/* loopback.c - command to add loopback devices.  */
/*
 *  VAS_EBOOT  --  GRand Unified Bootloader
 *  Copyright (C) 2005,2006,2007  Free Software Foundation, Inc.
 *
 *  VAS_EBOOT 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 3 of the License, or
 *  (at your option) any later version.
 *
 *  VAS_EBOOT 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 VAS_EBOOT.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <VasEBoot/dl.h>
#include <VasEBoot/misc.h>
#include <VasEBoot/file.h>
#include <VasEBoot/disk.h>
#include <VasEBoot/mm.h>
#include <VasEBoot/extcmd.h>
#include <VasEBoot/i18n.h>
#include <VasEBoot/safemath.h>

VAS_EBOOT_MOD_LICENSE ("GPLv3+");

struct VasEBoot_loopback
{
  char *devname;
  VasEBoot_file_t file;
  struct VasEBoot_loopback *next;
  unsigned long id;
  VasEBoot_uint64_t refcnt;
};

static struct VasEBoot_loopback *loopback_list;
static unsigned long last_id = 0;

static const struct VasEBoot_arg_option options[] =
  {
    /* TRANSLATORS: The disk is simply removed from the list of available ones,
       not wiped, avoid to scare user.  */
    {"delete", 'd', 0, N_("Delete the specified loopback drive."), 0, 0},
    {"decompress", 'D', 0, N_("Transparently decompress backing file."), 0, 0},
    {0, 0, 0, 0, 0, 0}
  };

/* Delete the loopback device NAME.  */
static VasEBoot_err_t
delete_loopback (const char *name)
{
  struct VasEBoot_loopback *dev;
  struct VasEBoot_loopback **prev;

  /* Search for the device.  */
  for (dev = loopback_list, prev = &loopback_list;
       dev;
       prev = &dev->next, dev = dev->next)
    if (VasEBoot_strcmp (dev->devname, name) == 0)
      break;

  if (! dev)
    return VasEBoot_error (VAS_EBOOT_ERR_BAD_DEVICE, "device not found");

  if (dev->refcnt > 0)
    return VasEBoot_error (VAS_EBOOT_ERR_STILL_REFERENCED, "device still referenced");
  /* Remove the device from the list.  */
  *prev = dev->next;

  VasEBoot_free (dev->devname);
  VasEBoot_file_close (dev->file);
  VasEBoot_free (dev);

  return 0;
}

/* The command to add and remove loopback devices.  */
static VasEBoot_err_t
VasEBoot_cmd_loopback (VasEBoot_extcmd_context_t ctxt, int argc, char **args)
{
  struct VasEBoot_arg_list *state = ctxt->state;
  VasEBoot_file_t file;
  enum VasEBoot_file_type type = VAS_EBOOT_FILE_TYPE_LOOPBACK;
  struct VasEBoot_loopback *newdev;
  VasEBoot_err_t ret;

  if (argc < 1)
    return VasEBoot_error (VAS_EBOOT_ERR_BAD_ARGUMENT, "device name required");

  /* Check if `-d' was used.  */
  if (state[0].set)
    return delete_loopback (args[0]);

  if (!state[1].set)
    type |= VAS_EBOOT_FILE_TYPE_NO_DECOMPRESS;

  if (argc < 2)
    return VasEBoot_error (VAS_EBOOT_ERR_BAD_ARGUMENT, N_("filename expected"));

  /* Check that a device with requested name does not already exist. */
  for (newdev = loopback_list; newdev; newdev = newdev->next)
    if (VasEBoot_strcmp (newdev->devname, args[0]) == 0)
      return VasEBoot_error (VAS_EBOOT_ERR_BAD_ARGUMENT, "device name already exists");

  file = VasEBoot_file_open (args[1], type);
  if (! file)
    return VasEBoot_errno;

  /* Unable to replace it, make a new entry.  */
  newdev = VasEBoot_malloc (sizeof (struct VasEBoot_loopback));
  if (! newdev)
    goto fail;

  newdev->devname = VasEBoot_strdup (args[0]);
  if (! newdev->devname)
    {
      VasEBoot_free (newdev);
      goto fail;
    }

  newdev->file = file;
  newdev->id = last_id++;
  newdev->refcnt = 0;

