ref: e20979d9e27342a2e5d54f12702e038df015de01
dir: /jbig2_arith.c/
/* Copyright (C) 2001-2019 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., 1305 Grant Avenue - Suite 200, Novato,
CA 94945, 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;
};
/*
Previous versions of this code had a #define to allow
us to choose between using the revised arithmetic decoding
specified in the 'Software Convention' section of the spec.
Back to back tests showed that the 'Software Convention'
version was indeed slightly faster. We therefore enable it
by default. We also strip the option out, because a) it
makes the code harder to read, and b) such things are an
invitation to bitrot.
*/
static void
jbig2_arith_bytein(Jbig2ArithState *as)
{
int new_bytes;
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;
new_bytes = ws->get_next_word(ws, as->offset, &as->next_word);
as->next_word_bytes = new_bytes;
as->offset += new_bytes;
B1 = (byte)((as->next_word >> 24) & 0xFF);
if (B1 > 0x8F) {
#ifdef JBIG2_DEBUG_ARITH
fprintf(stderr, "read %02x (aa)\n", B);
#endif
as->CT = 8;
as->next_word = 0xFF000000 | (as->next_word >> 8);
as->next_word_bytes = 4;
as->offset--;
} else {
#ifdef JBIG2_DEBUG_ARITH
fprintf(stderr, "read %02x (a)\n", B);
#endif
as->C += 0xFE00 - (B1 << 9);
as->CT = 7;
}
} else {
B1 = (byte)((as->next_word >> 16) & 0xFF);
if (B1 > 0x8F) {
#ifdef JBIG2_DEBUG_ARITH
fprintf(stderr, "read %02x (ba)\n", B);
#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
as->C += 0xFE00 - (B1 << 9);
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;
new_bytes = ws->get_next_word(ws, as->offset, &as->next_word);
as->offset += new_bytes;
as->next_word_bytes = new_bytes;
}
B = (byte)((as->next_word >> 24) & 0xFF);
as->C += 0xFF00 - (B << 8);
}
}
/** 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;
int new_bytes;
result = jbig2_new(ctx, Jbig2ArithState, 1);
if (result == NULL) {
jbig2_error(ctx, JBIG2_SEVERITY_FATAL, -1, "failed to allocate arithmetic coding state");
return NULL;
}
result->ws = ws;
new_bytes = ws->get_next_word(ws, 0, &result->next_word);
result->next_word_bytes = new_bytes;
result->offset = new_bytes;
/* Figure E.20 */
result->C = (~(result->next_word >> 8)) & 0xFF0000;
jbig2_arith_bytein(result);
result->C <<= 7;
result->CT -= 7;
result->A = 0x8000;
return result;
}
#define MAX_QE_ARRAY_SIZE 47
/* 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;
static const Jbig2ArithQe jbig2_arith_Qe[MAX_QE_ARRAY_SIZE] = {
{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, int *code)
{
Jbig2ArithCx cx = *pcx;
const Jbig2ArithQe *pqe;
unsigned int index = cx & 0x7f;
bool D;
if (index >= MAX_QE_ARRAY_SIZE) {
*code = -1;
return 0;
} else {
pqe = &jbig2_arith_Qe[index];
}
/* Figure E.15 */
as->A -= pqe->Qe;
if (
/* Note: I do not think this is correct. See above. */
(as->C >> 16) < as->A
) {
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);
*code = 0;
return D;
} else {
*code = 0;
return cx >> 7;
}
} else {
as->C -= (as->A) << 16;
/* 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);
*code = 0;
return D;
}
}
#ifdef TEST
static const byte test_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 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
static int
test_get_word(Jbig2WordStream *self, size_t offset, uint32_t *word)
{
uint32_t val = 0;
int ret = 0;
if (self == NULL || word == NULL)
return -1;
if (offset >= sizeof (test_stream))
return 0;
if (offset < sizeof(test_stream)) {
val |= test_stream[offset] << 24;
ret++;
}
if (offset + 1 < sizeof(test_stream)) {
val |= test_stream[offset + 1] << 16;
ret++;
}
if (offset + 2 < sizeof(test_stream)) {
val |= test_stream[offset + 2] << 8;
ret++;
}
if (offset + 3 < sizeof(test_stream)) {
val |= test_stream[offset + 3];
ret++;
}
*word = val;
return ret;
}
int
main(int argc, char **argv)
{
Jbig2Ctx *ctx;
Jbig2WordStream ws;
Jbig2ArithState *as;
int i;
Jbig2ArithCx cx = 0;
int code;
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++) {
#ifdef JBIG2_DEBUG_ARITH
bool D =
#else
(void)
#endif
jbig2_arith_decode(as, &cx, &code);
#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