source: trunk/kernel/libk/htab.c @ 563

Last change on this file since 563 was 563, checked in by alain, 3 years ago

Complete restructuration of kernel spinlocks.

File size: 5.9 KB
Line 
1/*
2 * htable.c - Generic, embedded hash table implementation.
3 *
4 * Author      Alain Greiner (2016,2017)
5 *
6 * Copyright (c) UPMC Sorbonne Universites
7 *
8 * This file is part of ALMOS-MKH.
9 *
10 * ALMOS-MKH is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; version 2.0 of the License.
13 *
14 * ALMOS-MKH is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with ALMOS-MKH; if not, write to the Free Software Foundation,
21 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24#include <kernel_config.h>
25#include <hal_kernel_types.h>
26#include <hal_special.h>
27#include <htab.h>
28#include <busylock.h>
29#include <list.h>
30#include <printk.h>
31#include <vfs.h>
32
33
34///////////////////////////////////////////////////////////////////////////////////////////
35//    Item type specific (static) functions (two functions for each item type).
36// Example below if for <vhs_inode_t>, where the identifier is the inum field.
37///////////////////////////////////////////////////////////////////////////////////////////
38
39///////////////////////////////////////////////////////////////////////////////////////////
40// These static functions compute the hash index from the key.
41///////////////////////////////////////////////////////////////////////////////////////////
42// @ key      : local pointer on key.
43// @ return the index value, from 0 to (HASHTAB_SIZE - 1)
44///////////////////////////////////////////////////////////////////////////////////////////
45static uint32_t htab_inode_index( void * key )
46{
47        uint32_t * inum = key;
48        return (((*inum) >> 16) ^ ((*inum) & 0xFFFF)) % HASHTAB_SIZE;
49}
50
51///////////////////////////////////////////////////////////////////////////////////////
52// These static functions are used by htab_lookup(), htab_insert(), and htab_remove().
53// They scan one sub-list identified by  <index> to find an item  identified by <key>.
54// The sub-list is not modified, but the lock must have been taken by the caller.
55///////////////////////////////////////////////////////////////////////////////////////
56// @ htab    : pointer on hash table.
57// @ index   : index of sub-list to be scanned.
58// @ key     : pointer on item identifier.
59// @ return pointer on item if found / return NULL if not found.
60///////////////////////////////////////////////////////////////////////////////////////
61static void * htab_inode_scan( htab_t  * htab,
62                               uint32_t  index,
63                               void    * key )
64{
65    list_entry_t * list_entry;   // pointer on list_entry_t (iterator)
66    vfs_inode_t  * inode;        // pointer on item
67   
68        LIST_FOREACH( &htab->roots[index] , list_entry )
69        {
70        inode = (vfs_inode_t *)LIST_ELEMENT( list_entry , vfs_inode_t , list );
71        if( inode->inum == *(uint32_t *)key ) return inode; 
72    }
73
74    // no matching item found
75        return NULL;
76}
77
78////////////////////////////////////////////////////////////////////////////////////////
79//         Generic access functions
80////////////////////////////////////////////////////////////////////////////////////////
81
82////////////////////////////////////////
83void htab_init( htab_t           * htab,
84                htab_item_type_t   type )
85{
86        uint32_t     i;
87
88    // initialize readlock
89    busylock_init( &htab->lock , LOCK_HTAB_STATE );
90
91    htab->items = 0;
92
93    if( type == HTAB_INODE_TYPE )
94    {
95        htab->scan    = &htab_inode_scan;
96        htab->index   = &htab_inode_index;
97    }
98    else
99    {
100        assert( false , "undefined item type\n" );
101    }
102
103    // initialize partial lists
104    for( i = 0 ; i < HASHTAB_SIZE ; i++ )
105    {
106        list_root_init( &htab->roots[i] );
107    }
108}
109
110/////////////////////////////////////////
111error_t htab_insert( htab_t       * htab, 
112                     void         * key,
113                     list_entry_t * list_entry )
114{
115    // compute index from key
116    uint32_t index = htab->index( key );
117
118    // take the lock
119    busylock_acquire( &htab->lock );
120
121    // scan sub-list to check if item exist
122    void * item = htab->scan( htab , index , key );
123
124    if( item != NULL ) // item exist => return error
125    {
126        // release lock
127        busylock_release( &htab->lock );
128
129        return 0xFFFFFFFF;
130    }
131    else               // item doesn't exist => register
132    {
133        // register item in hash table
134        list_add_last( &htab->roots[index] , list_entry );
135
136        // update items number
137        htab->items++;
138
139        // release lock
140        busylock_release( &htab->lock );
141
142        return 0;
143    }
144}
145
146/////////////////////////////////////////
147error_t htab_remove( htab_t       * htab, 
148                     void         * key,
149                     list_entry_t * list_entry )
150{
151    // compute index from key
152    uint32_t index = htab->index( key );
153
154    // take the lock
155    busylock_acquire( &htab->lock );
156
157    // scan sub-list to chek if item exist
158    void * item = htab->scan( htab , index , key );
159
160    if( item == NULL ) // item doesn't exist
161    {
162        // release lock
163        busylock_release( &htab->lock );
164
165        return 0xFFFFFFFF;
166    }
167    else               // item exist => remove it
168    {
169        // remove item from hash table
170        list_unlink( list_entry );
171
172        // update items number
173        htab->items--;
174
175        // release lock
176        busylock_release( &htab->lock );
177
178        return 0;
179    }
180}
181
182//////////////////////////////////
183void * htab_lookup( htab_t * htab, 
184                    void   * key )
185{
186    // compute index from key
187    uint32_t index = htab->index( key );
188
189    // take the lock
190    busylock_acquire( &htab->lock );
191
192    // scan sub-list
193    void * item = htab->scan( htab , index , key );
194
195    // release lock
196    busylock_release( &htab->lock );
197
198        return item;
199}
200
201
202
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