1/* dbmopen.c - Open the file for dbm operations. This looks like the 2 NDBM interface for dbm use. */ 3 4/* This file is part of GDBM, the GNU data base manager, by Philip A. Nelson. 5 Copyright (C) 1990, 1991, 1993 Free Software Foundation, Inc. 6 7 GDBM is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 2, or (at your option) 10 any later version. 11 12 GDBM is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with GDBM; see the file COPYING. If not, write to 19 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 20 21 You may contact the author by: 22 e-mail: phil@cs.wwu.edu 23 us-mail: Philip A. Nelson 24 Computer Science Department 25 Western Washington University 26 Bellingham, WA 98226 27 28*************************************************************************/ 29 30 31/* include system configuration before all else. */ 32#include "autoconf.h" 33 34#include "gdbmdefs.h" 35#include "gdbmerrno.h" 36#include "extern.h" 37 38/* Initialize ndbm system. FILE is a pointer to the file name. In 39 standard dbm, the database is found in files called FILE.pag and 40 FILE.dir. To make gdbm compatable with dbm using the dbminit call, 41 the same file names are used. Specifically, dbminit will use the file 42 name FILE.pag in its call to gdbm open. If the file (FILE.pag) has a 43 size of zero bytes, a file initialization procedure is performed, 44 setting up the initial structure in the file. Any error detected will 45 cause a return value of -1. No errors cause the return value of 0. 46 NOTE: file.dir will be ignored and will always have a size of zero. 47 FLAGS and MODE are the same as the open (2) call. This call will 48 look at the FLAGS and decide what call to make to gdbm_open. For 49 FLAGS == O_RDONLY, it will be a GDBM_READER, if FLAGS == O_RDWR|O_CREAT, 50 it will be a GDBM_WRCREAT (creater and writer) and if the FLAGS == O_RDWR, 51 it will be a GDBM_WRITER and if FLAGS contain O_TRUNC then it will be 52 a GDBM_NEWDB. All other values of FLAGS in the flags are 53 ignored. */ 54 55gdbm_file_info * 56dbm_open (file, flags, mode) 57 char *file; 58 int flags; 59 int mode; 60{ 61 char* pag_file; /* Used to construct "file.pag". */ 62 char* dir_file; /* Used to construct "file.dir". */ 63 struct stat dir_stat; /* Stat information for "file.dir". */ 64 gdbm_file_info *temp_dbf; /* Temporary file pointer storage. */ 65 66 67 /* Prepare the correct names of "file.pag" and "file.dir". */ 68 pag_file = (char *) malloc (strlen (file)+5); 69 dir_file = (char *) malloc (strlen (file)+5); 70 if ((pag_file == NULL) || (dir_file == NULL)) 71 { 72 gdbm_errno = GDBM_MALLOC_ERROR; /* For the hell of it. */ 73 return NULL; 74 } 75 76 strcpy (pag_file, file); 77 strcat (pag_file, ".pag"); 78 strcpy (dir_file, file); 79 strcat (dir_file, ".dir"); 80 81 82 /* Call the actual routine, saving the pointer to the file information. */ 83 flags &= O_RDONLY | O_RDWR | O_CREAT | O_TRUNC; 84 if (flags == O_RDONLY) 85 { 86 temp_dbf = gdbm_open (pag_file, 0, GDBM_READER, 0, NULL); 87 } 88 else if (flags == (O_RDWR | O_CREAT)) 89 { 90 temp_dbf = gdbm_open (pag_file, 0, GDBM_WRCREAT, mode, NULL); 91 } 92 else if ( (flags & O_TRUNC) == O_TRUNC) 93 { 94 temp_dbf = gdbm_open (pag_file, 0, GDBM_NEWDB, mode, NULL); 95 } 96 else 97 { 98 temp_dbf = gdbm_open (pag_file, 0, GDBM_WRITER, 0, NULL); 99 } 100 101 /* Did we successfully open the file? */ 102 if (temp_dbf == NULL) 103 { 104 gdbm_errno = GDBM_FILE_OPEN_ERROR; 105 goto done; 106 } 107 108 /* If the database is new, link "file.dir" to "file.pag". This is done 109 so the time stamp on both files is the same. */ 110 if (stat (dir_file, &dir_stat) == 0) 111 { 112 if (dir_stat.st_size == 0) 113 if (unlink (dir_file) != 0 || link (pag_file, dir_file) != 0) 114 { 115 gdbm_errno = GDBM_FILE_OPEN_ERROR; 116 gdbm_close (temp_dbf); 117 temp_dbf = NULL; 118 goto done; 119 } 120 } 121 else 122 { 123 /* Since we can't stat it, we assume it is not there and try 124 to link the dir_file to the pag_file. */ 125 if (link (pag_file, dir_file) != 0) 126 { 127 gdbm_errno = GDBM_FILE_OPEN_ERROR; 128 gdbm_close (temp_dbf); 129 temp_dbf = NULL; 130 goto done; 131 } 132 } 133 134done: 135 free (pag_file); 136 free (dir_file); 137 return temp_dbf; 138} 139