12fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Copyright 2010 Google Inc. All Rights Reserved. 22fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// 32fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Use of this source code is governed by a BSD-style license 42fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// that can be found in the COPYING file in the root of the source 52fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// tree. An additional intellectual property rights grant can be found 62fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// in the file PATENTS. All contributing project authors may 72fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// be found in the AUTHORS file in the root of the source tree. 82fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// ----------------------------------------------------------------------------- 92fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// 102fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Boolean decoder 112fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// 122fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Author: Skal (pascal.massimino@gmail.com) 132fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Vikas Arora (vikaas.arora@gmail.com) 142fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 152fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#ifndef WEBP_UTILS_BIT_READER_UTILS_H_ 162fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define WEBP_UTILS_BIT_READER_UTILS_H_ 172fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 184a56686b5b56db6803f90ad53514bf2fa190d9f7John Porto#include <assert.h> 192fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#ifdef _MSC_VER 202fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#include <stdlib.h> // _byteswap_ulong 212fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#endif 2246f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capens#include "src/webp/types.h" 232fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 2446f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capens#ifdef __cplusplus 2546f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capensextern "C" { 2646f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capens#endif 2746f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capens 2846f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capens// The Boolean decoder needs to maintain infinite precision on the value_ field. 2946f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capens// However, since range_ is only 8bit, we only need an active window of 8 bits 3046f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capens// for value_. Left bits (MSB) gets zeroed and shifted away when value_ falls 3146f4feaafea68c18e4384ac4bad2e012eec52e5fNicolas Capens// below 128, range_ is updated, and fresh bits read from the bitstream are 322fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// brought in as LSB. To avoid reading the fresh bits one by one (slow), we 332fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// cache BITS of them ahead. The total of (BITS + 8) bits must fit into a 342fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// natural register (with type bit_t). To fetch BITS bits from bitstream we 352fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// use a type lbit_t. 362fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// 372fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// BITS can be any multiple of 8 from 8 to 56 (inclusive). 382fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Pick values that fit natural register size. 392fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 402fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#if defined(__i386__) || defined(_M_IX86) // x86 32bit 412fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define BITS 24 425bff61c44841990680781892036adb17b3cff0c4Jim Stichnoth#elif defined(__x86_64__) || defined(_M_X64) // x86 64bit 434a56686b5b56db6803f90ad53514bf2fa190d9f7John Porto#define BITS 56 442fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#elif defined(__arm__) || defined(_M_ARM) // ARM 452fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define BITS 24 462fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#elif defined(__aarch64__) // ARM 64bit 472fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define BITS 56 482fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#elif defined(__mips__) // MIPS 492fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define BITS 24 504a56686b5b56db6803f90ad53514bf2fa190d9f7John Porto#else // reasonable default 512fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define BITS 24 522fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#endif 532fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 542fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto//------------------------------------------------------------------------------ 552fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Derived types and constants: 562fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// bit_t = natural register type for storing 'value_' (which is BITS+8 bits) 572fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// range_t = register for 'range_' (which is 8bits only) 582fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 592fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#if (BITS > 24) 602fea26cae5a6b140c67e18aec3dcf645a16694d5John Portotypedef uint64_t bit_t; 612fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#else 622fea26cae5a6b140c67e18aec3dcf645a16694d5John Portotypedef uint32_t bit_t; 632fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#endif 642fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 652fea26cae5a6b140c67e18aec3dcf645a16694d5John Portotypedef uint32_t range_t; 662fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 672fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto//------------------------------------------------------------------------------ 682fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Bitreader 692fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 702fea26cae5a6b140c67e18aec3dcf645a16694d5John Portotypedef struct VP8BitReader VP8BitReader; 712fea26cae5a6b140c67e18aec3dcf645a16694d5John Portostruct VP8BitReader { 722fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto // boolean decoder (keep the field ordering as is!) 732fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto bit_t value_; // current value 742fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto range_t range_; // current range minus 1. In [127, 254] interval. 752fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto int bits_; // number of valid bits left 762fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto // read buffer 772fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto const uint8_t* buf_; // next byte to be read 782fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto const uint8_t* buf_end_; // end of read buffer 792fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto const uint8_t* buf_max_; // max packed-read position on buffer 802fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto int eof_; // true if input is exhausted 812fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto}; 822fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 832fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Initialize the bit reader and the boolean decoder. 842fea26cae5a6b140c67e18aec3dcf645a16694d5John Portovoid VP8InitBitReader(VP8BitReader* const br, 852fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto const uint8_t* const start, size_t size); 862fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Sets the working read buffer. 872fea26cae5a6b140c67e18aec3dcf645a16694d5John Portovoid VP8BitReaderSetBuffer(VP8BitReader* const br, 882fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto const uint8_t* const start, size_t size); 892fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 902fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Update internal pointers to displace the byte buffer by the 912fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// relative offset 'offset'. 