1 /* PSPP - a program for statistical analysis.
2 Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc.
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.
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.
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/>. */
17 /* An interface to an array of octets that is stored on disk as a temporary
22 #include <libpspp/ext-array.h>
28 #include <libpspp/assertion.h>
29 #include <libpspp/cast.h>
35 #define _(msgid) gettext (msgid)
39 FILE *file; /* Underlying file. */
41 /* Current byte offset in file. We track this manually,
42 instead of using ftello, because in glibc ftello flushes
43 the stream buffer, making the common case of sequential
44 access to cases unreasonably slow. */
48 /* Creates and returns a new external array. */
50 ext_array_create (void)
52 struct ext_array *ea = xmalloc (sizeof *ea);
53 ea->file = tmpfile ();
55 error (0, errno, _("failed to create temporary file"));
60 /* Closes and destroys external array EA. Returns true if I/O on EA always
61 succeeded, false if an I/O error occurred at some point. */
63 ext_array_destroy (struct ext_array *ea)
68 ok = !ext_array_error (ea);
76 /* Seeks EA's underlying file to the start of `union value'
77 VALUE_IDX within case CASE_IDX.
78 Returns true if the seek is successful and EA is not
79 otherwise tainted, false otherwise. */
81 do_seek (const struct ext_array *ea_, off_t offset)
83 struct ext_array *ea = CONST_CAST (struct ext_array *, ea_);
85 if (!ext_array_error (ea))
87 if (ea->position == offset)
89 else if (fseeko (ea->file, offset, SEEK_SET) == 0)
91 ea->position = offset;
95 error (0, errno, _("seeking in temporary file"));
101 /* Reads BYTES bytes from EA's underlying file into BUFFER.
102 EA must not be tainted upon entry into this function.
103 Returns true if successful, false upon an I/O error (in which
104 case EA is marked tainted). */
106 do_read (const struct ext_array *ea_, void *buffer, size_t bytes)
108 struct ext_array *ea = CONST_CAST (struct ext_array *, ea_);
110 assert (!ext_array_error (ea));
111 if (bytes > 0 && fread (buffer, bytes, 1, ea->file) != 1)
113 if (ferror (ea->file))
114 error (0, errno, _("reading temporary file"));
115 else if (feof (ea->file))
116 error (0, 0, _("unexpected end of file reading temporary file"));
121 ea->position += bytes;
125 /* Writes BYTES bytes from BUFFER into EA's underlying file.
126 EA must not be tainted upon entry into this function.
127 Returns true if successful, false upon an I/O error (in which
128 case EA is marked tainted). */
130 do_write (struct ext_array *ea, const void *buffer, size_t bytes)
132 assert (!ext_array_error (ea));
133 if (bytes > 0 && fwrite (buffer, bytes, 1, ea->file) != 1)
135 error (0, errno, _("writing to temporary file"));
138 ea->position += bytes;
142 /* Reads N bytes from EA at byte offset OFFSET into DATA.
143 Returns true if successful, false on failure. */
145 ext_array_read (const struct ext_array *ea, off_t offset, size_t n, void *data)
147 return do_seek (ea, offset) && do_read (ea, data, n);
150 /* Writes the N bytes in DATA to EA at byte offset OFFSET.
151 Returns true if successful, false on failure. */
153 ext_array_write (struct ext_array *ea, off_t offset, size_t n,
156 return do_seek (ea, offset) && do_write (ea, data, n);
159 /* Returns true if an error has occurred in I/O on EA,
160 false if no error has been detected. */
162 ext_array_error (const struct ext_array *ea)
164 return ea->file == NULL || ferror (ea->file) || feof (ea->file);