ref: bcc1da0257a3f721a4ca95421a996969b8bfb2f6
dir: /jbig2_arith.c/
/*
jbig2dec
Copyright (c) 2001 artofcode LLC.
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., +1(415)492-9861.
$Id$
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "os_types.h"
#include <stdio.h>
#include <stdlib.h>
#include "jbig2.h"
#include "jbig2_priv.h"
#include "jbig2_arith.h"
#ifdef JBIG2_DEBUG
#include <stdio.h>
#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
printf ("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
printf ("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
printf ("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
printf ("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
printf ("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
}
}
#ifdef JBIG2_DEBUG
#include <stdio.h>
static void
jbig2_arith_trace (Jbig2ArithState *as, Jbig2ArithCx cx)
{
printf ("I = %2d, MPS = %d, A = %04x, CT = %2d, C = %08x\n",
cx & 0x7f, cx >> 7, as->A, as->CT, as->C);
}
#endif
Jbig2ArithState *
jbig2_arith_new (Jbig2Ctx *ctx, Jbig2WordStream *ws)
{
Jbig2ArithState *result = (Jbig2ArithState *)malloc (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 int32_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)
{
Jbig2WordStream ws;
Jbig2ArithState *as;
int i;
Jbig2ArithCx cx = 0;
ws.get_next_word = test_get_word;
as = jbig2_arith_new (NULL, &ws);
jbig2_arith_trace (as, cx);
for (i = 0; i < 256; i++)
{
bool D;
D = jbig2_arith_decode (as, &cx);
printf ("%3d: D = %d, ", i, D);
jbig2_arith_trace (as, cx);
}
return 0;
}
#endif