reactos/dll/win32/netapi32/nbnamecache.c

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/* Copyright (c) 2003 Juan Lang
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
*
* This implementation uses a linked list, because I don't have a decent
* hash table implementation handy. This is somewhat inefficient, but it's
* rather more efficient than not having a name cache at all.
*/
#include "netapi32.h"
typedef struct _NBNameCacheNode
{
DWORD expireTime;
NBNameCacheEntry *entry;
struct _NBNameCacheNode *next;
} NBNameCacheNode;
struct NBNameCache
{
HANDLE heap;
CRITICAL_SECTION cs;
DWORD entryExpireTimeMS;
NBNameCacheNode *head;
};
/* Unlinks the node pointed to by *prev, and frees any associated memory.
* If that node's next pointed to another node, *prev now points to it.
* Assumes the caller owns cache's lock.
*/
static void NBNameCacheUnlinkNode(struct NBNameCache *cache,
NBNameCacheNode **prev)
{
if (cache && prev && *prev)
{
NBNameCacheNode *next = (*prev)->next;
HeapFree(cache->heap, 0, (*prev)->entry);
HeapFree(cache->heap, 0, *prev);
*prev = next;
}
}
/* Walks the list beginning with cache->head looking for the node with name
* name. If the node is found, returns a pointer to the next pointer of the
* node _prior_ to the found node (or head if head points to it). Thus, if the
* node's all you want, dereference the return value twice. If you want to
* modify the list, modify the referent of the return value.
* While it's at it, deletes nodes whose time has expired (except the node
* you're looking for, of course).
* Returns NULL if the node isn't found.
* Assumes the caller owns cache's lock.
*/
static NBNameCacheNode **NBNameCacheWalk(struct NBNameCache *cache,
const char name[NCBNAMSZ])
{
NBNameCacheNode **ret = NULL;
if (cache && cache->head)
{
NBNameCacheNode **ptr;
ptr = &cache->head;
while (ptr && *ptr && (*ptr)->entry)
{
if (!memcmp((*ptr)->entry->name, name, NCBNAMSZ - 1))
ret = ptr;
else
{
if (GetTickCount() > (*ptr)->expireTime)
NBNameCacheUnlinkNode(cache, ptr);
}
if (*ptr)
ptr = &(*ptr)->next;
}
}
return ret;
}
struct NBNameCache *NBNameCacheCreate(HANDLE heap, DWORD entryExpireTimeMS)
{
struct NBNameCache *cache;
if (!heap)
heap = GetProcessHeap();
cache = HeapAlloc(heap, 0, sizeof(struct NBNameCache));
if (cache)
{
cache->heap = heap;
InitializeCriticalSection(&cache->cs);
cache->cs.DebugInfo->Spare[0] = (DWORD_PTR)(__FILE__ ": NBNameCache.cs");
cache->entryExpireTimeMS = entryExpireTimeMS;
cache->head = NULL;
}
return cache;
}
BOOL NBNameCacheAddEntry(struct NBNameCache *cache, NBNameCacheEntry *entry)
{
BOOL ret;
if (cache && entry)
{
NBNameCacheNode **node;
EnterCriticalSection(&cache->cs);
node = NBNameCacheWalk(cache, (char*)entry->name);
if (node)
{
(*node)->expireTime = GetTickCount() +
cache->entryExpireTimeMS;
HeapFree(cache->heap, 0, (*node)->entry);
(*node)->entry = entry;
ret = TRUE;
}
else
{
NBNameCacheNode *newNode = HeapAlloc(cache->heap, 0, sizeof(NBNameCacheNode));
if (newNode)
{
newNode->expireTime = GetTickCount() +
cache->entryExpireTimeMS;
newNode->entry = entry;
newNode->next = cache->head;
cache->head = newNode;
ret = TRUE;
}
else
ret = FALSE;
}
LeaveCriticalSection(&cache->cs);
}
else
ret = FALSE;
return ret;
}
const NBNameCacheEntry *NBNameCacheFindEntry(struct NBNameCache *cache,
const UCHAR name[NCBNAMSZ])
{
const NBNameCacheEntry *ret;
UCHAR printName[NCBNAMSZ];
memcpy(printName, name, NCBNAMSZ - 1);
printName[NCBNAMSZ - 1] = '\0';
if (cache)
{
NBNameCacheNode **node;
EnterCriticalSection(&cache->cs);
node = NBNameCacheWalk(cache, (const char *)name);
if (node)
ret = (*node)->entry;
else
ret = NULL;
LeaveCriticalSection(&cache->cs);
}
else
ret = NULL;
return ret;
}
void NBNameCacheDestroy(struct NBNameCache *cache)
{
if (cache)
{
cache->cs.DebugInfo->Spare[0] = 0;
DeleteCriticalSection(&cache->cs);
while (cache->head)
NBNameCacheUnlinkNode(cache, &cache->head);
HeapFree(cache->heap, 0, cache);
}
}