ref: 7fc72d14be2af5e15866a9124a99b6dafea65dcd
dir: /jbig2_huffman.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_huffman.c,v 1.8 2002/06/15 16:02:53 giles Exp $ */ /* Huffman table decoding procedures -- See Annex B of the JBIG2 draft spec */ #include <stdlib.h> #include "jbig2.h" #include "jbig2_priv.h" #include "jbig2_huffman.h" #define JBIG2_HUFFMAN_FLAGS_ISOOB 1 #define JBIG2_HUFFMAN_FLAGS_ISLOW 2 #define JBIG2_HUFFMAN_FLAGS_ISEXT 4 struct _Jbig2HuffmanState { /* The current bit offset is equal to (offset * 8) + offset_bits. The MSB of this_word is the current bit offset. The MSB of next_word is (offset + 4) * 8. */ uint32_t this_word; uint32_t next_word; int offset_bits; int offset; Jbig2WordStream *ws; }; Jbig2HuffmanState * jbig2_huffman_new (Jbig2WordStream *ws) { Jbig2HuffmanState *result = (Jbig2HuffmanState *)malloc (sizeof(Jbig2HuffmanState)); result->offset = 0; result->offset_bits = 0; result->this_word = ws->get_next_word (ws, 0); result->next_word = ws->get_next_word (ws, 4); result->ws = ws; return result; } int32_t jbig2_huffman_get (Jbig2HuffmanState *hs, const Jbig2HuffmanTable *table, bool *oob) { Jbig2HuffmanEntry *entry; byte flags; int offset_bits = hs->offset_bits; uint32_t this_word = hs->this_word; uint32_t next_word; int RANGELEN; int32_t result; for (;;) { int log_table_size = table->log_table_size; int PREFLEN; entry = &table->entries[this_word >> (32 - log_table_size)]; flags = entry->flags; PREFLEN = entry->PREFLEN; next_word = hs->next_word; offset_bits += PREFLEN; if (offset_bits >= 32) { Jbig2WordStream *ws = hs->ws; this_word = next_word; hs->offset += 4; next_word = ws->get_next_word (ws, hs->offset + 4); offset_bits -= 32; hs->next_word = next_word; PREFLEN = offset_bits; } this_word = (this_word << PREFLEN) | (next_word >> (32 - offset_bits)); if (flags & JBIG2_HUFFMAN_FLAGS_ISEXT) { table = entry->u.ext_table; } else break; } result = entry->u.RANGELOW; RANGELEN = entry->RANGELEN; if (RANGELEN > 0) { int32_t HTOFFSET; HTOFFSET = this_word >> (32 - RANGELEN); if (flags & JBIG2_HUFFMAN_FLAGS_ISLOW) result -= HTOFFSET; else result += HTOFFSET; offset_bits += RANGELEN; if (offset_bits >= 32) { Jbig2WordStream *ws = hs->ws; this_word = next_word; hs->offset += 4; next_word = ws->get_next_word (ws, hs->offset + 4); offset_bits -= 32; hs->next_word = next_word; RANGELEN = offset_bits; } this_word = (this_word << RANGELEN) | (next_word >> (32 - offset_bits)); } hs->this_word = this_word; hs->offset_bits = offset_bits; if (oob != NULL) *oob = (flags & JBIG2_HUFFMAN_FLAGS_ISOOB); return result; } #define LOG_TABLE_SIZE_MAX 8 Jbig2HuffmanTable * jbig2_build_huffman_table (const Jbig2HuffmanParams *params) { int LENCOUNT[256]; int LENMAX = -1; const Jbig2HuffmanLine *lines = params->lines; int n_lines = params->n_lines; int i, j; int log_table_size = 0; Jbig2HuffmanTable *result; Jbig2HuffmanEntry *entries; int CURLEN; int firstcode = 0; int CURCODE; int CURTEMP; /* B.3, 1. */ for (i = 0; i < params->n_lines; i++) { int PREFLEN = lines[i].PREFLEN; int lts; if (PREFLEN > LENMAX) { for (j = LENMAX + 1; j < PREFLEN + 1; j++) LENCOUNT[j] = 0; LENMAX = PREFLEN; } LENCOUNT[PREFLEN]++; lts = PREFLEN + lines[i].RANGELEN; if (lts > LOG_TABLE_SIZE_MAX) lts = PREFLEN; if (lts <= LOG_TABLE_SIZE_MAX && log_table_size < lts) log_table_size = lts; } result = (Jbig2HuffmanTable *)malloc (sizeof(Jbig2HuffmanTable)); result->log_table_size = log_table_size; entries = (Jbig2HuffmanEntry *)malloc (sizeof(Jbig2HuffmanEntry) << log_table_size); result->entries = entries; LENCOUNT[0] = 0; for (CURLEN = 1; CURLEN <= LENMAX; CURLEN++) { int shift = log_table_size - CURLEN; /* B.3 3.(a) */ firstcode = (firstcode + LENCOUNT[CURLEN - 1]) << 1; CURCODE = firstcode; /* B.3 3.(b) */ for (CURTEMP = 0; CURTEMP < n_lines; CURTEMP++) { int PREFLEN = lines[CURTEMP].PREFLEN; if (PREFLEN == CURLEN) { int RANGELEN = lines[CURTEMP].RANGELEN; int start_j = CURCODE << shift; int end_j = (CURCODE + 1) << shift; byte eflags = 0; /* todo: build extension tables */ if (params->HTOOB && CURTEMP == n_lines - 1) eflags |= JBIG2_HUFFMAN_FLAGS_ISOOB; if (CURTEMP == n_lines - (params->HTOOB ? 3 : 2)) eflags |= JBIG2_HUFFMAN_FLAGS_ISLOW; if (PREFLEN + RANGELEN > LOG_TABLE_SIZE_MAX) { for (j = start_j; j < end_j; j++) { entries[j].u.RANGELOW = lines[CURTEMP].RANGELOW; entries[j].PREFLEN = PREFLEN; entries[j].RANGELEN = RANGELEN; entries[j].flags = eflags; } } else { for (j = start_j; j < end_j; j++) { int32_t HTOFFSET = (j >> (shift - RANGELEN)) & ((1 << RANGELEN) - 1); if (eflags & JBIG2_HUFFMAN_FLAGS_ISLOW) entries[j].u.RANGELOW = lines[CURTEMP].RANGELOW - HTOFFSET; else entries[j].u.RANGELOW = lines[CURTEMP].RANGELOW + HTOFFSET; entries[j].PREFLEN = PREFLEN + RANGELEN; entries[j].RANGELEN = 0; entries[j].flags = eflags; } } CURCODE++; } } } return result; } #ifdef TEST #include <stdio.h> /* a test bitstream, and a list of the table indicies to use in decoding it. 1 = table B.1 (A), 2 = table B.2 (B), and so on */ /* this test stream should decode to { 8, 5, oob, 8 } */ const byte test_stream[] = { 0xe9, 0xcb, 0xf4, 0x00 }; const byte test_tabindex[] = { 4, 2, 2, 1 }; static uint32_t test_get_word (Jbig2WordStream *self, int offset) { /* assume test_stream[] is at least 4 bytes */ if (offset+3 > sizeof(test_stream)) return 0; else return ( (test_stream[offset] << 24) | (test_stream[offset+1] << 16) | (test_stream[offset+2] << 8) | (test_stream[offset+3]) ); } int main (int argc, char **argv) { Jbig2HuffmanTable *tables[5]; Jbig2HuffmanState *hs; Jbig2WordStream ws; bool oob; int32_t code; tables[0] = NULL; tables[1] = jbig2_build_huffman_table (&jbig_huffman_params_A); tables[2] = jbig2_build_huffman_table (&jbig_huffman_params_B); tables[3] = NULL; tables[4] = jbig2_build_huffman_table (&jbig_huffman_params_D); ws.get_next_word = test_get_word; hs = jbig2_huffman_new (&ws); printf("testing jbig2 huffmann decoding..."); printf("\t(should be 8 5 (oob) 8)\n"); { int i; int sequence_length = sizeof(test_tabindex); for (i = 0; i < sequence_length; i++) { code = jbig2_huffman_get (hs, tables[test_tabindex[i]], &oob); if (oob) printf("(oob) "); else printf("%d ", code); } } printf("\n"); return 0; } #endif