APG v2.0.0a0
This commit is contained in:
Adel I. Mirzazhanov
330
bloom.c
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330
bloom.c
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/*
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** Copyright (c) 2001
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** Adel I. Mirzazhanov. All rights reserved
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**
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** Redistribution and use in source and binary forms, with or without
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** modification, are permitted provided that the following conditions
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** are met:
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**
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** 1.Redistributions of source code must retain the above copyright notice,
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** this list of conditions and the following disclaimer.
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** 2.Redistributions in binary form must reproduce the above copyright
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** notice, this list of conditions and the following disclaimer in the
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** documentation and/or other materials provided with the distribution.
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** 3.The name of the author may not be used to endorse or promote products
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** derived from this software without specific prior written permission.
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**
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** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
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** OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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** WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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** ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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** DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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** GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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** INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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** NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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** SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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** C module for APG (Automated Password Generator)
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** Bloom filter implementation.
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** Functions:
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** insert_word - insert word in the filter file
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** check_word - check word
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** create_filter - create initial(empty) filter file
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** open_filter - open APG Bloom filter file
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** get_filtersize - get APG Bloom filter size
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** count_words - count words in plain dictionary file
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***************************************************************************
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** hash2bit - generates 4 values (should be 4 values of independent
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** hash functions) from input string.
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** getbit - get the bit value from file.
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** putbit - put the bit in the file.
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*/
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#include "bloom.h"
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h_val * hash2bit(char * word, h_val *b);
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int getbit(FILE * f, h_val bitnum);
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int putbit(FILE * f, h_val bitnum);
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/*
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** insert_word - insert word in the filter file
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** INPUT:
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** char *word - word to incert in the filter
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** FILE *file - filter file descriptor
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** h_val filter_size - filter size in bits
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** RETURN:
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** int
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** 0 - everything OK
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** -1 - something wrong
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*/
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int
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insert_word(char *word, FILE *file, h_val filter_size)
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{
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h_val h[4];
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int i = 0;
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hash2bit (word, &h[0]);
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for(i = 0; i < 4; i++)
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if (putbit (file, h[i] % filter_size)== -1)
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return (-1);
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return(0);
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}
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/*
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** check_word - check word
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** INPUT:
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** char *word - word to check
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** FILE *file - filter file descriptor
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** h_val filter_size - filter size in bits
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** RETURN:
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** int
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** 0 - word is not in dictionary
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** 1 - word is in dictionary
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** -1 - something wrong
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*/
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int
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check_word(char *word, FILE *file, h_val filter_size)
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{
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h_val h[4];
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int i = 0;
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hash2bit (word, &h[0]);
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for(i = 0; i < 4; i++)
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{
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switch(getbit(file, h[i] % filter_size))
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{
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case 0:
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return(0);
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break;
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case -1:
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return(-1);
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break;
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default:
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break;
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}
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}
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return (1);
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}
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/*
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** open_filter - open APG Bloom filter file
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** open filter file and check is this the real bloom filter file
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** INPUT:
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** char * f_name - filter filename
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** RETURN:
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** FILE * - file pointer
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** NULL - something wrong.
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*/
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FILE *
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open_filter(char * f_name)
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{
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FILE *f;
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struct apg_bf_hdr bf_hdr;
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if ((f = fopen (f_name, "r+")) == NULL)
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return(NULL);
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if(fread ( (void *)&bf_hdr, APGBFHDRSIZE, 1, f) < APGBFHDRSIZE)
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if (ferror (f) != 0)
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return(NULL);
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if( (bf_hdr.id[0] != 'A') || (bf_hdr.id[1] != 'P') ||
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(bf_hdr.id[2] != 'G') || (bf_hdr.id[3] != 'B') ||
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(bf_hdr.id[4] != 'F') || (bf_hdr.id[5] != '1') ||
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(bf_hdr.id[6] != '0') || (bf_hdr.id[7] != '0') ) return (NULL);
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else
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{
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if (fseek (f, 0, SEEK_SET) == -1)
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return(NULL);
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return(f);
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}
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}
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/*
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** get_filtersize - get APG Bloom filter size
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** INPUT:
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** FILE *f - filter file descriptor
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** RETURN:
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** h_val - size of APG Bloom filter.
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*/
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h_val
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get_filtersize(FILE * f)
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{
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struct apg_bf_hdr bf_hdr;
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fread ( (void *)&bf_hdr, APGBFHDRSIZE, 1, f);
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fseek (f, 0, SEEK_SET);
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return( (h_val)bf_hdr.fs);
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}
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/*
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** create_filter - create initial(empty) filter file
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** 4 - number of hash functions
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** 0.0001 (0.01%) - probability of false positives
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** INPUT:
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** char * f_name - filter filename
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** unsigned long int n_words - number of words in filter
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** RETURN:
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** FILE * - filter file descriptor
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** NULL - something wrong
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***********************************************************
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** n - number of words in the filter
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** N - size of filter(?)
