ref: 1c60d10318a37e1e2e1d343cf9bf89b530f6518c
dir: /jbig2_arith.c/
/* 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
*/
#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"
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)
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 = jbig2_new(ctx, Jbig2ArithState, 1);
if (result == NULL)
{
jbig2_error(ctx, JBIG2_SEVERITY_FATAL, -1,
"failed to allocate Jbig2ArithState in jbig2_arith_new");
return result;
}
result->ws = ws;
result->next_word = ws->get_next_word (ws, 0);
result->next_word_bytes = 4;
result->offset = 4;
/* Figure E.20 */
#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 E.15 */
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