nengel@2: /*
nengel@2:  * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
nengel@2:  *
nengel@2:  * This file is part of FFmpeg.
nengel@2:  *
nengel@2:  * FFmpeg is free software; you can redistribute it and/or
nengel@2:  * modify it under the terms of the GNU Lesser General Public
nengel@2:  * License as published by the Free Software Foundation; either
nengel@2:  * version 2.1 of the License, or (at your option) any later version.
nengel@2:  *
nengel@2:  * FFmpeg is distributed in the hope that it will be useful,
nengel@2:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
nengel@2:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
nengel@2:  * Lesser General Public License for more details.
nengel@2:  *
nengel@2:  * You should have received a copy of the GNU Lesser General Public
nengel@2:  * License along with FFmpeg; if not, write to the Free Software
nengel@2:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
nengel@2:  */
nengel@2: 
nengel@2: /**
nengel@2:  * @file
nengel@2:  * bitstream reader API header.
nengel@2:  */
nengel@2: 
nengel@2: #ifndef AVCODEC_GET_BITS_H
nengel@2: #define AVCODEC_GET_BITS_H
nengel@2: 
nengel@2: #include <stdint.h>
nengel@2: #include <stdlib.h>
nengel@2: #include <assert.h>
nengel@2: #include "libavutil/bswap.h"
nengel@2: #include "libavutil/common.h"
nengel@2: #include "libavutil/intreadwrite.h"
nengel@2: #include "libavutil/log.h"
nengel@2: #include "mathops.h"
nengel@2: 
nengel@2: 
nengel@2: typedef struct GetBitContext {
nengel@2:     uint8_t *rbsp;
nengel@2:     unsigned int rbsp_size;
nengel@2:     uint8_t *raw;
nengel@2:     const uint8_t *buffer, *buffer_end;
nengel@2:     unsigned int alloc_size;
nengel@2:     unsigned int buf_size;
nengel@2:     uint32_t *buffer_ptr;
nengel@2:     uint32_t cache0;
nengel@2:     uint32_t cache1;
nengel@2:     int bit_count;
nengel@2:     int size_in_bits;
nengel@2: } GetBitContext;
nengel@2: 
nengel@2: /* Bitstream reader API docs:
nengel@2: name
nengel@2:     arbitrary name which is used as prefix for the internal variables
nengel@2: 
nengel@2: gb
nengel@2:     getbitcontext
nengel@2: 
nengel@2: OPEN_READER(name, gb)
nengel@2:     loads gb into local variables
nengel@2: 
nengel@2: CLOSE_READER(name, gb)
nengel@2:     stores local vars in gb
nengel@2: 
nengel@2: UPDATE_CACHE(name, gb)
nengel@2:     refills the internal cache from the bitstream
nengel@2:     after this call at least MIN_CACHE_BITS will be available,
nengel@2: 
nengel@2: GET_CACHE(name, gb)
nengel@2:     will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)
nengel@2: 
nengel@2: SHOW_UBITS(name, gb, num)
nengel@2:     will return the next num bits
nengel@2: 
nengel@2: SHOW_SBITS(name, gb, num)
nengel@2:     will return the next num bits and do sign extension
nengel@2: 
nengel@2: SKIP_BITS(name, gb, num)
nengel@2:     will skip over the next num bits
nengel@2:     note, this is equivalent to SKIP_CACHE; SKIP_COUNTER
nengel@2: 
nengel@2: SKIP_CACHE(name, gb, num)
nengel@2:     will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)
nengel@2: 
nengel@2: SKIP_COUNTER(name, gb, num)
nengel@2:     will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
nengel@2: 
nengel@2: LAST_SKIP_CACHE(name, gb, num)
nengel@2:     will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing
nengel@2: 
nengel@2: LAST_SKIP_BITS(name, gb, num)
nengel@2:     is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER
nengel@2: 
nengel@2: for examples see get_bits, show_bits, skip_bits, get_vlc
nengel@2: */
nengel@2: 
nengel@2: #define MIN_CACHE_BITS 32
nengel@2: 
nengel@2: #define OPEN_READER(name, gb)\
nengel@2: 	int name##_bit_count=(gb)->bit_count;\
nengel@2: 	uint32_t name##_cache0= (gb)->cache0;\
nengel@2: 	uint32_t name##_cache1= (gb)->cache1;\
nengel@2: 	uint32_t * name##_buffer_ptr=(gb)->buffer_ptr;\
nengel@2: 
nengel@2: #define CLOSE_READER(name, gb)\
