/* 
   Copyright (C) 1994 Free Software Foundation

   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 2, 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */

#include "priv.h"

/* Implement io_read as described in <hurd/io.defs>. */
error_t
diskfs_S_io_read (struct protid *cred,
		  char **data,
		  unsigned int *datalen,
		  off_t offset,
		  int maxread)
{
  struct node *np;
  int err;
  int off = offset;
  char *buf;
  int ourbuf = 0;

  if (!cred)
    return EOPNOTSUPP;
  
  np = cred->po->np;
  if (!(cred->po->openstat & O_READ))
    return EBADF;
  if (maxread < 0)
    return EINVAL;
  
  mutex_lock (&np->i_toplock);

  err = ioserver_get_conch (&np->i_conch);
  if (err)
    goto out;
  
  if (off == -1)
    off = cred->po->filepointer;
  
  if (off + maxread > np->dn_stat.st_size)
    maxread = np->dn_stat.st_size - off;
  
  if (maxread > *datalen)
    {
      ourbuf = 1;
      vm_allocate (mach_task_self (), (u_int *) &buf, maxread, 1);
      *data = buf;
    }
  else
    buf = *data;

  *datalen = maxread;
  if (maxread)
    err = _diskfs_rdwr_internal (np, buf, off, maxread, 0);
  else
    err = 0;
  if (offset == -1 && !err)
    cred->po->filepointer += *datalen;
  if (err && ourbuf)
    vm_deallocate (mach_task_self (), (u_int) buf, maxread);
  
 out:
  mutex_unlock (&np->i_toplock);
  return err;
}