// 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 LBITS 64 // Number of bits prefetched.
#define WBITS 32 // Minimum number of bytes needed after VP8LFillBitWindow.
#define LOG8_WBITS 4 // Number of bytes needed to store 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;
}
// Special version that assumes br->pos_ <= br_len_.
static int IsEndOfStreamSpecial(const VP8LBitReader* const br) {
assert(br->pos_ <= br->len_);
return br->pos_ == br->len_ && br->bit_pos_ >= LBITS;
}
static int IsEndOfStream(const VP8LBitReader* const br) {
return (br->pos_ > br->len_) || IsEndOfStreamSpecial(br);
}
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;
br->eos_ = IsEndOfStream(br);
}
// If not at EOS, reload up to 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_]) << (LBITS - 8);
++br->pos_;
br->bit_pos_ -= 8;
}
}
void VP8LFillBitWindow(VP8LBitReader* const br) {
if (br->bit_pos_ >= 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_ >>= WBITS;
br->bit_pos_ -= 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_) <<
(LBITS - WBITS);
br->pos_ += LOG8_WBITS;
return;
}
#endif
ShiftBytes(br); // Slow path.
br->eos_ = IsEndOfStreamSpecial(br);
}
}
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;
// If this read is going to cross the read buffer, set the eos flag.
br->eos_ = IsEndOfStreamSpecial(br);
ShiftBytes(br);
return val;
} else {
br->error_ = 1;
return 0;
}
}
//------------------------------------------------------------------------------