jpc_mqdec.h

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/*
 * Copyright (c) 1999-2000 Image Power, Inc. and the University of
 *   British Columbia.
 * Copyright (c) 2001-2003 Michael David Adams.
 * All rights reserved.
 */

/* __START_OF_JASPER_LICENSE__
 * 
 * JasPer License Version 2.0
 * 
 * Copyright (c) 1999-2000 Image Power, Inc.
 * Copyright (c) 1999-2000 The University of British Columbia
 * Copyright (c) 2001-2003 Michael David Adams
 * 
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person (the
 * "User") obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge,
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 * persons to whom the Software is furnished to do so, subject to the
 * following conditions:
 * 
 * 1.  The above copyright notices and this permission notice (which
 * includes the disclaimer below) shall be included in all copies or
 * substantial portions of the Software.
 * 
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 * THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS
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 * __END_OF_JASPER_LICENSE__
 */

/*
 * MQ Arithmetic Decoder
 *
 * $Id: jpc_mqdec.h 1918 2005-07-24 14:12:08Z baford $
 */

#ifndef JPC_MQDEC_H
#define JPC_MQDEC_H

/******************************************************************************\
* Includes.
\******************************************************************************/

#include "jasper/jas_types.h"
#include "jasper/jas_stream.h"

#include "jpc_mqcod.h"

/******************************************************************************\
* Types.
\******************************************************************************/

/* MQ arithmetic decoder. */

typedef struct {

	/* The C register. */
	uint_fast32_t creg;

	/* The A register. */
	uint_fast32_t areg;

	/* The CT register. */
	uint_fast32_t ctreg;

	/* The current context. */
	jpc_mqstate_t **curctx;

	/* The per-context information. */
	jpc_mqstate_t **ctxs;

	/* The maximum number of contexts. */
	int maxctxs;

	/* The stream from which to read data. */
	jas_stream_t *in;

	/* The last character read. */
	uchar inbuffer;

	/* The EOF indicator. */
	int eof;

} jpc_mqdec_t;

/******************************************************************************\
* Functions/macros for construction and destruction.
\******************************************************************************/

/* Create a MQ decoder. */
jpc_mqdec_t *jpc_mqdec_create(int maxctxs, jas_stream_t *in);

/* Destroy a MQ decoder. */
void jpc_mqdec_destroy(jpc_mqdec_t *dec);

/******************************************************************************\
* Functions/macros for initialization.
\******************************************************************************/

/* Set the input stream associated with a MQ decoder. */
void jpc_mqdec_setinput(jpc_mqdec_t *dec, jas_stream_t *in);

/* Initialize a MQ decoder. */
void jpc_mqdec_init(jpc_mqdec_t *dec);

/******************************************************************************\
* Functions/macros for manipulating contexts.
\******************************************************************************/

/* Set the current context for a MQ decoder. */
#define	jpc_mqdec_setcurctx(dec, ctxno) \
	((mqdec)->curctx = &(mqdec)->ctxs[ctxno]);

/* Set the state information for a particular context of a MQ decoder. */
void jpc_mqdec_setctx(jpc_mqdec_t *dec, int ctxno, jpc_mqctx_t *ctx);

/* Set the state information for all contexts of a MQ decoder. */
void jpc_mqdec_setctxs(jpc_mqdec_t *dec, int numctxs, jpc_mqctx_t *ctxs);

/******************************************************************************\
* Functions/macros for decoding bits.
\******************************************************************************/

/* Decode a symbol. */
#if !defined(DEBUG)
#define	jpc_mqdec_getbit(dec) \
	jpc_mqdec_getbit_macro(dec)
#else
#define	jpc_mqdec_getbit(dec) \
	jpc_mqdec_getbit_func(dec)
#endif

/* Decode a symbol (assuming an unskewed probability distribution). */
#if !defined(DEBUG)
#define	jpc_mqdec_getbitnoskew(dec) \
	jpc_mqdec_getbit_macro(dec)
#else
#define	jpc_mqdec_getbitnoskew(dec) \
	jpc_mqdec_getbit_func(dec)
#endif

/******************************************************************************\
* Functions/macros for debugging.
\******************************************************************************/

/* Dump the MQ decoder state for debugging. */
void jpc_mqdec_dump(jpc_mqdec_t *dec, FILE *out);

/******************************************************************************\
* EVERYTHING BELOW THIS POINT IS IMPLEMENTATION SPECIFIC AND NOT PART OF THE
* APPLICATION INTERFACE.  DO NOT RELY ON ANY OF THE INTERNAL FUNCTIONS/MACROS
* GIVEN BELOW.
\******************************************************************************/

#define	jpc_mqdec_getbit_macro(dec) \
	((((dec)->areg -= (*(dec)->curctx)->qeval), \
	  (dec)->creg >> 16 >= (*(dec)->curctx)->qeval) ? \
	  ((((dec)->creg -= (*(dec)->curctx)->qeval << 16), \
	  (dec)->areg & 0x8000) ?  (*(dec)->curctx)->mps : \
	  jpc_mqdec_mpsexchrenormd(dec)) : \
	  jpc_mqdec_lpsexchrenormd(dec))

#define	jpc_mqdec_mpsexchange(areg, delta, curctx, bit) \
{ \
	if ((areg) < (delta)) { \
		register jpc_mqstate_t *state = *(curctx); \
		/* LPS decoded. */ \
		(bit) = state->mps ^ 1; \
		*(curctx) = state->nlps; \
	} else { \
		register jpc_mqstate_t *state = *(curctx); \
		/* MPS decoded. */ \
		(bit) = state->mps; \
		*(curctx) = state->nmps; \
	} \
}

#define	jpc_mqdec_lpsexchange(areg, delta, curctx, bit) \
{ \
	if ((areg) >= (delta)) { \
		register jpc_mqstate_t *state = *(curctx); \
		(areg) = (delta); \
		(bit) = state->mps ^ 1; \
		*(curctx) = state->nlps; \
	} else { \
		register jpc_mqstate_t *state = *(curctx); \
		(areg) = (delta); \
		(bit) = state->mps; \
		*(curctx) = state->nmps; \
	} \
}

#define	jpc_mqdec_renormd(areg, creg, ctreg, in, eof, inbuf) \
{ \
	do { \
		if (!(ctreg)) { \
			jpc_mqdec_bytein2(creg, ctreg, in, eof, inbuf); \
		} \
		(areg) <<= 1; \
		(creg) <<= 1; \
		--(ctreg); \
	} while (!((areg) & 0x8000)); \
}

#define	jpc_mqdec_bytein2(creg, ctreg, in, eof, inbuf) \
{ \
	int c; \
	unsigned char prevbuf; \
	if (!(eof)) { \
		if ((c = jas_stream_getc(in)) == EOF) { \
			(eof) = 1; \
			c = 0xff; \
		} \
		prevbuf = (inbuf); \
		(inbuf) = c; \
		if (prevbuf == 0xff) { \
			if (c > 0x8f) { \
				(creg) += 0xff00; \
				(ctreg) = 8; \
			} else { \
				(creg) += c << 9; \
				(ctreg) = 7; \
			} \
		} else { \
			(creg) += c << 8; \
			(ctreg) = 8; \
		} \
	} else { \
		(creg) += 0xff00; \
		(ctreg) = 8; \
	} \
}

int jpc_mqdec_getbit_func(jpc_mqdec_t *dec);
int jpc_mqdec_mpsexchrenormd(jpc_mqdec_t *dec);
int jpc_mqdec_lpsexchrenormd(jpc_mqdec_t *dec);

#endif