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Diffstat (limited to 'drivers/webp/utils/bit_reader.h')
-rw-r--r--drivers/webp/utils/bit_reader.h255
1 files changed, 59 insertions, 196 deletions
diff --git a/drivers/webp/utils/bit_reader.h b/drivers/webp/utils/bit_reader.h
index 98df98a767..36fc13e2da 100644
--- a/drivers/webp/utils/bit_reader.h
+++ b/drivers/webp/utils/bit_reader.h
@@ -1,10 +1,8 @@
// 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.
+// 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
@@ -19,86 +17,18 @@
#ifdef _MSC_VER
#include <stdlib.h> // _byteswap_ulong
#endif
+#include <string.h> // For memcpy
#include "../webp/types.h"
-#ifdef __cplusplus
+#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
-// The Boolean decoder needs to maintain infinite precision on the value_ field.
-// However, since range_ is only 8bit, we only need an active window of 8 bits
-// for value_. Left bits (MSB) gets zeroed and shifted away when value_ falls
-// below 128, range_ is updated, and fresh bits read from the bitstream are
-// brought in as LSB.
-// To avoid reading the fresh bits one by one (slow), we cache a few of them
-// ahead (actually, we cache BITS of them ahead. See below). There's two
-// strategies regarding how to shift these looked-ahead fresh bits into the
-// 8bit window of value_: either we shift them in, while keeping the position of
-// the window fixed. Or we slide the window to the right while keeping the cache
-// bits at a fixed, right-justified, position.
-//
-// Example, for BITS=16: here is the content of value_ for both strategies:
-//
-// !USE_RIGHT_JUSTIFY || USE_RIGHT_JUSTIFY
-// ||
-// <- 8b -><- 8b -><- BITS bits -> || <- 8b+3b -><- 8b -><- 13 bits ->
-// [unused][value_][cached bits][0] || [unused...][value_][cached bits]
-// [........00vvvvvvBBBBBBBBBBBBB000]LSB || [...........00vvvvvvBBBBBBBBBBBBB]
-// ||
-// After calling VP8Shift(), where we need to shift away two zeros:
-// [........vvvvvvvvBBBBBBBBBBB00000]LSB || [.............vvvvvvvvBBBBBBBBBBB]
-// ||
-// Just before we need to call VP8LoadNewBytes(), the situation is:
-// [........vvvvvv000000000000000000]LSB || [..........................vvvvvv]
-// ||
-// And just after calling VP8LoadNewBytes():
-// [........vvvvvvvvBBBBBBBBBBBBBBBB]LSB || [........vvvvvvvvBBBBBBBBBBBBBBBB]
-//
-// -> we're back to eight active 'value_' bits (marked 'v') and BITS cached
-// bits (marked 'B')
-//
-// The right-justify strategy tends to use less shifts and is often faster.
-
-//------------------------------------------------------------------------------
-// BITS can be any multiple of 8 from 8 to 56 (inclusive).
-// Pick values that fit natural register size.
-
-#if !defined(WEBP_REFERENCE_IMPLEMENTATION)
-
-#define USE_RIGHT_JUSTIFY
-
-#if defined(__i386__) || defined(_M_IX86) // x86 32bit
-#define BITS 16
-#elif defined(__x86_64__) || defined(_M_X64) // x86 64bit
-#define BITS 56
-#elif defined(__arm__) || defined(_M_ARM) // ARM
-#define BITS 24
-#else // reasonable default
-#define BITS 24
-#endif
-
-#else // reference choices
-
-#define USE_RIGHT_JUSTIFY
-#define BITS 8
-
-#endif
-
-//------------------------------------------------------------------------------
-// Derived types and constants
-
-// bit_t = natural register type
-// lbit_t = natural type for memory I/O
-
-#if (BITS > 32)
-typedef uint64_t bit_t;
-typedef uint64_t lbit_t;
-#elif (BITS == 32)
-typedef uint64_t bit_t;
-typedef uint32_t lbit_t;
-#elif (BITS == 24)
-typedef uint32_t bit_t;
-typedef uint32_t lbit_t;
+#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;
@@ -107,15 +37,8 @@ typedef uint32_t bit_t;
typedef uint8_t lbit_t;
#endif
-#ifndef USE_RIGHT_JUSTIFY
-typedef bit_t range_t; // type for storing range_
-#define MASK ((((bit_t)1) << (BITS)) - 1)
-#else
-typedef uint32_t range_t; // range_ only uses 8bits here. No need for bit_t.
