Sync with the latest libwebp version (0.2.0-rc1)

Change-Id: I15398a74aaec35cf235247d8e21ad9d9910772b8

1 files changed, 197 insertions, 0 deletions

diff --git a/src/utils/bit_reader.h b/src/utils/bit_reader.h
new file mode 100644
index 00000000..11a40a55
--- /dev/null
+++ b/src/utils/bit_reader.h
@@ -0,0 +1,197 @@
+// 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)
+//         Vikas Arora (vikaas.arora@gmail.com)
+
+#ifndef WEBP_UTILS_BIT_READER_H_
+#define WEBP_UTILS_BIT_READER_H_
+
+#include <assert.h>
+#ifdef _MSC_VER
+#include <stdlib.h>  // _byteswap_ulong
+#endif
+#include <string.h>  // For memcpy
+#include "webp/types.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+#define BITS 32     // can be 32, 16 or 8
+#define MASK ((((bit_t)1) << (BITS)) - 1)
+#if (BITS == 32)
+typedef uint64_t bit_t;   // natural register type
+typedef uint32_t lbit_t;  // natural type for memory I/O
+#elif (BITS == 16)
+typedef uint32_t bit_t;
+typedef uint16_t lbit_t;
+#else
+typedef uint32_t bit_t;
+typedef uint8_t lbit_t;
+#endif
+
+//------------------------------------------------------------------------------
+// Bitreader and code-tree reader
+
+typedef struct VP8BitReader VP8BitReader;
+struct VP8BitReader {
+  const uint8_t* buf_;        // next byte to be read
+  const uint8_t* buf_end_;    // end of read buffer
+  int eof_;                   // true if input is exhausted
+
+  // boolean decoder
+  bit_t range_;            // current range minus 1. In [127, 254] interval.
+  bit_t value_;            // current value
+  int missing_;            // number of missing bits in value_ (8bit)
+};
+
+// Initialize the bit reader and the boolean decoder.
+void VP8InitBitReader(VP8BitReader* const br,
+                      const uint8_t* const start, const uint8_t* const end);
+
+// return the next value made of 'num_bits' bits
+uint32_t VP8GetValue(VP8BitReader* const br, int num_bits);
+static WEBP_INLINE uint32_t VP8Get(VP8BitReader* const br) {
+  return VP8GetValue(br, 1);
+}
+
+// return the next value with sign-extension.
+int32_t VP8GetSignedValue(VP8BitReader* const br, int num_bits);
+
+// Read a bit with proba 'prob'. Speed-critical function!
+extern const uint8_t kVP8Log2Range[128];
+extern const bit_t kVP8NewRange[128];
+
+void VP8LoadFinalBytes(VP8BitReader* const br);    // special case for the tail
+
+static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
+  assert(br && br->buf_);
+  // Read 'BITS' bits at a time if possible.
+  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_;
+    br->buf_ += (BITS) >> 3;
+#if !defined(__BIG_ENDIAN__)
+#if (BITS == 32)
+#if defined(__i386__) || defined(__x86_64__)
+    __asm__ volatile("bswap %k0" : "=r"(in_bits) : "0"(in_bits));
+    bits = (bit_t)in_bits;   // 32b -> 64b zero-extension
+#elif defined(_MSC_VER)
+    bits = _byteswap_ulong(in_bits);
+#else
+    bits = (bit_t)(in_bits >> 24) | ((in_bits >> 8) & 0xff00)
+         | ((in_bits << 8) & 0xff0000)  | (in_bits << 24);
+#endif  // x86
+#elif (BITS == 16)
+    // gcc will recognize a 'rorw $8, ...' here:
+    bits = (bit_t)(in_bits >> 8) | ((in_bits & 0xff) << 8);
+#endif
+#else    // LITTLE_ENDIAN
+    bits = (bit_t)in_bits;
+#endif
+    br->value_ |= bits << br->missing_;
+    br->missing_ -= (BITS);
+  } else {
+    VP8LoadFinalBytes(br);    // no need to be inlined
+  }
+}
+
+static WEBP_INLINE int VP8BitUpdate(VP8BitReader* const br, bit_t split) {
+  const bit_t value_split = split | (MASK);
+  if (br->missing_ > 0) {  // Make sure we have a least BITS bits in 'value_'
+    VP8LoadNewBytes(br);
+  }
+  if (br->value_ > value_split) {
+    br->range_ -= value_split + 1;
+    br->value_ -= value_split + 1;
+    return 1;
+  } else {
+    br->range_ = value_split;
+    return 0;
+  }
+}
+
+static WEBP_INLINE void VP8Shift(VP8BitReader* const br) {
+  // range_ is in [0..127] interval here.
+  const int idx = br->range_ >> (BITS);
+  const int shift = kVP8Log2Range[idx];
+  br->range_ = kVP8NewRange[idx];
+  br->value_ <<= shift;
+  br->missing_ += shift;
+}
+
+static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) {
+  // It's important to avoid generating a 64bit x 64bit multiply here.
+  // We just need an 8b x 8b after all.
+  const bit_t split =
+      (bit_t)((uint32_t)(br->range_ >> (BITS)) * prob) << ((BITS) - 8);
+  const int bit = VP8BitUpdate(br, split);
+  if (br->range_ <= (((bit_t)0x7e << (BITS)) | (MASK))) {
+    VP8Shift(br);
+  }
+  return bit;
+}
+
+static WEBP_INLINE int VP8GetSigned(VP8BitReader* const br, int v) {
+  const bit_t split = (br->range_ >> 1);
+  const int bit = VP8BitUpdate(br, split);
+  VP8Shift(br);
+  return bit ? -v : v;
+}
+
+
+// -----------------------------------------------------------------------------
+// Bitreader
+
+typedef struct {
+  uint64_t       val_;
+  const uint8_t* buf_;
+  size_t         len_;
+  size_t         pos_;
+  int            bit_pos_;
+  int            eos_;
+  int            error_;
+} VP8LBitReader;
+
+void VP8LInitBitReader(VP8LBitReader* const br,
+                       const uint8_t* const start,
+                       size_t length);
+
+//  Sets a new data buffer.
+void VP8LBitReaderSetBuffer(VP8LBitReader* const br,
+                            const uint8_t* const buffer, size_t length);
+
+// Reads the specified number of bits from Read Buffer.
+// Flags an error in case end_of_stream or n_bits is more than allowed limit.
+// Flags eos if this read attempt is going to cross the read buffer.
+uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits);
+
+// Reads one bit from Read Buffer. Flags an error in case end_of_stream.
+// Flags eos after reading last bit from the buffer.
+uint32_t VP8LReadOneBit(VP8LBitReader* const br);
+
+// VP8LReadOneBitUnsafe is faster than VP8LReadOneBit, but it can be called only
+// 32 times after the last VP8LFillBitWindow. Any subsequent calls
+// (without VP8LFillBitWindow) will return invalid data.
+static WEBP_INLINE uint32_t VP8LReadOneBitUnsafe(VP8LBitReader* const br) {
+  const uint32_t val = (br->val_ >> br->bit_pos_) & 1;
+  ++br->bit_pos_;
+  return val;
+}
+
+// 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)
+}    // extern "C"
+#endif
+
+#endif  /* WEBP_UTILS_BIT_READER_H_ */