path: root/ftpfs/ccache.c

/* Remote file contents caching

   Copyright (C) 1997 Free Software Foundation, Inc.
   Written by Miles Bader <miles@gnu.ai.mit.edu>
   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 <unistd.h>
#include <string.h>

#include <hurd/netfs.h>

#include "ccache.h"

#define READ_CHUNK_SIZE   (8*1024)
#define ALLOC_CHUNK_SIZE  (64*1024)

/* Read LEN bytes at OFFS in the file referred to by CC into DATA, or return
   an error.  */
error_t
ccache_read (struct ccache *cc, off_t offs, size_t len, void *data)
{
  error_t err = 0;
  size_t max = offs + len;

  mutex_lock (&cc->lock);

  if (max > cc->size)
    max = cc->size;

  while (cc->max < max && !err)
    {
      if (cc->fetching_active)
	/* Some thread is fetching data, so just let it do its thing, but get
	   a wakeup call when it's done.  */
	{
	  if (hurd_condition_wait (&cc->wakeup, &cc->lock))
	    err = EINTR;
	}
      else
	{
	  int re_connected = 0;
	  struct netnode *nn = cc->node->nn;

	  cc->fetching_active = 1;

	  while (cc->max < max && !err)
	    {
	      mutex_unlock (&cc->lock);

	      if (! cc->conn)
		/* We need to setup a connection to fetch data over.  */
		{
		  err = ftpfs_get_ftp_conn (nn->fs, &cc->conn);
		  if (! err)
		    {
		      err = ftp_conn_start_retrieve (cc->conn, nn->rmt_path,
						     &cc->data_conn);
		      if (err == ENOENT)
			err = ESTALE;
		      if (err)
			{
			  ftpfs_release_ftp_conn (nn->fs, cc->conn);
			  cc->conn = 0;
			}
		      else
			cc->data_conn_pos = 0;
		    }
		  re_connected = 1;
		}

	      if (! err)
		/* Try and read some data over the connection.  */
		{
		  size_t new_end = cc->max + READ_CHUNK_SIZE;

		  if (new_end > cc->size)
		    new_end = cc->size;

		  if (new_end > cc->alloced)
		    /* Make some room in memory for the new part of the
		       image.  */
		    {
		      size_t alloc_end = cc->alloced + ALLOC_CHUNK_SIZE;

		      if (alloc_end < new_end)
			alloc_end = new_end;
		      else if (alloc_end > cc->size)
			alloc_end = cc->size;

		      if (cc->alloced == 0)
			{
			  vm_address_t addr = 0;
			  err = vm_allocate (mach_task_self (),
					     &addr, alloc_end, 1);
			  if (! err)
			    cc->image = (char *)addr;
			}
		      else
			{
			  vm_address_t addr =
			    (vm_address_t)cc->image + cc->alloced;
			  err = vm_allocate (mach_task_self (),
					     &addr, alloc_end - cc->alloced,
					     0);
			  if (err == EKERN_NO_SPACE)
			    /* Gack.  We've goota move the whole splooge.  */
			    {
			      addr = 0;
			      err = vm_allocate (mach_task_self (),
						 &addr, alloc_end, 1);
			      if (! err)
				/* That worked; copy what's already-fetched. */
				{
				  bcopy (cc->image, (void *)addr, cc->max);
				  vm_deallocate (mach_task_self (),
						 (vm_address_t)cc->image,
						 cc->alloced);
				  cc->image = (char *)addr;
				}
			    }
			}
		      if (! err)
			cc->alloced = alloc_end;
		    }

		  if (! err)
		    {
		      ssize_t rd =
			read (cc->data_conn,
			      cc->image + cc->data_conn_pos,
			      new_end - cc->data_conn_pos);
		      if (rd < 0)
			err = errno;
		      else if (rd == 0)
			/* EOF.  This either means the file changed size, or
			   our data-connection got closed; we just try to
			   open the connection a second time, and then if
			   that fails, assume the size changed.  */
			{
			  if (re_connected)
			    err = EIO; /* Something's fucked */
			  else
			    /* Try opening the connection again.  */
			    {
			      close (cc->data_conn);
			      ftp_conn_finish_transfer (cc->conn);
			      ftpfs_release_ftp_conn (nn->fs, cc->conn);
			      cc->conn = 0;
			    }
			}
		      else
			{
			  cc->max += rd;
			  cc->data_conn_pos += rd;
			}
		    }
		}

	      mutex_lock (&cc->lock);

	      if (cc->max < max && !err)
		/* If anyone's waiting for data, let them look (if we're done
		   fetching, this gets delayed until below).  */
		condition_broadcast (&cc->wakeup);
	    }

	  if (!err && cc->conn && cc->max == cc->size)
	    /* We're finished reading all data, close the data connection.  */
	    {
	      close (cc->data_conn);
	      ftp_conn_finish_transfer (cc->conn);
	      ftpfs_release_ftp_conn (nn->fs, cc->conn);
	      cc->conn = 0;
	    }

	  /* We're done, error or no.  */
	  cc->fetching_active = 0;

	  /* Let others know something's going on.  */
	  condition_broadcast (&cc->wakeup);
	}
    }

  if (! err)
    bcopy (cc->image + offs, data, max - offs);

  mutex_unlock (&cc->lock);

  return err;
}

/* Discard any cached contents in CC.  */
error_t
ccache_invalidate (struct ccache *cc)
{
  error_t err = 0;

  mutex_lock (&cc->lock);

  while  (cc->fetching_active && !err)
    /* Some thread is fetching data, so just let it do its thing, but get
       a wakeup call when it's done.  */
    {
      if (hurd_condition_wait (&cc->wakeup, &cc->lock))
	err = EINTR;
    }

  if (! err)
    {
      if (cc->alloced > 0)
	{
	  vm_deallocate (mach_task_self (),
			 (vm_address_t)cc->image, cc->alloced);
	  cc->image = 0;
	  cc->alloced = 0;
	  cc->max = 0;
	}
      if (cc->conn)
	{
	  close (cc->data_conn);
	  ftp_conn_finish_transfer (cc->conn);
	  ftpfs_release_ftp_conn (cc->node->nn->fs, cc->conn);
	  cc->conn = 0;
	}
    }

  mutex_unlock (&cc->lock);

  return err;
}

/* Return a ccache object for NODE in CC.  */
error_t
ccache_create (struct node *node, struct ccache **cc)
{
  struct ccache *new = malloc (sizeof (struct ccache));

  if (! new)
    return ENOMEM;

  new->node = node;
  new->image = 0;
  new->size = node->nn_stat.st_size;
  new->max = 0;
  new->alloced = 0;
  mutex_init (&new->lock);
  condition_init (&new->wakeup);
  new->fetching_active = 0;
  new->conn = 0;
  new->data_conn = -1;

  *cc = new;

  return 0;
}

/* Free all resources used by CC.  */
void
ccache_free (struct ccache *cc)
{
  if (cc->alloced > 0)
    vm_deallocate (mach_task_self (), (vm_address_t)cc->image, cc->alloced);
  if (cc->data_conn >= 0)
    close (cc->data_conn);
  if (cc->conn)
    {
      ftp_conn_finish_transfer (cc->conn);
      ftpfs_release_ftp_conn (cc->node->nn->fs, cc->conn);
    }
  free (cc);
}