  /* Add the new entry to the list.  */
  newdev->next = loopback_list;
  loopback_list = newdev;

  return 0;

fail:
  ret = VasEBoot_errno;
  VasEBoot_file_close (file);
  return ret;
}


static int
VasEBoot_loopback_iterate (VasEBoot_disk_dev_iterate_hook_t hook, void *hook_data,
		       VasEBoot_disk_pull_t pull)
{
  struct VasEBoot_loopback *d;
  if (pull != VAS_EBOOT_DISK_PULL_NONE)
    return 0;
  for (d = loopback_list; d; d = d->next)
    {
      if (hook (d->devname, hook_data))
	return 1;
    }
  return 0;
}

static VasEBoot_err_t
VasEBoot_loopback_open (const char *name, VasEBoot_disk_t disk)
{
  struct VasEBoot_loopback *dev;

  for (dev = loopback_list; dev; dev = dev->next)
    if (VasEBoot_strcmp (dev->devname, name) == 0)
      break;

  if (! dev)
    return VasEBoot_error (VAS_EBOOT_ERR_UNKNOWN_DEVICE, "can't open device");

  if (VasEBoot_add (dev->refcnt, 1, &dev->refcnt))
    VasEBoot_fatal ("Reference count overflow");

  /* Use the filesize for the disk size, round up to a complete sector.  */
  if (dev->file->size != VAS_EBOOT_FILE_SIZE_UNKNOWN)
    disk->total_sectors = ((dev->file->size + VAS_EBOOT_DISK_SECTOR_SIZE - 1)
			   / VAS_EBOOT_DISK_SECTOR_SIZE);
  else
    disk->total_sectors = VAS_EBOOT_DISK_SIZE_UNKNOWN;
  /* Avoid reading more than 512M.  */
  disk->max_agglomerate = 1 << (29 - VAS_EBOOT_DISK_SECTOR_BITS
				- VAS_EBOOT_DISK_CACHE_BITS);

  disk->id = dev->id;

  disk->data = dev;

  return 0;
}

static void
VasEBoot_loopback_close (VasEBoot_disk_t disk)
{
  struct VasEBoot_loopback *dev = disk->data;

  if (VasEBoot_sub (dev->refcnt, 1, &dev->refcnt))
    VasEBoot_fatal ("Reference count underflow");
}

static VasEBoot_err_t
VasEBoot_loopback_read (VasEBoot_disk_t disk, VasEBoot_disk_addr_t sector,
		    VasEBoot_size_t size, char *buf)
{
  VasEBoot_file_t file = ((struct VasEBoot_loopback *) disk->data)->file;
  VasEBoot_off_t pos;

  VasEBoot_file_seek (file, sector << VAS_EBOOT_DISK_SECTOR_BITS);

  VasEBoot_file_read (file, buf, size << VAS_EBOOT_DISK_SECTOR_BITS);
  if (VasEBoot_errno)
    return VasEBoot_errno;

  /* In case there is more data read than there is available, in case
     of files that are not a multiple of VAS_EBOOT_DISK_SECTOR_SIZE, fill
     the rest with zeros.  */
  pos = (sector + size) << VAS_EBOOT_DISK_SECTOR_BITS;
  if (pos > file->size)
    {
      VasEBoot_size_t amount = pos - file->size;
      VasEBoot_memset (buf + (size << VAS_EBOOT_DISK_SECTOR_BITS) - amount, 0, amount);
    }

  return 0;
}

static VasEBoot_err_t
VasEBoot_loopback_write (VasEBoot_disk_t disk __attribute ((unused)),
		     VasEBoot_disk_addr_t sector __attribute ((unused)),
		     VasEBoot_size_t size __attribute ((unused)),
		     const char *buf __attribute ((unused)))
{
  return VasEBoot_error (VAS_EBOOT_ERR_NOT_IMPLEMENTED_YET,
		     "loopback write is not supported");
}

static struct VasEBoot_disk_dev VasEBoot_loopback_dev =
  {
    .name = "loopback",
    .id = VAS_EBOOT_DISK_DEVICE_LOOPBACK_ID,
    .disk_iterate = VasEBoot_loopback_iterate,
    .disk_open = VasEBoot_loopback_open,
    .disk_close = VasEBoot_loopback_close,
    .disk_read = VasEBoot_loopback_read,
    .disk_write = VasEBoot_loopback_write,
    .next = 0
  };

static VasEBoot_extcmd_t cmd;

VAS_EBOOT_MOD_INIT(loopback)
{
  cmd = VasEBoot_register_extcmd ("loopback", VasEBoot_cmd_loopback, 0,
			      N_("[-d] [-D] DEVICENAME FILE."),
			      /* TRANSLATORS: The file itself is not destroyed
				 or transformed into drive.  */
			      N_("Make a virtual drive from a file."), options);
  VasEBoot_disk_dev_register (&VasEBoot_loopback_dev);
}

VAS_EBOOT_MOD_FINI(loopback)
{
  VasEBoot_unregister_extcmd (cmd);
  VasEBoot_disk_dev_unregister (&VasEBoot_loopback_dev);
}