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/* Copyright (C) 2009 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 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.
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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <limits.h>
#include <stdbool.h>
#include <sys/param.h>
#if __WORDSIZE == 64 && !defined PREADV
/* Hide the preadv64 declaration. */
# define preadv64 __redirect_preadv64
#endif
#include <sys/uio.h>
#include <bits/wordsize.h>
#ifndef PREADV
# define PREADV preadv
# define PREAD __pread
# define OFF_T off_t
#endif
static void
ifree (char **ptrp)
{
free (*ptrp);
}
/* Read data from file descriptor FD at the given position OFFSET
without change the file pointer, and put the result in the buffers
described by VECTOR, which is a vector of COUNT 'struct iovec's.
The buffers are filled in the order specified. Operates just like
'pread' (see <unistd.h>) except that data are put in VECTOR instead
of a contiguous buffer. */
ssize_t
PREADV (int fd, const struct iovec *vector, int count, OFF_T offset)
{
/* Find the total number of bytes to be read. */
size_t bytes = 0;
for (int i = 0; i < count; ++i)
{
/* Check for ssize_t overflow. */
if (SSIZE_MAX - bytes < vector[i].iov_len)
{
__set_errno (EINVAL);
return -1;
}
bytes += vector[i].iov_len;
}
/* Allocate a temporary buffer to hold the data. We should normally
use alloca since it's faster and does not require synchronization
with other threads. But we cannot if the amount of memory
required is too large. */
char *buffer;
char *malloced_buffer __attribute__ ((__cleanup__ (ifree))) = NULL;
if (__libc_use_alloca (bytes))
buffer = (char *) __alloca (bytes);
else
{
malloced_buffer = buffer = (char *) malloc (bytes);
if (buffer == NULL)
return -1;
}
/* Read the data. */
ssize_t bytes_read = PREAD (fd, buffer, bytes, offset);
if (bytes_read < 0)
return -1;
/* Copy the data from BUFFER into the memory specified by VECTOR. */
bytes = bytes_read;
for (int i = 0; i < count; ++i)
{
size_t copy = MIN (vector[i].iov_len, bytes);
(void) memcpy ((void *) vector[i].iov_base, (void *) buffer, copy);
buffer += copy;
bytes -= copy;
if (bytes == 0)
break;
}
return bytes_read;
}
#if __WORDSIZE == 64 && defined preadv64
# undef preadv64
strong_alias (preadv, preadv64)
#endif
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