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/*

    jbig2dec

    Copyright (C) 2001-2005 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 further licensing information refer to http://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.

*/

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "os_types.h"

#include 

#include 

#include "jbig2.h"

#include "jbig2_priv.h"

#include "jbig2_arith.h"

#ifdef JBIG2_DEBUG

#include 

#endif

struct _Jbig2ArithState {

  uint32_t C;

  int A;

  int CT;

  uint32_t next_word;

  int next_word_bytes;

  Jbig2WordStream *ws;

  int offset;

};

#undef SOFTWARE_CONVENTION

/*

  A note on the "software conventions".

  Previously, I had misinterpreted the spec, and had thought that the

  spec's description of the "software convention" was wrong. Now I

  believe that this code is both correct and matches the spec, with

  SOFTWARE_CONVENTION defined or not. Thanks to William Rucklidge for

  the clarification.

  In any case, my benchmarking indicates no speed difference at all.

  Therefore, for now we will just use the normative version.

 */

static void

jbig2_arith_bytein (Jbig2ArithState *as)

{

  byte B;

  /* invariant: as->next_word_bytes > 0 */

  /* Figure G.3 */

  B = (byte)((as->next_word >> 24) & 0xFF);

  if (B == 0xFF)

    {

      byte B1;

      if (as->next_word_bytes == 1)

	{

	  Jbig2WordStream *ws = as->ws;

	  as->next_word = ws->get_next_word (ws, as->offset);

	  as->offset += 4;

	  B1 = (byte)((as->next_word >> 24) & 0xFF);

	  if (B1 > 0x8F)

	    {

#ifdef JBIG2_DEBUG_ARITH

	      fprintf(stderr, "read %02x (aa)\n", B);

#endif

#ifndef SOFTWARE_CONVENTION

	      as->C += 0xFF00;

#endif

	      as->CT = 8;

	      as->next_word = (0xFF00 | B1) << 16;

	      as->next_word_bytes = 2;

	    }

	  else

	    {

#ifdef JBIG2_DEBUG_ARITH

	      fprintf(stderr, "read %02x (a)\n", B);

#endif

#ifdef SOFTWARE_CONVENTION

	      as->C += 0xFE00 - (B1 << 9);

#else

	      as->C += B1 << 9;

#endif

	      as->CT = 7;

	      as->next_word_bytes = 4;

	    }

	}

      else

	{

	  B1 = (byte)((as->next_word >> 16) & 0xFF);

	  if (B1 > 0x8F)

	    {

#ifdef JBIG2_DEBUG_ARITH

	      fprintf(stderr, "read %02x (ba)\n", B);

#endif

#ifndef SOFTWARE_CONVENTION

	      as->C += 0xFF00;

#endif

	      as->CT = 8;

	    }

	  else

	    {

	      as->next_word_bytes--;

	      as->next_word <<= 8;

#ifdef JBIG2_DEBUG_ARITH

	      fprintf(stderr, "read %02x (b)\n", B);

#endif

#ifdef SOFTWARE_CONVENTION

	      as->C += 0xFE00 - (B1 << 9);

#else

	      as->C += (B1 << 9);

#endif

	      as->CT = 7;

	    }

	}

    }

  else

    {

#ifdef JBIG2_DEBUG_ARITH

      fprintf(stderr, "read %02x\n", B);

#endif

      as->CT = 8;

      as->next_word <<= 8;

      as->next_word_bytes--;

      if (as->next_word_bytes == 0)

	{

	  Jbig2WordStream *ws = as->ws;

	  as->next_word = ws->get_next_word (ws, as->offset);

	  as->offset += 4;

	  as->next_word_bytes = 4;

	}

      B = (byte)((as->next_word >> 24) & 0xFF);

#ifdef SOFTWARE_CONVENTION

      as->C += 0xFF00 - (B << 8);

#else

      as->C += (B << 8);

#endif

    }

}

#if defined(JBIG2_DEBUG) || defined(JBIG2_DEBUG_ARITH)

#include 

static void

jbig2_arith_trace (Jbig2ArithState *as, Jbig2ArithCx cx)

{

  fprintf(stderr, "I = %2d, MPS = %d, A = %04x, CT = %2d, C = %08x\n",

	  cx & 0x7f, cx >> 7, as->A, as->CT, as->C);

}

#endif

/** Allocate and initialize a new arithmetic coding state

 *  the returned pointer can simply be freed; this does

 *  not affect the associated Jbig2WordStream.

