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__
 * 
 * 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.
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 */
 
/*
 * 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"
 
/******************************************************************************\
* 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. */
        jas_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