1 /* Copyright (C) 2002-2003, 2005, 2006 Free Software Foundation, Inc.
2 Contributed by Andy Vaught and Janne Blomqvist
4 This file is part of the GNU Fortran runtime library (libgfortran).
6 Libgfortran is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 In addition to the permissions in the GNU General Public License, the
12 Free Software Foundation gives you unlimited permission to link the
13 compiled version of this file into combinations with other programs,
14 and to distribute those combinations without any restriction coming
15 from the use of this file. (The General Public License restrictions
16 do apply in other respects; for example, they cover modification of
17 the file, and distribution when not linked into a combine
20 Libgfortran is distributed in the hope that it will be useful,
21 but WITHOUT ANY WARRANTY; without even the implied warranty of
22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23 GNU General Public License for more details.
25 You should have received a copy of the GNU General Public License
26 along with Libgfortran; see the file COPYING. If not, write to
27 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
28 Boston, MA 02110-1301, USA. */
32 #include "libgfortran.h"
35 /* file_pos.c-- Implement the file positioning statements, i.e. BACKSPACE,
36 ENDFILE, and REWIND as well as the FLUSH statement. */
39 /* formatted_backspace(fpp, u)-- Move the file back one line. The
40 current position is after the newline that terminates the previous
41 record, and we have to sift backwards to find the newline before
42 that or the start of the file, whichever comes first. */
44 #define READ_CHUNK 4096
47 formatted_backspace (st_parameter_filepos *fpp, gfc_unit *u)
53 base = file_position (u->s) - 1;
57 n = (base < READ_CHUNK) ? base : READ_CHUNK;
60 p = salloc_r_at (u->s, &n, base);
64 /* We have moved backwards from the current position, it should
65 not be possible to get a short read. Because it is not
66 clear what to do about such thing, we ignore the possibility. */
68 /* There is no memrchr() in the C library, so we have to do it
85 /* base is the new pointer. Seek to it exactly. */
87 if (sseek (u->s, base) == FAILURE)
90 u->endfile = NO_ENDFILE;
95 generate_error (&fpp->common, ERROR_OS, NULL);
99 /* unformatted_backspace(fpp) -- Move the file backwards for an unformatted
100 sequential file. We are guaranteed to be between records on entry and
101 we have to shift to the previous record. */
104 unformatted_backspace (st_parameter_filepos *fpp, gfc_unit *u)
110 length = sizeof (gfc_offset);
112 p = salloc_r_at (u->s, &length,
113 file_position (u->s) - length);
117 /* Only CONVERT_NATIVE and CONVERT_SWAP are valid here. */
118 if (u->flags.convert == CONVERT_NATIVE)
119 memcpy (&m, p, sizeof (gfc_offset));
121 reverse_memcpy (&m, p, sizeof (gfc_offset));
123 if ((new = file_position (u->s) - m - 2*length) < 0)
126 if (sseek (u->s, new) == FAILURE)
133 generate_error (&fpp->common, ERROR_OS, NULL);
137 extern void st_backspace (st_parameter_filepos *);
138 export_proto(st_backspace);
141 st_backspace (st_parameter_filepos *fpp)
145 library_start (&fpp->common);
147 u = find_unit (fpp->common.unit);
150 generate_error (&fpp->common, ERROR_BAD_UNIT, NULL);
154 /* Ignore direct access. Non-advancing I/O is only allowed for formatted
155 sequential I/O and the next direct access transfer repositions the file
158 if (u->flags.access == ACCESS_DIRECT)
161 /* Check for special cases involving the ENDFILE record first. */
163 if (u->endfile == AFTER_ENDFILE)
165 u->endfile = AT_ENDFILE;
171 if (file_position (u->s) == 0)
172 goto done; /* Common special case */
174 if (u->mode == WRITING)
181 if (u->flags.form == FORM_FORMATTED)
182 formatted_backspace (fpp, u);
184 unformatted_backspace (fpp, u);
186 u->endfile = NO_ENDFILE;
187 u->current_record = 0;
199 extern void st_endfile (st_parameter_filepos *);
200 export_proto(st_endfile);
203 st_endfile (st_parameter_filepos *fpp)
207 library_start (&fpp->common);
209 u = find_unit (fpp->common.unit);
212 if (u->current_record)
215 dtp.common = fpp->common;
216 memset (&dtp.u.p, 0, sizeof (dtp.u.p));
217 dtp.u.p.current_unit = u;
218 next_record (&dtp, 1);
223 u->endfile = AFTER_ENDFILE;
231 extern void st_rewind (st_parameter_filepos *);
232 export_proto(st_rewind);
235 st_rewind (st_parameter_filepos *fpp)
239 library_start (&fpp->common);
241 u = find_unit (fpp->common.unit);
244 if (u->flags.access != ACCESS_SEQUENTIAL)
245 generate_error (&fpp->common, ERROR_BAD_OPTION,
246 "Cannot REWIND a file opened for DIRECT access");
249 /* Flush the buffers. If we have been writing to the file, the last
250 written record is the last record in the file, so truncate the
251 file now. Reset to read mode so two consecutive rewind
252 statements do not delete the file contents. */
254 if (u->mode == WRITING)
259 if (sseek (u->s, 0) == FAILURE)
260 generate_error (&fpp->common, ERROR_OS, NULL);
262 u->endfile = NO_ENDFILE;
263 u->current_record = 0;
267 /* Update position for INQUIRE. */
268 u->flags.position = POSITION_REWIND;
276 extern void st_flush (st_parameter_filepos *);
277 export_proto(st_flush);
280 st_flush (st_parameter_filepos *fpp)
284 library_start (&fpp->common);
286 u = find_unit (fpp->common.unit);