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**
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** a=(1-(4/N))^n
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** 0.0001=(1-a)^4 ==> 1-a=0.1 ==> a=0.9 ==>
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** 0.9=(1-(4/N))^n ==> 0.9^(1/n)=1-(4/N) ==>
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**
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** N=4/(1-[0.9^(1/n)])
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**
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** 4
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** N = ----------
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** 1/n
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** 1 - 0.9
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*/
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FILE *
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create_filter(char * f_name, unsigned long int n_words)
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{
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FILE *f;
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char zero = 0x00;
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long int i = 0L;
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struct apg_bf_hdr bf_hdr;
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bf_hdr.id[0] = 'A';
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bf_hdr.id[1] = 'P';
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bf_hdr.id[2] = 'G';
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bf_hdr.id[3] = 'B';
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bf_hdr.id[4] = 'F';
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bf_hdr.id[5] = '1';
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bf_hdr.id[6] = '0';
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bf_hdr.id[7] = '0';
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bf_hdr.fs = FSIZE_BIT(n_words);
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if ((f = fopen (f_name, "w+")) == NULL)
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return(NULL);
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if (fwrite ( (void *)&bf_hdr, APGBFHDRSIZE, 1, f) < APGBFHDRSIZE)
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if (ferror (f) != 0)
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return(NULL);
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for (i = 0; i < FSIZE_BYTE(n_words); i++)
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if ( fwrite ( (void *)&zero, 1, 1, f) < 1)
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if (ferror (f) != 0)
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return(NULL);
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if (fseek (f, 0, SEEK_SET) == -1)
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return (NULL);
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return (f);
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}
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/*
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** count_words - count words in plain dictionary file
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** INPUT:
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** FILE *dict_file -plain dicionary file descriptor
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** RETURN:
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** h_val - amount of words in dictionary file
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*/
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h_val
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count_words(FILE *dict_file)
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{
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h_val i = 0L; /* word counter */
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char *string; /* temp string holder */
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string = (char *) calloc(1,MAX_DICT_STRLEN);
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while ((fgets(string, MAX_DICT_STRLEN, dict_file) != NULL))
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i++;
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fseek (dict_file, 0, SEEK_SET);
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free ((void *) string);
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return (i);
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}
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/*
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** hash2bit - generates 4 values (should be 4 values of independent
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** hash functions) from input string.
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** INPUT:
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** char *word - word to hash
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** h_val *b - pointer to bitnumber array
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** RETURN
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** h_val * - pointer to bitnumber array
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*/
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h_val *
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hash2bit(char * word, h_val *b)
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{
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struct apg_MD5Context context;
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unsigned char cs[16];
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apg_MD5Init (&context);
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apg_MD5Update (&context, word, strlen(word));
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apg_MD5Final (cs, &context);
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return ( (h_val *)memcpy( (void *)b, (void *)&cs[0], 16));
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}
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/*
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** getbit - get the bit value from file.
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** INPUT:
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** FILE *f - file descriptor
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** h_val bitnum - bit number
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** RETURN:
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** int
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** 0,1 - bit value
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** -1 - something wrong
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*/
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int
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getbit(FILE * f, h_val bitnum)
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{
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long int bytenum = 0L;
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short int bit_in_byte = 0;
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unsigned char read_byte = 0x00;
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unsigned char test_byte = 0x01;
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int i = 0;
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bit_in_byte = bitnum % 8;
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bytenum = APGBFHDRSIZE + (bitnum/8);
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if (fseek (f, bytenum, SEEK_SET) == -1)
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return(-1);
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if (fread ((void*)&read_byte,1,1,f) < 1)
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if (ferror(f) != 0)
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return (-1);
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for (i=0;i < bit_in_byte;i++)
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test_byte = test_byte*2;
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if ((read_byte & test_byte) > 0) return (1);
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else return (0);
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}
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/*
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** putbit - put the bit in the file.
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** INPUT:
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** FILE *f - file descriptor
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** h_val bitnum - bit number
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** RETURN:
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** int
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** 0 - everything OK
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** -1 - something wrong
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*/
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int
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putbit(FILE * f, h_val bitnum)
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{
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long int bytenum = 0L;
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short int bit_in_byte = 0;
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unsigned char read_byte = 0x00;
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unsigned char test_byte = 0x01;
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int i = 0;
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bit_in_byte = bitnum % 8;
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bytenum = APGBFHDRSIZE + (bitnum/8);
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if (fseek (f, bytenum, SEEK_SET) == -1)
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return(-1);
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if (fread ((void*)&read_byte,1,1,f) < 1)
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if (ferror(f) != 0)
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return (-1);
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for (i=0;i < bit_in_byte;i++)
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test_byte = test_byte*2;
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read_byte = read_byte | test_byte;
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if (fseek (f, bytenum, SEEK_SET) == -1)
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return(-1);
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if (fwrite ((void*)&read_byte,1,1,f) < 1)
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if (ferror(f) != 0)
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return (-1);
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return (0);
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}
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/* END OF bloom.c file */
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