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 "nbnamecache.h"
  23
  24 typedef struct _NBNameCacheNode
  25 {
  26     DWORD expireTime;
  27     NBNameCacheEntry *entry;
  28     struct _NBNameCacheNode *next;
  29 } NBNameCacheNode;
  30
  31 struct NBNameCache
  32 {
  33     HANDLE heap;
  34     CRITICAL_SECTION cs;
  35     DWORD entryExpireTimeMS;
  36     NBNameCacheNode *head;
  37 };
  38
  39 /* Unlinks the node pointed to by *prev, and frees any associated memory.
  40  * If that node's next pointed to another node, *prev now points to it.
  41  * Assumes the caller owns cache's lock.
  42  */
  43 static void NBNameCacheUnlinkNode(struct NBNameCache *cache,
  44  NBNameCacheNode **prev)
  45 {
  46     if (cache && prev && *prev)
  47     {
  48         NBNameCacheNode *next = (*prev)->next;
  49
  50         HeapFree(cache->heap, 0, (*prev)->entry);
  51         HeapFree(cache->heap, 0, *prev);
  52         *prev = next;
  53     }
  54 }
  55
  56 /* Walks the list beginning with cache->head looking for the node with name
  57  * name.  If the node is found, returns a pointer to the next pointer of the
  58  * node _prior_ to the found node (or head if head points to it).  Thus, if the
  59  * node's all you want, dereference the return value twice.  If you want to
  60  * modify the list, modify the referent of the return value.
  61  * While it's at it, deletes nodes whose time has expired (except the node
  62  * you're looking for, of course).
  63  * Returns NULL if the node isn't found.
  64  * Assumes the caller owns cache's lock.
  65  */
  66 static NBNameCacheNode **NBNameCacheWalk(struct NBNameCache *cache,
  67  const char name[NCBNAMSZ])
  68 {
  69     NBNameCacheNode **ret = NULL;
  70
  71     if (cache && cache->head)
  72     {
  73         NBNameCacheNode **ptr;
  74
  75         ptr = &cache->head;
  76         while (ptr && *ptr && (*ptr)->entry)
  77         {
  78             if (!memcmp((*ptr)->entry->name, name, NCBNAMSZ - 1))
  79                 ret = ptr;
  80             else
  81             {
  82                 if (GetTickCount() > (*ptr)->expireTime)
  83                     NBNameCacheUnlinkNode(cache, ptr);
  84             }
  85             if (*ptr)
  86                 ptr = &(*ptr)->next;
  87         }
  88     }
  89     return ret;
  90 }
  91
  92 struct NBNameCache *NBNameCacheCreate(HANDLE heap, DWORD entryExpireTimeMS)
  93 {
  94     struct NBNameCache *cache;
  95
  96
  97     if (!heap)
  98         heap = GetProcessHeap();
  99     cache = HeapAlloc(heap, 0, sizeof(struct NBNameCache));
 100     if (cache)
 101     {
 102         cache->heap = heap;
 103         InitializeCriticalSection(&cache->cs);
 104         cache->cs.DebugInfo->Spare[0] = (DWORD_PTR)(__FILE__ ": NBNameCache.cs");
 105         cache->entryExpireTimeMS = entryExpireTimeMS;
 106         cache->head = NULL;
 107     }
 108     return cache;
 109 }
 110
 111 BOOL NBNameCacheAddEntry(struct NBNameCache *cache, NBNameCacheEntry *entry)
 112 {
 113     BOOL ret;
 114
 115     if (cache && entry)
 116     {
 117         NBNameCacheNode **node;
 118
 119         EnterCriticalSection(&cache->cs);
 120         node = NBNameCacheWalk(cache, (char*)entry->name);
 121         if (node)
 122         {
 123             (*node)->expireTime = GetTickCount() +
 124              cache->entryExpireTimeMS;
 125             HeapFree(cache->heap, 0, (*node)->entry);
 126             (*node)->entry = entry;
 127             ret = TRUE;
 128         }
 129         else
 130         {
 131             NBNameCacheNode *newNode = HeapAlloc(cache->heap, 0, sizeof(NBNameCacheNode));
 132             if (newNode)
 133             {
 134                 newNode->expireTime = GetTickCount() +
 135                  cache->entryExpireTimeMS;
 136                 newNode->entry = entry;
 137                 newNode->next = cache->head;
 138                 cache->head = newNode;
 139                 ret = TRUE;
 140             }
 141             else
 142                 ret = FALSE;
 143         }
 144         LeaveCriticalSection(&cache->cs);
 145     }
 146     else
 147         ret = FALSE;
 148     return ret;
 149 }
 150
 151 const NBNameCacheEntry *NBNameCacheFindEntry(struct NBNameCache *cache,
 152  const UCHAR name[NCBNAMSZ])
 153 {
 154     const NBNameCacheEntry *ret;
 155     UCHAR printName[NCBNAMSZ];
 156
 157     memcpy(printName, name, NCBNAMSZ - 1);
 158     printName[NCBNAMSZ - 1] = '\0';
 159     if (cache)
 160     {
 161         NBNameCacheNode **node;
 162
 163         EnterCriticalSection(&cache->cs);
 164         node = NBNameCacheWalk(cache, (const char *)name);
 165         if (node)
 166             ret = (*node)->entry;
 167         else
 168             ret = NULL;
 169         LeaveCriticalSection(&cache->cs);
 170     }
 171     else
 172         ret = NULL;
 173     return ret;
 174 }
 175
 176 void NBNameCacheDestroy(struct NBNameCache *cache)
 177 {
 178     if (cache)
 179     {
 180         cache->cs.DebugInfo->Spare[0] = 0;
 181         DeleteCriticalSection(&cache->cs);
 182         while (cache->head)
 183             NBNameCacheUnlinkNode(cache, &cache->head);
 184         HeapFree(cache->heap, 0, cache);
 185     }
 186 }