jbig2_arith_iaid.c

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/*
    jbig2dec

    Copyright (C) 2001 Artifex Software, Inc.

    This software is provided AS-IS with no warranty,
    either express or implied.

    This software is distributed under license and may not
    be copied, modified or distributed except as expressly
    authorized under the terms of the license contained in
    the file LICENSE in this distribution.

    For information on commercial licensing, go to
    http://www.artifex.com/licensing/ or contact
    Artifex Software, Inc.,  101 Lucas Valley Road #110,
    San Rafael, CA  94903, U.S.A., [phone].

    $Id: jbig2_arith_iaid.c 467 2008-05-17 00:08:26Z giles $
*/

/* Annex A.3 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "os_types.h"

#include <stddef.h>
#include <string.h> /* memset() */

#ifdef VERBOSE
#include <stdio.h> /* for debug printing only */
#endif

#include "jbig2.h"
#include "jbig2_priv.h"
#include "jbig2_arith.h"
#include "jbig2_arith_iaid.h"

struct _Jbig2ArithIaidCtx {
  int SBSYMCODELEN;
  Jbig2ArithCx *IAIDx;
};

Jbig2ArithIaidCtx *
jbig2_arith_iaid_ctx_new(Jbig2Ctx *ctx, int SBSYMCODELEN)
{
  Jbig2ArithIaidCtx *result = jbig2_new(ctx, Jbig2ArithIaidCtx, 1);
  int ctx_size = 1 << SBSYMCODELEN;

  result->SBSYMCODELEN = SBSYMCODELEN;
  result->IAIDx = jbig2_alloc(ctx->allocator, ctx_size);
  memset(result->IAIDx, 0, ctx_size);

  return result;
}

/* A.3 */
/* Return value: -1 on error, 0 on normal value */
int
jbig2_arith_iaid_decode(Jbig2ArithIaidCtx *ctx, Jbig2ArithState *as,
		       int32_t *p_result)
{
  Jbig2ArithCx *IAIDx = ctx->IAIDx;
  int SBSYMCODELEN = ctx->SBSYMCODELEN;
  int PREV = 1;
  int D;
  int i;

  /* A.3 (2) */
  for (i = 0; i < SBSYMCODELEN; i++)
    {
      D = jbig2_arith_decode(as, &IAIDx[PREV]);
#ifdef VERBOSE
      fprintf(stderr, "IAID%x: D = %d\n", PREV, D);
#endif
      PREV = (PREV << 1) | D;
    }
  /* A.3 (3) */
  PREV -= 1 << SBSYMCODELEN;
#ifdef VERBOSE
  fprintf(stderr, "IAID result: %d\n", PREV);
#endif
  *p_result = PREV;
  return 0;
}

void
jbig2_arith_iaid_ctx_free(Jbig2Ctx *ctx, Jbig2ArithIaidCtx *iax)
{
  jbig2_free(ctx->allocator, iax->IAIDx);
  jbig2_free(ctx->allocator, iax);
}