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/* fsusage.c -- return space usage of mounted file systems
Copyright (C) 1991, 1992, 1996, 1998, 1999, 2002, 2003, 2004, 2005, 2006
Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* POSIX 1003.1-2001 (and later) with XSI */
#include "fsusage.h"
#include <limits.h>
#include <sys/types.h>
#include <sys/statvfs.h>
/* The results of open() in this file are not used with fchdir,
therefore save some unnecessary work in fchdir.c. */
#undef open
#undef close
/* Many space usage primitives use all 1 bits to denote a value that is
not applicable or unknown. Propagate this information by returning
a uintmax_t value that is all 1 bits if X is all 1 bits, even if X
is unsigned and narrower than uintmax_t. */
#define PROPAGATE_ALL_ONES(x) \
((sizeof (x) < sizeof (uintmax_t) \
&& (~ (x) == (sizeof (x) < sizeof (int) \
? - (1 << (sizeof (x) * CHAR_BIT)) \
: 0))) \
? UINTMAX_MAX : (uintmax_t) (x))
/* Extract the top bit of X as an uintmax_t value. */
#define EXTRACT_TOP_BIT(x) ((x) \
& ((uintmax_t) 1 << (sizeof (x) * CHAR_BIT - 1)))
/* If a value is negative, many space usage primitives store it into an
integer variable by assignment, even if the variable's type is unsigned.
So, if a space usage variable X's top bit is set, convert X to the
uintmax_t value V such that (- (uintmax_t) V) is the negative of
the original value. If X's top bit is clear, just yield X.
Use PROPAGATE_TOP_BIT if the original value might be negative;
otherwise, use PROPAGATE_ALL_ONES. */
#define PROPAGATE_TOP_BIT(x) ((x) | ~ (EXTRACT_TOP_BIT (x) - 1))
/* Fill in the fields of FSP with information about space usage for
the file system on which FILE resides.
DISK is the device on which FILE is mounted, for space-getting
methods that need to know it.
Return 0 if successful, -1 if not. When returning -1, ensure that
ERRNO is either a system error value, or zero if DISK is NULL
on a system that requires a non-NULL value. */
int get_fs_usage (char const *file, char const *disk, struct fs_usage *fsp) {
(void)disk;
struct statvfs fsd;
if (statvfs (file, &fsd) < 0)
return -1;
/* f_frsize isn't guaranteed to be supported. */
fsp->fsu_blocksize = (fsd.f_frsize
? PROPAGATE_ALL_ONES (fsd.f_frsize)
: PROPAGATE_ALL_ONES (fsd.f_bsize));
fsp->fsu_blocks = PROPAGATE_ALL_ONES (fsd.f_blocks);
fsp->fsu_bfree = PROPAGATE_ALL_ONES (fsd.f_bfree);
fsp->fsu_bavail = PROPAGATE_TOP_BIT (fsd.f_bavail);
fsp->fsu_bavail_top_bit_set = EXTRACT_TOP_BIT (fsd.f_bavail) != 0;
fsp->fsu_files = PROPAGATE_ALL_ONES (fsd.f_files);
fsp->fsu_ffree = PROPAGATE_ALL_ONES (fsd.f_ffree);
return 0;
}
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