1 /* An ftello() function that works around platform bugs.
2 Copyright (C) 2007, 2009-2021 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 <https://www.gnu.org/licenses/>. */
28 #include "stdio-impl.h"
37 #if _GL_WINDOWS_64_BIT_OFF_T
39 # if HAVE__FTELLI64 /* msvc, mingw64 */
40 # define ftello _ftelli64
42 # define ftello ftello64
46 #if FTELLO_BROKEN_AFTER_UNGETC /* macOS >= 10.15 */
47 /* The system's ftello() is completely broken, because it calls __sflush,
48 which makes side effects on the stream. */
50 /* Handle non-seekable files first. */
51 if (fp->_file < 0 || fp->_seek == NULL)
57 /* Determine the current offset, ignoring buffered and pushed-back bytes. */
60 if (fp->_flags & __SOFF)
64 pos = fp->_seek (fp->_cookie, 0, SEEK_CUR);
67 if (fp->_flags & __SOPT)
74 if (fp->_flags & __SRD)
76 /* Now consider buffered and pushed-back bytes from ungetc. */
77 if (fp->_ub._base != NULL)
78 /* Considering the buffered bytes, we are at position
80 Considering also the pushed-back bytes, we are at position
81 pos - fp->_ur - fp->_r. */
82 pos = pos - fp->_ur - fp->_r;
84 /* Considering the buffered bytes, we are at position
93 else if ((fp->_flags & __SWR) && fp->_p != NULL)
95 /* Consider the buffered bytes. */
96 off_t buffered = fp->_p - fp->_bf._base;
98 /* Compute pos + buffered, with overflow check. */
100 if (! INT_ADD_OK (pos, buffered, &sum))
112 # if LSEEK_PIPE_BROKEN
113 /* mingw gives bogus answers rather than failure on non-seekable files. */
114 if (lseek (fileno (fp), 0, SEEK_CUR) == -1)
118 # if FTELLO_BROKEN_AFTER_SWITCHING_FROM_READ_TO_WRITE /* Solaris */
119 /* The Solaris stdio leaves the _IOREAD flag set after reading from a file
120 reaches EOF and the program then starts writing to the file. ftello
121 gets confused by this. */
122 if (fp_->_flag & _IOWRT)
126 /* Call ftello nevertheless, for the side effects that it does on fp. */
129 /* Compute the file position ourselves. */
130 pos = lseek (fileno (fp), (off_t) 0, SEEK_CUR);
133 if ((fp_->_flag & _IONBF) == 0 && fp_->_base != NULL)
134 pos += fp_->_ptr - fp_->_base;
140 # if defined __SL64 && defined __SCLE /* Cygwin */
141 if ((fp->_flags & __SL64) == 0)
143 /* Cygwin 1.5.0 through 1.5.24 failed to open stdin in 64-bit
144 mode; but has an ftello that requires 64-bit mode. */
145 FILE *tmp = fopen ("/dev/null", "r");
148 fp->_flags |= __SL64;
149 fp->_seek64 = tmp->_seek64;