922fea26cae5a6b140c67e18aec3dcf645a16694d5John Portovoid VP8RemapBitReader(VP8BitReader* const br, ptrdiff_t offset); 932fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 942fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// return the next value made of 'num_bits' bits 952fea26cae5a6b140c67e18aec3dcf645a16694d5John Portouint32_t VP8GetValue(VP8BitReader* const br, int num_bits); 962fea26cae5a6b140c67e18aec3dcf645a16694d5John Portostatic WEBP_INLINE uint32_t VP8Get(VP8BitReader* const br) { 972fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto return VP8GetValue(br, 1); 982fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto} 992fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1002fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// return the next value with sign-extension. 1012fea26cae5a6b140c67e18aec3dcf645a16694d5John Portoint32_t VP8GetSignedValue(VP8BitReader* const br, int num_bits); 1022fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1032fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// bit_reader_inl.h will implement the following methods: 1042fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) 1052fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// static WEBP_INLINE int VP8GetSigned(VP8BitReader* const br, int v) 1062fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// and should be included by the .c files that actually need them. 1072fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// This is to avoid recompiling the whole library whenever this file is touched, 1082fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// and also allowing platform-specific ad-hoc hacks. 1092fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1102fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// ----------------------------------------------------------------------------- 1112fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Bitreader for lossless format 1122fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1132fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// maximum number of bits (inclusive) the bit-reader can handle: 1142fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define VP8L_MAX_NUM_BIT_READ 24 1152fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1162fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define VP8L_LBITS 64 // Number of bits prefetched (= bit-size of vp8l_val_t). 1172fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#define VP8L_WBITS 32 // Minimum number of bytes ready after VP8LFillBitWindow. 1182fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1192fea26cae5a6b140c67e18aec3dcf645a16694d5John Portotypedef uint64_t vp8l_val_t; // right now, this bit-reader can only use 64bit. 1202fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1212fea26cae5a6b140c67e18aec3dcf645a16694d5John Portotypedef struct { 1222fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto vp8l_val_t val_; // pre-fetched bits 1232fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto const uint8_t* buf_; // input byte buffer 1242fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto size_t len_; // buffer length 1252fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto size_t pos_; // byte position in buf_ 1262fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto int bit_pos_; // current bit-reading position in val_ 1272fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto int eos_; // true if a bit was read past the end of buffer 1282fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto} VP8LBitReader; 1292fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1302fea26cae5a6b140c67e18aec3dcf645a16694d5John Portovoid VP8LInitBitReader(VP8LBitReader* const br, 1312fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto const uint8_t* const start, 1322fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto size_t length); 1332fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1342fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Sets a new data buffer. 1352fea26cae5a6b140c67e18aec3dcf645a16694d5John Portovoid VP8LBitReaderSetBuffer(VP8LBitReader* const br, 1362fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto const uint8_t* const buffer, size_t length); 1372fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1382fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Reads the specified number of bits from read buffer. 1392fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Flags an error in case end_of_stream or n_bits is more than the allowed limit 1402fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// of VP8L_MAX_NUM_BIT_READ (inclusive). 1412fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Flags eos_ if this read attempt is going to cross the read buffer. 1422fea26cae5a6b140c67e18aec3dcf645a16694d5John Portouint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits); 1432fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1442fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Return the prefetched bits, so they can be looked up. 1452fea26cae5a6b140c67e18aec3dcf645a16694d5John Portostatic WEBP_INLINE uint32_t VP8LPrefetchBits(VP8LBitReader* const br) { 1462fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto return (uint32_t)(br->val_ >> (br->bit_pos_ & (VP8L_LBITS - 1))); 1472fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto} 1482fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1492fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Returns true if there was an attempt at reading bit past the end of 1502fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// the buffer. Doesn't set br->eos_ flag. 1512fea26cae5a6b140c67e18aec3dcf645a16694d5John Portostatic WEBP_INLINE int VP8LIsEndOfStream(const VP8LBitReader* const br) { 1522fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto assert(br->pos_ <= br->len_); 1532fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto return br->eos_ || ((br->pos_ == br->len_) && (br->bit_pos_ > VP8L_LBITS)); 1542fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto} 1552fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1562fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// For jumping over a number of bits in the bit stream when accessed with 1572fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// VP8LPrefetchBits and VP8LFillBitWindow. 1582fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// This function does *not* set br->eos_, since it's speed-critical. 1592fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Use with extreme care! 1602fea26cae5a6b140c67e18aec3dcf645a16694d5John Portostatic WEBP_INLINE void VP8LSetBitPos(VP8LBitReader* const br, int val) { 1612fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto br->bit_pos_ = val; 1622fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto} 1632fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1642fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Advances the read buffer by 4 bytes to make room for reading next 32 bits. 1652fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto// Speed critical, but infrequent part of the code can be non-inlined. 1662fea26cae5a6b140c67e18aec3dcf645a16694d5John Portoextern void VP8LDoFillBitWindow(VP8LBitReader* const br); 1672fea26cae5a6b140c67e18aec3dcf645a16694d5John Portostatic WEBP_INLINE void VP8LFillBitWindow(VP8LBitReader* const br) { 1682fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto if (br->bit_pos_ >= VP8L_WBITS) VP8LDoFillBitWindow(br); 1692fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto} 1702fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1712fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#ifdef __cplusplus 1722fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto} // extern "C" 1732fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#endif 1742fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto 1752fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto#endif /* WEBP_UTILS_BIT_READER_UTILS_H_ */ 1762fea26cae5a6b140c67e18aec3dcf645a16694d5John Porto