bitstream.h

This the source release kit for the following system configuration(s): - AMD Alchemy(TM) DBAu1200(

/*
 * copyright (c) 2004 Michael Niedermayer <[e-mail]>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file bitstream.h
 * bitstream api header.
 */

#ifndef BITSTREAM_H
#define BITSTREAM_H

#include "log.h"
#include "debug.h"

extern int g_code;
extern const uint8_t ff_reverse[256];

#define NEG_SSR32(a,s) ((( int32_t)(a))>>(32-(s)))
#define NEG_USR32(a,s) (((uint32_t)(a))>>(32-(s)))

/* bit output */

/* buf and buf_end must be present and used by every alternative writer. */
typedef struct PutBitContext 
{
    uint32_t bit_buf;
    int bit_left;
    uint8_t *buf, *buf_ptr, *buf_end;
} PutBitContext;

static inline void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
{
    if(buffer_size < 0) {
        buffer_size = 0;
        buffer = NULL;
    }

    s->buf = buffer;
    s->buf_end = s->buf + buffer_size;
    s->buf_ptr = s->buf;
    s->bit_left=32;
    s->bit_buf=0;
}

/* bit input */
/* buffer, buffer_end and size_in_bits must be present and used by every reader */
typedef struct GetBitContext {
    const uint8_t *buffer, *buffer_end;
    int index;
    int size_in_bits;
} GetBitContext;

#define VLC_TYPE int16_t

typedef struct VLC 
{
    int bits;
    VLC_TYPE (*table)[2]; ///< code, bits
    int table_size, table_allocated;
} VLC;

typedef struct RL_VLC_ELEM 
{
    int16_t level;
    int8_t len;
    uint8_t run;
} RL_VLC_ELEM;

#if defined(ARCH_MIPS)
#define UNALIGNED_STORES_ARE_BAD
#endif

#define unaligned16(x) *(__unaligned uint16_t*)x
#define unaligned32(x) *(__unaligned uint32_t*)x
#define unaligned64(x) *(__unaligned uint64_t*)x

static inline void put_bits(PutBitContext *s, int n, unsigned int value)
{
    unsigned int bit_buf;
    int bit_left;

    assert(n == 32 || value < (1U << n));

    bit_buf = s->bit_buf;
    bit_left = s->bit_left;

    /* XXX: optimize */
    if (n < bit_left) {
        bit_buf = (bit_buf<<n) | value;
        bit_left-=n;
    } else {
        bit_buf<<=bit_left;
        bit_buf |= value >> (n - bit_left);
#ifdef UNALIGNED_STORES_ARE_BAD
        if (3 & (intptr_t) s->buf_ptr) {
            s->buf_ptr[0] = bit_buf >> 24;
            s->buf_ptr[1] = bit_buf >> 16;
            s->buf_ptr[2] = bit_buf >>  8;
            s->buf_ptr[3] = bit_buf      ;
        } else
#endif
        *(uint32_t *)s->buf_ptr = be2me_32(bit_buf);
        s->buf_ptr+=4;
        bit_left+=32 - n;
        bit_buf = value;
    }

    s->bit_buf = bit_buf;
    s->bit_left = bit_left;
}

/* Bitstream reader API docs:
name
    abritary name which is used as prefix for the internal variables

gb
    getbitcontext

OPEN_READER(name, gb)
    loads gb into local variables

CLOSE_READER(name, gb)
    stores local vars in gb

UPDATE_CACHE(name, gb)
    refills the internal cache from the bitstream
    after this call at least MIN_CACHE_BITS will be available,

GET_CACHE(name, gb)
    will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)

SHOW_UBITS(name, gb, num)
    will return the next num bits

SHOW_SBITS(name, gb, num)
    will return the next num bits and do sign extension

SKIP_BITS(name, gb, num)
    will skip over the next num bits
    note, this is equivalent to SKIP_CACHE; SKIP_COUNTER

SKIP_CACHE(name, gb, num)
    will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)

SKIP_COUNTER(name, gb, num)
    will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)

LAST_SKIP_CACHE(name, gb, num)
    will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing

LAST_SKIP_BITS(name, gb, num)
    is equivalent to SKIP_LAST_CACHE; SKIP_COUNTER

for examples see get_bits, show_bits, skip_bits, get_vlc
*/

#define MIN_CACHE_BITS 25

#define OPEN_READER(name, gb)\
    int name##_index= (gb)->index;\
    int name##_cache= 0;\
  
#define CLOSE_READER(name, gb)\
    (gb)->index= name##_index;\
  
#define UPDATE_CACHE(name, gb)\
    {\
      const uint8_t *p=((const uint8_t *)(gb)->buffer)+(name##_index>>3);\
      name##_cache = (int)((((p[0]<<8) | p[1])<<16) | (p[2]<<8) | (p[3])) << (name##_index&0x07);\
    }\
  
#define SKIP_CACHE(name, gb, num)\
    name##_cache <<= (num);

// FIXME name?
#define SKIP_COUNTER(name, gb, num)\
    name##_index += (num);\

#define SKIP_BITS(name, gb, num)\
    {\
        SKIP_CACHE(name, gb, num)\
        SKIP_COUNTER(name, gb, num)\
    }\

#define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
#define LAST_SKIP_CACHE(name, gb, num) ;

#define SHOW_UBITS(name, gb, num)\
    NEG_USR32(name##_cache, num)

#define SHOW_SBITS(name, gb, num)\
    NEG_SSR32(name##_cache, num)

#define GET_CACHE(name, gb)\
    ((uint32_t)name##_cache)

