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git.ipfire.org Git - thirdparty/gcc.git/blob - libgfortran/io/file_pos.c
1 /* Copyright (C) 2002-2003, 2005 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 new = file_position (u
->s
) - m
- 2*length
;
124 if (sseek (u
->s
, new) == FAILURE
)
131 generate_error (&fpp
->common
, ERROR_OS
, NULL
);
135 extern void st_backspace (st_parameter_filepos
*);
136 export_proto(st_backspace
);
139 st_backspace (st_parameter_filepos
*fpp
)
143 library_start (&fpp
->common
);
145 u
= find_unit (fpp
->common
.unit
);
148 generate_error (&fpp
->common
, ERROR_BAD_UNIT
, NULL
);
152 /* Ignore direct access. Non-advancing I/O is only allowed for formatted
153 sequential I/O and the next direct access transfer repositions the file
156 if (u
->flags
.access
== ACCESS_DIRECT
)
159 /* Check for special cases involving the ENDFILE record first. */
161 if (u
->endfile
== AFTER_ENDFILE
)
162 u
->endfile
= AT_ENDFILE
;
165 if (file_position (u
->s
) == 0)
166 goto done
; /* Common special case */
168 if (u
->mode
== WRITING
)
175 if (u
->flags
.form
== FORM_FORMATTED
)
176 formatted_backspace (fpp
, u
);
178 unformatted_backspace (fpp
, u
);
180 u
->endfile
= NO_ENDFILE
;
181 u
->current_record
= 0;
192 extern void st_endfile (st_parameter_filepos
*);
193 export_proto(st_endfile
);
196 st_endfile (st_parameter_filepos
*fpp
)
200 library_start (&fpp
->common
);
202 u
= find_unit (fpp
->common
.unit
);
205 if (u
->current_record
)
208 dtp
.common
= fpp
->common
;
209 memset (&dtp
.u
.p
, 0, sizeof (dtp
.u
.p
));
210 dtp
.u
.p
.current_unit
= u
;
211 next_record (&dtp
, 1);
216 u
->endfile
= AFTER_ENDFILE
;
224 extern void st_rewind (st_parameter_filepos
*);
225 export_proto(st_rewind
);
228 st_rewind (st_parameter_filepos
*fpp
)
232 library_start (&fpp
->common
);
234 u
= find_unit (fpp
->common
.unit
);
237 if (u
->flags
.access
!= ACCESS_SEQUENTIAL
)
238 generate_error (&fpp
->common
, ERROR_BAD_OPTION
,
239 "Cannot REWIND a file opened for DIRECT access");
242 /* If we have been writing to the file, the last written record
243 is the last record in the file, so truncate the file now.
244 Reset to read mode so two consecutive rewind statements do not
245 delete the file contents. Flush buffer when switching mode. */
246 if (u
->mode
== WRITING
)
253 if (sseek (u
->s
, 0) == FAILURE
)
254 generate_error (&fpp
->common
, ERROR_OS
, NULL
);
256 u
->endfile
= NO_ENDFILE
;
257 u
->current_record
= 0;
260 /* Update position for INQUIRE. */
261 u
->flags
.position
= POSITION_REWIND
;
269 extern void st_flush (st_parameter_filepos
*);
270 export_proto(st_flush
);
273 st_flush (st_parameter_filepos
*fpp
)
277 library_start (&fpp
->common
);
279 u
= find_unit (fpp
->common
.unit
);