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#ifndef __GOLOMB_H
#define __GOLOMB_H
#include "bitcoder.h"
static inline
unsigned int required_bits (unsigned int x)
{
int bits = 31;
while ((x & (1 << bits)) == 0 && bits)
bits--;
return bits;
}
static inline
void write_number_binary (BitCoderState *b, unsigned int x, int bits, int u)
{
/*printf ("wrote %i with %i bits (%i+%i)\n", x, u+bits, u, bits); */
while (bits) {
bits--;
bitcoder_write_bit (b, (x >> bits) & 1);
}
}
static inline
unsigned int read_number_binary (BitCoderState *b, int bits)
{
unsigned int x = 0;
while (bits) {
bits--;
x |= bitcoder_read_bit (b) << bits;
}
return x;
}
static inline
void golomb_write_number (BitCoderState *b, unsigned int x, int bits)
{
unsigned int q, r;
int i = 0;
assert (x > 0);
while ((q = (x - 1) >> bits) > 0) {
bitcoder_write_bit (b, 1); /* fast temporary adaption, write */
bits++; /* unary representation of q */
i++;
};
bitcoder_write_bit (b, 0);
r = x - 1 - (q << bits);
write_number_binary (b, r, bits, i+1);
}
static inline
unsigned int golomb_read_number (BitCoderState *b, int bits)
{
unsigned int q = 0, r, x;
while (bitcoder_read_bit (b) != 0) {
bits++;
}
r = read_number_binary (b, bits);
x = (q << bits) + r + 1;
return x;
}
typedef struct {
uint8_t count;
uint8_t bits; /* a 5.3 fixed point integer */
} GolombAdaptiveCoderState;
#define GOLOMB_ADAPTIVE_CODER_STATE_INITIALIZER { 8<<3, 0 }
static const int golomb_w_tab [] = { 256, 128, 64 };
static inline
void golombcoder_encode_number (GolombAdaptiveCoderState *g,
BitCoderState *b,
unsigned int x)
{
golomb_write_number (b, x, g->bits >> 3);
g->bits = ((256 - golomb_w_tab[g->count]) * (int) g->bits +
golomb_w_tab[g->count] * (required_bits(x)<<3)) / 256;
g->count++;
if (g->count > 2)
g->count = 2;
}
static inline
unsigned int golombcoder_decode_number (GolombAdaptiveCoderState *g,
BitCoderState *b)
{
unsigned int x;
x = golomb_read_number (b, g->bits >> 3);
g->bits = ((256 - golomb_w_tab[g->count]) * g->bits +
golomb_w_tab[g->count] * (required_bits(x)<<3)) / 256;
g->count++;
if (g->count > 2)
g->count = 2;
return x;
}
#endif
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