nengel@2: 	(gb)->bit_count= name##_bit_count;\
nengel@2: 	(gb)->cache0= name##_cache0;\
nengel@2: 	(gb)->cache1= name##_cache1;\
nengel@2: 	(gb)->buffer_ptr= name##_buffer_ptr;\
nengel@2: 
nengel@2: #define UPDATE_CACHE(name, gb)\
nengel@2: 	if(name##_bit_count > 0){\
nengel@2: 		const uint32_t next= be2me_32( *name##_buffer_ptr );\
nengel@2: 		name##_cache0 |= NEG_USR32(next,name##_bit_count);\
nengel@2: 		name##_cache1 |= next<<name##_bit_count;\
nengel@2: 		name##_buffer_ptr++;\
nengel@2: 		name##_bit_count-= 32;\
nengel@2: 	}\
nengel@2: 
nengel@2: #if ARCH_X86
nengel@2: #   define SKIP_CACHE(name, gb, num)\
nengel@2:         __asm__(\
nengel@2:             "shldl %2, %1, %0          \n\t"\
nengel@2:             "shll %2, %1               \n\t"\
nengel@2:             : "+r" (name##_cache0), "+r" (name##_cache1)\
nengel@2:             : "Ic" ((uint8_t)(num))\
nengel@2:            );
nengel@2: #else
nengel@2: #   define SKIP_CACHE(name, gb, num)\
nengel@2:         name##_cache0 <<= (num);\
nengel@2:         name##_cache0 |= NEG_USR32(name##_cache1,num);\
nengel@2:         name##_cache1 <<= (num);
nengel@2: #endif
nengel@2: 
nengel@2: #define SKIP_COUNTER(name, gb, num)\
nengel@2: 	name##_bit_count += (num);\
nengel@2: 
nengel@2: #define SKIP_BITS(name, gb, num)\
nengel@2: 	{\
nengel@2: 		SKIP_CACHE(name, gb, num)\
nengel@2: 		SKIP_COUNTER(name, gb, num)\
nengel@2: 	}\
nengel@2: 
nengel@2: #define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
nengel@2: #define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
nengel@2: 
nengel@2: #define SHOW_UBITS(name, gb, num)\
nengel@2: 	NEG_USR32(name##_cache0, num)
nengel@2: 
nengel@2: #define SHOW_SBITS(name, gb, num)\
nengel@2:         NEG_SSR32(name##_cache0, num)
nengel@2: 
nengel@2: #define GET_CACHE(name, gb)\
nengel@2: 	(name##_cache0)
nengel@2: 
nengel@2: static inline int get_bits_count(const GetBitContext *s){
nengel@2:     return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
nengel@2: }
nengel@2: 
nengel@2: static inline void skip_bits_long(GetBitContext *s, int n){
nengel@2:     OPEN_READER(re, s)
nengel@2:     re_bit_count += n;
nengel@2:     re_buffer_ptr += re_bit_count>>5;
nengel@2:     re_bit_count &= 31;
nengel@2:     re_cache0 = be2me_32( re_buffer_ptr[-1] ) << re_bit_count;
nengel@2:     re_cache1 = 0;
nengel@2:     UPDATE_CACHE(re, s)
nengel@2:     CLOSE_READER(re, s)
nengel@2: }
nengel@2: 
nengel@2: /**
nengel@2:  * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
nengel@2:  * if MSB not set it is negative
nengel@2:  * @param n length in bits
nengel@2:  * @author BERO
nengel@2:  */
nengel@2: static inline int get_xbits(GetBitContext *s, int n){
nengel@2:     register int sign;
nengel@2:     register int32_t cache;
nengel@2:     OPEN_READER(re, s)
nengel@2:     UPDATE_CACHE(re, s)
nengel@2:     cache = GET_CACHE(re,s);
nengel@2:     sign=(~cache)>>31;
nengel@2:     LAST_SKIP_BITS(re, s, n)
nengel@2:     CLOSE_READER(re, s)
nengel@2:     return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
nengel@2: }
nengel@2: 
nengel@2: static inline int get_sbits(GetBitContext *s, int n){
nengel@2:     register int tmp;
nengel@2:     OPEN_READER(re, s)
nengel@2:     UPDATE_CACHE(re, s)
nengel@2:     tmp= SHOW_SBITS(re, s, n);
nengel@2:     LAST_SKIP_BITS(re, s, n)
nengel@2:     CLOSE_READER(re, s)
nengel@2:     return tmp;
nengel@2: }
nengel@2: 
nengel@2: /**
nengel@2:  * reads 1-17 bits.
nengel@2:  * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
nengel@2:  */
nengel@2: static inline unsigned int get_bits(GetBitContext *s, int n){
nengel@2:     register int tmp;
nengel@2:     OPEN_READER(re, s)
nengel@2:     UPDATE_CACHE(re, s)
nengel@2:     tmp= SHOW_UBITS(re, s, n);
nengel@2:     LAST_SKIP_BITS(re, s, n)
nengel@2:     CLOSE_READER(re, s)
nengel@2:     return tmp;
nengel@2: }
nengel@2: 
nengel@2: /**
nengel@2:  * shows 1-17 bits.
