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make VP8LSetBitPos() set br->eos_ flag

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ReadSymbol() finishes with a VP8LSetBitPos() call only and could miss an eos_ during the decode loop.

Things are faster because of inlining too.

Change-Id: I2d2a275f38834ba005bc767d45c5de72d032103e
This commit is contained in:
Pascal Massimino 2014-09-06 08:40:20 +02:00
parent a9decb5584
commit d3242aee16
3 changed files with 40 additions and 36 deletions
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2
src/dec/vp8l.c
View File

@ -891,6 +891,7 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
ok = 0;
goto End;
}
assert(br->eos_ == VP8LIsEndOfStream(br));
ok = !br->error_;
if (!ok) goto End;
}
@ -1008,6 +1009,7 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
ok = 0;
goto End;
}
assert(br->eos_ == VP8LIsEndOfStream(br));
ok = !br->error_;
if (!ok) goto End;
}

57
src/utils/bit_reader.c
View File

@ -105,9 +105,7 @@ int32_t VP8GetSignedValue(VP8BitReader* const br, int bits) {
//------------------------------------------------------------------------------
// 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.
#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__) || \
@ -151,16 +149,6 @@ void VP8LInitBitReader(VP8LBitReader* const br, const uint8_t* const start,
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);
@ -168,38 +156,39 @@ void VP8LBitReaderSetBuffer(VP8LBitReader* const br,
assert(len < 0xfffffff8u); // can't happen with a RIFF chunk.
br->buf_ = buf;
br->len_ = len;
br->eos_ = IsEndOfStream(br);
// 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 LBITS byte-by-byte
// 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_]) << (LBITS - 8);
br->val_ |= ((vp8l_val_t)br->buf_[br->pos_]) << (VP8L_LBITS - 8);
++br->pos_;
br->bit_pos_ -= 8;
}
br->eos_ = VP8LIsEndOfStream(br);
}
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.
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_ >>= 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);
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) {
@ -210,8 +199,6 @@ uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits) {
(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 {

17
src/utils/bit_reader.h
View File

@ -107,6 +107,9 @@ int32_t VP8GetSignedValue(VP8BitReader* const br, int num_bits);
// 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 {
@ -138,14 +141,26 @@ 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"