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/* Map a dev_t device number to a small integer.
Copyright 2009-2010 Free Software Foundation, Inc.
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 3 of the License, 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, see <http://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include <config.h>
#include "dev-map.h"
#include <stdio.h>
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
struct dev_map_ent
{
dev_t dev;
uint32_t mapped_dev;
};
enum { INITIAL_DEV_MAP_TABLE_SIZE = 31 };
static size_t
dev_hash (void const *x, size_t table_size)
{
struct dev_map_ent const *p = x;
return (uintmax_t) p->dev % table_size;
}
/* Compare two dev_map_ent structs on "dev".
Return true if they are the same. */
static bool
dev_compare (void const *x, void const *y)
{
struct dev_map_ent const *a = x;
struct dev_map_ent const *b = y;
return a->dev == b->dev ? true : false;
}
/* Initialize state. */
int
dev_map_init (struct dev_map *dev_map)
{
assert (dev_map != NULL);
dev_map->n_device = 0;
dev_map->dev_map = hash_initialize (INITIAL_DEV_MAP_TABLE_SIZE, NULL,
dev_hash, dev_compare, free);
return dev_map->dev_map ? 0 : -1;
}
void
dev_map_free (struct dev_map *dev_map)
{
hash_free (dev_map->dev_map);
}
/* Insert device number, DEV, into the map, DEV_MAP if it's not there already,
and return the nonnegative, mapped and usually smaller, number.
If DEV is already in DEV_MAP, return the existing mapped value.
Upon memory allocation failure, return -1. */
int
dev_map_insert (struct dev_map *dev_map, dev_t dev)
{
/* Attempt to insert <DEV,n_device> in the map.
Possible outcomes:
- DEV was already there, with a different necessarily smaller value
- DEV was not there, (thus was just inserted)
- insert failed: out of memory
Return -1 on out of memory.
*/
struct dev_map_ent *ent_from_table;
struct dev_map_ent *ent = malloc (sizeof *ent);
if (!ent)
return -1;
ent->dev = dev;
ent->mapped_dev = dev_map->n_device;
ent_from_table = hash_insert (dev_map->dev_map, ent);
if (ent_from_table == NULL)
{
/* Insertion failed due to lack of memory. */
return -1;
}
if (ent_from_table == ent)
{
/* Insertion succeeded: new device. */
return dev_map->n_device++;
}
/* That DEV value is already in the table, so ENT was not inserted.
Free it and return the already-associated value. */
free (ent);
return ent_from_table->mapped_dev;
}
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