nengel@2:  * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
nengel@2:  */
nengel@2: static inline unsigned int show_bits(GetBitContext *s, int n){
nengel@2:     register int tmp;
nengel@2:     OPEN_READER(re, s)
nengel@2:     UPDATE_CACHE(re, s)
nengel@2:     tmp= SHOW_UBITS(re, s, n);
nengel@2: //    CLOSE_READER(re, s)
nengel@2:     return tmp;
nengel@2: }
nengel@2: 
nengel@2: static inline void skip_bits(GetBitContext *s, int n){
nengel@2:  //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
nengel@2:     OPEN_READER(re, s)
nengel@2:     UPDATE_CACHE(re, s)
nengel@2:     LAST_SKIP_BITS(re, s, n)
nengel@2:     CLOSE_READER(re, s)
nengel@2: }
nengel@2: 
nengel@2: static inline unsigned int get_bits1(GetBitContext *s){
nengel@2:     return get_bits(s, 1);
nengel@2: }
nengel@2: 
nengel@2: static inline unsigned int show_bits1(GetBitContext *s){
nengel@2:     return show_bits(s, 1);
nengel@2: }
nengel@2: 
nengel@2: static inline void skip_bits1(GetBitContext *s){
nengel@2:     skip_bits(s, 1);
nengel@2: }
nengel@2: 
nengel@2: /**
nengel@2:  * reads 0-32 bits.
nengel@2:  */
nengel@2: static inline unsigned int get_bits_long(GetBitContext *s, int n){
nengel@2:     if(n<=MIN_CACHE_BITS) return get_bits(s, n);
nengel@2:     else{
nengel@2:         int ret= get_bits(s, 16) << (n-16);
nengel@2:         return ret | get_bits(s, n-16);
nengel@2:     }
nengel@2: }
nengel@2: 
nengel@2: /**
nengel@2:  * reads 0-32 bits as a signed integer.
nengel@2:  */
nengel@2: static inline int get_sbits_long(GetBitContext *s, int n) {
nengel@2:     return sign_extend(get_bits_long(s, n), n);
nengel@2: }
nengel@2: 
nengel@2: /**
nengel@2:  * shows 0-32 bits.
nengel@2:  */
nengel@2: static inline unsigned int show_bits_long(GetBitContext *s, int n){
nengel@2:     if(n<=MIN_CACHE_BITS) return show_bits(s, n);
nengel@2:     else{
nengel@2:         GetBitContext gb= *s;
nengel@2:         return get_bits_long(&gb, n);
nengel@2:     }
nengel@2: }
nengel@2: 
nengel@2: static inline int check_marker(GetBitContext *s, const char *msg)
nengel@2: {
nengel@2:     int bit= get_bits1(s);
nengel@2:     if(!bit)
nengel@2:         av_log(AV_LOG_INFO, "Marker bit missing %s\n", msg);
nengel@2: 
nengel@2:     return bit;
nengel@2: }
nengel@2: 
nengel@2: /**
nengel@2:  * init GetBitContext.
nengel@2:  * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
nengel@2:  * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
nengel@2:  * @param bit_size the size of the buffer in bits
nengel@2:  *
nengel@2:  * While GetBitContext stores the buffer size, for performance reasons you are
nengel@2:  * responsible for checking for the buffer end yourself (take advantage of the padding)!
nengel@2:  */
nengel@2: static inline void init_get_bits(GetBitContext *s,
nengel@2:                    const uint8_t *buffer, int bit_size)
nengel@2: {
nengel@2:     int buffer_size= (bit_size+7)>>3;
nengel@2:     if(buffer_size < 0 || bit_size < 0) {
nengel@2:         buffer_size = bit_size = 0;
nengel@2:         buffer = NULL;
nengel@2:     }
nengel@2: 
nengel@2:     s->buffer= buffer;
nengel@2:     s->size_in_bits= bit_size;
nengel@2:     s->buffer_end= buffer + buffer_size;
nengel@2: 
nengel@2:     s->buffer_ptr = (uint32_t*)((intptr_t)buffer&(~3));
nengel@2:     s->bit_count = 32 + 8*((intptr_t)buffer&3);
nengel@2:     skip_bits_long(s, 0);
nengel@2: }
nengel@2: 
nengel@2: static inline void align_get_bits(GetBitContext *s)
nengel@2: {
nengel@2:     int n= (-get_bits_count(s)) & 7;
nengel@2:     if(n) skip_bits(s, n);
nengel@2: }
nengel@2: 
nengel@2: #define tprintf(p, ...) {}
nengel@2: 
nengel@2: static inline int get_bits_left(GetBitContext *gb)
nengel@2: {
nengel@2:     return gb->size_in_bits - get_bits_count(gb);
nengel@2: }
nengel@2: 
nengel@2: #endif /* AVCODEC_GET_BITS_H */