ref: 66b303cfa844f3f8afcebb5d212520cf6de77f7a
dir: /jbig2_arith.c/
/* jbig2dec Copyright (c) 2001 artofcode LLC. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. $Id: jbig2_arith.c,v 1.10 2002/07/08 14:54:01 giles Exp $ */ #ifdef HAVE_CONFIG_H #include "config.h" #include "config_types.h" #elif _WIN32 #include "config_win32.h" #endif #ifdef HAVE_STDINT_H #include <stdint.h> #endif #include <stdio.h> #include <stdlib.h> #include "jbig2.h" #include "jbig2_priv.h" #include "jbig2_arith.h" #ifdef 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 = (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 = (as->next_word >> 24) & 0xFF; if (B1 > 0x8F) { #ifdef 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 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 = (as->next_word >> 16) & 0xFF; if (B1 > 0x8F) { #ifdef 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 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 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 = (as->next_word >> 24) & 0xFF; #ifdef SOFTWARE_CONVENTION as->C += 0xFF00 - (B << 8); #else as->C += (B << 8); #endif } } #ifdef 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