/src/jasper/src/libjasper/jpc/jpc_mqdec.h

Source
/*
 * 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) 2001-2006 Michael David Adams
 * Copyright (c) 1999-2000 Image Power, Inc.
 * Copyright (c) 1999-2000 The University of British Columbia
 * 
 * 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,
 * publish, distribute, and/or sell copies of the Software, and to permit
 * 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.
 * 
 * 2.  The name of a copyright holder shall not be used to endorse or
 * promote products derived from the Software without specific prior
 * written permission.
 * 
 * THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS
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 * 
 * __END_OF_JASPER_LICENSE__
 */

/*
 * MQ Arithmetic Decoder
 *
 * $Id$
 */

#ifndef JPC_MQDEC_H
#define JPC_MQDEC_H

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

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

#include "jpc_mqcod.h"

#include <stdio.h>

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

/* MQ arithmetic decoder. */

typedef struct {

  /* The C register. */
  uint_least32_t creg;

  /* The A register. */
  uint_least32_t areg;

  /* The CT register. */
  uint_least32_t ctreg;

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

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

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

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

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

  /* The EOF indicator. */
  bool eof;

} jpc_mqdec_t;

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

/* Create a MQ decoder. */
jpc_mqdec_t *jpc_mqdec_create(unsigned 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. */
static inline void jpc_mqdec_setcurctx(jpc_mqdec_t *dec, unsigned ctxno)
{
  dec->curctx = &dec->ctxs[ctxno];
}

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

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

/* Decode a symbol. */
#ifdef NDEBUG
#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). */
#ifdef NDEBUG
#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(const jpc_mqdec_t *dec);

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

bool jpc_mqdec_mpsexchrenormd(jpc_mqdec_t *dec);
bool jpc_mqdec_lpsexchrenormd(jpc_mqdec_t *dec);

JAS_FORCE_INLINE
static bool jpc_mqdec_getbit_macro(jpc_mqdec_t *dec)
{
  const jpc_mqstate_t *const state = *dec->curctx;

  dec->areg -= state->qeval;

  if (dec->creg >= (uint_least32_t)state->qeval << 16) {
    dec->creg -= (uint_least32_t)state->qeval << 16;
    return dec->areg & 0x8000
      ? state->mps
      : jpc_mqdec_mpsexchrenormd(dec);
  } else {
    return jpc_mqdec_lpsexchrenormd(dec);
  }
}

JAS_FORCE_INLINE
static bool jpc_mqdec_mpsexchange(uint_least32_t areg, uint_least32_t delta, const jpc_mqstate_t **curctx)
{
  if (areg < delta) {
    const jpc_mqstate_t *state = *curctx;
    /* LPS decoded. */
    *curctx = state->nlps;
    return !state->mps;
  } else {
    const jpc_mqstate_t *state = *curctx;
    /* MPS decoded. */
    *curctx = state->nmps;
    return state->mps;
  }
}

JAS_FORCE_INLINE
static bool jpc_mqdec_lpsexchange(uint_least32_t *areg_p, uint_least32_t delta, const jpc_mqstate_t **curctx)
{
  if (*areg_p >= delta) {
    const jpc_mqstate_t *state = *curctx;
    *areg_p = delta;
    *curctx = state->nlps;
    return !state->mps;
  } else {
    const jpc_mqstate_t *state = *curctx;
    *areg_p = delta;
    *curctx = state->nmps;
    return state->mps;
  }
}

bool jpc_mqdec_getbit_func(jpc_mqdec_t *dec);

#endif

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Created: 2026-04-01 07:49