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