 */

Jbig2ArithState *

jbig2_arith_new (Jbig2Ctx *ctx, Jbig2WordStream *ws)

{

  Jbig2ArithState *result;

  result = (Jbig2ArithState *)jbig2_alloc(ctx->allocator,

	sizeof(Jbig2ArithState));

  result->ws = ws;

  result->next_word = ws->get_next_word (ws, 0);

  result->next_word_bytes = 4;

  result->offset = 4;

  /* Figure G.1 */

#ifdef SOFTWARE_CONVENTION

  result->C = (~(result->next_word >> 8)) & 0xFF0000;

#else

  result->C = (result->next_word >> 8) & 0xFF0000;

#endif

  jbig2_arith_bytein (result);

  result->C <<= 7;

  result->CT -= 7;

  result->A = 0x8000;

  return result;

}

/* could put bit fields in to minimize memory usage */

typedef struct {

  unsigned short Qe;

  byte mps_xor; /* mps_xor = index ^ NMPS */

  byte lps_xor; /* lps_xor = index ^ NLPS ^ (SWITCH << 7) */

} Jbig2ArithQe;

const Jbig2ArithQe jbig2_arith_Qe[] = {

  { 0x5601,  1 ^  0,  1 ^  0 ^ 0x80 },

  { 0x3401,  2 ^  1,  6 ^  1 },

  { 0x1801,  3 ^  2,  9 ^  2 },

  { 0x0AC1,  4 ^  3, 12 ^  3 },

  { 0x0521,  5 ^  4, 29 ^  4 },

  { 0x0221, 38 ^  5, 33 ^  5 },

  { 0x5601,  7 ^  6,  6 ^  6 ^ 0x80 },

  { 0x5401,  8 ^  7, 14 ^  7 },

  { 0x4801,  9 ^  8, 14 ^  8 },

  { 0x3801, 10 ^  9, 14 ^  9 },

  { 0x3001, 11 ^ 10, 17 ^ 10 },

  { 0x2401, 12 ^ 11, 18 ^ 11 },

  { 0x1C01, 13 ^ 12, 20 ^ 12 },

  { 0x1601, 29 ^ 13, 21 ^ 13 },

  { 0x5601, 15 ^ 14, 14 ^ 14 ^ 0x80 },

  { 0x5401, 16 ^ 15, 14 ^ 15 },

  { 0x5101, 17 ^ 16, 15 ^ 16 },

  { 0x4801, 18 ^ 17, 16 ^ 17 },

  { 0x3801, 19 ^ 18, 17 ^ 18 },

  { 0x3401, 20 ^ 19, 18 ^ 19 },

  { 0x3001, 21 ^ 20, 19 ^ 20 },

  { 0x2801, 22 ^ 21, 19 ^ 21 },

  { 0x2401, 23 ^ 22, 20 ^ 22 },

  { 0x2201, 24 ^ 23, 21 ^ 23 },

  { 0x1C01, 25 ^ 24, 22 ^ 24 },

  { 0x1801, 26 ^ 25, 23 ^ 25 },

  { 0x1601, 27 ^ 26, 24 ^ 26 },

  { 0x1401, 28 ^ 27, 25 ^ 27 },

  { 0x1201, 29 ^ 28, 26 ^ 28 },

  { 0x1101, 30 ^ 29, 27 ^ 29 },

  { 0x0AC1, 31 ^ 30, 28 ^ 30 },

  { 0x09C1, 32 ^ 31, 29 ^ 31 },

  { 0x08A1, 33 ^ 32, 30 ^ 32 },

  { 0x0521, 34 ^ 33, 31 ^ 33 },

  { 0x0441, 35 ^ 34, 32 ^ 34 },

  { 0x02A1, 36 ^ 35, 33 ^ 35 },

  { 0x0221, 37 ^ 36, 34 ^ 36 },

  { 0x0141, 38 ^ 37, 35 ^ 37 },

  { 0x0111, 39 ^ 38, 36 ^ 38 },

  { 0x0085, 40 ^ 39, 37 ^ 39 },

  { 0x0049, 41 ^ 40, 38 ^ 40 },

  { 0x0025, 42 ^ 41, 39 ^ 41 },

  { 0x0015, 43 ^ 42, 40 ^ 42 },

  { 0x0009, 44 ^ 43, 41 ^ 43 },

  { 0x0005, 45 ^ 44, 42 ^ 44 },

  { 0x0001, 45 ^ 45, 43 ^ 45 },

  { 0x5601, 46 ^ 46, 46 ^ 46 }

};

static void

jbig2_arith_renormd (Jbig2ArithState *as)

