jpc_mqdec.c

/*
 * 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
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 */

/*
 * MQ Arithmetic Decoder
 *
 * $Id: jpc_mqdec.c,v 1.2 2008-05-26 09:40:52 vp153 Exp $
 */

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

#include <assert.h>
#include <stdlib.h>
#include <stdarg.h>

#include "jasper/jas_types.h"
#include "jasper/jas_malloc.h"
#include "jasper/jas_math.h"
#include "jasper/jas_debug.h"

#include "jpc_mqdec.h"

/******************************************************************************\
* Local macros.
\******************************************************************************/

#if defined(DEBUG)
#define	MQDEC_CALL(n, x) \
    ((jas_getdbglevel() >= (n)) ? ((void)(x)) : ((void)0))
#else
#define	MQDEC_CALL(n, x)
#endif

/******************************************************************************\
* Local function prototypes.
\******************************************************************************/

static void jpc_mqdec_bytein(jpc_mqdec_t *mqdec);

/******************************************************************************\
* Code for creation and destruction of a MQ decoder.
\******************************************************************************/

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

    /* There must be at least one context. */
    assert(maxctxs > 0);

    /* Allocate memory for the MQ decoder. */
    if (!(mqdec = jas_malloc(sizeof(jpc_mqdec_t)))) {
        goto error;
    }
    mqdec->in = in;
    mqdec->maxctxs = maxctxs;
    /* Allocate memory for the per-context state information. */
    if (!(mqdec->ctxs = jas_alloc2(mqdec->maxctxs, sizeof(jpc_mqstate_t *)))) {
        goto error;
    }
    /* Set the current context to the first context. */
    mqdec->curctx = mqdec->ctxs;

    /* If an input stream has been associated with the MQ decoder,
      initialize the decoder state from the stream. */
    if (mqdec->in) {
        jpc_mqdec_init(mqdec);
    }
    /* Initialize the per-context state information. */
    jpc_mqdec_setctxs(mqdec, 0, 0);

    return mqdec;

error:
    /* Oops...  Something has gone wrong. */
    if (mqdec) {
        jpc_mqdec_destroy(mqdec);
    }
    return 0;
}

/* Destroy a MQ decoder. */
void jpc_mqdec_destroy(jpc_mqdec_t *mqdec)
{
    if (mqdec->ctxs) {
        jas_free(mqdec->ctxs);
    }
    jas_free(mqdec);
}

/******************************************************************************\
* Code for initialization of a MQ decoder.
\******************************************************************************/

/* Initialize the state of a MQ decoder. */

void jpc_mqdec_init(jpc_mqdec_t *mqdec)
{
    int c;

    mqdec->eof = 0;
    mqdec->creg = 0;
    /* Get the next byte from the input stream. */
    if ((c = jas_stream_getc(mqdec->in)) == EOF) {
        /* We have encountered an I/O error or EOF. */
        c = 0xff;
        mqdec->eof = 1;
    }
    mqdec->inbuffer = c;
    mqdec->creg += mqdec->inbuffer << 16;
    jpc_mqdec_bytein(mqdec);
    mqdec->creg <<= 7;
    mqdec->ctreg -= 7;
    mqdec->areg = 0x8000;
}

/* Set the input stream for a MQ decoder. */

void jpc_mqdec_setinput(jpc_mqdec_t *mqdec, jas_stream_t *in)
{
    mqdec->in = in;
}

/* Initialize one or more contexts. */

void jpc_mqdec_setctxs(jpc_mqdec_t *mqdec, int numctxs, jpc_mqctx_t *ctxs)
{
    jpc_mqstate_t **ctx;
    int n;

    ctx = mqdec->ctxs;
    n = JAS_MIN(mqdec->maxctxs, numctxs);
    while (--n >= 0) {
        *ctx = &jpc_mqstates[2 * ctxs->ind + ctxs->mps];
        ++ctx;
        ++ctxs;
    }
    n = mqdec->maxctxs - numctxs;
    while (--n >= 0) {
        *ctx = &jpc_mqstates[0];
        ++ctx;
    }
}