-#endif
-
//------------------------------------------------------------------------------
-// Bitreader
+// Bitreader and code-tree reader
typedef struct VP8BitReader VP8BitReader;
struct VP8BitReader {
@@ -124,9 +47,9 @@ struct VP8BitReader {
int eof_; // true if input is exhausted
// boolean decoder
- range_t range_; // current range minus 1. In [127, 254] interval.
- bit_t value_; // current value
- int bits_; // number of valid bits left
+ 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.
@@ -144,160 +67,98 @@ 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 range_t kVP8NewRange[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 != NULL && br->buf_ != NULL);
+ 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;
- const lbit_t in_bits = *(const lbit_t*)br->buf_;
+ lbit_t in_bits = *(lbit_t*)br->buf_;
br->buf_ += (BITS) >> 3;
#if !defined(__BIG_ENDIAN__)
-#if (BITS > 32)
-// gcc 4.3 has builtin functions for swap32/swap64
-#if defined(__GNUC__) && \
- (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
- bits = (bit_t)__builtin_bswap64(in_bits);
-#elif defined(_MSC_VER)
- bits = (bit_t)_byteswap_uint64(in_bits);
-#elif defined(__x86_64__)
- __asm__ volatile("bswapq %0" : "=r"(bits) : "0"(in_bits));
-#else // generic code for swapping 64-bit values (suggested by bdb@)
- bits = (bit_t)in_bits;
- bits = ((bits & 0xffffffff00000000ull) >> 32) |
- ((bits & 0x00000000ffffffffull) << 32);
- bits = ((bits & 0xffff0000ffff0000ull) >> 16) |
- ((bits & 0x0000ffff0000ffffull) << 16);
- bits = ((bits & 0xff00ff00ff00ff00ull) >> 8) |
- ((bits & 0x00ff00ff00ff00ffull) << 8);
-#endif
- bits >>= 64 - BITS;
-#elif (BITS >= 24)
+#if (BITS == 32)
#if defined(__i386__) || defined(__x86_64__)
- {
- lbit_t swapped_in_bits;
- __asm__ volatile("bswap %k0" : "=r"(swapped_in_bits) : "0"(in_bits));
- bits = (bit_t)swapped_in_bits; // 24b/32b -> 32b/64b zero-extension
- }
+ __asm__ volatile("bswap %k0" : "=r"(in_bits) : "0"(in_bits));
+ bits = (bit_t)in_bits; // 32b -> 64b zero-extension
#elif defined(_MSC_VER)
- bits = (bit_t)_byteswap_ulong(in_bits);
+ 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
- bits >>= (32 - BITS);
#elif (BITS == 16)
// gcc will recognize a 'rorw $8, ...' here:
bits = (bit_t)(in_bits >> 8) | ((in_bits & 0xff) << 8);
-#else // BITS == 8
- bits = (bit_t)in_bits;
#endif
-#else // BIG_ENDIAN
+#else // LITTLE_ENDIAN
bits = (bit_t)in_bits;
- if (BITS != 8 * sizeof(bit_t)) bits >>= (8 * sizeof(bit_t) - BITS);
-#endif
-#ifndef USE_RIGHT_JUSTIFY
- br->value_ |= bits << (-br->bits_);
-#else
- br->value_ = bits | (br->value_ << (BITS));
#endif
- br->bits_ += (BITS);
+ br->value_ |= bits << br->missing_;
+ br->missing_ -= (BITS);
} else {
VP8LoadFinalBytes(br); // no need to be inlined
}
}
-static WEBP_INLINE int VP8BitUpdate(VP8BitReader* const br, range_t split) {
- if (br->bits_ < 0) { // Make sure we have a least BITS bits in 'value_'
+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);
}
-#ifndef USE_RIGHT_JUSTIFY
- split |= (MASK);
- if (br->value_ > split) {
- br->range_ -= split + 1;
- br->value_ -= split + 1;
+ if (br->value_ > value_split) {
+ br->range_ -= value_split + 1;
+ br->value_ -= value_split + 1;
return 1;
} else {
- br->range_ = split;
+ br->range_ = value_split;
return 0;
}
-#else
- {
- const int pos = br->bits_;
- const range_t value = (range_t)(br->value_ >> pos);
- if (value > split) {
- br->range_ -= split + 1;
- br->value_ -= (bit_t)(split + 1) << pos;
- return 1;
- } else {
- br->range_ = split;
- return 0;
- }
- }
-#endif
}
static WEBP_INLINE void VP8Shift(VP8BitReader* const br) {
-#ifndef USE_RIGHT_JUSTIFY
// range_ is in [0..127] interval here.
