dlls/netapi32/nbnamecache.c

   1 /* Copyright (c) 2003 Juan Lang
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public
   5  * License as published by the Free Software Foundation; either
   6  * version 2.1 of the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  16  *
  17  * This implementation uses a linked list, because I don't have a decent
  18  * hash table implementation handy.  This is somewhat inefficient, but it's
  19  * rather more efficient than not having a name cache at all.
  20  */
  21
  22 #include "wine/debug.h"
  23 #include "nbnamecache.h"
  24
  25 WINE_DEFAULT_DEBUG_CHANNEL(netbios);
  26
  27 typedef struct _NBNameCacheNode
  28 {
  29     DWORD expireTime;
  30     NBNameCacheEntry *entry;
  31     struct _NBNameCacheNode *next;
  32 } NBNameCacheNode;
  33
  34 struct NBNameCache
  35 {
  36     HANDLE heap;
  37     CRITICAL_SECTION cs;
  38     DWORD entryExpireTimeMS;
  39     NBNameCacheNode *head;
  40 };
  41
  42 /* Unlinks the node pointed to by *prev, and frees any associated memory.
  43  * If that node's next pointed to another node, *prev now points to it.
  44  * Assumes the caller owns cache's lock.
  45  */
  46 static void NBNameCacheUnlinkNode(struct NBNameCache *cache,
  47  NBNameCacheNode **prev)
  48 {
  49     if (cache && prev && *prev)
  50     {
  51         NBNameCacheNode *next = (*prev)->next;
  52
  53         if ((*prev)->entry)
  54             HeapFree(cache->heap, 0, (*prev)->entry);
  55         HeapFree(cache->heap, 0, *prev);
  56         *prev = next;
  57     }
  58 }
  59
  60 /* Walks the list beginning with cache->head looking for the node with name
  61  * name.  If the node is found, returns a pointer to the next pointer of the
  62  * node _prior_ to the found node (or head if head points to it).  Thus, if the
  63  * node's all you want, dereference the return value twice.  If you want to
  64  * modify the list, modify the referent of the return value.
  65  * While it's at it, deletes nodes whose time has expired (except the node
  66  * you're looking for, of course).
  67  * Returns NULL if the node isn't found.
  68  * Assumes the caller owns cache's lock.
  69  */
  70 static NBNameCacheNode **NBNameCacheWalk(struct NBNameCache *cache,
  71  const char name[NCBNAMSZ])
  72 {
  73     NBNameCacheNode **ret = NULL;
  74
  75     if (cache && cache->head)
  76     {
  77         NBNameCacheNode **ptr;
  78
  79         ptr = &cache->head;
  80         while (ptr && *ptr && (*ptr)->entry)
  81         {
  82             if (!memcmp((*ptr)->entry->name, name, NCBNAMSZ - 1))
  83                 ret = ptr;
  84             else
  85             {
  86                 if (GetTickCount() > (*ptr)->expireTime)
  87                     NBNameCacheUnlinkNode(cache, ptr);
  88             }
  89             if (*ptr)
  90                 ptr = &(*ptr)->next;
  91         }
  92     }
  93     return ret;
  94 }
  95
  96 struct NBNameCache *NBNameCacheCreate(HANDLE heap, DWORD entryExpireTimeMS)
  97 {
  98     struct NBNameCache *cache;
  99
 100
 101     if (!heap)
 102         heap = GetProcessHeap();
 103     cache = (struct NBNameCache *)HeapAlloc(heap, 0,
 104      sizeof(struct NBNameCache));
 105     if (cache)
 106     {
 107         cache->heap = heap;
 108         InitializeCriticalSection(&cache->cs);
 109         cache->entryExpireTimeMS = entryExpireTimeMS;
 110         cache->head = NULL;
 111     }
 112     return cache;
 113 }
 114
 115 BOOL NBNameCacheAddEntry(struct NBNameCache *cache, NBNameCacheEntry *entry)
 116 {
 117     BOOL ret;
 118
 119     if (cache && entry)
 120     {
 121         NBNameCacheNode **node;
 122
 123         EnterCriticalSection(&cache->cs);
 124         node = NBNameCacheWalk(cache, entry->name);
 125         if (node)
 126         {
 127             (*node)->expireTime = GetTickCount() +
 128              cache->entryExpireTimeMS;
 129             HeapFree(cache->heap, 0, (*node)->entry);
 130             (*node)->entry = entry;
 131             ret = TRUE;
 132         }
 133         else
 134         {
 135             NBNameCacheNode *newNode = (NBNameCacheNode *)HeapAlloc(
 136              cache->heap, 0, sizeof(NBNameCacheNode));
 137             if (newNode)
 138             {
 139                 newNode->expireTime = GetTickCount() +
 140                  cache->entryExpireTimeMS;
 141                 newNode->entry = entry;
 142                 newNode->next = cache->head;
 143                 cache->head = newNode;
 144                 ret = TRUE;
 145             }
 146             else
 147                 ret = FALSE;
 148         }
 149         LeaveCriticalSection(&cache->cs);
 150     }
 151     else
 152         ret = FALSE;
 153     return ret;
 154 }
 155
 156 const NBNameCacheEntry *NBNameCacheFindEntry(struct NBNameCache *cache,
 157  const UCHAR name[NCBNAMSZ])
 158 {
 159     const NBNameCacheEntry *ret;
 160     UCHAR printName[NCBNAMSZ];
 161
 162     memcpy(printName, name, NCBNAMSZ - 1);
 163     printName[NCBNAMSZ - 1] = '\0';
 164     if (cache)
 165     {
 166         NBNameCacheNode **node;
 167
 168         EnterCriticalSection(&cache->cs);
 169         node = NBNameCacheWalk(cache, name);
 170         if (node)
 171             ret = (*node)->entry;
 172         else
 173             ret = NULL;
 174         LeaveCriticalSection(&cache->cs);
 175     }
 176     else
 177         ret = NULL;
 178     return ret;
 179 }
 180
 181 BOOL NBNameCacheUpdateNBName(struct NBNameCache *cache,
 182  const UCHAR name[NCBNAMSZ], const UCHAR nbname[NCBNAMSZ])
 183 {
 184     BOOL ret;
 185
 186     if (cache)
 187     {
 188         NBNameCacheNode **node;
 189
 190         EnterCriticalSection(&cache->cs);
 191         node = NBNameCacheWalk(cache, name);
 192         if (node && *node && (*node)->entry)
 193         {
 194             memcpy((*node)->entry->nbname, nbname, NCBNAMSZ);
 195             ret = TRUE;
 196         }
 197         else
 198             ret = FALSE;
 199         LeaveCriticalSection(&cache->cs);
 200     }
 201     else
 202         ret = FALSE;
 203     return ret;
 204 }
 205
 206 void NBNameCacheDestroy(struct NBNameCache *cache)
 207 {
 208     if (cache)
 209     {
 210         DeleteCriticalSection(&cache->cs);
 211         while (cache->head)
 212             NBNameCacheUnlinkNode(cache, &cache->head);
 213         HeapFree(cache->heap, 0, cache);
 214     }
 215 }