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/*
* Header file for the arithmetic encoder and decoder of
* the portable JBIG compression library
*
* Markus Kuhn -- http://www.cl.cam.ac.uk/~mgk25/jbigkit/
*/
#ifndef JBG_AR_H
#define JBG_AR_H
/*
* Status of arithmetic encoder
*/
struct jbg_arenc_state {
unsigned char st[4096]; /* probability status for contexts, MSB = MPS */
unsigned long c; /* register C: base of coding interval, *
* layout as in Table 23 */
unsigned long a; /* register A: normalized size of coding interval */
long sc; /* number of buffered 0xff values that might still overflow */
int ct; /* bit shift counter, determines when next byte will be written */
int buffer; /* buffer for most recent output byte != 0xff */
void (*byte_out)(int, void *); /* function that receives all PSCD bytes */
void *file; /* parameter passed to byte_out */
};
/*
* Status of arithmetic decoder
*/
struct jbg_ardec_state {
unsigned char st[4096]; /* probability status for contexts, MSB = MPS */
unsigned long c; /* register C: base of coding interval, *
* layout as in Table 25 */
unsigned long a; /* register A: normalized size of coding interval */
unsigned char *pscd_ptr; /* pointer to next PSCD data byte */
unsigned char *pscd_end; /* pointer to byte after PSCD */
int ct; /* bit-shift counter, determines when next byte will be read;
* special value -1 signals that zero-padding has started */
int startup; /* boolean flag that controls initial fill of s->c */
int nopadding; /* boolean flag that triggers return -2 between
* reaching PSCD end and decoding the first symbol
* that might never have been encoded in the first
* place */
};
void arith_encode_init(struct jbg_arenc_state *s, int reuse_st);
void arith_encode_flush(struct jbg_arenc_state *s);
void arith_encode(struct jbg_arenc_state *s, int cx, int pix);
void arith_decode_init(struct jbg_ardec_state *s, int reuse_st);
int arith_decode(struct jbg_ardec_state *s, int cx);
#endif /* JBG_AR_H */
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