- const bit_t idx = br->range_ >> (BITS);
+ const int idx = br->range_ >> (BITS);
const int shift = kVP8Log2Range[idx];
br->range_ = kVP8NewRange[idx];
br->value_ <<= shift;
- br->bits_ -= shift;
-#else
- const int shift = kVP8Log2Range[br->range_];
- assert(br->range_ < (range_t)128);
- br->range_ = kVP8NewRange[br->range_];
- br->bits_ -= shift;
-#endif
+ br->missing_ += shift;
}
static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) {
-#ifndef USE_RIGHT_JUSTIFY
// It's important to avoid generating a 64bit x 64bit multiply here.
// We just need an 8b x 8b after all.
- const range_t split =
- (range_t)((uint32_t)(br->range_ >> (BITS)) * prob) << ((BITS) - 8);
+ const bit_t split =
+ (bit_t)((uint32_t)(br->range_ >> (BITS)) * prob) << ((BITS) - 8);
const int bit = VP8BitUpdate(br, split);
- if (br->range_ <= (((range_t)0x7e << (BITS)) | (MASK))) {
+ if (br->range_ <= (((bit_t)0x7e << (BITS)) | (MASK))) {
VP8Shift(br);
}
return bit;
-#else
- const range_t split = (br->range_ * prob) >> 8;
- const int bit = VP8BitUpdate(br, split);
- if (br->range_ <= (range_t)0x7e) {
- VP8Shift(br);
- }
- return bit;
-#endif
}
static WEBP_INLINE int VP8GetSigned(VP8BitReader* const br, int v) {
- const range_t split = (br->range_ >> 1);
+ const bit_t split = (br->range_ >> 1);
const int bit = VP8BitUpdate(br, split);
VP8Shift(br);
return bit ? -v : v;
}
-// -----------------------------------------------------------------------------
-// Bitreader for lossless format
-typedef uint64_t vp8l_val_t; // right now, this bit-reader can only use 64bit.
+// -----------------------------------------------------------------------------
+// Bitreader
typedef struct {
- vp8l_val_t val_; // pre-fetched bits
- const uint8_t* buf_; // input byte buffer
- size_t len_; // buffer length
- size_t pos_; // byte position in buf_
- int bit_pos_; // current bit-reading position in val_
- int eos_; // bitstream is finished
- int error_; // an error occurred (buffer overflow attempt...)
+ 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,
@@ -313,21 +174,23 @@ void VP8LBitReaderSetBuffer(VP8LBitReader* const br,
// Flags eos if this read attempt is going to cross the read buffer.
uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits);
-// Return the prefetched bits, so they can be looked up.
-static WEBP_INLINE uint32_t VP8LPrefetchBits(VP8LBitReader* const br) {
- return (uint32_t)(br->val_ >> br->bit_pos_);
-}
-
-// 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;
+// 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.
+// Advances the Read buffer by 4 bytes to make room for reading next 32 bits.
void VP8LFillBitWindow(VP8LBitReader* const br);
-#ifdef __cplusplus
+#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-27 17:08:07 +0000