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Diffstat (limited to '')
| -rw-r--r-- | lib/ftello.c | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/lib/ftello.c b/lib/ftello.c new file mode 100644 index 0000000..989614a --- /dev/null +++ b/lib/ftello.c @@ -0,0 +1,157 @@ +/* An ftello() function that works around platform bugs. + Copyright (C) 2007, 2009-2022 Free Software Foundation, Inc. + + This file is free software: you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License as + published by the Free Software Foundation; either version 2.1 of the + License, or (at your option) any later version. + + This file is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +#include <config.h> + +/* Specification. */ +#include <stdio.h> + +#include <errno.h> +#include "intprops.h" + +/* Get lseek. */ +#include <unistd.h> + +#include "stdio-impl.h" + +off_t +ftello (FILE *fp) +#undef ftello +#if !HAVE_FTELLO +# undef ftell +# define ftello ftell +#endif +#if _GL_WINDOWS_64_BIT_OFF_T +# undef ftello +# if HAVE__FTELLI64 /* msvc, mingw64 */ +# define ftello _ftelli64 +# else /* mingw */ +# define ftello ftello64 +# endif +#endif +{ +#if FTELLO_BROKEN_AFTER_UNGETC /* macOS >= 10.15 */ + /* The system's ftello() is completely broken, because it calls __sflush, + which makes side effects on the stream. */ + + /* Handle non-seekable files first. */ + if (fp->_file < 0 || fp->_seek == NULL) + { + errno = ESPIPE; + return -1; + } + + /* Determine the current offset, ignoring buffered and pushed-back bytes. */ + off_t pos; + + if (fp->_flags & __SOFF) + pos = fp->_offset; + else + { + pos = fp->_seek (fp->_cookie, 0, SEEK_CUR); + if (pos < 0) + return -1; + if (fp->_flags & __SOPT) + { + fp->_offset = pos; + fp->_flags |= __SOFF; + } + } + + if (fp->_flags & __SRD) + { + /* Now consider buffered and pushed-back bytes from ungetc. */ + if (fp->_ub._base != NULL) + /* Considering the buffered bytes, we are at position + pos - fp->_ur. + Considering also the pushed-back bytes, we are at position + pos - fp->_ur - fp->_r. */ + pos = pos - fp->_ur - fp->_r; + else + /* Considering the buffered bytes, we are at position + pos - fp->_r. */ + pos = pos - fp->_r; + if (pos < 0) + { + errno = EIO; + return -1; + } + } + else if ((fp->_flags & __SWR) && fp->_p != NULL) + { + /* Consider the buffered bytes. */ + off_t buffered = fp->_p - fp->_bf._base; + + /* Compute pos + buffered, with overflow check. */ + off_t sum; + if (! INT_ADD_OK (pos, buffered, &sum)) + { + errno = EOVERFLOW; + return -1; + } + pos = sum; + } + + return pos; + +#else + +# if LSEEK_PIPE_BROKEN + /* mingw gives bogus answers rather than failure on non-seekable files. */ + if (lseek (fileno (fp), 0, SEEK_CUR) == -1) + return -1; +# endif + +# if FTELLO_BROKEN_AFTER_SWITCHING_FROM_READ_TO_WRITE /* Solaris */ + /* The Solaris stdio leaves the _IOREAD flag set after reading from a file + reaches EOF and the program then starts writing to the file. ftello + gets confused by this. */ + if (fp_->_flag & _IOWRT) + { + off_t pos; + + /* Call ftello nevertheless, for the side effects that it does on fp. */ + ftello (fp); + + /* Compute the file position ourselves. */ + pos = lseek (fileno (fp), (off_t) 0, SEEK_CUR); + if (pos >= 0) + { + if ((fp_->_flag & _IONBF) == 0 && fp_->_base != NULL) + pos += fp_->_ptr - fp_->_base; + } + return pos; + } +# endif + +# if defined __SL64 && defined __SCLE /* Cygwin */ + if ((fp->_flags & __SL64) == 0) + { + /* Cygwin 1.5.0 through 1.5.24 failed to open stdin in 64-bit + mode; but has an ftello that requires 64-bit mode. */ + FILE *tmp = fopen ("/dev/null", "r"); + if (!tmp) + return -1; + fp->_flags |= __SL64; + fp->_seek64 = tmp->_seek64; + fclose (tmp); + } +# endif + + return ftello (fp); + +#endif +} |