56 lines
1.8 KiB
C
56 lines
1.8 KiB
C
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/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 2; tab-width: 2 -*- */
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/* GeoIPBitReader.c
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*
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* Copyright (C) 2002 MaxMind.com. All Rights Reserved.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include "GeoIPBitReader.h"
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GeoIPBitReader * GeoIPBitReader_new(const char * filename) {
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GeoIPBitReader *gibr = (GeoIPBitReader *)malloc(sizeof(GeoIPBitReader));
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gibr->GeoIPBitFH = fopen(filename,"rb");
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if (gibr->GeoIPBitFH == NULL) {
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fprintf(stderr, "Error Opening file %s\n",filename);
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return NULL;
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}
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gibr->position = 8;
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return gibr;
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}
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unsigned long GeoIPBitReader_read(GeoIPBitReader * gibr, short int numBits) {
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unsigned long num = 0;
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int i, bit;
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int bytes_read;
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for (i = 0; i < numBits; ++i) {
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if (BITS_IN_BYTE == gibr->position) {
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/* read in next byte */
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bytes_read = fread(&gibr->bits, 1, 1, gibr->GeoIPBitFH);
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if (bytes_read == 0) {
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fprintf(stderr, "Warning: EOF reached\n");
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gibr->bits = 0;
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}
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gibr->position = 0;
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}
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bit = ((gibr->bits & (1 << (BITS_IN_BYTE - gibr->position - 1))) > 0) ? 1 : 0;
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bit <<= i;
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num += bit;
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++(gibr->position);
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}
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return num;
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}
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