytes(br);
+#endif
+  }
+  if (br->pos_ == br->len_ && br->bit_pos_ == 64) {
+    br->eos_ = 1;
+  }
+}
+
+uint32_t VP8LReadOneBit(VP8LBitReader* const br) {
+  const uint32_t val = (br->val_ >> br->bit_pos_) & 1;
+  // Flag an error at end_of_stream.
+  if (!br->eos_) {
+    ++br->bit_pos_;
+    if (br->bit_pos_ >= 32) {
+      ShiftBytes(br);
+    }
+    // After this last bit is read, check if eos needs to be flagged.
+    if (br->pos_ == br->len_ && br->bit_pos_ == 64) {
+      br->eos_ = 1;
+    }
+  } else {
+    br->error_ = 1;
+  }
+  return val;
+}
+
+uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits) {
+  uint32_t val = 0;
+  assert(n_bits >= 0);
+  // Flag an error if end_of_stream or n_bits is more than allowed limit.
+  if (!br->eos_ && n_bits < MAX_NUM_BIT_READ) {
+    // If this read is going to cross the read buffer, set the eos flag.
+    if (br->pos_ == br->len_) {
+      if ((br->bit_pos_ + n_bits) >= 64) {
+        br->eos_ = 1;
+        if ((br->bit_pos_ + n_bits) > 64) return val;
+      }
+    }
+    val = (br->val_ >> br->bit_pos_) & kBitMask[n_bits];
+    br->bit_pos_ += n_bits;
+    if (br->bit_pos_ >= 40) {
+      if (br->pos_ + 5 < br->len_) {
+        br->val_ >>= 40;
+        br->val_ |=
+            (((uint64_t)br->buf_[br->pos_ + 0]) << 24) |
+            (((uint64_t)br->buf_[br->pos_ + 1]) << 32) |
+            (((uint64_t)br->buf_[br->pos_ + 2]) << 40) |
+            (((uint64_t)br->buf_[br->pos_ + 3]) << 48) |
+            (((uint64_t)br->buf_[br->pos_ + 4]) << 56);
+        br->pos_ += 5;
+        br->bit_pos_ -= 40;
+      }
+      if (br->bit_pos_ >= 8) {
+        ShiftBytes(br);
+      }
+    }
+  } else {
+    br->error_ = 1;
+  }
+  return val;
+}
+
+//------------------------------------------------------------------------------
 
 #if defined(__cplusplus) || defined(c_plusplus)
 }    // extern "C"
 #endif