ref: 1eb7ae738d7af4508d7cbc547c0e386d55821820
dir: /jbig2_arith.c/
/* jbig2dec Copyright (c) 2001-2005 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 /** 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 jbig2_arith_trace (as, cx); #endif for (i = 0; i < 256; i++) { bool D; D = jbig2_arith_decode (as, &cx); #ifdef JBIG2_DEBUG printf ("%3d: D = %d, ", i, D); jbig2_arith_trace (as, cx); #endif } jbig2_free(ctx->allocator, as); jbig2_ctx_free(ctx); return 0; } #endif