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56 lines
2.3 KiB
C
56 lines
2.3 KiB
C
/*
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* Header file for the arithmetic encoder and decoder of
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* the portable JBIG compression library
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*
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* Markus Kuhn -- http://www.cl.cam.ac.uk/~mgk25/jbigkit/
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*
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* $Id: jbig_ar.h,v 1.1 2008/09/05 15:05:54 rick Exp $
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*/
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#ifndef JBG_AR_H
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#define JBG_AR_H
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/*
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* Status of arithmetic encoder
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*/
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struct jbg_arenc_state {
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unsigned char st[4096]; /* probability status for contexts, MSB = MPS */
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unsigned long c; /* register C: base of coding intervall, *
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* layout as in Table 23 */
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unsigned long a; /* register A: normalized size of coding interval */
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long sc; /* number of buffered 0xff values that might still overflow */
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int ct; /* bit shift counter, determines when next byte will be written */
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int buffer; /* buffer for most recent output byte != 0xff */
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void (*byte_out)(int, void *); /* function that receives all PSCD bytes */
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void *file; /* parameter passed to byte_out */
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};
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/*
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* Status of arithmetic decoder
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*/
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struct jbg_ardec_state {
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unsigned char st[4096]; /* probability status for contexts, MSB = MPS */
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unsigned long c; /* register C: base of coding intervall, *
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* layout as in Table 25 */
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unsigned long a; /* register A: normalized size of coding interval */
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unsigned char *pscd_ptr; /* pointer to next PSCD data byte */
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unsigned char *pscd_end; /* pointer to byte after PSCD */
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int ct; /* bit-shift counter, determines when next byte will be read;
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* special value -1 signals that zero-padding has started */
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int startup; /* boolean flag that controls initial fill of s->c */
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int nopadding; /* boolean flag that triggers return -2 between
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* reaching PSCD end and decoding the first symbol
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* that might never have been encoded in the first
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* place */
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};
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void arith_encode_init(struct jbg_arenc_state *s, int reuse_st);
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void arith_encode_flush(struct jbg_arenc_state *s);
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void arith_encode(struct jbg_arenc_state *s, int cx, int pix);
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void arith_decode_init(struct jbg_ardec_state *s, int reuse_st);
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int arith_decode(struct jbg_ardec_state *s, int cx);
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#endif /* JBG_AR_H */
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