jpc_mqdec.h

/*
 * 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__
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 * JasPer License Version 2.0
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 * Copyright (c) 2001-2006 Michael David Adams
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/*
 * MQ Arithmetic Decoder
 *
 * $Id: jpc_mqdec.h,v 1.2 2008-05-26 09:40:52 vp153 Exp $
 */

#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