/* Copyright (C) 2001-2012 Artifex Software, Inc.

   All Rights Reserved.

   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.

   Refer to licensing information at http://www.artifex.com or contact

   Artifex Software, Inc.,  7 Mt. Lassen Drive - Suite A-134, San Rafael,

   CA  94903, U.S.A., +1(415)492-9861, for further information.

*/

/*

    jbig2dec

*/

/* Annex A */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "os_types.h"

#include <stddef.h>

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

#include "jbig2.h"

#include "jbig2_priv.h"

#include "jbig2_arith.h"

#include "jbig2_arith_int.h"

struct _Jbig2ArithIntCtx {

    Jbig2ArithCx IAx[512];

};

Jbig2ArithIntCtx *

jbig2_arith_int_ctx_new(Jbig2Ctx *ctx)

{

    Jbig2ArithIntCtx *result = jbig2_new(ctx, Jbig2ArithIntCtx, 1);

    if (result == NULL) {

        jbig2_error(ctx, JBIG2_SEVERITY_FATAL, -1, "failed to allocate Jbig2ArithIntCtx in jbig2_arith_int_ctx_new");

    } else {

        memset(result->IAx, 0, sizeof(result->IAx));

    }

    return result;

}

/* A.2 */

/* Return value: -1 on error, 0 on normal value, 1 on OOB return. */

int

jbig2_arith_int_decode(Jbig2ArithIntCtx *ctx, Jbig2ArithState *as, int32_t *p_result)

{

    Jbig2ArithCx *IAx = ctx->IAx;

    int PREV = 1;

    int S, V;

    int bit;

    int n_tail, offset;

    int i;

    S = jbig2_arith_decode(as, &IAx[PREV]);

    PREV = (PREV << 1) | S;

    bit = jbig2_arith_decode(as, &IAx[PREV]);

    PREV = (PREV << 1) | bit;

    if (bit) {

        bit = jbig2_arith_decode(as, &IAx[PREV]);

        PREV = (PREV << 1) | bit;

        if (bit) {

            bit = jbig2_arith_decode(as, &IAx[PREV]);

            PREV = (PREV << 1) | bit;

            if (bit) {

                bit = jbig2_arith_decode(as, &IAx[PREV]);

                PREV = (PREV << 1) | bit;

                if (bit) {

                    bit = jbig2_arith_decode(as, &IAx[PREV]);

                    PREV = (PREV << 1) | bit;

                    if (bit) {

                        n_tail = 32;

                        offset = 4436;

                    } else {

                        n_tail = 12;

                        offset = 340;

                    }

                } else {

                    n_tail = 8;

                    offset = 84;

                }

            } else {

                n_tail = 6;

                offset = 20;

            }

        } else {

            n_tail = 4;

            offset = 4;

        }

    } else {

        n_tail = 2;

        offset = 0;

    }

    V = 0;

    for (i = 0; i < n_tail; i++) {

        bit = jbig2_arith_decode(as, &IAx[PREV]);

        PREV = ((PREV << 1) & 511) | (PREV & 256) | bit;

        V = (V << 1) | bit;

    }

    V += offset;

    V = S ? -V : V;

    *p_result = V;

    return S && V == 0 ? 1 : 0;

}

void

jbig2_arith_int_ctx_free(Jbig2Ctx *ctx, Jbig2ArithIntCtx *iax)

{

    jbig2_free(ctx->allocator, iax);

}