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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, 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 "config.h"
  23 #include "wine/port.h"
  24
  25 #include "nbnamecache.h"
  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         HeapFree(cache->heap, 0, (*prev)->entry);
  54         HeapFree(cache->heap, 0, *prev);
  55         *prev = next;
  56     }
  57 }
  58
  59 /* Walks the list beginning with cache->head looking for the node with name
  60  * name.  If the node is found, returns a pointer to the next pointer of the
  61  * node _prior_ to the found node (or head if head points to it).  Thus, if the
  62  * node's all you want, dereference the return value twice.  If you want to
  63  * modify the list, modify the referent of the return value.
  64  * While it's at it, deletes nodes whose time has expired (except the node
  65  * you're looking for, of course).
  66  * Returns NULL if the node isn't found.
  67  * Assumes the caller owns cache's lock.
  68  */
  69 static NBNameCacheNode **NBNameCacheWalk(struct NBNameCache *cache,
  70  const char name[NCBNAMSZ])
  71 {
  72     NBNameCacheNode **ret = NULL;
  73
  74     if (cache && cache->head)
  75     {
  76         NBNameCacheNode **ptr;
  77
  78         ptr = &cache->head;
  79         while (ptr && *ptr && (*ptr)->entry)
  80         {
  81             if (!memcmp((*ptr)->entry->name, name, NCBNAMSZ - 1))
  82                 ret = ptr;
  83             else
  84             {
  85                 if (GetTickCount() > (*ptr)->expireTime)
  86                     NBNameCacheUnlinkNode(cache, ptr);
  87             }
  88             if (*ptr)
  89                 ptr = &(*ptr)->next;
  90         }
  91     }
  92     return ret;
  93 }
  94
  95 struct NBNameCache *NBNameCacheCreate(HANDLE heap, DWORD entryExpireTimeMS)
  96 {
  97     struct NBNameCache *cache;
  98
  99
 100     if (!heap)
 101         heap = GetProcessHeap();
 102     cache = HeapAlloc(heap, 0, sizeof(struct NBNameCache));
 103     if (cache)
 104     {
 105         cache->heap = heap;
 106         InitializeCriticalSection(&cache->cs);
 107         cache->cs.DebugInfo->Spare[0] = (DWORD_PTR)(__FILE__ ": NBNameCache.cs");
 108         cache->entryExpireTimeMS = entryExpireTimeMS;
 109         cache->head = NULL;
 110     }
 111     return cache;
 112 }
 113
 114 BOOL NBNameCacheAddEntry(struct NBNameCache *cache, NBNameCacheEntry *entry)
 115 {
 116     BOOL ret;
 117
 118     if (cache && entry)
 119     {
 120         NBNameCacheNode **node;
 121
 122         EnterCriticalSection(&cache->cs);
 123         node = NBNameCacheWalk(cache, (char*)entry->name);
 124         if (node)
 125         {
 126             (*node)->expireTime = GetTickCount() +
 127              cache->entryExpireTimeMS;
 128             HeapFree(cache->heap, 0, (*node)->entry);
 129             (*node)->entry = entry;
 130             ret = TRUE;
 131         }
 132         else
 133         {
 134             NBNameCacheNode *newNode = HeapAlloc(cache->heap, 0, sizeof(NBNameCacheNode));
 135             if (newNode)
 136             {
 137                 newNode->expireTime = GetTickCount() +
 138                  cache->entryExpireTimeMS;
 139                 newNode->entry = entry;
 140                 newNode->next = cache->head;
 141                 cache->head = newNode;
 142                 ret = TRUE;
 143             }
 144             else
 145                 ret = FALSE;
 146         }
 147         LeaveCriticalSection(&cache->cs);
 148     }
 149     else
 150         ret = FALSE;
 151     return ret;
 152 }
 153
 154 const NBNameCacheEntry *NBNameCacheFindEntry(struct NBNameCache *cache,
 155  const UCHAR name[NCBNAMSZ])
 156 {
 157     const NBNameCacheEntry *ret;
 158     UCHAR printName[NCBNAMSZ];
 159
 160     memcpy(printName, name, NCBNAMSZ - 1);
 161     printName[NCBNAMSZ - 1] = '\0';
 162     if (cache)
 163     {
 164         NBNameCacheNode **node;
 165
 166         EnterCriticalSection(&cache->cs);
 167         node = NBNameCacheWalk(cache, (const char *)name);
 168         if (node)
 169             ret = (*node)->entry;
 170         else
 171             ret = NULL;
 172         LeaveCriticalSection(&cache->cs);
 173     }
 174     else
 175         ret = NULL;
 176     return ret;
 177 }
 178
 179 void NBNameCacheDestroy(struct NBNameCache *cache)
 180 {
 181     if (cache)
 182     {
 183         cache->cs.DebugInfo->Spare[0] = 0;
 184         DeleteCriticalSection(&cache->cs);
 185         while (cache->head)
 186             NBNameCacheUnlinkNode(cache, &cache->head);
 187         HeapFree(cache->heap, 0, cache);
 188     }
 189 }