/**
 * reads 0-17 bits.
 * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
 */
static always_inline unsigned int get_bits(GetBitContext *s, int n)
{
    register int tmp;
    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)
    tmp= SHOW_UBITS(re, s, n);
    LAST_SKIP_BITS(re, s, n)
    CLOSE_READER(re, s)
    return tmp;
}

/**
 * shows 0-17 bits.
 * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
 */
static inline unsigned int show_bits(GetBitContext *s, int n)
{
    register int tmp;
    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)
    tmp= SHOW_UBITS(re, s, n);
//    CLOSE_READER(re, s)
    return tmp;
}

static always_inline void skip_bits(GetBitContext *s, int n)
{
    //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)
    LAST_SKIP_BITS(re, s, n)
    CLOSE_READER(re, s)
}

static always_inline unsigned int get_bits1(GetBitContext *s)
{
    int index= s->index;
    uint8_t result= s->buffer[ index>>3 ];
    result<<= (index&0x07);
    result>>= 8 - 1;
    index++;
    s->index= index;

    return result;
}

extern GetBitContext* s;

#define show_bits1(s) show_bits(s, 1)
#define skip_bits1(s) skip_bits(s, 1)

/**
 * reads 0-32 bits.
 */
static inline unsigned int get_bits_long(GetBitContext *s, int n)
{
    if(n<=17) return get_bits(s, n);
    else
    {
#ifdef ALT_BITSTREAM_READER_LE
        int ret= get_bits(s, 16);
        return ret | (get_bits(s, n-16) << 16);
#else
        int ret= get_bits(s, 16) << (n-16);
        return ret | get_bits(s, n-16);
#endif
    }
}

/**
 * init GetBitContext.
 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
 * @param bit_size the size of the buffer in bits
 */
static inline void init_get_bits(GetBitContext *s,
                   const uint8_t *buffer, int bit_size)
{
    int buffer_size= (bit_size+7)>>3;
    if(buffer_size < 0 || bit_size < 0) {
        buffer_size = bit_size = 0;
        buffer = NULL;
    }

    s->buffer= buffer;
    s->size_in_bits= bit_size;
    s->buffer_end= buffer + buffer_size;
    s->index=0;
}

static always_inline void align_get_bits(GetBitContext *s)
{
    int n= (-s->index) & 7;
    if(n) skip_bits(s, n);
}

int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
             const void *bits, int bits_wrap, int bits_size,
             const void *codes, int codes_wrap, int codes_size,
             int flags);
#define INIT_VLC_USE_STATIC 1
#define INIT_VLC_LE         2
void free_vlc(VLC *vlc);

/**
 *
 * if the vlc code is invalid and max_depth=1 than no bits will be removed
 * if the vlc code is invalid and max_depth>1 than the number of bits removed
 * is undefined
 */
#define GET_VLC(code, name, gb, table, bits, max_depth)\
{\
    int n, index, nb_bits;\
\
    index= SHOW_UBITS(name, gb, bits);\
    code = table[index][0];\
    n    = table[index][1];\
\
    if(max_depth > 1 && n < 0){\
        LAST_SKIP_BITS(name, gb, bits)\
        UPDATE_CACHE(name, gb)\
\
        nb_bits = -n;\
\
        index= SHOW_UBITS(name, gb, nb_bits) + code;\
        code = table[index][0];\
        n    = table[index][1];\
        if(max_depth > 2 && n < 0){\
            LAST_SKIP_BITS(name, gb, nb_bits)\
            UPDATE_CACHE(name, gb)\
\
            nb_bits = -n;\
\
            index= SHOW_UBITS(name, gb, nb_bits) + code;\
            code = table[index][0];\
            n    = table[index][1];\
        }\
    }\
    SKIP_BITS(name, gb, n)\
}

#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update)\
{\
    int n, index, nb_bits;\
\
    index= SHOW_UBITS(name, gb, bits);\
    level = table[index].level;\
    n     = table[index].len;\
\
    if(max_depth > 1 && n < 0){\
        SKIP_BITS(name, gb, bits)\
        if(need_update){\
            UPDATE_CACHE(name, gb)\
        }\
\
        nb_bits = -n;\
\
        index= SHOW_UBITS(name, gb, nb_bits) + level;\
        level = table[index].level;\
        n     = table[index].len;\
    }\
    run= table[index].run;\
    SKIP_BITS(name, gb, n)\
}


/**
 * parses a vlc code, faster then get_vlc()
 * @param bits is the number of bits which will be read at once, must be
 *             identical to nb_bits in init_vlc()
 * @param max_depth is the number of times bits bits must be readed to completly
 *                  read the longest vlc code
 *                  = (max_vlc_length + bits - 1) / bits
 */
#define GET_VLC2(s, table, bits, max_depth)\
{\
    OPEN_READER(re, s);\
    UPDATE_CACHE(re, s);\
\
    GET_VLC(g_code, re, s, table, bits, max_depth);\
\
    CLOSE_READER(re, s);\
}

/*
STATIC_FUNC always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2], int bits, int max_depth)
{
    int code;

    OPEN_READER(re, s)
    UPDATE_CACHE(re, s)

    GET_VLC(code, re, s, table, bits, max_depth)

    CLOSE_READER(re, s)
    return code;
}
*/
static inline int decode012(GetBitContext *gb)
{
    int n;
    n = get_bits1(gb);
    if (n == 0)
        return 0;
    else
        return get_bits1(gb) + 1;
}

#endif /* BITSTREAM_H */