{

  /* Figure E.18 */

  do

    {

      if (as->CT == 0)

	jbig2_arith_bytein (as);

      as->A <<= 1;

      as->C <<= 1;

      as->CT--;

    }

  while ((as->A & 0x8000) == 0);

}

bool

jbig2_arith_decode (Jbig2ArithState *as, Jbig2ArithCx *pcx)

{

  Jbig2ArithCx cx = *pcx;

  const Jbig2ArithQe *pqe = &jbig2_arith_Qe[cx & 0x7f];

  bool D;

  /* Figure G.2 */

  as->A -= pqe->Qe;

  if (

#ifdef SOFTWARE_CONVENTION

      /* Note: I do not think this is correct. See above. */

      (as->C >> 16) < as->A

#else

      !((as->C >> 16) < pqe->Qe)

#endif

      )

    {

#ifndef SOFTWARE_CONVENTION

      as->C -= pqe->Qe << 16;

#endif

      if ((as->A & 0x8000) == 0)

	{

	  /* MPS_EXCHANGE, Figure E.16 */

	  if (as->A < pqe->Qe)

	    {

	      D = 1 - (cx >> 7);

	      *pcx ^= pqe->lps_xor;

	    }

	  else

	    {

	      D = cx >> 7;

	      *pcx ^= pqe->mps_xor;

	    }

	  jbig2_arith_renormd (as);

	  return D;

	}

      else

	return cx >> 7;

    }

  else

    {

#ifdef SOFTWARE_CONVENTION

      as->C -= (as->A) << 16;

#endif

      /* LPS_EXCHANGE, Figure E.17 */

      if (as->A < pqe->Qe)

	{

	  as->A = pqe->Qe;

	  D = cx >> 7;

	  *pcx ^= pqe->mps_xor;

	}

      else

	{

	  as->A = pqe->Qe;

	  D = 1 - (cx >> 7);

	  *pcx ^= pqe->lps_xor;

	}

      jbig2_arith_renormd (as);

      return D;

    }

}

#ifdef TEST

static uint32_t

test_get_word (Jbig2WordStream *self, int offset)

{

  byte stream[] = {

    0x84, 0xC7, 0x3B, 0xFC, 0xE1, 0xA1, 0x43, 0x04, 0x02, 0x20, 0x00, 0x00,

    0x41, 0x0D, 0xBB, 0x86, 0xF4, 0x31, 0x7F, 0xFF, 0x88, 0xFF, 0x37, 0x47,

    0x1A, 0xDB, 0x6A, 0xDF, 0xFF, 0xAC,

    0x00, 0x00

  };

  if (offset >= sizeof(stream))

    return 0;

  else

    return (stream[offset] << 24) | (stream[offset + 1] << 16) |

      (stream[offset + 2] << 8) | stream[offset + 3];

}

int

main (int argc, char **argv)

{

  Jbig2Ctx *ctx;

  Jbig2WordStream ws;

  Jbig2ArithState *as;

  int i;

  Jbig2ArithCx cx = 0;

  ctx = jbig2_ctx_new(NULL, 0, NULL, NULL, NULL);

  ws.get_next_word = test_get_word;

  as = jbig2_arith_new (ctx, &ws);

#ifdef JBIG2_DEBUG_ARITH

  jbig2_arith_trace (as, cx);

#endif

  for (i = 0; i < 256; i++)

    {

      bool D;

      D = jbig2_arith_decode (as, &cx);

#ifdef JBIG2_DEBUG_ARITH

      fprintf(stderr, "%3d: D = %d, ", i, D);

      jbig2_arith_trace (as, cx);

#endif

    }

  jbig2_free(ctx->allocator, as);

  jbig2_ctx_free(ctx);

  return 0;

}

#endif