/* Initialize a context. */

void jpc_mqdec_setctx(jpc_mqdec_t *mqdec, int ctxno, jpc_mqctx_t *ctx)
{
    jpc_mqstate_t **ctxi;
    ctxi = &mqdec->ctxs[ctxno];
    *ctxi = &jpc_mqstates[2 * ctx->ind + ctx->mps];
}

/******************************************************************************\
* Code for decoding a bit.
\******************************************************************************/

/* Decode a bit. */

int jpc_mqdec_getbit_func(register jpc_mqdec_t *mqdec)
{
    int bit;
    JAS_DBGLOG(100, ("jpc_mqdec_getbit_func(%p)\n", mqdec));
    MQDEC_CALL(100, jpc_mqdec_dump(mqdec, stderr));
    bit = jpc_mqdec_getbit_macro(mqdec);
    MQDEC_CALL(100, jpc_mqdec_dump(mqdec, stderr));
    JAS_DBGLOG(100, ("ctx = %d, decoded %d\n", mqdec->curctx -
      mqdec->ctxs, bit));
    return bit;
}

/* Apply MPS_EXCHANGE algorithm (with RENORMD). */
int jpc_mqdec_mpsexchrenormd(register jpc_mqdec_t *mqdec)
{
    int ret;
    register jpc_mqstate_t *state = *mqdec->curctx;
    jpc_mqdec_mpsexchange(mqdec->areg, state->qeval, mqdec->curctx, ret);
    jpc_mqdec_renormd(mqdec->areg, mqdec->creg, mqdec->ctreg, mqdec->in,
      mqdec->eof, mqdec->inbuffer);
    return ret;
}

/* Apply LPS_EXCHANGE algorithm (with RENORMD). */
int jpc_mqdec_lpsexchrenormd(register jpc_mqdec_t *mqdec)
{
    int ret;
    register jpc_mqstate_t *state = *mqdec->curctx;
    jpc_mqdec_lpsexchange(mqdec->areg, state->qeval, mqdec->curctx, ret);
    jpc_mqdec_renormd(mqdec->areg, mqdec->creg, mqdec->ctreg, mqdec->in,
      mqdec->eof, mqdec->inbuffer);
    return ret;
}

/******************************************************************************\
* Support code.
\******************************************************************************/

/* Apply the BYTEIN algorithm. */
static void jpc_mqdec_bytein(jpc_mqdec_t *mqdec)
{
    int c;
    unsigned char prevbuf;

    if (!mqdec->eof) {
        if ((c = jas_stream_getc(mqdec->in)) == EOF) {
            mqdec->eof = 1;
            c = 0xff;
        }
        prevbuf = mqdec->inbuffer;
        mqdec->inbuffer = c;
        if (prevbuf == 0xff) {
            if (c > 0x8f) {
                mqdec->creg += 0xff00;
                mqdec->ctreg = 8;
            } else {
                mqdec->creg += c << 9;
                mqdec->ctreg = 7;
            }
        } else {
            mqdec->creg += c << 8;
            mqdec->ctreg = 8;
        }
    } else {
        mqdec->creg += 0xff00;
        mqdec->ctreg = 8;
    }
}

/******************************************************************************\
* Code for debugging.
\******************************************************************************/

/* Dump a MQ decoder to a stream for debugging. */

void jpc_mqdec_dump(jpc_mqdec_t *mqdec, FILE *out)
{
    fprintf(out, "MQDEC A = %08lx, C = %08lx, CT=%08lx, ",
      (unsigned long) mqdec->areg, (unsigned long) mqdec->creg,
      (unsigned long) mqdec->ctreg);
    fprintf(out, "CTX = %d, ", (int)(mqdec->curctx - mqdec->ctxs));
    fprintf(out, "IND %d, MPS %d, QEVAL %x\n", (int)(*mqdec->curctx -
      jpc_mqstates), (int)(*mqdec->curctx)->mps, (int)(*mqdec->curctx)->qeval);
}