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/*
* libdpkg - Debian packaging suite library routines
* fdio.c - safe file descriptor based input/output
*
* Copyright © 2009-2010 Guillem Jover <guillem@debian.org>
*
* This 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 2 of the License, or
* (at your option) any later version.
*
* This 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/>.
*/
#include <config.h>
#include <compat.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <dpkg/fdio.h>
ssize_t
fd_read(int fd, void *buf, size_t len)
{
ssize_t total = 0;
char *ptr = buf;
while (len > 0) {
ssize_t n;
n = read(fd, ptr + total, len);
if (n == -1) {
if (errno == EINTR || errno == EAGAIN)
continue;
return total ? -total : n;
}
if (n == 0)
break;
total += n;
len -= n;
}
return total;
}
ssize_t
fd_write(int fd, const void *buf, size_t len)
{
ssize_t total = 0;
const char *ptr = buf;
while (len > 0) {
ssize_t n;
n = write(fd, ptr + total, len);
if (n == -1) {
if (errno == EINTR || errno == EAGAIN)
continue;
return total ? -total : n;
}
if (n == 0)
break;
total += n;
len -= n;
}
return total;
}
#ifdef USE_DISK_PREALLOCATE
#ifdef HAVE_F_PREALLOCATE
static void
fd_preallocate_setup(fstore_t *fs, int flags, off_t offset, off_t len)
{
fs->fst_flags = flags;
fs->fst_posmode = F_PEOFPOSMODE;
fs->fst_offset = offset;
fs->fst_length = len;
fs->fst_bytesalloc = 0;
}
#endif
/**
* Request the kernel to allocate the specified size for a file descriptor.
*
* We only want to send a hint that we will be using the requested size. But
* we do not want to unnecessarily write the file contents. That is why we
* are not using posix_fallocate(3) directly if possible, and not at all
* on glibc based systems (except on GNU/kFreeBSD).
*/
int
fd_allocate_size(int fd, off_t offset, off_t len)
{
int rc;
/* Do not preallocate on very small files as that degrades performance
* on some filesystems. */
if (len < (4 * 4096) - 1)
return 0;
#if defined(HAVE_F_PREALLOCATE)
/* On Mac OS X. */
fstore_t fs;
fd_preallocate_setup(&fs, F_ALLOCATECONTIG, offset, len);
rc = fcntl(fd, F_PREALLOCATE, &fs);
if (rc < 0 && errno == ENOSPC) {
/* If we cannot get a contiguous allocation, then try
* non-contiguous. */
fd_preallocate_setup(&fs, F_ALLOCATEALL, offset, len);
rc = fcntl(fd, F_PREALLOCATE, &fs);
}
#elif defined(HAVE_F_ALLOCSP64)
/* On Solaris. */
struct flock64 fl;
fl.l_whence = SEEK_SET;
fl.l_start = offset;
fl.l_len = len;
rc = fcntl(fd, F_ALLOCSP64, &fl);
#elif defined(HAVE_FALLOCATE)
/* On Linux. */
do {
rc = fallocate(fd, 0, offset, len);
} while (rc < 0 && errno == EINTR);
#elif defined(HAVE_POSIX_FALLOCATE) && \
((defined(__GLIBC__) && defined(__FreeBSD_kernel__)) || \
!defined(__GLIBC__))
/*
* On BSDs, newer GNU/kFreeBSD and other non-glibc based systems
* we can use posix_fallocate(2) which should be a simple syscall
* wrapper. But not on other glibc systems, as there the function
* will try to allocate the size by writing a '\0' to each block
* if the syscall is not implemented or not supported by the
* kernel or the filesystem, which we do not want.
*/
rc = posix_fallocate(fd, offset, len);
#else
errno = ENOSYS;
rc = -1;
#endif
return rc;
}
#else
int
fd_allocate_size(int fd, off_t offset, off_t len)
{
errno = ENOSYS;
return -1;
}
#endif
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