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/* readv supports all Linux kernels >= 2.0.
Copyright (C) 1997 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
read to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <errno.h>
#include <stddef.h>
#include <sys/param.h>
#include <sys/uio.h>
extern ssize_t __syscall_readv __P ((int, __const struct iovec *, int));
/* Not all versions of the kernel support the large number of records. */
#undef MAX_IOVEC
#ifdef UIO_FASTIOV
# define MAX_IOVEC UIO_FASTIOV
#else
# define MAX_IOVEC 8 /* 8 is a safe number. */
#endif
/* We should deal with kernel which have a smaller UIO_MAXIOV as well
as a very big count. */
ssize_t
readv (fd, vector, count)
int fd;
const struct iovec *vector;
int count;
{
int errno_saved = errno;
ssize_t bytes_read;
bytes_read = __syscall_readv (fd, vector, count);
if (bytes_read < 0 && errno == EINVAL && count > MAX_IOVEC)
{
int i;
/* Restore the old error value as if nothing happened. */
__set_errno (errno_saved);
bytes_read = 0;
for (i = 0; i < count; i += MAX_IOVEC)
{
ssize_t bytes = __syscall_readv (fd, vector + i,
MIN (count - i, MAX_IOVEC));
if (bytes < 0)
return bytes;
bytes_read += bytes;
}
}
return bytes_read;
}
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