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/*
Copyright (C) 1995, 1996, 1997, 1999 Free Software Foundation, Inc.
Written by Michael I. Bushnell, p/BSG.
This file is part of the GNU Hurd.
The GNU Hurd 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, or (at
your option) any later version.
The GNU Hurd 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, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA. */
#include "netfs.h"
#include "io_S.h"
#include <fcntl.h>
#include <sys/mman.h>
error_t
netfs_S_io_read (struct protid *user,
char **data,
mach_msg_type_number_t *datalen,
off_t offset,
mach_msg_type_number_t amount)
{
error_t err;
off_t start;
struct node *node;
int alloced = 0;
if (!user)
return EOPNOTSUPP;
node = user->po->np;
mutex_lock (&user->po->np->lock);
if ((user->po->openstat & O_READ) == 0)
{
mutex_unlock (&node->lock);
return EBADF;
}
if (amount > *datalen)
{
alloced = 1;
*data = mmap (0, amount, PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
}
*datalen = amount;
start = (offset == -1 ? user->po->filepointer : offset);
if (start < 0)
err = EINVAL;
else if (S_ISLNK (node->nn_stat.st_mode))
/* Read from a symlink. */
{
off_t size = node->nn_stat.st_size;
if (start + amount > size)
amount = size - start;
if (amount > size)
amount = size;
if (start >= size)
{
*datalen = 0;
err = 0;
}
else if (amount < size || start > 0)
{
char *whole_link = alloca (size);
err = netfs_attempt_readlink (user->user, node, whole_link);
if (! err)
{
memcpy (*data, whole_link + start, amount);
*datalen = amount;
}
}
else
{
err = netfs_attempt_readlink (user->user, node, *data);
*datalen = amount;
}
}
else
/* Read from a normal file. */
err = netfs_attempt_read (user->user, node, start, datalen, *data);
if (offset == -1 && !err)
user->po->filepointer += *datalen;
mutex_unlock (&node->lock);
if (err && alloced)
munmap (*data, amount);
if (!err && alloced && (round_page (*datalen) < round_page (amount)))
munmap (*data + round_page (*datalen),
round_page (amount) - round_page (*datalen));
return err;
}
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