1/* bigram -- list bigrams for locate 2 Copyright (C) 1994, 2000, 2003, 2004, 2005, 2007 Free Software Foundation, Inc. 3 4 This program is free software: you can redistribute it and/or modify 5 it under the terms of the GNU General Public License as published by 6 the Free Software Foundation, either version 3 of the License, or 7 (at your option) any later version. 8 9 This program is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU General Public License for more details. 13 14 You should have received a copy of the GNU General Public License 15 along with this program. If not, see <http://www.gnu.org/licenses/>. 16*/ 17 18/* Usage: bigram < text > bigrams 19 Use `code' to encode a file using this output. 20 21 Read a file from stdin and write out the bigrams (pairs of 22 adjacent characters), one bigram per line, to stdout. To reduce 23 needless duplication in the output, it starts finding the 24 bigrams on each input line at the character where that line 25 first differs from the previous line (i.e., in the ASCII 26 remainder). Therefore, the input should be sorted in order to 27 get the least redundant output. 28 29 Written by James A. Woods <jwoods@adobe.com>. 30 Modified by David MacKenzie <djm@gnu.ai.mit.edu>. */ 31 32#include <config.h> 33#include <stdio.h> 34 35#if defined(HAVE_STRING_H) || defined(STDC_HEADERS) 36#include <string.h> 37#else 38#include <strings.h> 39#endif 40 41#ifdef STDC_HEADERS 42#include <stdlib.h> 43#endif 44#include <sys/types.h> 45 46#include <xalloc.h> 47#include "closeout.h" 48 49/* The name this program was run with. */ 50char *program_name; 51 52/* Return the length of the longest common prefix of strings S1 and S2. */ 53 54static int 55prefix_length (char *s1, char *s2) 56{ 57 register char *start; 58 59 for (start = s1; *s1 == *s2 && *s1 != '\0'; s1++, s2++) 60 ; 61 return s1 - start; 62} 63 64int 65main (int argc, char **argv) 66{ 67 char *path; /* The current input entry. */ 68 char *oldpath; /* The previous input entry. */ 69 size_t pathsize, oldpathsize; /* Amounts allocated for them. */ 70 int line_len; /* Length of input line. */ 71 72 program_name = argv[0]; 73 (void) argc; 74 atexit (close_stdout); 75 76 pathsize = oldpathsize = 1026; /* Increased as necessary by getline. */ 77 path = xmalloc (pathsize); 78 oldpath = xmalloc (oldpathsize); 79 80 /* Set to empty string, to force the first prefix count to 0. */ 81 oldpath[0] = '\0'; 82 83 while ((line_len = getline (&path, &pathsize, stdin)) > 0) 84 { 85 register int count; /* The prefix length. */ 86 register int j; /* Index into input line. */ 87 88 path[line_len - 1] = '\0'; /* Remove the newline. */ 89 90 /* Output bigrams in the remainder only. */ 91 count = prefix_length (oldpath, path); 92 for (j = count; path[j] != '\0' && path[j + 1] != '\0'; j += 2) 93 { 94 putchar (path[j]); 95 putchar (path[j + 1]); 96 putchar ('\n'); 97 } 98 99 { 100 /* Swap path and oldpath and their sizes. */ 101 char *tmppath = oldpath; 102 size_t tmppathsize = oldpathsize; 103 oldpath = path; 104 oldpathsize = pathsize; 105 path = tmppath; 106 pathsize = tmppathsize; 107 } 108 } 109 110 free (path); 111 free (oldpath); 112 113 return 0; 114} 115