gstreamer/ext/tarkin/bitcoder.h

#ifndef __BITCODER_H
#define __BITCODER_H

#include "mem.h"

#if defined(BITCODER)

#define OUTPUT_BIT(coder,bit)             bitcoder_write_bit(coder,bit)
#define INPUT_BIT(coder)                  bitcoder_read_bit(coder)
#define OUTPUT_BIT_DIRECT(coder,bit)      bitcoder_write_bit(coder,bit)
#define INPUT_BIT_DIRECT(coder)           bitcoder_read_bit(coder)
#define ENTROPY_CODER                     BitCoderState
#define ENTROPY_ENCODER_init(coder,limit) bitcoder_coder_init(coder,limit)
#define ENTROPY_ENCODER_DONE(coder)       bitcoder_encoder_done(coder)
#define ENTROPY_ENCODER_FLUSH(coder)      bitcoder_flush(coder)
#define ENTROPY_DECODER_INIT(coder,bitstream,limit) \
   bitcoder_decoder_init(coder,bitstream,limit)
#define ENTROPY_DECODER_DONE(coder)       /* nothing to do ... */
#define ENTROPY_CODER_BITSTREAM(coder)    (coder)->bitstream

#define ENTROPY_CODER_SYMBOL(coder)       1
#define ENTROPY_CODER_RUNLENGTH(coder)    0
#define ENTROPY_CODER_SKIP(coder,skip)

#endif


typedef struct {
   int32_t  bit_count;           /*  number of valid bits in byte    */
   uint8_t   byte;               /*  buffer to save bits             */
   uint32_t  byte_count;         /*  number of bytes written         */
   uint8_t  *bitstream;
   uint32_t  limit;              /*  don't write more bytes to bitstream ... */
   int       eos;                /*  end of stream reached           */
} BitCoderState;



static inline
void bitcoder_encoder_init (BitCoderState *s, uint32_t limit)
{
   s->bit_count = 0;
   s->byte = 0;
   s->byte_count = 0;
   s->bitstream = (uint8_t*) MALLOC (limit);
   s->limit = limit;
   s->eos = 0;
}


static inline
void bitcoder_encoder_done (BitCoderState *s)
{
   FREE (s->bitstream);
}


static inline
void bitcoder_decoder_init (BitCoderState *s, uint8_t *bitstream, uint32_t limit)
{
   s->bit_count = -1;
   s->byte = 0;
   s->byte_count = 0;
   s->bitstream = bitstream;
   s->limit = limit;
   s->eos = 0;
}


static inline
uint32_t bitcoder_flush (BitCoderState *s)
{
   if (s->bit_count > 0 && s->byte_count < s->limit)
      s->bitstream [s->byte_count++] = s->byte << (8 - s->bit_count);

/*printf ("%s: %i bytes written.\n", __FUNCTION__, s->byte_count); */
/*printf ("%s: last bit %i\n", __FUNCTION__, s->bit_count); */
   return s->byte_count;
}



static inline
void bitcoder_write_bit (BitCoderState *s, int bit)
{
   s->byte <<= 1;
   s->byte |= bit & 1;

   s->bit_count++;

   if (s->bit_count == 8) {
      if (s->byte_count < s->limit) {
         s->bitstream [s->byte_count++] = s->byte;
         s->bit_count = 0;
      } else {
         s->eos = 1;
      }
   }
}


static inline
int bitcoder_read_bit (BitCoderState *s)
{
   int ret;

   if (s->bit_count <= 0) {
      if (!s->bitstream) {
         s->eos = 1;
         return 0;
      }

      if (s->byte_count < s->limit) {
         s->byte = s->bitstream [s->byte_count++];
      } else {
         s->eos = 1;
         s->byte = 0;
      }

      s->bit_count = 8;
   }

   ret = s->byte >> 7;
   s->byte <<= 1; 
   s->bit_count--;

   return ret & 1;
}






static inline
void bit_print (TYPE byte)
{
   int bit = 8*sizeof(TYPE);

   do {
      bit--;
      printf ((byte & (1 << bit)) ? "1" : "0");
   } while (bit);
   printf ("\n");
}

#endif